Removal of contaminants of emerging concern from multicomponent systems using carbon dioxide activated biochar from lignocellulosic feedstocks

Ecological risk assessment of emerging contaminants on soil and terrestrial ecosystems (2005-2024): a bibliometric and scientometric review

Growing awareness exists regarding the dangers posed by emerging contaminants (ECs) to terrestrial ecosystems and human health. This study reviewed ecological risk assessment studies on ECs, emphasizing their environmental presence, toxicological effects, behavior, and potential negative impacts on soil and terrestrial ecosystems. The work aims to identify key trends, research hotspots, and gaps to provide policy recommendations, inform regulatory frameworks, and suggest future research directions for the sustainable management of ECs in terrestrial environments. A systematic literature review was conducted using the Web of Science database, selecting studies from the past decade related to ECs, soil, terrestrial ecosystems, and ecological risk assessment. A total of 450 documents were analyzed using VOSviewer and CiteSpace to visualize key research patterns. Results indicate a 26.26% annual growth in publications, highlighting increasing scholarly interest. Citation analysis identifies China, the USA, and Italy as leading contributors, with Switzerland exhibiting the highest citation impact per article. Co-authorship network analysis reveals key researchers and collaboration clusters, though cross-group interactions remain limited. Institutional analysis underscores the dominance of the Chinese Academy of Sciences, with notable global partnerships from CSIC (Spain) and King Saud University. Journal analysis highlights Environmental Toxicology and Chemistry and Journal of Environmental Monitoring as highly influential sources. Temporal keyword trends indicate a shift toward ecological risk assessment and contaminant interactions. The study underscores the need for advanced monitoring techniques to manage ECs. Understanding broader ecological impacts, including ecosystem responses and bioaccumulation, is crucial for informed environmental management and policy-making. The findings have significant implications for environmental policy, management strategies, and mitigation measures to protect ecosystem and human health.

Adsorption of organic contaminants of emerging concern using microalgae-derived hydrochars

This study explored the adsorption capacity of hydrochars derived from a strain of microalgae biomass native to northern Sweden for contaminants of emerging concern (CECs) such as caffeine, chloramphenicol, trimethoprim, carbamazepine, bisphenol A, diclofenac, and triclosan. The findings indicate that the surface functionality of the microalgae-derived hydrochars - a blend of alkane/alkene and aromatic structures, coupled with different oxygen-containing functional groups (hydroxyl, carboxyl, and lactone) - significantly influenced the adsorption of the contaminants. The alkane/alkene and aromatic structures increased with increasing hydrothermal treatment temperature, while the oxygen- and nitrogen-containing groups diminished. Bisphenol A and triclosan, which were the compounds with the highest distribution coefficients, displayed improved adsorption on the hydrochars. The study measured peak adsorption values for the hydrochars processed at 180 °C, which achieved adsorption levels of 25.8 mg g- 1 for bisphenol A and 58.8 mg g- 1 for triclosan. The hydrochars produced using lower carbonisation temperatures (180 and 220 °C) exhibited enhanced adsorption of positively charged molecules such as trimethoprim, which was attributed to the increased presence of negatively charged oxygen-containing functional groups. Contrastingly, negatively charged molecules such as diclofenac and chloramphenicol demonstrated either low adsorption (2.5 mg g- 1 for chloramphenicol on hydrochar prepared at 180 °C) or no adsorption (diclofenac) due to repulsion by the negatively charged functional groups on the surface of the hydrochars.

Mycelium-Doped Straw Biochars for Antibiotic Control

Straw, a predominant agricultural residue, represents a significant waste product. Harnessing its potential is of paramount importance both in terms of research and economic value. In this study, chemically pretreated corn straw was infused with distinct microbial fungal mycelium variants and subsequently transformed into a series of biochars through a process involving carbonization and activation. The findings revealed enhancements in the specific surface area and total pore volume of mycelium-doped straw biochars compared to the original corn straw biochar (BCS). Additionally, discernible disparities were observed in their physical and chemical attributes, encompassing functional groups, surface chemistry, and micro-morphology. Notably, in water-based antibiotic removal experiments focusing on tetracycline hydrochloride (TH) and chloramphenicol (CP), the mycelium-doped straw biochars outperformed BCS. Their maximum adsorption capacities for TH and CP surpassed those of alternative adsorbents, including other biochars. Impressively, even after five cycles, the biochar exhibited a removal rate exceeding 80%, attesting to its robust stability. This study successfully emphasized the efficacy of incorporating fungal mycelium to enhance the adsorption properties of straw-based biochar, introducing a new theoretical basis for the development of lignocellulosic materials.

Pharmaceutical Pollutants: Ecotoxicological Impacts and the Use of Agro-Industrial Waste for Their Removal from Aquatic Environments

Medicines are pharmaceutical substances used to treat, prevent, or relieve symptoms of different diseases in animals and humans. However, their large-scale production and use worldwide cause their release to the environment. Pharmaceutical molecules are currently considered emerging pollutants that enter water bodies due to inadequate management, affecting water quality and generating adverse effects on aquatic organisms. Hence, different alternatives for pharmaceuticals removal from water have been sought; among them, the use of agro-industrial wastes has been proposed, mainly because of its high availability and low cost. This review highlights the adverse ecotoxicological effects related to the presence of different pharmaceuticals on aquatic environments and analyzes 94 investigations, from 2012 to 2024, on the removal of 17 antibiotics, highlighting sulfamethoxazole as the most reported, as well as 6 non-steroidal anti-inflammatory drugs (NSAIDs) such as diclofenac and ibuprofen, and 27 pharmaceutical drugs with different pharmacological activities. The removal of these drugs was evaluated using agro-industrial wastes such as wheat straw, mung bean husk, bagasse, bamboo, olive stones, rice straw, pinewood, rice husk, among others. On average, 60% of the agro-industrial wastes were transformed into biochar to be used as a biosorbents for pharmaceuticals removal. The diversity in experimental conditions among the removal studies makes it difficult to stablish which agro-industrial waste has the greatest removal capacity; therefore, in this review, the drug mass removal rate (DMRR) was calculated, a parameter used with comparative purposes. Almond shell-activated biochar showed the highest removal rate for antibiotics (1940 mg/g·h), while cork powder (CP) (10,420 mg/g·h) showed the highest for NSAIDs. Therefore, scientific evidence demonstrates that agro-industrial waste is a promising alternative for the removal of emerging pollutants such as pharmaceuticals substances.

Conversion of char from pyrolysis of plastic wastes into alternative activated carbons for heavy metal removal

The valorization of post-consumer mixed plastics in pyrolysis processes represents an abundant reservoir of carbon that can be effectively converted into useful chars. This process not only holds appeal in terms of improving plastic waste concerns but also contributes to the reduction of greenhouse gas emissions, thus aligning with the principles of a circular economy paradigm. In this study, the char produced from the pyrolysis of post-consumer mixed plastic waste has been activated with Na2CO3, KOH, NaOH, and K2CO3 to improve the textural, structural, and composition characteristics, leading to improved adsorption capability. These characteristics were studied by N2 adsorption-desorption isotherms, scanning electron microscopy, elemental and immediate analysis, and X-ray photoelectron spectroscopy. The developed surface area (SBET) was 573, 939, 704 and 592 m2 g-1 for Na2CO3, KOH, NaOH and K2CO3 activated carbons, respectively. These activated chars (ACs) were tested for the adsorption of heavy metals in both synthetic waters containing Pb, Cd, and Cu and industrial wastewater collected at an agrochemical production plant. Na2CO3-AC was the best performing material. The metal uptake in synthetic waters using a batch set-up was 40, 13 and 12 mg g-1 for Pb, Cd and Cu. Experiments in a column set-up using Na2CO3-AC resulted in a saturation time of 290, 16, and 80 min for Pb, Cd, and Cu synthetic waters, respectively, and metal uptakes of 26.8, 4.1, and 7.9 mg g-1, respectively. The agrochemical effluents, containing mainly Cr, Cu, Mn, and Zn were tested in a plug-flow column. The metal uptake notably decreased compared to synthetic water due to a competition effect for active sites.

Adsorption and leaching of fluorotelomer compounds and perfluoroalkyl acids in aqueous media by activated carbon prepared from municipal biosolids

Perfluoroalkyl acids (PFAAs) are ubiquitous in nature and pose serious health risks to humans and animals. Limiting PFAA exposure requires novel technology for their effective removal from water. We investigated the efficacy of biosolid-based activated carbon (Bio-SBAC) in removing frequently detected PFAAs and their precursor fluorotelomer compounds at environmentally relevant concentrations (∼50 μg/L). Batch experiments were performed to investigate adsorption kinetics, isotherms, and leachability. Bio-SBAC achieved >95% removal of fluorotelomeric compounds, indicating that the need for PFAA removal from the environment could be minimised if the precursors were targeted. Kinetic data modelling suggested that chemisorption is the dominant PFAA adsorption mechanism. As evidenced by the isotherm modelling results, Freundlich adsorption intensity, n-1, values of <1 (0.707-0.938) indicate chemisorption. Bio-SBAC showed maximum capacities for the adsorption of perfluorooctanoic acid (1429 μg/g) and perfluorononanoic acid (1111 μg/g). Batch desorption tests with 100 mg/L humic acid and 10 g/L NaCl showed that Bio-SBAC effectively retained the adsorbed PFAA with little or no leaching, except perfluorobutanoic acid. Overall, this study revealed that Bio-SBAC is a value-added material with promising characteristics for PFAA adsorption and no leachability. Additionally, it can be incorporated into biofilters to remove PFAAs from stormwater, presenting a sustainable approach to minimise biosolid disposal and improve the quality of wastewater before discharge into receiving waters.

Chitosan/functionalized fruit stones as a highly efficient adsorbent biomaterial for adsorption of brilliant green dye: Comprehensive characterization and statistical optimization

In this research, a highly efficient adsorbent biomaterial (hereinafter, CTS/PPS-HS) of chitosan/functionalized fruit stones (peach and plum) with H2SO4 was produced for the adsorption of brilliant green (BG) dye from aquatic systems. The developed biomaterial was characterized by several techniques like SEM-EDX, FTIR, XRD, BET, and pHpzc. To systematically optimize the adsorption performance of CTS/PPS-HS, the Box-Behnken design (BBD) based on response surface methodology (RSM) was attained. The factors considered for optimization included A: CTS/PPS-HS dosage (0.02-0.08 g), B: pH (4-10), and C: removal time (10-60 min). The pseudo-first-order and Langmuir isotherm models exhibited excellent agreement with the experimental results of BG adsorption by CTS/PPS-HS. The outstanding adsorption capacity (409.63 mg/g) of CTS/PPS-HS was obtained. The remarkable adsorption of BG onto CTS/PPS-HS can be primarily attributed to electrostatic forces between the acidic sites of CTS/PPS-HS and the BG cations, accompanied by interactions such as π-π, Yoshida H-bonding, n-π, and H-bond interactions. The current data underscores the significant potential inherent in combining biomass with CTS polymer to create an exceptionally effective adsorbent biomaterial tailored for the elimination of cationic dyes.

Promoting the circular economy: Valorization of a residue from industrial char to activated carbon with potential environmental applications as adsorbents

Pyrolysis of residues enriched with carbon, such as in agroforestry or industrial activities, has been postulated as an emerging technology to promote the production of biofuels, contributing to the circular economy and minimizing waste. However, during the pyrolysis processes a solid fraction residue is generated. This work aims to study the viability of these chars to develop porous carbonaceous materials that can be used for environmental applications. Diverse chars discharged by an industrial pyrolysis factory have been activated with KOH. Concretely, the char residues came from the pyrolysis of olive stone, pine, and acacia splinters, spent residues fuel, and cellulose artificial casings. The changes in the textural, structural, and composition characteristics after the activation process were studied by N2 adsorption-desorption isotherms, scanning electron microscopy, FTIR, elemental analysis, and XPS. A great porosity was developed, SBET within 776-1186 m2 g-1 and pore volume of 0.37-0.59 cm3 g-1 with 70-90% of micropores contribution. The activated chars were used for the adsorption of CO2, leading to CO2 maximum uptakes of 90-130 mg g-1. There was a good correlation between the CO2 uptake with microporosity and oxygenated surface groups of the activated chars. Moreover, their ability to adsorption of contaminants in aqueous solution was also evaluated. Concretely, there was studied the adsorption of aqueous heavy metals, i.e., Cd, Cu, Ni, Pb, and Zn, and organic pollutants of emerging concern such as caffeine, diclofenac, and acetaminophen.

Facilitate the preparation of naturally modified and self-healing superhydrophobic/superoleophilic biochar-based foams for efficient oil-water separation

Oil spills are sudden, complex, and long-term hazardous, and the existing adsorption materials still have the disadvantages of small selective adsorption capacity, easy secondary contamination, and difficult to repair after breakage in practical applications. Herein, melamine foam (MF) coated by ball milled biochar (BMBC) and natural beeswax (Wax@BMBC@MF) was prepared by a bio-inspired functionalization method and further added with self-healing function (SH-Wax@BMBC@MF) to cope with complex environments, and applied to oil-water separation for oil adsorption. SEM and FTIR results showed that BMBC and natural beeswax nanoparticles successfully encapsulated the smooth surface of the melamine foam skeleton. The loading of natural beeswax increased the foam's ability to absorb oil and organic solvents from 0.6108-1.134 g to 0.850-1.391 g, and the oil-absorbing capacity of the foam remained at 0. 758-1.263 g after being cut by a knife and self-healing. The oil-absorbing capacity of SH-Wax@BMBC@MF remained in the range of 0.936-1.336 g under acid/alkali environment (pH =1-13). The surface functional groups of BMBC improved the surface roughness of the material and strengthen the MF skeleton to adsorb oils and organic solvents by capillary action. The generation of the di-coordinated structure by Fe3+ and catechol group contributed the restoration of SH-Wax@BMBC@MF structure and oil absorption capacity. SH-Wax@BMBC@MF has superiority of superhydrophobic, superoleophilic, self-healing after damage, and environmental friendliness, which provides a promising solution for the treatment of oil spills at sea.

Exploration of the biodegradation pathway and enhanced removal of imazethapyr from soil by immobilized Bacillus marcorestinctum YN1

Excessive or inappropriate applications of imazethapyr cause severe ecological deteriorations and health risks in human. A novel bacterial strain, i.e., Bacillus marcorestinctum YN1, was isolated to efficiently degrade imazethapyr, with the degradation pathways and intermediates predicted. Protein mass spectrometry analysis identified enzymes in strain YN1 potentially involved in imazethapyr biodegradation, including methylenetetrahydrofolate dehydrogenase, carbon-nitrogen family hydrolase, heme degrading monooxygenase, and cytochrome P450. The strain YN1 was further immobilized with biochar (BC600) prepared from mushroom waste (i.e., spent mushroom substrate) by pyrolysis at 600 °C to evaluate its degrading characteristics of imazethapyr. Scanning electron microscope observation showed that strain YN1 was adsorbed in the rich pore structure of BC600 and the adsorption efficiency reached the maximum level of 88.02% in 6 h. Both energy dispersive X-ray and Fourier transform infrared spectroscopy analyses showed that BC600 contained many elements and functional groups. The results of liquid chromatography showed that biochar-immobilized strain YN1 (IBC-YN1) improved the degradation rate of imazethapyr from 79.2% to 87.4%. The degradation rate of imazethapyr by IBC-YN1 could still reach 81.0% in the third recycle, while the bacterial survival rate was 67.73% after 180 d storage at 4 °C. The treatment of IBC-YN1 significantly shortened the half-life of imazethapyr in non-sterilized soil from 35.51 to 11.36 d, and the vegetative growth of imazethapyr sensitive crop plant (i.e., Cucumis sativus L.) was significantly increased in soil remediated, showing that the inhibition rate of root length and fresh weight were decreased by 12.45% and 38.49% respectively. This study exhanced our understanding of microbial catabolism of imazethapyr, and provided a potential in situ remediation strategy for improving the soil environment polluted by imazethapyr.

Synthesis and efficiency comparison of reed straw-based biochar as a mesoporous adsorbent for ionic dyes removal

The reed straw is assessed as a potential source of widely available renewable biomass for biochar production and compared with two other waste-based biomasses, namely fruit stones blend, and brewery spent grains. The biochars were activated via steam and CO2. While steam activation yielded 12 % carbon from reed biomass, CO2 activation resulted in biomass degradation. The characterization of reed biochar showed a mesoporous structure and a high surface area of 514 m2/g. The adsorption tests displayed a decent adsorption capacity of biochar, with values of 92.6 mg/g for methylene violet dye and 35.7 mg/g for acid green dye. Only 1 g/L dosage of reed biochar was able to remove 99 % of the 50 mg/L methylene violet solution in 15 min and 60 % of the 50 mg/L acid green solution in 10 min. The obtained results demonstrate reed biomass as a suitable source for biochar production as well as reed-based biochar as a promising dye adsorbent.

Biochar amendment combined with partial root-zone drying irrigation alleviates salinity stress and improves root morphology and water use efficiency in cotton plant

An adsorption experiment and a pot experiment were executed in order to explore the mechanisms by which biochar amendment in combination with reduced irrigation affects sodium and potassium uptake, root morphology, water use efficiency, and salinity tolerance of cotton plants. In the adsorption experiment, ten NaCl concentration gradients (0, 50, 100, 150, 200, 250, 300, 350, 400, and 500 mM) were set for testing isotherm adsorption of Na+ by biochar. It was found that the isotherms of Na+ adsorption by wheat straw biochar (WSP) and softwood biochar (SWP) were in accordance with the Langmuir isotherm model, and the Na+ adsorption ability of WSP (55.20 mg g-1) was superior to that of SWP (47.38 mg g-1). The pot experiment consisted three factors, viz., three biochar amendments (no biochar, WSP, and SWP), three irrigation strategies (deficit irrigation, partial root-zone drying irrigation - PRD, full irrigation), and two NaCl concentrations gradients (0 mM and 200 mM). The findings indicated that salinity stress lowered K+ concentration, root length, root surface area, and root volume (RV), but increased Na+ concentration, root average diameter, and root tissue density. However, biochar amendment decreased Na+ concentration, increased K+ concentration, and improved root morphology. In particular, the combination of WSP and PRD increased K+/Na+ ratio, RV, root weight density, root surface area density, water use efficiency, and partial factor productivity under salt stress, which can be a promising strategy to cope with drought and salinity stress in cotton production.

Biomimetic Dispersive Solid-Phase Microextraction: A Novel Concept for High-Throughput Estimation of Human Oral Absorption of Organic Compounds

There is a quest for a novel in vitro analytical methodology that is properly validated for the prediction of human oral absorption and bioaccumulation of organic compounds with no need of animal models. The traditional log P parameter might not serve to predict bioparameters accurately inasmuch as it merely accounts for the hydrophobicity of the compound, but the actual interaction with the components of eukaryotic cells is neglected. This contribution proposes for the first time a novel biomimetic microextraction approach capitalized on immobilized phosphatidylcholine as a plasma membrane surrogate onto organic polymeric sorptive phases for the estimation of human intestinal effective permeability of a number of pharmaceuticals that are also deemed contaminants of emerging concern in environmental settings. A comprehensive exploration of the conformation of the lipid structure onto the surfaces is undertaken so as to discriminate the generation of either lipid monolayers or bilayers or the attachment of lipid nanovesicles. The experimentally obtained biomimetic extraction data is proven to be a superb parameter against other molecular descriptors for the development of reliable prediction models of human jejunum permeability with R2 = 0.76, but the incorporation of log D and the number of aromatic rings in multiple linear regression equations enabled improved correlations up to R2 = 0.88. This work is expected to open new avenues for expeditious in vitro screening methods for oral absorption of organic contaminants of emerging concern in human exposomics.

The efficient removal of ibuprofen, caffeine, and bisphenol A using engineered egusi seed shells biochar: adsorption kinetics, equilibrium, thermodynamics, and mechanism

Contaminants of emerging concern (CECs), also known as micropollutants, have been recognized in recent years as substantial water pollutants because of the potential threats they pose to the environment and human health. This study was aimed at preparing biochar (BC) based on egusi seed shells (ESS) with well-developed porosity and excellent adsorption capacity towards CECs including ibuprofen (IBP), caffeine (CAF), and bisphenol A (BPA). BC samples were prepared by pyrolysis at different temperatures (400 to 800 °C) and were characterized using nitrogen sorption, FTIR, powder X-ray diffraction (PXRD), SEM/EDS, elemental analysis, and thermal analysis. The nitrogen sorption and SEM results showed that the textural properties were more prominent as the pyrolysis temperature increased. The BC sample obtained at 800 °C which exhibited the largest specific surface area (688 m2/g) and the highest pore volume (0.320 cm3/g) was selected for the adsorption study of CECs. The kinetic study shows that the adsorption equilibrium of CAF and BPA was faster than that of IBP. The pseudo-first- and pseudo-second-order kinetic models best fitted the adsorption data. The Langmuir maximum monolayer adsorption capacities of biochar were found to be ~ 180, 121, and 73 mg/g respectively for IBP, CAF, and BPA. The thermodynamic study shows that the adsorption process was spontaneous and endothermic for the three CECs. The results of the adsorption and the analysis of BC after adsorption showed that hydrogen bonding, van der Waals, π-π, n-π interactions, and pore filling were involved in the adsorption mechanism. The prepared biochar BC from ESS displayed a large surface area and good morphology and significantly promotes adsorption of CECs and good efficiency on synthetic effluent. Finally, it offers a low-cost and cleaner production method.

Mixed pollutants adsorption potential of Eichhornia crassipes biochar on Manihot esculenta processing industry effluents

The starch is one of the most essential food stuff and serves as a raw material for number of food products for the welfare of human. During the production process enormous volume of effluents are being released into the environment. In this regard, this study was performed to evaluate the physicochemical traits of Manihot esculenta processing effluent and possible sustainable approach to treat this issue using Eichhornia crassipes based biochar. The standard physicochemical properties analysis revealed that the most the parameters (EC was recorded as 4143.17 ± 67.12 mhom^-1, TDS: 5825.62 ± 72.14 mg L^-1, TS: 7489.21 ± 165.24 mg L^-1, DO: 2.12 ± 0.21 mg L^-1, BOD 2673.74 ± 153.53 mg L^-1, COD: 6672.66 ± 131.21 mg L^-1, and so on) were beyond the permissible limits and which can facilitate eutrophication. Notably, the DO level was considerably poor and thus can support the eutrophication. The trouble causing E. crassipes biomass was used as raw material for biochar preparation through pyrolysis process. The temperature ranging from 250 to 350 °C with residence time of 20-60 min were found as suitable temperature to provide high yield (56-33%). Furthermore, 10 g L^-1 concentration of biochar showed maximum pollutant adsorption than other concentrations (5 g L^-1 and 15 g L^-1) from 1 L of effluent. The suitable temperature required to remediate the pollutants from the effluent by biochar was found as 45 °C and 35 °C at 10 g L^-1 concentration. These results conclude that at such optimized condition, the E. crassipes effectively adsorbed most of the pollutants from the M. esculenta processing effluent. Furthermore, such pollutants adsorption pattern on biochar was confirmed by SEM analysis.

CO2-Activation Nanofiber Carbon Paper as a High-Performance Interlayer for Trapping Polysulfides in Li-S Batteries

Lithium-sulfur (Li-S) batteries have high theoretical energy density but low sulfur utilization due to the inherent insulating nature of sulfur and the shuttle effect of polysulfides. Herein, the CO₂-activation carbon paper was prepared by poly(p-phenylenebenzobisoxazole) (PBO) nanofiber and was first applied as an interlayer for efficiently alleviating the shuttle effect of polysulfides in Li-S batteries. This interlayer exhibits good flexibility and strength with rich -C═O and -COOH functional groups on the three-dimensional porous structure, which improves chemical adsorption on Li₂S_x species and ion rapid diffusion via interconnected diffusion channels and thus enhances the electrochemical kinetics. The initial specific capacity is 1367.4 mAh g^-1 and remains 999.8 mAh g^-1 after 200 cycles at 0.2C and 780.1 mAh g^-1 at 5C, and the Coulombic efficiency is high, up to 99.8%, which is much better than that for the carbon paper without CO₂ activation. The highly conductive flexible PBO carbon paper may bring breakthroughs in performance and thus lead to more practical applications of Li-S batteries.

Preparation of Biochar with Developed Mesoporous Structure from Poplar Leaf Activated by KHCO3 and Its Efficient Adsorption of Oxytetracycline Hydrochloride

The effective removal of oxytetracycline hydrochloride (OTC) from the water environment is of great importance. Adsorption as a simple, stable, and cost-effective technology is regarded as an important method for removing OTC. Herein, a low-cost biochar with a developed mesoporous structure was synthesized via pyrolysis of poplar leaf with potassium bicarbonate (KHCO₃) as the activator. KHCO₃ can endow biochar with abundant mesopores, but excessive KHCO₃ cannot continuously promote the formation of mesoporous structures. In comparison with all of the prepared biochars, PKC-4 (biochar with a poplar leaf to KHCO₃ mass ratio of 5:4) shows the highest adsorption performance for OTC as it has the largest surface area and richest mesoporous structure. The pseudo-second-order kinetic model and the Freundlich equilibrium model are more consistent with the experimental data, which implies that the adsorption process is multi-mechanism and multi-layered. In addition, the maximum adsorption capacities of biochar are slightly affected by pH changes, different metal ions, and different water matrices. Moreover, the biochar can be regenerated by pyrolysis, and its adsorption capacity only decreases by approximately 6% after four cycles. The adsorption of biochar for OTC is mainly controlled by pore filling, though electrostatic interactions, hydrogen bonding, and π-π interaction are also involved. This study realizes biomass waste recycling and highlights the potential of poplar leaf-based biochar for the adsorption of antibiotics.

Rapid and efficient removal of multiple aqueous pesticides by one-step construction boric acid modified biochar

Tricyclazole, propiconazole, imidacloprid, and thiamethoxam are commonly used pesticides in paddy fields. It is necessary and practical to remove pesticides from the water environment because the low utilization rate of pesticides will produce residues in the water environment. It is known that there are few studies on the preparation of biochar adsorption pesticides by the walnut shell and few studies on the removal of tricyclazole and propiconazole. Based on this, this paper used the walnut shell as raw material and boric acid as an activator to prepare biochar by the one-step method. The boric acid modified walnut shell biochar (WAB4) with a specific surface area of 640.6 m2 g-1, exhibited the high adsorption capacity of all four pesticides (>70%) at pH 3-9. The adsorption capacities of tricyclazole, propiconazole, imidacloprid, and thiamethoxam were 171.67, 112.27, 156.40, and 137.46 mg g-1, respectively. The adsorption kinetics fitted the pseudo-second-order kinetic model and the adsorption isotherm curves conformed to the Freundlich isotherm model. The adsorption of pesticides by WAB4 was associated with hydrogen bonding, pore filling, hydrophobic effects, and π-π interactions. More significantly, WAB4 has excellent adsorption capacity compared to other adsorbents for real water samples. Finally, walnut shell biochar has no significant acute toxicity to Daphnia magna. This work shows that walnut shell-based biochar has a good effect on the removal of pesticides at a wide range of pH and is economical and safe, providing a new idea for the removal of pesticides in water.

Magnetically engineered sulfurized peat-based activated carbon for remediation of emerging pharmaceutical contaminants

Activated carbon derived from peat-based biomass was sulfurized and magnetized forming magnetically-engineered sulfurized peat-based activated carbon (MEPBAC) and used for adsorption of caffeine (CFN) and sulfamethoxazole (SMX) from aqueous media. Modification increased the surface area (724 m²/g) and introduced sulphur-groups and Fe-based nano-structures in MEPBAC. Sulphur-groups enhanced adsorption efficiency, whereas Fe-based nano-structures facilitated easy magnetic separation of MEPBAC after intended use leading to high reusability with consistent removal efficiency (∼95 %). Response surface methodology was employed for design of experiments and process optimization. The results revealed that the maximum removal (SMX 94 %; CFN 97 %) could be achieved at an adsorbent dose of 1.4 and 1.6 g/L, respectively (pH 11, 311 K). Adsorption kinetics was best explained by a pseudo-second-order kinetic model. Adsorption data of SMX was fitted better to Langmuir (linear) and Freundlich (non-linear) isotherms, whereas that of CFN was fitted well with Freundlich (linear) and Langmuir (non-linear) isotherms (R² ≥ 0.99).

Enhanced removal of diclofenac via coupling Pd catalytic and microbial processes in a H2-based membrane biofilm reactor: Performance, mechanism and biofilm microbial ecology

Diclofenac (DCF) is a most widely used anti-inflammatory drug, which has attracted worldwide attention given its low biodegradability and ecological damage, especially toxic effects on mammals including humans. In this study, a H₂-based membrane biofilm reactor (H₂-MBfR) was constructed with well-dispersed Pd nanoparticles generated in situ. The Pd-MBfR was applied for catalytic reductive dechlorination of DCF. In batch tests, DCF concentration had significantly effect on the rate and extent DCF removal, and NO₃^- had negative impact on DCF reductive dechlorination. Over 67% removal of 0.5 mg/L DCF and 99% removal of 10 mg/L NO₃^--N were achieved in 90 min, and the highest removal of 97% was obtained at 0.5 mg/L DCF in the absence of NO₃^-. Over 78 days of continuous operation, the highest steady-state removal flux of DCF was 0.0097 g/m²/d. LC-MS analysis indicated that the major product was 2-anilinephenylacetic acid (APA). Dechlorination was the main removal process of DCF mainly owing to the catalytic reduction by PdNPs, microbial reduction, and the synergistic reduction of microbial and PdNPs catalysis using direct delivery of H₂. Moreover, DCF reductive Dechlorination shifted the microbial community in the biofilms and Sporomusa was responsible for DCF degradation. In summary, this work expands a remarkable feasibility of sustainable catalytic removal of DCF.

Integrated Electro-Ozonation and Fixed-Bed Column for the Simultaneous Removal of Emerging Contaminants and Heavy Metals from Aqueous Solutions

In the current study, an integrated physiochemical method was utilized to remove tonalide (TND) and dimethyl phthalate (DMP) (as emerging contaminants, ECs), and nickel (Ni) and lead (Pb) (as heavy metals), from synthetic wastewater. In the first step of the study, pH, current (mA/cm2), and voltage (V) were set to 7.0, 30, and 9, respectively; then the removal of TND, DMP, Ni, and Pb with an electro-ozonation reactor was optimized using response surface methodology (RSM). At the optimum reaction time (58.1 min), ozone dosage (9.4 mg L−1), initial concentration of ECs (0.98 mg L−1), and initial concentration of heavy metals (28.9 mg L−1), the percentages of TND, DMP, Ni, and Pb removal were 77.0%, 84.5%, 59.2%, and 58.2%, respectively. For the electro-ozonation reactor, the ozone consumption (OC) ranged from 1.1 kg to 3.9 kg (kg O3/kg Ecs), and the specific energy consumption (SEC) was 6.95 (kWh kg−1). After treatment with the optimum electro-ozonation parameters, the synthetic wastewater was transferred to a fixed-bed column, which was filled with a new composite adsorbent (named BBCEC), as the second step of the study. BBCEC improved the efficacy of the removal of TND, DMP, Ni, and Pb to more than 92%.

Environmental remediation by tea waste and its derivative products: A review on present status and technological advancements

The rising consumption of the popular non-alcoholic beverage tea and its derivative products caused massive growth in worldwide tea production in the last decade, leading to the generation of huge quantities of waste tea residues every year. Most of these wastes are usually burnt or disposed in landfills without proper treatment which results in serious environmental issues by polluting water, air and soil. In the recent times, 'waste to wealth' is a fast-growing concept for environment friendly sustainable development. Utilization of the large amount of tea wastes for the production of low-cost adsorbents to reduce the expenses of water and wastewater treatment can be a sustainable way of management of these wastes which at the same time will improve circular economy also. This review endeavours to evaluate the potential of both raw and modified tea wastes towards the adsorption of pollutants from wastewater. The production of various adsorptive materials such as biochar, activated carbon, nanocomposites, hydrogels, nanoparticles from tea wastes are summarized. The advancements in their applications for the removal of different emerging contaminants from wastewater as well as potable water, air and soil are exhaustively reviewed. The outcome of the present review reveals that tea waste and its derivatives are appropriate candidates to be used as adsorbents that show tremendous effectiveness in cleaning the environment. This article will provide the readers with an in-depth knowledge on the sustainable utilization of tea waste as adsorbent materials and will assist them to explore this abundant cheap waste biomass for environmental remediation.

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.

Removing Pollutants from Sewage Waters with Ground Apricot Kernel Shell Material

For the first time, a comprehensive review of the literature data on the use of apricot (Prunus armeniaca) biomass components as a sorption material for the treatment of wastewater and environmental water from various pollutants is carried out in the present study. In addition to a comprehensive analysis of contemporary studies, the current work carried out its own microstructural and energy dispersive studies. It shows that apricot kernel shell is a promising raw material for obtaining sorption materials that can be used to extract various pollutants from aqueous media. The parameters of sorption interaction are presented, at which the highest rate of removal of pollutants was achieved. It is shown that the sorption capacity of apricot biomass components can be increased by modifying it with various chemical reagents, as well as other physical and physicochemical methods. We reveal that most publications consider the use of the latter as a raw material for the production of activated carbons. It is established that the surface area and total pore space of activated carbons from apricot kernel shells depend on the modes of carbonization and activation. It is shown that activated carbons are effective adsorbents for removing various pollutants (metal ions, dyes, oil and oil products) from aqueous media. It was found that the adsorption isotherms of pollutants in most cases are best described by the Langmuir and Freundlich models, and the process kinetics is most often described by the pseudo-second-order model. The possibility of improving the sorption characteristics of apricot biomass during chemical or physicochemical treatment is also shown.

Characteristics and Applications of Biochar in Soil–Plant Systems: A Short Review of Benefits and Potential Drawbacks

The available literary data suggest the general applicability and benefits of different biochar products in various soil–plant–environment systems. Due to its high porosity, biochar might generally improve the physicochemical and biological properties of supplemented soils. Among the direct and indirect effects are (i) improved water-retention capacity, (ii) enhanced soil organic matter content, (iii) pH increase, (iv) better N and P availability, and (v) greater potential uptake of meso- and micronutrients. These are connected to the advantage of an enhanced soil oxygen content. The large porous surface area of biochar might indirectly protect the survival of microorganisms, while the adsorbed organic materials may improve the growth of both bacteria and fungi. On the other hand, N2-fixing Rhizobium bacteria and P-mobilizing mycorrhiza fungi might respond negatively to biochar’s application. In arid circumstances with limited water and nutrient availability, a synergistic positive effect was found in biochar–microbial combined applications. Biochar seems to be a valuable soil supplement if its application is connected with optimized soil–plant–environment conditions. This work aims to give a general review of the potential benefits and drawbacks of biochar application to soil, highlighting its impacts on the soil–plant–microbe system.

Potential of Flax Shives and Beech Wood-Derived Biochar in Methylene Blue and Carbamazepine Removal from Aqueous Solutions

Flax shives and beech wood residues represent biomass streams that are abundant in Northwest Europe. These primary feedstocks were evaluated for their suitability to produce biochar as a low environmental-impact adsorbent. The efficacy of the produced biochars was tested by their adsorption capacity towards methylene blue (MB). A series of adsorption tests with carbamazepine is also presented, focusing on the better performing beech wood biochar. Post treatment of the biochars with citric acid (CA) and oxidation of the surface by heating at 250 °C in a muffle oven were carried out to enhance the adsorption capacities of both flax shives biochar (FSBC) and beech biochar (BBC). The resulting physicochemical characteristics are described. The thermally treated biochars have specific surface areas of 388 m²·g⁻¹ and 272 m²·g⁻¹ compared to the untreated biochars with 368 and 142 m²·g⁻¹ for BBC and FSBC, respectively. CA treatment leads to enhancement of the oxygenated surface functional groups and the adsorption capacities of both studied biochars. The non-linear Langmuir and Freundlich models show the best fit for both the isotherm data for MB and the CMZ adsorption with a good correlation between the experimental and calculated adsorption capacities. The effect of adsorbent dosages and initial concentrations of MB and CMZ on the adsorption efficiency is discussed. It can be concluded that beech biochar is a very promising pollutant adsorbent only requiring a mild, low-cost, and low-environmental impact activation treatment for best performance.

Recent Advances on Innovative Materials from Biowaste Recycling for the Removal of Environmental Estrogens from Water and Soil

New technologies have been developed around the world to tackle current emergencies such as biowaste recycling, renewable energy production and reduction of environmental pollution. The thermochemical and biological conversions of waste biomass for bioenergy production release solid coproducts and byproducts, namely biochar (BC), hydrochar (HC) and digestate (DG), which can have important environmental and agricultural applications. Due to their physicochemical properties, these carbon-rich materials can behave as biosorbents of contaminants and be used for both wastewater treatment and soil remediation, representing a valid alternative to more expensive products and sophisticated strategies. The alkylphenols bisphenol A, octylphenol and nonylphenol possess estrogenic activity comparable to that of the human steroid hormones estrone, 17β-estradiol (and synthetic analog 17α-ethinyl estradiol) and estriol. Their ubiquitous presence in ecosystems poses a serious threat to wildlife and humans. Conventional wastewater treatment plants often fail to remove environmental estrogens (EEs). This review aims to focus attention on the urgent need to limit the presence of EEs in the environment through a modern and sustainable approach based on the use of recycled biowaste. Materials such as BC, HC and DG, the last being examined here for the first time as a biosorbent, appear appropriate for the removal of EEs both for their negligible cost and continuously improving performance and because their production contributes to solving other emergencies, such as virtuous management of organic waste, carbon sequestration, bioenergy production and implementation of the circular economy. Characterization of biosorbents, qualitative and quantitative aspects of the adsorption/desorption process and data modeling are examined.

Advances in bioconversion of spent tea leaves to value-added products

Spent tea leaves (STL) are generated after the extraction of liquor from processed tea leaves and are regarded as an underutilized waste. STL are rich in essential amino acids, ω-6 and ω-3 fatty acids, alkaloids (theobromine and caffeine), polyphenols (catechin, theaflavins and rutin) and minerals (Ca, P, K, Mg, Mn) that could be utilized for the production of industrially important products. Vermicomposting, anaerobic digestion, silage preparation and fermentation are currently used as low cost methods for the bioconversion of STL to a usable form. Structural, morphological and chemical modification of STL after suitable bioconversion enables its application in the development of biopolymers, biofuels, catechin derivatives, biochar, absorbents for dye, and for removal of Cd, Hg, Cr(IV), As(V) and aspirin. This review discusses the composition, characterization, bioconversion and value added product generation from STL while highlighting prospective applications of STL in developing battery electrodes, nanocatalysts, insulation materials and edible bioactive peptides.

Manganese oxide-modified biochar: production, characterization and applications for the removal of pollutants from aqueous environments - a review

The development of manganese (Mn) oxides (MnOx) modified biochar (MnOBC) for the removal of pollutants from water has received significant attention. However, a comprehensive review focusing on the use of MnOBC for the removal of organic and inorganic pollutants from water is missing. Therefore, the preparation and characterization of MnOBC, and its capacity for the removal of inorganic (e.g., toxic elements) and organic (e.g., antibiotics and dyes) from water have been discussed in relation to feedstock properties, pyrolysis temperature, modification ratio, and environmental conditions here. The removal mechanisms of pollutants by MnOBC and the fate of the sorbed pollutants onto MnOBC have been reviewed. The impregnation of biochar with MnOx improved its surface morphology, functional group modification, and elemental composition, and thus increased its sorption capacity. This review establishes a comprehensive understanding of synthesizing and using MnOBC as an effective biosorbent for remediation of contaminated aqueous environments.