Application of macroalgal biomass derived biochar and bioelectrochemical system with Shewanella for the adsorptive removal and biodegradation of toxic azo dye

Surface engineering-based S, N co-doped biochar for improved anaerobic digestion: Enhancing microbial-pollutant and inter-microbial electron transfer synergistic EPS protection

Enhancing extracellular electron transfer (EET) efficiency is crucial for improving the anaerobic digestion (AD) system's capability to treat recalcitrant wastewater. In this study, a novel S, N co-doped biochar (S-N-BC) was prepared through surface engineering to optimize EET within AD systems. The addition of S-N-BC significantly enhanced the performance of a mesophilic AD system treating Congo red wastewater, increasing the decolorization rate by 78 %, COD degradation rate by 82 %, and methane yield by 87 % compared to the control. Additionally, the shock resistance of anaerobic granular sludge was improved, as evidenced by the formation of the protective extracellular polymeric substances (EPS) barrier and the enhanced activities of the electron transport system. Mechanistic analysis revealed that adding S-N-BC did not alter the Congo red decolorization pathway but significantly enriched various electrochemically active bacteria and established EET pathways between microbial-pollutant and inter-microbial. This significantly accelerated EET efficiency within the AD system, ensuring stable and efficient operation under challenging conditions. This study proposed a novel approach using S-N-BC to simultaneously enhance "dual-pathway EET" between microbial-pollutant and inter-microbial while constructing an EPS protective barrier, addressing the issues of low efficiency and fragile stability of AD systems for treating recalcitrant wastewater.

Microalgae to bioenergy production: Recent advances, influencing parameters, utilization of wastewater - A critical review

Fossil fuel limitations and their influence on climate change through atmospheric greenhouse gas emissions have made the excessive use of fossil fuels widely recognized as unsustainable. The high lipid content, carbon-neutral nature and potential as a biofuel source have made microalgae a subject of global study. Microalgae are a promising supply of biomass for third-generation biofuels production since they are renewable. They have the potential to produce significant amounts of biofuel and are considered a sustainable alternative to non-renewable energy sources. Microalgae are currently incapable to synthesize algal biofuel on an extensive basis in a sustainable manner, despite their significance in the global production of biofuels. Wastewater contains nutrients (both organic and inorganic) which is essential for the development of microalgae. Microalgae and wastewater can be combined to remediate waste effectively. Wastewater of various kinds such as industrial, agricultural, domestic, and municipal can be used as a substrate for microalgal growth. This process helps reduce carbon dioxide emissions and makes the production of biofuels more cost-effective. This critical review provides a detailed analysis of the utilization of wastewater as a growth medium for microalgal - biofuel production. The review also highlights potential future strategies to improve the commercial production of biofuels from microalgae.

Garlic Peel-Based Biochar Prepared under Weak Carbonation Conditions for Efficient Removal of Methylene Blue from Wastewater

BACKGROUND

Due to it containing cellulose, hemicellulose, and lignin with abundant specific functional groups which could interact with organic dyes, garlic peel (GP) might be used as an efficient biosorbent. The aim of this study is to evaluate the adsorption performances of GP-based bio-adsorbents and obtain optimum preparation conditions.

METHODS

GP-based bio-adsorbents were prepared by thermal pyrolysis under different temperatures (150-400 °C). The morphologies, chemical states, and surface functional groups of the adsorbents were analyzed by X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and thermogravimetric analysis (TGA). Batch experiments were conducted to investigate the adsorption of methylene blue (MB) under various conditions, including contact time, contact temperature, initial dye concentration, and initial pH value. The equilibrium adsorption data were fitted to different kinetic and isothermal models, and the adsorption thermodynamics were also calculated. Significant Findings: The physicochemical properties of the GP-based bio-adsorbents were primarily dominated by the pyrolysis temperature, because their morphologies and surface functional groups of GP-based bio-adsorbents significantly varied with the changes in pyrolysis temperature. The adsorption capacity of GP materials for MB decreased as the pyrolysis temperature increased. At an initial concentration of 50.00 mg L-1, GP150 possessed a higher adsorption capacity of 167.74 mg g-1 toward MB. The possible adsorbate-adsorbent interactions, including electrostatic attraction, hydrogen bonding, and π-π stacking, were recognized. After 10 consecutive adsorption-desorption cycles, GP150 maintained a high removal rate (88%) for MB, demonstrating its excellent adsorption performance, good reusability, and potential application in the treatment of MB-contaminated water.

Synergistic enhancement of microbes-to-pollutants and inter-microbes electron transfer by Fe, N modified ordered mesoporous biochar in anaerobic digestion

Extracellular electron transfer was essential for degrading recalcitrant pollutants by anaerobic digestion (AD). Therefore, existing studies improved AD efficiency by enhancing the electron transfer from microbes-to-pollutants or inter-microbes. This study synthesized a novel Fe, N co-doped biochar (Fe, N-BC), which could enhance both the microbes-to-pollutants and inter-microbes electron transfer in AD. Detailed characterization data indicated that Fe, N-BC has an ordered mesoporous structure, high specific surface area (463.46 m2/g), and abundant redox functional groups (Fe2+/Fe3+, pyrrolic-N), which translate into excellent biocompatibility and electrochemical properties of Fe, N-BC. By adding Fe, N-BC, the stability and efficiency of the medium-temperature AD system in the treatment of methyl orange (MO) wastewater were improved: obtained a high degradation efficiency of MO (96.8 %) and enhanced the methane (CH4) production by 65 % compared to the control group. Meanwhile, Fe, N-BC reduced the accumulation of volatile fatty acids in the AD system, and the activity of anaerobic granular sludge electron transport system and coenzyme F420 was enhanced. In addition, Fe, N-BC showed positive enrichment of azo dyes decolorization bacteria (Georgenia) and direct interspecies electron transfer (DIET) synergistic partners (Syntrophobacter, Methanosarcina). Overall, the rapid degradation of MO and enhanced CH4 production in AD systems by Fe, N-BC is associated with enhancing two electronic pathways, i.e., microbes to MO and DIET between syntrophic bacteria and methanogenic archaea. This study introduced an enhanced "two-pathways of electron transfer" theory, realized by Fe, N-BC. These findings provided new insights into the interactions within AD systems and offer strategies for enhancing their performance with recalcitrant pollutants.

Plant and yeast consortium for efficient remediation of dyes and effluents: a biochemical and toxicological study

Textile effluent carries a range of dyes that may be recalcitrant and resistant to biodegradation. A unique consortium of the Fimbristylis dichotoma and Saccharomyces cerevisiae is exploited for the biodegradation of an azo dye Rubine GFL and actual textile effluent. This consortium enhances the rate of biodegradation of Rubine GFL and actual textile effluent with an excellent rate of biodegradation of 92% for Rubine GFL and 68% for actual textile effluent when compared to the individual one within 96 h. Speedy decolorization of Rubine GFL and actual textile effluent was observed due to the induction of oxido-reductive enzymes of the FD-SC consortium. Along with the significant reduction in the values of COD, BOD, ADMI, TSS, and TDS with 70, 64, 65, 41, and 52%, respectively, in experimental sets treated with FD-SC consortium. The biodegradation of Rubine GFL was confirmed with UV-Vis spectroscopy at the preliminary level, and then, metabolites formed after degradation were detected and identified by FTIR, HPLC, and GC-MS techniques. Also, decolorization of the dye was observed in the sections of the root cortex of Fimbristylis dichotoma. The toxicity of dye and metabolites formed after degradation was assessed by seed germination and bacterial count assay, where increased germination % and bacterial count from 31×107CFUs to 92 × 107 CFUs reflect the nontoxic nature of metabolites. Furthermore, the nontoxic nature of metabolites was confirmed by fish toxicity on Cirrhinus mrigala showed normal structures of fish gills and liver in the groups treated with FD-SC consortium proving the better tactic for biodegradation of dyes and textile effluent.

Synthesis, delineation and technological advancements of algae biochar for sustainable remediation of the emerging pollutants from wastewater-a review

The use of algae for value-added product and biorefining applications is enchanting attention among researchers in recent years due to its remarkable photosynthetic ability, adaptability, and capacity to accumulate lipids and carbohydrates. Algae biomass, based on its low manufacturing costs, is relatively renewable, sustainable, environmentally friendly and economical in comparison with other species. High production rate of algae provides a unique opportunity for its conversion to biochar with excellent physicochemical properties, viz. high surface area and pore volume, high adsorption capacity, abundant functional groups over surface, etc. Despite several potential algal-biochar, a detailed study on its application for removal of emerging contaminants from wastewater is limited. Therefore, this technical review is being carried out to evaluate the specific elimination of inorganic and organic pollutants from wastewater, with a view to assessing adsorption performances of biochar obtained from various algae species. Species-specific adsorption of emerging pollutants from wastewater have been discussed in the present review. The promising methods like pyrolysis, gasification, dry and wet torrefaction for the production of algae biochar are highlighted. The strategies include chemical and structural modifications of algae biochar for the removal of toxic contaminants have also been considered in the current work. The overall aim of this review is to confer about the synthesis, technological advancements, delineation and application of algae biochar for the treatment of wastewater.

A polyfunctionalized carbon framework composite for efficient decontamination of Cr(VI) and polycyclic aromatic nitrides from acidic wastewater

Developing multifunctional engineered adsorbents is an effective strategy for decontaminating the environment from various pollutants. In this study, a polyfunctionalized carbon-framework composite, MSC-CFM, was synthesized. The composite comprises an aromatic carbon framework enriched with various functional groups, including magnetic nanoparticles, hydroxyl, and amino groups. MSC-CFM was used to decontaminate Cr(VI) and polycyclic aromatic nitrides (p-dimethylaminoazobenzene sulfonate (DAS) and diphenyl-4, 4 '-di [sodium (azo-2 -) -1-amino-naphthalene-4-sulfonate] (DANS)) from acidic wastewater. The adsorption capacities of MSC-CFM for Cr(VI), DAS and DANS, quantified using the Langmuir isotherm model, were 161.28, 310.83, and 1566.09 mg/g, respectively. Cr(VI) and PAHs (DAS and DANS) were monolayer adsorbed controlled by chemisorption. MSC-CFM could maintain good adsorption efficiency after up to 6 adsorption and desorption cycles. The presence of polycyclic aromatic nitrides promoted the adsorption of Cr(VI) in the Cr(VI)-DAS/DANS binary systems. Removal of pollutants by MSC-CFM involved a variety of unreported reaction mechanisms, such as electrostatic attraction, redox reaction, anion exchange, intermolecular hydrogen bonding, complexation reaction, π-π interaction, and anion-π interaction. MSC-CFM, enriched with a variety of functional groups, is a promising new material for environmental protection. It has good potential for practical application in treating polluted wastewater.

Activated carbon and their nanocomposites derived from vegetable and fruit residues for water treatment

Water pollution remains a pressing environmental issue, with diverse pollutants such as heavy metals, pharmaceuticals, dyes, and aromatic hydrocarbon compounds posing a significant threat to clean water access. Historically, biomass-derived activated carbons (ACs) have served as effective adsorbents for water treatment, owing to their inherent porosity and expansive surface area. Nanocomposites have emerged as a means to enhance the absorption properties of ACs, surpassing conventional AC performance. Biomass-based activated carbon nanocomposites (ACNCs) hold promise due to their high surface area and cost-effectiveness. This review explores recent advancements in biomass-based ACNCs, emphasizing their remarkable adsorption efficiencies and paving the way for future research in developing efficient and affordable ACNCs. Leveraging real-time communication for ACNC applications presents a viable approach to addressing cost concerns.

Biodegradation of commercial textile reactive dye mixtures by industrial effluent adapted bacterial consortium VITPBC6: a potential technique for treating textile effluents

Textile industries release major fraction of dyestuffs in effluents leading to a major environmental concern. These effluents often contain more than one dyestuff, which complicates dye degradation. In this study ten reactive dyes (Reactive Yellow 145, Reactive Yellow 160, Reactive Orange 16, Reactive Orange 107, Reactive Red 195, Reactive Blue 21, Reactive Blue 198, Reactive Blue 221, Reactive Blue 250, and Reactive Black 5) that are used in textile industries were subjected to biodegradation by a bacterial consortium VITPBC6, formulated in our previous study. Consortium VITPBC6 caused single dye degradation of all the mentioned dyes except for Reactive Yellow 160. Further, VITPBC6 efficiently degraded a five-dye mixture (Reactive Red 195, Reactive Orange 16, Reactive Black 5, Reactive Blue 221, and Reactive Blue 250). Kinetic studies revealed that the five-dye mixture was decolorized by VITPBC6 following zero order reaction kinetic; Vmax and Km values of the enzyme catalyzed five-dye decolorization were 128.88 mg L-1 day-1 and 1003.226 mg L-1 respectively. VITPBC6 degraded the dye mixture into delta-3,4,5,6-Tetrachlorocyclohexene, sulfuric acid, 1,2-dichloroethane, and hydroxyphenoxyethylaminohydroxypropanol. Phytotoxicity, cytogenotoxicity, microtoxicity, and biotoxicity assays conducted with the biodegraded metabolites revealed that VITPBC6 lowered the toxicity of five-dye mixture significantly after biodegradation.

Sequential use of a continuous-flow electrocoagulation reactor and a (photo)electro-Fenton recirculation system for the treatment of Acid Brown 14 diazo dye

The decolorization and TOC removal of solutions of Acid Brown 14 (AB14) diazo dye containing 50 mg L-1 of total organic carbon (TOC) have been first studied in a continuous-flow electrocoagulation (EC) reactor of 3 L capacity with Fe electrodes of ∼110 cm2 area each. Total loss of color with poor TOC removal was found in chloride, sulfate, and/or hydrogen carbonate matrices after 18 min of this treatment. The best performance was found using 5 anodes and 4 cathodes of Fe at 13.70 A and low liquid flow rate of 10 L h-1, in aerated 39.6 mM NaCl medium within a pH range of 4.0-10.0. The effluent obtained from EC was further treated by electro-Fenton (EF) using a 2.5 L pre-pilot flow plant, which was equipped with a filter-press cell comprising a Pt anode and an air-diffusion cathode for H2O2 electrogeneration. Operating with 0.10-1.0 mM Fe2+ as catalyst at pH 3.0 and 50 mA cm-2, a similar TOC removal of 68 % was found as maximal in chloride and sulfate media using the sequential EC-EF process. The EC-treated solutions were also treated by photoelectro-Fenton (PEF) employing a photoreactor with a 125 W UVA lamp. The sequential EC-PEF process yielded a much higher TOC reduction, close to 90 % and 97 % in chloride and sulfate media, respectively, due to the rapid photolysis of the final Fe(III)-carboxylate complexes. The formation of recalcitrant chloroderivatives from generated active chlorine limited the mineralization in the chloride matrix. For practical applications of this two-step technology, the high energy consumption of the UVA lamp in PEF could be reduced by using free sunlight.

A response surface model to examine the reactive red 239 sorption behaviors on Rhizoclonium hieroglyphicum: isotherms, kinetics, thermodynamics and toxicity analyses

The present study is an attempt to investigate the potentiality of Rhizoclonium hieroglyphicum in the removal of reactive red 239 (RR239) from aqueous solution and to assess the toxicity of the treated dye solution. Optimisation of the process variables namely dye and biosorbent concentrations, pH, temperature and incubation time for RR239 removal was performed using Response Surface Methodology (RSM) assisted Box Behnken Design (BBD) model. The recycling and regeneration efficiency of the dye adsorbed alga was evaluated using different eluents under optimized conditions. Further to understand the adsorption mechanism, isotherms, kinetics and thermodynamic studies were performed. UV-vis and FT-IR spectroscopy was employed to confirm the interaction between the adsorbate and biosorbent. The nature of the treated dye solution was assessed using phyto, microbial and brine shrimp toxicity studies. On the basis of quadratic polynomial equation and response surfaces given by RSM, 90% decolorization of RR239 was recorded at room temperature under specified optimal conditions (300 mg/L of dye, 500 mg/L of biosorbent, pH 8 and 72 h of contact time). Desorption experiments demonstrated 88% of RR239 recovery using 0.1 N acetic acid as an eluent and 81% of dye removal in regeneration studies. The data closely aligned with Freundlich isotherm (R2 - 0.98) and pseudo-second-order kinetic model (R2 - 0.9671). Thermodynamic analysis revealed that the process of adsorption was endothermic, spontaneous, and favorable. UV-Vis and FT-IR analyses provided evidence for adsorbate-biosorbent interaction, substantiating the process of decolorization. In addition, the results of phyto, microbial and brine shrimp toxicity assays consistently confirmed the non-toxic nature of the treated dye. Thus, the study demonstrated that R. hieroglyphicum can act as a potent bioremediation agent in alleviating the environmental repercussions of textile dyeing processes.

New and effective cassava bagasse-modified biochar to adsorb Food Red 17 and Acid Blue 9 dyes in a binary mixture

A promissory technic for reducing environmental contaminants is the production of biochar from waste reuse and its application for water treatment. This study developed biochar (CWb) and NH4Cl-modified biochar (MCWb) using cassava residues as precursors. CWb and MCWb were characterized and evaluated in removing dyes (Acid Blue 9 and Food Red 17) in a binary system. The adsorbent demonstrated high adsorption capacity at all pH levels studied, showing its versatility regarding this process parameter. The equilibrium of all adsorption experiments was reached in 30 min. The adsorption process conformed to pseudo-first-order kinetics and extended Langmuir isotherm model. The thermodynamic adsorption experiments demonstrated that the adsorption process is physisorption, exhibiting exothermic and spontaneous characteristics. MCWb exhibited highly efficient and selective adsorption behavior towards the anionic dyes, indicating maximum adsorption capacity of 131 and 150 mg g-1 for Food Red 17 and Acid Blue 9, respectively. Besides, MCWb could be reused nine times, maintaining its original adsorption capacity. This study demonstrated an excellent adsorption capability of biochars in removing dyes. In addition, it indicated the recycling of wastes as a precursor of bio composts, a strategy for utilization in water treatment with binary systems. It showed the feasibility of the reuse capacity that indicated that the adsorbent may have many potential applications.

Preparation of 1,8-dichloroanthraquinone/graphene oxide/poly (vinylidene fluoride) (1,8-AQ/GO/PVDF) mediator membrane and its application to catalyzing biodegradation of azo dyes

Anthraquinone is a redox mediator that can effectively catalyze the degradation of azo dyes by promoting the electron transfer. In this study, a mediator membrane with poly (vinylidene fluoride) (PVDF) as the membrane support and 1,8-dichloroanthraquinone (1,8-AQ) and graphene oxide (GO) as the additives was prepared and characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), mercury intrusion porosimetry (MIP), atomic force microscopy (AFM) and water contact angle. The introduction of GO increases the pure water flux of the membrane to 258.56±12.93 L/(m2·h). Its catalytic performances for the biodegradation of azo dyes were evaluated. Under the optimized conditions, the 1,8-AQ/GO/PVDF composite membrane is able to improve the dye degradation efficiency 2.2 times for reactive red X-3B and 1.1 times for acid red B, as compared with PVDF membrane. In addition, the mediator membrane maintains stable and high catalytic efficiency in the cyclic test and over 90 % dye degradation efficiency is still obtained after 5 cycles of decolorization. These results suggest the great application potentials of the 1,8-AQ/GO/PVDF membrane in the dye wastewater treatment.

Tailoring carboxylatopillar[5]arene-modified magnetic graphene oxide nanocomposites for the efficient removal of cationic dyes

A carboxylatopillar[5]arene-embellished (CP5) magnetic graphene oxide nanocomposite (MGO@CP5) was smoothly constructed via a mild layer-by-layer method. The morphology, structure, and surface characteristics of this nanocomposite was investigated by field-emission scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, zeta potential, and other techniques. Benefiting from a high capture ability for small molecules of CP5 as a supramolecular host molecule, along with a negative surface charge and large surface area of MGO@CP5, this nanocomposite exhibits an ultrafast, efficient adsorption property for representative cationic dyes: methylene blue (MB) and basic fuchsin (BF). The removal efficiency of MB and BF can reach nearly 99% within 3 min, while the maximum adsorption capacity of the two dyes reaches 240 mg g-1 for MB and 132 mg g-1 for BF. Furthermore, owing to excellent magnetic responsiveness from the tight loading of Fe3O4 nanoparticles on graphene oxide, MGO@CP5 could be easily and magnetically separated, regenerated, and reused four times without an evident reduction in the removal efficiency (>95%). Impressively, the adsorption property of MGO@CP5 reveals a strong tolerance to pH changes and ionic strength interference, which renders it a promising adsorbent in the field of water treatment.

The potential of self-activated carbon for adsorptive removal of toxic phenoxyacetic acid herbicide from water

Phenoxyacetic acid herbicides are widely used in agriculture for controlling weeds. These organic compounds are persistent and recalcitrant, often contaminating water and soil. Therefore, we studied five pristine biochars (BCs), and southern yellow pine (SYP) based self-activated carbon (SAC) for the adsorptive removal of 2,4-Dichlorophenoxyacetic acid (2,4-D) herbicide. Among the tested adsorbents, SYP-SAC-15 demonstrated higher (>90%) 2,4-D removal from water. The SYP-SAC-15 was produced using a facile and green route where the biomass pyrolysis gases worked as activating agents creating a highly porous structure with a surface area of 1499.79 m2/g. Different adsorption kinetics and isotherm models were assessed for 2,4-D adsorption on SYP-SAC-15, where the data fitted best to pseudo-second order (R2 > 0.999) and Langmuir (R2 > 0.991) models, respectively. Consequently, the adsorption process was mainly dominated by the chemisorption mechanism with monolayer coverage of SYP-SAC-15 surface with 2,4-D molecules. At the optimum pH of 2, the maximum 2,4-D adsorption capacity of SYP-SAC-15 reached 471.70 mg/g. Furthermore, an increase in the water salinity demonstrated a positive influence on 2,4-D adsorption, whereas humic acid (HA) showed a negative impact on 2,4-D adsorption. The regeneration ability of SYP-SAC-15 showed excellent performance by retaining 71.09% adsorption capability at the seventh adsorption-desorption cycle. Based on the operating pH, surface area, spectroscopic data, kinetics, and isotherm modeling, the adsorption mechanism was speculated. The 2,4-D adsorption on SYP-SAC-15 was mainly governed by pore filling, electrostatic interactions, hydrogen bonding, hydrophobic and π-π interactions.

Removal of methylene blue by porous biochar obtained by KOH activation from bamboo biochar

A series of activated biochar (KBBC-700, KBBC-800 and KBBC-900) which were modified by KOH and pyrolysis at various temperatures from ball-milling bamboo powder were obtained. The physicochemical properties and pore structures of activated biochar were investigated by scanning electron microscopy (SEM), fourier transform infrared spectoscopy (FT-IR), X-ray diffraction (XRD) and N2 adsorption/desorption. The adsorption performance for the removal of methylene blue (MB) was deeply studied. The results showed that KBBC-900 obtained at activation temperature of 900 °C exhibited a great surface area which reached 562 m2/g with 0.460 cm3/g of total pore volume. The enhancement of adsorption capacity could be ascribed to the increase of surface oxygen-containing functional groups, aromatization and mesoporous channels. The adsorption capacity was up to 67.46 mg/g under the optimum adsorption parameters with 2 g/L of adsorbent dose, 11 of initial solution pH and 298 K of the reactive temperature. The adsorption capacity was 70.63% of the first time after the material was recycled for three cycles. The kinetics indicated that the adsorption equilibrium time for MB on KBBC-900 was of about 20 min with the data fitted better to the pseudo-second-order kinetics model. The adsorption process was mainly dominated by chemical adsorption. Meanwhile, the adsorption isotherm showed that the Langmuir model fitted the best, and thermodynamic parameters revealed that the adsorption reaction was the endothermic nature and the spontaneous process. Adsorption of MB mainly attributed to electrostatic interactions, cation-π electron interaction and redox reaction. This study suggested that the activated biochar obtained by KOH activation from bamboo biochar has great potentials in the practical application to remove MB from wastewater.

Current application of seaweed waste for composting and biochar: A review

To address the origins of ocean acidification, seaweed aquaculture is emerging as a key biosequestration strategy. Nevertheless, seaweed biomass is involved in developing food and animal feed, whereas seaweed waste from commercial hydrocolloid extraction is dumped in landfills, which together limit the carbon cycle and carbon sequestration. This work sought to evaluate the production, properties, and applications of seaweed compost and biochar to strengthen the "carbon sink" implications of aquaculture sectors. Due to their unique characteristics, the production of seaweed-derived biochar and compost, as well as their existing applications, are distinct when compared to terrestrial biomass. This paper outlines the benefits of composting and biochar production as well as proposes ideas and perspectives to overcome technical shortcomings. If properly synchronized, progression in the aquaculture sector, composting, and biochar production, potentially promote various Sustainable Development Goals.

Bimetallic core-shell nanoparticle arrays at liquid-liquid interface for the degradation and monitoring of dye pollutants in situ by surface-enhanced Raman spectroscopy

In situ monitoring of chemical reactions has attracted great attention in many fields. Herein, we successfully in situ track the degradation reaction process of a dye pollutant, methylene blue (MB), on the liquid-liquid interface (LLI) of bimetallic gold core-silver shell nanoparticles (Au@AgNPs) by surface-enhanced Raman spectroscopy (SERS). The optimized LLI bimetallic array of Au₅₀@Ag₁₀NPs exhibits ultrahigh SERS enhancement and excellent catalytic activity. Results evidenced a detection limit of MB down to 1 ppb, and the degradation rate of Au@AgNPs was as high as 85.2% in 30 s, relying on the excellent self-healing properties of nanoarrays. Furthermore, as a practical SERS analyzer, the LLI bimetallic array was used to detect trace amounts of other harmful dyes, including Rhodamine 6G (R6G) and crystal violet (CV) in pure or complex media. Our LLI bimetallic array exhibits a new orientation for monitoring catalytic reactions involving highly toxic, hazardous, or costly targets in food security fields in the future.

Bioremediation of reactive orange 16 by industrial effluent-adapted bacterial consortium VITPBC6: process optimization using response surface methodology (RSM), enzyme kinetics, pathway elucidation, and detoxification

Textile effluent is one of the most hazardous industrial pollutant sources. It is generated in huge volumes and contains a wide array of toxicants. Reactive azo dyes, which are xenobiotic compounds, are predominantly utilized by textile industries for dyeing cotton, viscose, wool, and silk. The conventional physicochemical treatments used by industrial effluent treatment plants are ineffective in dye degradation. The present study thus attempted to find a potential treatment for reactive azo dyes. A novel bacterial consortium VITPBC6 was constructed with the most potent and compatible reactive orange 16 (RO-16) decolorizing isolates of tannery and textile effluents, and the isolates were identified as Bacillus flexus VITSP6, Bacillus paraflexus VITSPB7, Bacillus megaterium VITSPB9, Bacillus firmus VITEPB1, B. flexus VITEPB2, and Bacillus aryabhattai VITEPB3. The physicochemical factors of RO-16 decolorization were optimized by response surface methodology. Consortium VITPBC6 was able to tolerate a high concentration of RO-16 up to 800 mg L^-1. A cocktail of enzymes including azoreductase, tyrosinase, laccase, lignin peroxidase, and manganese peroxidase was involved in RO-16 degradation by VITPBC6. Consortium VITPBC6 degraded RO-16 following zero-order reaction. The enzymes of consortium VITPBC6 had a V_max of 352 mg L^-1 day^-1 for RO-16 degradation; however, the K_m value was high. VITPBC6 biodegraded RO-16 resulting in the formation of small aromatic compounds. Lastly, different toxicity assays conducted with untreated RO-16 and its corresponding biodegraded metabolite revealed that the toxicity of biodegraded metabolites was significantly lower than the untreated dye.

Algal biochar mediated detoxification of plant biomass hydrolysate: Mechanism study and valorization into polyhydroxyalkanoates

In this study, fourteen types of biochar produced using seven biomasses at temperatures 300 °C and 600 °C were screened for phenolics (furfural and hydroxymethylfurfural (HMF)) removal. Eucheuma spinosum biochar (EB-BC 600) showed higher adsorption capacity to furfural (258.94 ± 3.2 mg/g) and HMF (222.81 ± 2.3 mg/g). Adsorption kinetics and isotherm experiments interpreted that EB-BC 600 biochar followed the pseudo-first-order kinetic and Langmuir isotherm model for both furfural and HMF adsorption. Different hydrolysates were detoxified using EB-BC 600 biochar and used as feedstock for engineered Escherichia coli. An increased polyhydroxyalkanoates (PHA) production with detoxified barley biomass hydrolysate (DBBH: 1.71 ± 0.07 g PHA/L), detoxified miscanthus biomass hydrolysate (DMBH: 0.87 ± 0.03 g PHA/L) and detoxified pine biomass hydrolysate (DPBH: 1.28 ± 0.03 g PHA/L) was recorded, which was 2.8, 6.4 and 3.4 folds high as compared to undetoxified hydrolysates. This study reports the mechanism involved in furfural and HMF removal using biochar and valorization of hydrolysate into PHA.

Effect of salinity on removal performance of anaerobic membrane bioreactor treating azo dye wastewater

Membrane bioreactor (MBR) is an attractive option method for treating azo dye wastewater under extreme conditions. The present study assessed the effect of salinity on the performance of anaerobic MBR in treating azo dye wastewater. Increased salinity showed adverse effects on the decolorization efficiency and chemical oxygen demand (COD) removal efficiency. The decolorization efficiency decreased from 95.8% to 82.3% and 73.1% with a stepwise increasing of salinity from 0 to 3% and 5%, respectively. The COD removal efficiency decreased from 80.7% to 71.3% when the salinity increased from 0 to 3% and then decreased to 58.6% at 5% salinity. The volatile fatty acids (VFAs) concentration also increased as the salinity increased. Furthermore, increased salinity led to the elevated production of soluble microbial products (SMP) and extracellular polymeric substances (EPS), which can provide a protective barrier against harsh environments. More serious membrane fouling was observed as the SMP and EPS concentrations increased. The concentration of loosely bound EPS (LB-EPS), tightly bound EPS (TB-EPS), and the polysaccharide/protein (PS/PN) ratios in LB-EPS and TB-EPS all increased when the salinity was elevated. The production of SMP and EPS was caused by the generation of PS in response to the saline environment. Lactobacillus, Lactococcus, Anaerosporobacter, and Pectinatus were the dominant bacteria, and Lactobacillus and Lactococcus were the decolorization bacteria in the MBR. The lack of halophilic bacteria was the main reason for the decreased decolorization efficiency in the salinity environment.

An investigation on the adsorption and removal performance of a carboxymethylcellulose-based 4-aminophenazone@MWCNT nanocomposite against crystal violet and brilliant green dyes

The multistep chemical modification of carboxymethylcellulose (CMC) in the presence of 4-aminophenazone (A-PH) and multiwall carbon nanotubes (MWCNTs) has been successfully conducted. The environmental performance of this material has been thoroughly investigated. Crystal violet (CV) and brilliant green (BG) were eliminated by utilising a new hybrid nanocomposite material (A-PH-CMC/MWCNTs) from a simulated textile wastewater solution. Using SEM, EDX, XRD and FTIR spectroscopy methods, the detailed characterisation of A-PH-CMC/MWCNT nanocomposites was investigated. The results indicated that the adsorption capacity was dependent on six factors (e.g., contact duration, starting concentration, adsorbent mass, the effect of the solution pH, temperature and the effect of KNO3). In addition, thermodynamic and regeneration studies have been reported. According to the theories of pseudo-second-order kinetics, the removal process involves chemical adsorption. The experimental results were best suited by the Langmuir model, in which maximum adsorption capacities of 20.83 and 22.42 mg g-1 were predicted for the BG and CV dyes, respectively. The research is a preliminary case study demonstrating the excellent potential of A-PH-CMC/MWCNT nanocomposites as a material for CV and BG dye removal.

Refractory azo dye wastewater treatment by combined process of microbial electrolytic reactor and plant-microbial fuel cell

An innovative design of microbial electrolytic reactor (MER) coupled with Ipomoea aquaticaForsk. plant microbial fuel cell (IAF-PMFC) was developed for azo dye wastewater treatment and electricity generation. This study aims to assess the sequential degradation of azo dye and the feasibility of energy self-sufficiency in the MER/IAF-PMFC system. The decomposition of azo dye into aromatic amines and dye decolorization occurred in the MER at high hydraulic loading of 0.28 m³/(m²·d), while dye intermediates were mainly mineralized in the IAF-PMFC at low hydraulic loading of 0.06 m³/(m²·d). The final decolorization efficiency and COD removal of the combined system reached 99.64% and 92.06% respectively, even at influent dye concentration of 1000 mg/L. The effects of open/closed circuit conditions, presence/absence of aquatic plant and different cathode areas on the performance of the IAF-PMFC for treating the effluent of the MER were systematically tested, and the results showed that closed-circuit condition, plant involvement and larger cathode area were more beneficial to decolorization, detoxification and mineralization of dye wastewater, bioelectricity output, plant growth and photosynthetic rate. The power consumption by the MER was 0.0163 kWh/m³ of dye wastewater, while the highest power generation of the IAF-PMFC reached 0.0183 kWh/m³. The current efficiency of the MER for dye decolorization was as high as 942.83%, while the maximum coulombic efficiency of the IAF-PMFC for intermediates metabolism was only 6.30%, which still had much space of bioelectricity generation promotion. The MER/IAF-PMFC technology can simultaneously realize refractory wastewater treatment and balance of electricity production and consumption.

Rapid degradation of organic pollutants by Fe3O4@PDA/Ag catalyst in advanced oxidation process

Over the past decades, the development of novel catalysts on the degradation of organic pollutants has attracted increasing attention. In this work, we synthesized silver decorated magnetic nanoparticles (Fe₃O₄@PDA/Ag NPs) to activate H₂O₂ for organic pollutants removal via advanced oxidation processes (AOPs). The catalyst was prepared through in-situ reduction of AgNO₃ by the polydopamine (PDA) layer on Fe₃O₄ NPs. Chemiluminescence results obtained from luminol/H₂O₂ system revealed that the catalyst exhibited excellent catalytic effect on the decomposition of H₂O₂ into reactive oxygen species (ROS) and superoxide radical (O₂^-) was mainly responsible for the oxidative degradation. Importantly, the fast evolution frequency of oxygen gas bubbles produced in the reaction of Ag NPs and H₂O₂ could generate vigorous fluid convection and autonomous motion of catalyst when H₂O₂ concentration reached 1%. Additionally, the catalyst can suspend in solution for several minutes. Therefore, by coupling the vigorous motion with slow sedimentation velocity, the catalyst can realize rapid degradation of organic pollutants without external mixing force. The Fe₃O₄@PDA/Ag NPs catalysts not only showed a high removal efficiency of malachite green, but also can be applied for the degradation of other dyes, making it to be a promise candidate for environmental remediation. With the merits of excellent catalytic effect, fast degradation speed, and simplicity of operation, the prepared catalysts exhibits great potential in the practical field.

Innovative binary sorption of Cobalt(II) and methylene blue by Sargassum latifolium using Taguchi and hybrid artificial neural network paradigms

The present investigation has been designed by Taguchi and hybrid artificial neural network (ANN) paradigms to improve and optimize the binary sorption of Cobalt(II) and methylene blue (MB) from an aqueous solution, depending on modifying physicochemical conditions to generate an appropriate constitution for a highly efficient biosorption by the alga; Sargassum latifolium. Concerning Taguchi's design, the predicted values of the two responses were comparable to actual ones. The biosorption of Cobalt(II) ions was more efficient than MB, the supreme biosorption of Cobalt(II) was verified in run L21 (93.28%), with the highest S/N ratio being 39.40. The highest biosorption of MB was reached in run L22 (74.04%), with a S/N ratio of 37.39. The R2 and adjusted R2 were in reasonable values, indicating the validity of the model. The hybrid ANN model has exclusively emerged herein to optimize the biosorption of both Cobalt(II) and MB simultaneously, therefore, the ANN model was better than the Taguchi design. The predicted values of Cobalt(II) and MB biosorption were more obedience to the ANN model. The SEM analysis of the surface of S. latifolium showed mosaic form with massive particles, as crosslinking of biomolecules of the algal surface in the presence of Cobalt(II) and MB. Viewing FTIR analysis showed active groups e.g., hydroxyl, α, β-unsaturated ester, α, β-unsaturated ketone, N-O, and aromatic amine. To the best of our knowledge, there are no reports deeming the binary sorption of Cobalt(II) and MB ions by S. latifolium during Taguchi orthogonal arrays and hybrid ANN.

Raspberry stalks-derived biochar, magnetic biochar and urea modified magnetic biochar - Synthesis, characterization and application for As(V) and Cr(VI) removal from river water

Raspberry stalks-derived biochar (BC), magnetic biochar-iron oxide composite (BC-Fe) and its derivative modified with urea (BC-Fe-U) were synthesized, characterized and tested as(V) and Cr(VI) ion sorbents. The surface area of BC, BC-Fe and BC-Fe-U was 259, 163 and 117 m² g^-1, respectively. The structure of BC was dominated by micropores, while in BC-Fe and BC-Fe-U mesopores predominated. Based on the XRD results, it was found that the magnetic properties of the biochar-iron oxide composites are due to the presence of ferrimagnetic magnetite (Fe₃O₄) and maghemite (Fe₂O₃). The optimal pH of As(V) and Cr(VI) adsorption onto the studied sorbents is in the range of 2.3-5.7. Pristine biochar (BC) does not adsorb As(V) ions; however, it enables rapid adsorption of Cr(VI) with the static adsorption capacity of 19.2 mg g^-1. The maximum static adsorption capacities of As(V) and Cr(VI) ions onto BC-Fe and BC-Fe-U are within the range of 13.5-16.3 mg g^-1. For most adsorption systems tested, adsorption equilibrium is reached within 4 h, though even a few minutes is enough to reach half of the adsorption static value. Phosphates over 0.005 mol L^-1 hinder adsorption of As(V) and Cr(VI) ions. Application of at least 5 mol L^-1 nitric acid allows about 95% of Cr(VI) and As(V) to be desorbed from adsorbate-loaded BC-Fe material. For other materials, the desorption efficiencies are significantly lower. BC-Fe and BC-Fe-U materials were successfully used for simultaneous Cr(VI) and As(V) removal from river water.

Progress in microalgal mediated bioremediation systems for the removal of antibiotics and pharmaceuticals from wastewater

Worldwide demand for antibiotics and pharmaceutical products is continuously increasing for the control of disease and improvement of human health. Poor management and partial metabolism of these compounds result in the pollution of aquatic systems, leading to hazardous effects on flora, fauna, and ecosystems. In the past decade, the importance of microalgae in micropollutant removal has been widely reported. Microalgal systems are advantageous as their cultivation does not require additional nutrients: they can recover resources from wastewater and degrade antibiotics and pharmaceutical pollutants simultaneously. Bioadsorption, degradation, and accumulation are the main mechanisms involved in pollutant removal by microalgae. Integration of microalgae-mediated pollutant removal with other technologies, such as biodiesel, biochemical, and bioelectricity production, can make this technology more economical and efficient. This article summarizes the current scenario of antibiotic and pharmaceutical removal from wastewater using microalgae-mediated technologies.

An Overview on Co-Pyrolysis of Biodegradable and Non-Biodegradable Wastes

Continuous urbanization and modernization have increased the burning of fossil fuels to meet energy needs across the globe, emanating environmental pollution and depleting fossil fuels. Therefore, a shift towards sustainable and renewable energy is necessary. Several techniques to exploit biomass to yield energy are trending, with pyrolysis one of them. Usually, a single feedstock is employed in pyrolysis for anoxygenic generation of biochar together with bio-oil at elevated temperatures (350–600 °C). Bio-oil produced through pyrolysis can be upgraded to crude oil after some modification. However, these modifications of bio-oil are one of the major drawbacks for its large-scale adoption, as upgradation increases the overall cost. Therefore, in recent years the scientific community has been researching co-pyrolysis technology that involves the pyrolysis of lignocellulosic biomass waste with non-biodegradable waste. Co-pyrolysis reduces the need for post-modification of bio-oil, unlike pyrolysis of a single feedstock. This review article discusses the recent advancements and technological challenges in waste biomass co-pyrolysis, the mechanism of co-pyrolysis, and factors that affect co-pyrolysis. The current study critically analyzes different recent research articles presented in databases such as PubMed, MDPI, ScienceDirect, Springer, etc. Hence, this review is one-of-a-kind in that it attempts to explain each and every aspect of the co-pyrolysis process and its current progress in the scientific field. Consequently, this review also compiles the remarkable achievements in co-pyrolysis and recommendations for the future.

Adsorptive removal of synthetic plastic components bisphenol-A and solvent black-3 dye from single and binary solutions using pristine pinecone biochar

The existing study deals with adsorptive removal of the endocrine-disrupting chemical bisphenol-A and toxic azo dye solvent black-3 from single and binary solutions. These two chemicals are commonly used as an additive in the synthetic plastic industries. Among the tested twenty pristine and modified biochars, the pristine pinecone biochar produced at 750 °C revealed greater bisphenol-A removal. Simulation of the experimental data obtained for bisphenol-A and dye removal from the single-component solution offered a best-fit to Elovich (R² > 0.98) and pseudo-second-order (R² > 0.99) kinetic models, respectively. Whereas for the bisphenol-A + dye removal from binary solution, the values for bisphenol-A adsorption were best suited to Elovich (R² > 0.98), while pseudo-second-order (R² > 0.99) for dye removal. Similarly, the two-compartment model also demonstrated better values (R² > 0.92) for bisphenol-A and dye removal from single and binary solutions with greater F_fast values (except for bisphenol-A in binary solution). The Langmuir isotherm model demonstrated the highest regression coefficient values (R² > 0.99) for bisphenol-A and dye removal with the highest adsorption capacity of 38.387 mg g^-1 and 346.856 mg g^-1, correspondingly. Besides, the co-existence of humic acid revealed a positive impact on bisphenol-A removal, while the dye removal rate was slightly hindered in presence of humic acid. The absorption process showed monolayer coverage of biochar surface with contaminants using a chemisorption mechanism with fast reactions between functional groups on the adsorbate and adsorbent. Whereas the adsorption mechanism was primarily controlled by hydrogen bonding, hydrophobic and π-π electron-donor-acceptor interactions as confirmed by FTIR, XPS, and pH investigations.

A Review of the Removal of Dyestuffs from Effluents onto Biochar

The study provides a review of various applications of biomass-derived biochars, waste-derived biochars, and modified biochars as adsorbent materials for removing dyestuff from process effluents. Processing significant amounts of dye effluent discharges into receiving waters can supply major benefits to countries which are affected by the water crisis and anticipated future stress in many areas in the world. When compared to most conventional adsorbents, biochars can provide an economically attractive solution. In comparison to many other textile effluent treatment processes, adsorption technology provides an economic, easily managed, and highly effective treatment option. Several tabulated data values are provided that summarize the main characteristics of various biochar adsorbents according to their ability to remove dyestuffs from wastewaters.

Recent advances and perspectives of g-C3N4-based materials for photocatalytic dyes degradation

Photocatalytic degradation technology is regarded as a promising technology for dye-contained wastewater treatment due to its superior efficiency and recycling. The key to the implementation of photocatalytic degradation technology is the selection of sunlight-active photocatalyst. Graphitic carbon nitride (g-C₃N₄) photocatalyst has been put into a lot of research in the field of organic pollutant degradation because of its low cost, suitable electronic structure and high chemical stability. In this perspective review, we comprehensively discuss the recent advance of photocatalytic dyes degradation over g-C₃N₄-based materials. The properties, structure and preparation methods of g-C₃N₄ are briefly introduced. Furthermore, the progress in improving the degradation efficiency of g-C₃N₄-based photocatalyst is highlighted in the article. The possible pathways and different active species for dyes decomposition are also summarized. We expect this review can provide instructive application of g-C₃N₄-based catalysts for environmental remediation.

Novel pure α-, β-, and mixed-phase α/β-Bi2O3 photocatalysts for enhanced organic dye degradation under both visible light and solar irradiation

Combining the pure α- and β-phases of bismuth oxide enhances its photocatalytic activity under both visible and solar irradiation. α-Bi₂O₃, β-Bi₂O_3, and α/β-Bi₂O₃ were synthesized by a solvothermal calcination method. The structural, optical, and morphological properties of the as-synthesized catalysts were analyzed using XRD, UV-DRS, XPS, SEM, TEM, and PL. The bandgaps of α/β-Bi₂O₃, α-Bi₂O₃, and β-Bi₂O₃ were calculated to be 2.59, 2.73, and 2.34 eV, respectively. The photocatalytic activities of the catalysts under visible and solar irradiation were examined by the degradation of carcinogenic reactive blue 198 and reactive black 5 dyes. The kinetic plots of the degradation reactions followed pseudo-first-order kinetics. α/β-Bi₂O₃ exhibited higher photocatalytic activity (∼99%) than α-Bi₂O₃ and β-Bi₂O₃ under visible and solar irradiation. The TOC and COD results confirmed the maximum degradation ability of α/β-Bi₂O₃, and the decolorization percentage remained above 90%, even after five cycles under visible irradiation. The photocatalytic dye degradation mechanism employed by α/β-Bi₂O₃ was proposed based on active species trapping experiments.

The effective removal of Congo Red using a bio-nanocluster: Fe3O4 nanoclusters modified bacteria

A bio-nanocluster (Fe₃O₄@bacteria) was prepared by simply mixture using the bacterial suspension and Fe₃O₄ nanoclusters to remove Congo red (CR) contamination from water resources. The bio-nanocluster was characterized by SEM, TEM and XPS. Adsorption efficiency, adsorption process and adsorption mechanism were comprehensively investigated. The maximum adsorption capacity (Q_m) of CR dye onto the Fe₃O₄@bacteria peaked at 320.1 mg/g, which was 2.88 times that of Fe₃O₄ under the same condition. Based on the equilibrium and kinetic studies, the Langmuir isotherm theory and pseudo-first-order model is appropriate to describe the adsorption process. The adsorption of CR is spontaneous and exothermic according to the thermodynamics parameters (ΔG^θ, ΔH^θ and ΔS^θ). The adsorption force dominated the Van der Waals force, biofloculation and chemisorption. The Fe₃O₄@bacteria could be applied potentially as an absorbent with high efficiency and environmentally friendly remediation of dyeing wastewater.

Fast anisotropic growth of the biomineralized zinc phosphate nanocrystals for a facile and instant construction of laccase@Zn3(PO4)2 hybrid nanoflowers

Organic-inorganic hybrid nanoflowers (HNFs) of laccase@Zn₃(PO₄)₂ were fabricated through a facile, simple, and rapid one-step strategy. In this process, laccase was involved in nucleation and fast anisotropic growth reactions with Zn (II) and phosphate ions. The average pore size of the prepared HNFs was 54.5 nm, and its BET-specific surface area was 59.5 m² g^-1. In comparison with the free laccase, the entrapped enzyme activity in the constructed HNFs was 86.4%. In addition, the hybrid biocatalyst displayed a maximum rate of reaction (V_max) of 1640.2 ± 3.6 μmol min^-1 with respect to the native enzyme. The constructed HNFs maintained 45.1% and 60% of the original laccase activity after 12 successive reusability cycles and 30 days of storage at 4 °C, respectively. The as-obtained HNFs demonstrated a high bioremoval percentage of Direct blue-71 (94.1%) within a 10-h-treatment at 40 °C and 15 mg l^-1 of the dye concentration. The pseudo-first order and second order were the best-fitted kinetic models for the dye removal using Zn₃(PO₄)₂ nanoflakes and the fabricated HNFs, respectively. Besides, liquid chromatography-mass spectrometry (LC-MS) revealed biotransformation of the dye into less toxic metabolites as verified by testing on some bacterial strains.

Enhanced adsorption of metal ions onto Vetiveria zizanioides biochar via batch and fixed bed studies

The study highlights the potential of Vetiveria Zizanioides derived biochar for heavy metal removal in multicomponent systems. Biochar efficiency varies with pH, metal ion concentration and residence time. Maximum removal efficiency was found to be 66.34, 67.23, 46.54, 69.92, 68.23 and 63.34% for Arsenic, Copper, Nickel, Cadmium, Lead and Chromium at 90 min respectively. Ternary system revealed that Copper ions have inhibitory effect on Lead ions and have lower adsorption capacity than binary system. Multicomponent isotherm model was used to analyse simultaneous adsorption of metal ions and shows a good fit with modified Langmuir model for binary and ternary systems. Fixed-bed column was tested for scale-up feasibility and maximum adsorption capacity of 139, 130, and 123 mg/g for Lead, Copper, and Nickel ions were obtained at 1.5 L/h and a bed height of 12 cm. In fixed bed column, multicomponent sequence provides more protection against premature exhaustion of biochar.

Biochar for agronomy, animal farming, anaerobic digestion, composting, water treatment, soil remediation, construction, energy storage, and carbon sequestration: a review

In the context of climate change and the circular economy, biochar has recently found many applications in various sectors as a versatile and recycled material. Here, we review application of biochar-based for carbon sink, covering agronomy, animal farming, anaerobic digestion, composting, environmental remediation, construction, and energy storage. The ultimate storage reservoirs for biochar are soils, civil infrastructure, and landfills. Biochar-based fertilisers, which combine traditional fertilisers with biochar as a nutrient carrier, are promising in agronomy. The use of biochar as a feed additive for animals shows benefits in terms of animal growth, gut microbiota, reduced enteric methane production, egg yield, and endo-toxicant mitigation. Biochar enhances anaerobic digestion operations, primarily for biogas generation and upgrading, performance and sustainability, and the mitigation of inhibitory impurities. In composts, biochar controls the release of greenhouse gases and enhances microbial activity. Co-composted biochar improves soil properties and enhances crop productivity. Pristine and engineered biochar can also be employed for water and soil remediation to remove pollutants. In construction, biochar can be added to cement or asphalt, thus conferring structural and functional advantages. Incorporating biochar in biocomposites improves insulation, electromagnetic radiation protection and moisture control. Finally, synthesising biochar-based materials for energy storage applications requires additional functionalisation.

Algae biorefinery: a promising approach to promote microalgae industry and waste utilization

Microalgae have a number of intriguing characteristics that make them a viable raw material aimed at usage in a variety of applications when refined using a bio-refining process. They offer unique capabilities that allow them to be used in biotechnology-related applications. As a result, this review explores how to increase the extent to which microalgae may be integrated with various additional biorefinery uses in order to improve their maintainability. In this study, the use of microalgae as potential animal feed, manure, medicinal, cosmeceutical, ecological, and other biotechnological uses is examined in its entirety. It also includes information on the boundaries, openings, and improvements of microalgae and the possibilities of increasing the range of microalgae through techno-economic analysis. According to the findings of this review, financing supported research and shifting the focus of microalgal investigations from biofuels production to biorefinery co-products can help guarantee that they remain a viable resource. Furthermore, innovation collaboration is unavoidable if one wishes to avoid the high cost of microalgae biomass handling. This review is expected to be useful in identifying the possible role of microalgae in biorefinery applications in the future.

Bioelectrochemical system as an innovative technology for treatment of produced water from oil and gas industry: A review

Disposal of the high volume of produced water (PW) is a big challenge to the oil and gas industry. High cost of conventional treatment facilities, increasing energy prices and environmental concern had focused governments and the industry itself on more efficient treatment methods. Bioelectrochemical system (BES) has attracted the attention of researchers because it represents a sustainable way to treat wastewater. This is the first review that summarizes the progress done in PW-fed BESs with a critical analysis of the parameters that influence their performances. Inoculum, temperature, hydraulic retention time, external resistance, and the use of real or synthetic produced water were found to be deeply related to the performance of BES. Microbial fuel cells are the most analyzed BES in this field followed by different types of microbial desalination cells. High concentration of sulfates in PW suggests that most of hydrocarbons are removed mainly by using sulfates as terminal electron acceptor (TEA), but other TEAs such as nitrate or metals can also be employed. The use of real PW as feed in experiments is highly recommended because biofilms when using synthetic PW are not the same. This review is believed to be helpful in guiding the research directions on the use of BES for PW treatment, and to speed up the practical application of BES technology in oil and gas industry.

Trends in renewable energy production employing biomass-based biochar

Tremendous population growth and industrialization have increased energy consumption unprecedentedly. The depletion of fossil-based energy supplies necessitates the exploration of solar, geothermal, wind, hydrogen, biodiesel, etc. as a clean and renewable energy source. Most of these energy sources are intermittent, while bioelectricity, biodiesel, and biohydrogen can be produced using abundantly available organic wastes regularly. The production of various energy resources requires materials that are costly and affect the applicability at a large scale. Biomass-derived materials (biochar) are getting attention in the field of bioenergy due to their simple method of synthesis, high surface area, porosity, and availability of functional groups for easy modification. Biochar synthesis using various techniques is discussed and their use as an electrode (anodic/cathodic) in a microbial fuel cell (MFC), catalysts in transesterification, and anaerobic digestion for energy production are reviewed. Renewable energy production using biochar would be a sustainable approach to create an energy secure world.

The use of eggshell membrane for the treatment of dye-containing wastewater: Batch, kinetics and reusability studies

The worldwide consumption of eggs is very high, leading to about 250,000 tons of eggshell membrane (ESM) waste annually. The present research thus investigated the potential use of ESM as an inexpensive and abundant adsorbent for Reactive Red 120 (RR120) in aqueous solutions, a widespread hydrophilic azo dye used in the textile industry. The chemical structure and morphology of ESM were characterized using various spectroscopic methods, including scanning electron microscopy, Fourier transform infrared spectroscopy, and elemental analysis. It was found that natural ESM has a porous structure and surface functional groups that are suitable for the adsorption of the target molecules. The impact of the operating conditions, including the variation in the pH and temperature, on the RR120 sorption capacity and mechanisms of ESM was also analyzed. The maximum monolayer adsorption ability of ESM for RR120 was found to be 191.5 mg/g at 318 K, and the sorption process was spontaneous and endothermic. The adsorption of RR120 onto ESM was significantly influenced by the solution pH and the use of NaOH as eluent, indicating that the driving force for this adsorption was electrostatic attraction. Subsequent desorption experiments using 0.1 M NaOH resulted in satisfactory recovery efficiency. Kinetic, isothermic, and thermodynamic analysis was also conducted to support the experimental findings. The experimental results for the adsorption kinetics of ESM were fitted by a pseudo-second-order model. In conclusion, ESM has the potential to be utilized as an eco-friendly and cost-effective adsorbent for the removal of RR120 from aqueous solutions.

Resource utilization of organic spent adsorbent to prepare three-dimensional sulfate-functionalized layered double oxide for superior removal of azo dye

Developing superior, rapid, cost-effective adsorbents derived from organic spent adsorbent is an economically sustainable way for purifying azo dye wastewater. Herein, we report a precursor-calcination strategy for the recycle of the organic spent adsorbent to a high value-added three-dimensional sulfate-functionalized MgAl-layered double oxide (3S-LDO). Thanks to the unique property of the sulfate group and LDO, 3S-LDO exhibited a superior (4340.71 mg/g) and ultrafast (<1 h) adsorption toward methyl orange (MO, as the representative of azo dye). A thermodynamic study revealed that the reaction process was spontaneous and exothermic. FT-IR, XPS, and XRD results confirmed that the sulfate from 3S-LDO played a vital role in MO removal wherein the S=O bond (with the electrophilic character) from SO₄^2- interacted with the N=N double bond (with rich electron) in MO through the electron donor-acceptor mechanism. And the "memory effect" and surface complexation of 3S-LDO further strengthened the MO adsorption. More importantly, 3S-LDO could work efficiently in a wide pH range and even in the presence of competitive anions (e.g., Cl^-, NO₃^-, and CO₃^2-). Multiple cyclic runs and selective tests demonstrated the excellent reusability and explicit selectivity of 3S-LDO. This work not only provides a prospective sulfate-functionalized adsorbent from organic waste for rapid azo dye removal from wastewater but also achieves the high value-added utilization of organic waste.

Bio-electrocatalytic remediation of hydrocarbons contaminated soil with integrated natural attenuation and chemical oxidant

The present study aimed to assess the possibility of integrating natural attenuation (NA) and chemical oxidation (O) with the bio-electrocatalytic remediation (BET) process to remediate petroleum hydrocarbons contaminated soil. Six different reactors were operated, wherein in the first reactor was a NA system, and the second condition to the NA was supplemented with a chemical oxidant (NAO). These systems were compared with BET systems which were differentiated based on the position and distance between the electrodes. The study was performed by considering NA as a common condition in all the six different reactors viz., NA, NAO, NA + BET with 0.5 cm space amid electrodes (BET_H-0.5), NAO + BET with 0.5 cm space amid electrodes (BETO_H-0.5), NAO + BET with 1.0 cm space amid electrodes (BETO_H-1.₀), and NAO + BET with vertical electrodes at 1.0 cm distance (BETO_V-1.₀). The highest total petroleum hydrocarbons (TPH) degradation efficiency was observed with BETO_H-0.5 (67 ± 0.8%) followed by BETO_H-1.0 (62 ± 0.6%), BET_H-0.5 (60%), BETO_V-1.0 (56 ± 0.5%), NAO (46.6%), and NA (27.7%). In NA, the indigenous microorganisms remediate the organic contaminants. In the NAO system, KMnO₄ actively breakdown the carbon-carbon double bond functional group. Further, in BETO_H-0.5, an anodophilic bacteria enriched around the electrode reported enhanced treatment efficiency along with a maximum of 260 mV (1.65 mA). BET systems integrated with chemical oxidation processes were much more effective in the TPH removal process than an individual process. The BET method adopted here thus provides a good opportunity for bio-electrocatalytic remediation of TPH and resource recovery in the form of bioelectricity.

Emerging technologies for conversion of sustainable algal biomass into value-added products: A state-of-the-art review

Concerns regarding high energy demand and gradual depletion of fossil fuels have attracted the desire of seeking renewable and sustainable alternatives. Similar to but better than the first- and second-generation biomass, algae derived third-generation biorefinery aims to generate value-added products by microbial cell factories and has a great potential due to its abundant, carbohydrate-rich and lignin-lacking properties. However, it is crucial to establish an efficient process with higher competitiveness over the current petroleum industry to effectively utilize algal resources. In this review, we summarize the recent technological advances in maximizing the bioavailability of different algal resources. Following an overview of approaches to enhancing the hydrolytic efficiency, we review prominent opportunities involved in microbial conversion into various value-added products including alcohols, organic acids, biogas and other potential industrial products, and also provide key challenges and trends for future insights into developing biorefineries of marine biomass.

Adsorptive removal of crude petroleum oil from water using floating pinewood biochar decorated with coconut oil-derived fatty acids

The present investigation deals with the adsorptive removal of crude petroleum oil from the water surface using coconut oil-modified pinewood biochar. Biochar generated at higher pyrolysis temperature (700 °C) revealed higher fatty acid-binding efficiency responsible for the excellent hydrophobicity of the biochar. Fatty acids composition attached to the biochar produced at 700 °C was (mg g^-1 BC) lauric acid (9.024), myristic acid (5.065), palmitic acid (2.769), capric acid (1.639), oleic acid (1.362), stearic acid (1.114), and linoleic acid (0.130). Simulation of the experimental adsorption data of pristine and modified pinewood biochar generated at 700 °C offered the best fit to pseudo-first-order kinetics (R² > 0.97) and Langmuir isotherm model (R² > 0.99) based on the highest regression coefficients. Consequently, the adsorption process was mainly driven by surface hydrophobic interactions including π-π electron-donor-acceptor between electron-rich (π-donor) polycyclic aromatic hydrocarbons from the crude oil and biochar (π-acceptor). A maximum adsorption capacity (Q_max) of 5.315 g g^-1 was achieved by modified floating biochar within 60 min. Whereas the reusability testing revealed 49.39% and 51.40% was the adsorption efficiency of pristine and modified biochar at the fifth adsorption-desorption cycle.

Facile synthesis of recyclable laccase-mineral hybrid complexes with enhanced activity and stability for biodegradation of Evans Blue dye

Two morphologies of laccase-mineral hybrid complexes, i.e., laccase-mineral hybrid nanoflowers (La-HNF) and nanopetals (La-HNP), were synthesized via biomineralization using Cu₃ (PO₄)₂·3H₂O as the mineral for Evans Blue (EB) dye biodegradation. XRD patterns and FT-IR spectra results revealed the successful immobilization of laccase via in-situ formed Cu₃(PO₄)₂·3H₂O crystals. Compared with free laccase, laccase-mineral hybrid complexes showed higher enzymatic activity due to the activation effect induced by copper ions of Cu₃(PO₄)₂·3H₂O, further, the improved kinetic parameters of laccase-mineral hybrid complexes could be ascribed to nanoscale-dispersed laccase molecules within hybrid complexes. For EB dye biodegradation, the reason why the biodegradation efficiency (94.9%) of La-HNF was higher than that (86.8%) of La-HNP could be synergistic effect of immobilized laccase within 3D hierarchical structure of La-HNF. In addition, the optimized biodegradation conditions (pH 4.6 and 40 °C) of La-HNF were obtained, moreover, 93.2% and 48.1% of EB dye were biodegraded by La-HNF after stored for 30 days and reused for 10 cycles, respectively, demonstrating La-HNF have good practicability.

Understanding of the mechanism of crystal violet adsorption on modified halloysite: Hydrophobicity, performance, and interaction

Halloysite was processed at 600 °C and then by acid leaching with HCl solutions of different concentrations, i.e. 0.5, 3 and 5 N (H600-xN; x = 0.5, 3 or 5). The resulting materials underwent chemical, textural, and laser diffraction analyses and were used in crystal violet (CV) adsorption. Bath experiments were conducted to evaluate the parameters influencing adsorption. A hydrophobicity study by adsorption of water/toluene and a spectroscopic investigation by FTIR and Raman were conducted, to understand the interaction mechanism. The affinity for CV is as follows: H600-0.5N (115 m²g^-1) > H600-3N (434 m²g^-1) > H600-5N (503 m²g^-1) > H600-0N (61 m²g^-1). The maximum adsorption of H600-0.5N would be explained by optimal hydrophilic and hydrophobic properties. Dealumination leads to the creation of more silanols responsible for hydrophilicity. Dehydroxylation at 600 °C combined with dealumination would induce a partial transformation of silanols into siloxanes which are responsible for organophilicity. The CV-H600-0.5N interaction implies two mechanisms: hydrophobic interactions and hydrogen bond. This study focused on hydrophobic interaction as a non-negligible component governing the interaction of organic contaminants with 1:1 clay minerals, while it was not sufficiently considered in the scientific literature.

Sorption of brilliant green dye using soybean straw-derived biochar: characterization, kinetics, thermodynamics and toxicity studies

The present study was aimed to investigate brilliant green (BG) dye sorption onto soybean straw biochar (SSB) prepared at 800 °C and further understanding the sorption mechanism. Sorption kinetic models such as pseudo-first and pseudo-second order were executed for demonstrating sorption mechanism between the dye and biochar. Results of kinetics study were fitted well to pseudo-second-order kinetic model (R2 0.997) indicating that the reaction followed chemisorption mechanism. Furthermore, the effect of various parameters like sorbent dose, dye concentration, incubation time, pH and temperature on dye sorption was also studied. The maximum dye removal percentage and sorption capacity for SSB (800 °C) within 60 min were found to be 99.73% and 73.50 mg g- 1, respectively, at pH 8 and 60 °C temperature, whereas adsorption isotherm studies showed a higher correlation coefficient values for Freundlich model (R2 0.990-0.996) followed by Langmuir model suggesting that sorption process was multilayer. The characterization of biomass and biochar was performed with the aid of analytical techniques like scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), Brunauer-Emmett-Teller (BET) theory, X-ray diffraction (XRD) and thermo-gravimetric analysis (TGA). FTIR analysis showed active groups on biochar surface. BET study revealed higher surface area of biochar (194.7 m2/g) than the biomass (12.84 m2/g). Besides, phyto- and cytogenotoxic studies revealed significant decrease in the toxicity of dye containing water after treating with SSB. Therefore, this study has proved the sorption potential of soybean straw biochar for BG dye and could be further considered as sustainable cost-effective strategy for treating the textile dye-contaminated wastewater.