Biochars derived from bamboo and rice straw for sorption of basic red dyes

Enhanced cadmium immobilization in soil using Fe- and Zn-doped biochar: Mechanisms and safety implications for Cicer arietinum L

Cd toxicity emerges as a major environmental concern with detrimental impacts on global agricultural systems and food safety. Therefore, there is an urgent need to cope with the high concentration of Cd in the soil and crops. This study elucidates the potential of iron (FeBC) and zinc doped biochar (ZnBC) on the growth and yield of chickpea (Cicer arietinum L.) in Cd-contaminated soil. The parallels of biochemical attributes and Cd absorption of Cicer arietinum L. were investigated after a 120-day pot trial under 1% (w/w) biochar doses and two Cd concentrations (25 and 50 mg kg-1). The results demonstrated that FeBC was more effective in promoting plant growth by reducing Cd mobility in soil than ZnBC and normal biochar (NBC). Additionally, the application of FeBC resulted in significant improvement in photosynthesis rate (53.98%), transpiration rate (91.53%), stomatal conductance (197%), and sub-stomatal conductance (213.33%) compared to other applied treatments. Cd uptake in roots, shoots, and grains was reduced by 44.19%, 56.89%, and 88.25% respectively with the application of FeBC. Notably, the highest decrease in Cd bioaccumulation factor (99.72% and 99.65%) and Cd translocation factor (99.89% and 99.85%) were recorded under FeBC application in 25 and 50 mg kg-1 Cd-contaminated soils, respectively. The improved plant growth and reduced Cd buildup with FeBC under Cd stress suggest that FeBC is a promising strategy to remediate Cd-contaminated soil and simultaneously promote sustainable production of legume crops in Cd-contaminated soils.

Efficient water purification: CuO-enhanced biochar from banana peels for removing Congo red dye

Treating dye-containing wastewater poses numerous challenges due to its high chemical complexity and its persistent nature. Thus, the present study aims to synthesize biochar derived from banana peel (BC) and its nanocomposites with copper oxide nanoparticles (CuOx/BC1-x) for the purpose of adsorptive removing Congo red (CR) dye from water. Several analytical methods were utilized to describe the physicochemical features of the CuOx/BC1-x nanocomposites. It was found that the crystallinity of the nanocomposites gradually improved, while the specific surface area and the surface electronegativity were reduced with increasing x value. The effects of x values (0-0.5), interaction time (10-120 min), adsorbent dose (0.01-0.05 g), initial CR concentration (20-200 mg/L), and the solution temperature (20-60 °C) were evaluated on CR removal. The obtained results revealed that the CuO0.5/BC0.5 nanocomposite showed the highest adsorption efficiency with a maximum adsorption capacity of 233.6 mgg-1. Analysis of the equilibrium experimental data revealed that the Langmuir and the pseudo-2nd-order models were the most proper to describe the current adsorption process. Moreover, the thermodynamics studies demonstrated that the adsorption process was spontaneous, endothermic, and random.

Functionality of wheat straw-derived biochar enhanced its efficiency for actively capping Cd and Pb in contaminated water and soil matrices: Insights through batch adsorption and flow-through experiments

The impact of functionality of biochar on pressing environmental issue of cadmium (Cd) and lead (Pb) co-contamination in simultaneous soil and water systems has not sufficiently reported. This study investigated the impact of Fe- and Mg-functionalized wheat straw biochar (Fe-WSBC and Mg-WSBC) on Cd and Pb adsorption/immobilization through batch sorption and column leaching trials. Importantly, Fe-WSBC was more effective in adsorbing Cd and Pb (82.84 and 111.24 mg g-1), regeneration ability (removal efficiency 94.32 and 92.365), and competitive ability under competing cations (83.15 and 84.36%) compared to other materials (WSBC and Mg-WSBC). The practical feasibility of Fe-WSBC for spiked river water verified the 92.57% removal of Cd and 85.73% for Pb in 50 mg L-1 and 100 mg L-1 contamination, respectively. Besides, the leaching of Cd and Pb with Fe-WSBC under flow-through conditions was lowered to (0.326 and 17.62 mg L-1), respectively as compared to control (CK) (0.836 and 40.40 mg L-1). In short, this study presents the applicable approach for simultaneous remediation of contaminated water and soil matrices, offering insights into environmentally friendly green remediation strategies for heavy metals co-contaminated matrices.

Adsorption properties and mechanism of Cu(II) on virgin and aged microplastics in the aquatic environment

Microplastics (MPs) migrate by adsorbing heavy metals in aquatic environments and act as their carriers. However, the aging mechanisms of MPs in the environment and the interactions between MPs and heavy metals in aquatic environments require further study. In this study, two kinds of materials, polyamide (PA) and polylactic acid (PLA) were used as target MPs, and the effects of UV irradiation on the physical and chemical properties of the MPs and the adsorption behavior of Cu(II) were investigated. The results showed that after UV irradiation, pits, folds and pores appeared on the surface of aged MPs, the specific surface area (SSA) increased, the content of oxygen-containing functional groups increased, and the crystallinity decreased. These changes enhanced the adsorption capacity of aged MPs for Cu(II) pollutants. The adsorption behavior of the PA and PLA MPs for Cu(II) conformed to the pseudo-second-order model and Langmuir isotherm model, indicating that the monolayer chemical adsorption was dominant. The maximum amounts of aged PA and PLA reached 1.415 and 1.398 mg/g, respectively, which were 1.59 and 1.76 times of virgin MPs, respectively. The effects of pH and salinity on the adsorption of Cu(II) by the MPs were significant. Moreover, factors such as pH, salinity and dosage had significant effects on the adsorption of Cu(II) by MPs. Oxidative complexation between the oxygen-containing groups of the MPs and Cu(II) is an important adsorption mechanism. These findings reveal that the UV irradiation aging of MPs can enhance the adsorption of Cu(II) and increase their role as pollutant carriers, which is crucial for assessing the ecological risk of MPs and heavy metals coexisting in aquatic environments.

Strategies for economic utilization of rice straw residues into value-added by-products and prevention of environmental pollution

Rice straw management, along with the prevalent practice of residue burning, poses multifaceted challenges with substantial environmental and human health implications. After harvest, a considerable amount of straw is left behind, often disposed of through burning, releasing several pollutants into the environment. Carbon dioxide (CO2) dominates at 70%, accompanied by methane (CH4) at 0.66%, carbon monoxide (CO) at 7%, and nitrous oxide (N2O) at 2.09%. This process further compounds issues by depleting soil nutrients like nitrogen and organic matter. This review focuses on strategies for residue management and using straw as value-added by-products. We address research gaps and offer potential recommendations for rice straw management using economically feasible and practical routes. We elaborate that to improve rice straw digestibility, utilization in mushroom cultivation, and other value-added products, low silica (Si) rice varieties must be developed using modern technologies including marker-assisted selection breeding or genome editing. Developing low Si rice could also reduce arsenic uptake by rice, as rice plants use the same transporters for the uptake of both elements. Conversely, silica is also indispensable for quality rice production; hence, optimizing silicon content in rice is worth investigating. More research is required to understand the extent of silicon's effect on the utilization of straw for various purposes. This review also discusses the importance of educating farmers about the straw burning issue and its environmental consequences. We highlight the significance of tailoring rice straw management methods to local suitability, moving away from a universal approach. More extension work is needed to encourage farmers to opt for environmentally and economically sound options for rice straw management. Policy intervention to incentivize farmers and develop technologies for the widespread use of rice straw for various industries and product development could help in the management of rice straw and will also create a circular economy.

Agrowaste-generated biochar for the sustainable remediation of refractory pollutants

The rapid growth of various industries has led to a significant, alarming increase in recalcitrant pollutants in the environment. Hazardous dyes, heavy metals, pesticides, pharmaceutical products, and other associated polycyclic aromatic hydrocarbons (such as acenaphthene, fluorene, fluoranthene, phenanthrene, and pyrene) have posed a significant threat to the surroundings due to their refractory nature. Although activated carbon has been reported to be an adsorbent for removing contaminants from wastewater, it has its limitations. Hence, this review provides an elaborate account of converting agricultural waste into biochar with nanotextured surfaces that can serve as low-cost adsorbents with promising pollutant-removing properties. A detailed mechanism rationalized that this strategy involves the conversion of agrowaste to promising adsorbents that can be reduced, reused, and recycled. The potential of biowaste-derived biochar can be exploited for developing biofuel for renewable energy and also for improving soil fertility. This strategy can provide a solution to control greenhouse gas emissions by preventing the open burning of agricultural residues in fields. Furthermore, this serves a dual purpose for environmental remediation as well as effective management of agricultural waste rich in both organic and inorganic components that are generated during various agricultural operations. In this manner, this review provides recent advances in the use of agrowaste-generated biochar for cleaning the environment.

Black carbon derived PET plastic bottle waste and rice straw for sorption of Acid Red 27 dye: Machine learning approaches, kinetics, isotherm and thermodynamic studies

This study focuses on the probable use of PET waste black carbon (PETWBC) and rice straw black carbon (RSBC) as an adsorbent for Acid Red 27 (AR 27) adsorption. The prepared adsorbent is characterized by FE-SEM and FT-IR. Batch adsorption experiments were conducted with the influencing of different operational conditions namely time of contact (1-180 min), AR 27 concentration (5-70 mg/L), adsorbent dose (0.5-20 g/L), pH (2-10), and temperature (25-60°C). High coefficient value [PETWBC (R2 = 0.94), and RSBC (R2 = 0.97)] of process optimization model suggesting that this model was significant, where pH and adsorbent dose expressively stimulus removal efficiency including 99.88, and 99.89% for PETWBC, and RSBC at pH (2). Furthermore, the machine learning approaches (ANN and BB-RSM) revealed a good association between the tested and projected value. Pseudo-second-order was the well-suited kinetics, where Freundlich isotherm could explain better equilibrium adsorption data. Thermodynamic study shows AR 27 adsorption is favourable, endothermic, and spontaneous. Environmental friendliness properties are confirmed by desorption studies and satisfactory results also attain from real wastewater experiments. Finally, this study indicates that PETWBC and RSBC could be potential candidates for the adsorption of AR 27 from wastewater.

An efficient biosorbent material for green remediation of contaminated water medium

The discharge of large amounts of wastewater carrying various contaminants from many anthropogenic activities into the receiving water environment is a multidimensional issue negatively affecting the ecological system and natural balance in many ways. The removal of pollutants by the biologically-originated materials is an emerging area of interest due to profoundly their environmental friendliness, renewability, sustainability, readily availability, biodegradability, multiplicity, low (or no) economic cost, high affinity, capacity, and stability. In the present study, a popular ornamental plant, Pyracantha coccinea M. J. Roemer, was converted into a green sorbent material with the goal to effectively remove a widespread contaminant (synthetic dye, C. I. Basic Red 46) from synthetic wastewater. The physicochemical characteristics of the prepared biosorbent were determined by the instrumental analyses of FTIR and SEM. The batch experiments of various operational influence parameters were conducted to maximize the system efficiency. The wastewater remediation behavior by the material was investigated by the kinetics, thermodynamics, and isotherm experiments. The biosorbent had a non-uniform and rough surface architecture with a diversity of functional groups. The maximum remediation yield was achieved with the contact duration of 360 min, the pollutant load of 30 mg L-1, the pH of 8, and the biosorbent quantity of 10 mg (0.1 g L-1). The kinetics of the contaminant removal showed good agreement with the pseudo-second-order model. Thermodynamics study indicated that the treatment process was spontaneous and occurred by physisorption. Langmuir model fitted the isotherm data of the biosorption operation well and the maximum pollutant cleanup capacity of the material was determined to be 169.354 mg g-1. These outcomes showed that P. coccinea M. J. Roemer could be used as a promising material for low-cost and green treatment of wastewater.

Adsorption of the non-steroidal anti-inflammatory drug (ibuprofen) onto biochar and magnetic biochar prepared from chrysanthemum waste of the beverage industry

Biochar and magnetic biochar prepared from chrysanthemum waste of the beverage industry are effective adsorbents for the removal of the non-steroidal anti-inflammatory drug, ibuprofen (IBP), from aqueous systems. The development of magnetic biochar using iron chloride, overcame poor separation characteristics from the liquid phase of the powdered biochar after adsorption. Characterisation of biochars was achieved through Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), N₂ adsorption/desorption porosimetry, scanning electron microscopy (SEM), electron dispersive X-ray analysis (EDX), X-ray photoelectron spectroscopy (XPS), vibrating sample magnetometer (VSM), moisture and ash content, bulk density, pH and zero-point charge (pH_pzc). The specific surface area of non-magnetic and magnetic biochars was 220 and 194 m² g^-1, respectively. Adsorption of ibuprofen was optimised with respect to contact time (5-180 min), solution pH (2-12) and initial drug concentration (5-100 mg L^-1), with equilibrium being reached in 1 hour, and the maximum ibuprofen removal occurred at pH 2 and 4 for biochar and magnetic biochars, respectively. Investigation of the adsorption kinetics was achieved through application of the pseudo-first order, pseudo-second order, Elovich and intra-particle diffusion models. Adsorption equilibrium was evaluated using Langmuir, Freundlich and Langmuir-Freundlich isotherm models. The adsorption kinetics and isotherms for both biochars are well described by pseudo-second order kinetic and Langmuir-Freundlich isotherm models, respectively, with the maximum adsorption capacity of biochar and magnetic biochar being 167 and 140 mg g^-1, respectively. Chrysanthemum derived non-magnetic and magnetic biochars exhibited significant potential as sustainable adsorbents toward the removal of emerging pharmaceutical pollutants such as ibuprofen from aqueous solution.

Production of non-activated biochar based on Biden pilosa and its application in removing methylene blue from aqueous solutions

Biden pilosa (BP) is a type of weed commonly found in Thailand that needs to be removed from agricultural areas for protecting main crops. This research proposed a method to reduce BP by using BP as a feedstock for biochar production. Non-activated BP biochar from fresh BP was produced in pilot scale using a drum kiln with a heat-transferring duct at a pyrolysis temperature of 550 °C at a slow heating rate. The physical properties of the non-activated BP biochar were investigated using scanning electron microscopy, Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction, and a surface area analyzer. A batch experiment was used to study the adsorption behavior of methylene blue (MB) on BP biochar. The microstructure study of the BP biochar indicated that it has a cell structure similar to that of BP, which shows the non-destructive nature of the proposed technique for BP production. Six dominant peaks at 3283, 2915, 1559, 1403, 1116, and 863/839 cm^⁻1 were observed in the FTIR spectrum. The BP biochar exhibited a surface area of 5.21 m²/g and a pore size of 8 nm. The adsorption of MB on the BP biochar followed the Langmuir adsorption isotherm and pseudo-second-order kinetics. The Langmuir-based maximum adsorption capacity of MB on the BP biochar was 200 mg/g at 303 K.

Bamboo-derived adsorbents for environmental remediation: A review of recent progress

The bamboo family of plants is one of the fastest-growing species in the world. As such, there is an abundance of bamboo residues available for exploitation, especially in southeast Asian, central African and south American regions. The preparation of efficient adsorbents from bamboo residues is an emerging exploitation pathway. Biochars, activated carbons or raw bamboo fibers embedded with nanoparticles, each class of materials has been shown to be highly efficient in adsorption processes. This review aims to summarize recent findings in the application of bamboo-based adsorbents in the removal of organic, inorganic, or gaseous pollutants. Therefore, this review first discusses the preparation methods and surface modification methodologies and their effects on the adsorbent elemental content and other basic properties. The following sections assess the recent progress in the adsorption of heavy metals, organics, and gaseous substances by bamboo-based adsorbents, focusing on the optimum adsorption capacities, adsorption mechanisms and the optimum-fitting kinetic models and isotherms. Finally, research gaps were identified and directions for future research are proposed.

Preparation and performance of bionanocomposites based on grafted chitosan, GO and TiO2-NPs for removal of lead ions and basic-red 46

Wastewater rich in heavy metals and organic compounds represents one of the essential environmental pollutants. Therefore, a practical approach is to fabricate eco-friendly polymer-based systems with a high ability to absorb pollutants. Herein, bionanocomposites consisting of chitosan (Cs) grafted by various monomers, such as acrylamide (Am), acrylic acid (AA), and 4-styrene sulfonic acid (SSA), and hybrid nanoparticles of graphene oxide/titanium dioxide nanoparticles (GO@TiO₂-NPs) were fabricated. The prepared nanomaterials and bionanocomposites characterized via various tools. The data illustrated that the prepared GO had a thickness of 10 nm and TiO₂-NPs had a diameter of 25 nm. In addition, the grafted chitosan (gCs) using Am and SSA had the largest surface area (gCs2; 22.89 nm) and its bionanocomposite (NC5; 104.79 nm). In addition, the sorption ability of the 0.15 g of prepared bionanocomposites to the (100 mg/L) of lead ions (Pb²⁺) and (25 mg/L) of basic-red 46 (BR46) under various conditions has been studied. The results showed that gCs3 and NC5 had the highest adsorption of Pb²⁺ (79.54 %) and BR46 (79.98 %), respectively. The kinetic study results of the sorbents obeyed the Pseudo second-order model. In contrast, the isothermal study followed the Freundlich adsorption model for Pb²⁺ and the Langmuir adsorption model for BR46.

Removal of reactive violet 5 azodye (V5R) using bamboo, and calabash biochar

We assess the adsorption capacity of bamboo and calabash biochar (BB and CB). Using 10-50 mg/L Reactive Violet 5 Azo dye (V5R) adsorbate, the kinetics, and adsorption isotherms are investigated. We pyrolyzed the bamboo, and calabash biomass at 500 °C, washed, and oven dried at 120 °C for 48 h. The Brunauer-Emmett-Teller (BET) method indicates that the BB and CB average pore diameters are 21.1 nm and 26.5 nm, with specific surface areas of 174.67 m²/g and 44.78 m²/g, respectively. The SEM reveals a larger granular shape of the CB having pinholes on the surface, but the BB exhibited interconnected structures like a mesh. The FTIR shows C=C, C=O, O-H, and C-O-C as the predominant functional groups on both BB and CB. The adsorption of V5R on BB and CB follows pseudo-second-order kinetics and favors Langmuir isotherm with maximum adsorption capacities of 5.106 mg/g, and 0.010 mg/g, respectively. The BB adsorbs 70.9-96% V5R, whilst CB adsorbs 0.1-0.2 % only. The results suggest that bamboo biochar has the potential to eliminate 70.9-96% of 10-50 mg/L V5R from an aqueous solution, hence suitable for removing V5R. In this study, we have also presented a prototype expected to eliminate 91.6%-99.8% of the V5R from an aqueous solution.

Synergetic effects of biochar addition on mesophilic and high total solids anaerobic digestion of chicken manure

High solids anaerobic digestion (AD) of chicken manure (CM) is often challenging due to ammonia-N inhibition and accumulation of volatile fatty acids (VFAs). This study evaluated the effect of adding biochars from different feedstock to ameliorate semi-dry AD of fresh CM during batch fermentation. Experiments were performed in 300 mL at two total solid (TS) levels (12% and 15%) under mesophilic (36 ±1ᵒC) conditions for 55 d, using activated sludge as inoculum. Treatments included: fresh CM (at 12% or 15% TS) mixed separately with rice husks char (RB), wood char (WB) and bamboo char (BB) at biochar dosages of 2.5%, 5% and 10% of TS in the CM, inoculum only and inoculum plus CM without addition of char as the control. Results indicated that addition of biochar reduced the lag phases to 4-5.4 d and AD performances were significantly improved with total volatile solids removal of 53-67% and 62-71%, and cumulative methane of 277-380 mL/gVS (CH₄ content ≈ 51-63%) and 297-438 mL/gVS (CH₄ content ≈ 49-67%) at 12% and 15% TS, respectively. Biochar buffered over acidification and stabilized pH in the range of 6.5-7.8 but mild ammonia inhibition still occurred in all biochar treatments due to the high residual total ammonia-N (4.3 g-5.6 g/L). For all the investigated parameters, WB amended digesters exhibited the best results owing to its high specific surface area, porosity, cationic exchange capacity, and elemental composition which were superior to those of RB and BB. At 10% dosage of all tested biochars, the AD process was more stable and methane content neared optimal of >65% CH₄. Therefore, addition of biochar from lignocellulosic materials at a given threshold dosage could promote semi-dry and dry biogas production from chicken manure and thus add value to this waste which in most cases is improperly managed.

Removal of Reactive Black 5 Dye by Banana Peel Biochar and Evaluation of Its Phytotoxicity on Tomato

Removal of Reactive Black 5 (RB5) dye from an aqueous solution was studied by its adsorption on banana peel biochars (BPBs). The factors affecting RB5 dye adsorption such as pH, exposure time, RB5 dye concentration, adsorbent dose, particle size and temperature were investigated. Maximum 97% RB5 dye removal was obtained at pH 3 with 75 mg/L adsorbate concentration by banana peel biochars. Fourier transform infrared (FTIR) and scanning electron microscopy (SEM) were used to characterize the adsorbent material. The data of equilibrium were analyzed by Langmuir and Freundlich isotherm models. The experimental results were best reflected by Langmuir isotherm with maximum 7.58 mg/g adsorption capacity. Kinetic parameters were explored and pseudo-second order was found suitable which reflected that rate of adsorption was controlled by physisorption. Thermodynamic variables exhibited that the sorption process was feasible, spontaneous, and exothermic in nature. Banana peel biochar showed excellent regeneration efficiency up to five cycles of successive adsorption-desorption. Banana peel biochar maintained >38% sorption potential of RB5 dye even after five cycles of adsorption-desorption. The phytotoxic study exhibited the benign nature of BPB-treated RB5 dye on tomato seeds.

Adsorption of Arsenic on Fe-Modified Biochar and Monitoring Using Spectral Induced Polarization

This work demonstrates the potential of Fe-modified biochar for the treatment of arsenic (As) simulated wastewater and the monitoring of adsorption in real-time. Specifically, we propose the utilization of date-palm leaves for the production of biochar, further modified with Fe in order to improve its adsorption function against inorganic pollutants, such as As. Both the original biochar and the Fe-modified biochar were used for adsorption of As in laboratory batch and column experiments. The monitoring of the biochar(s) performance and As treatment was also enhanced by using the spectral induced polarization (SIP) method, offering real-time monitoring, in addition to standard chemical monitoring. Both the original and the Fe-modified biochar achieved high removal rates with Fe-modified biochar achieving up to 98% removal of As compared to the 17% by sand only (control). In addition, a correlation was found between post-adsorption measurements and SIP measurements.