Characterization and evaluation of surface modified materials based on porous biochar and its adsorption properties for 2,4-dichlorophenoxyacetic acid

Enhancing the adsorption capacity of organic and inorganic pollutants onto impregnated olive stone derived activated carbon

This study presents a sustainable approach to activated carbon production from olive stones in comparison to commercial ones, using various activating agents such as H3PO4, KOH, and ZnCl2, for enhancing the adsorption properties and versatile adsorption capability to remove a range of pollutants including copper ion, methylene blue, and 2,4-Dichlorophenoxyacetic acid from aqueous solutions. The performances of activated carbons across varying conditions such as pollutant concentrations, temperatures, pH levels, and adsorbent amounts were tested. Increased initial pollutant concentrations correlated with higher adsorption capacities. Maximum adsorption capacities were achieved at pH levels of 5, 10, and 2 for Cu, MB, and 2,4-D, respectively. For KOSAC, Cu removal rose from 27 % to 52 %, for ZOSAC, MB removal increased from 39 % to 65 %, and for ZOSAC, 2,4-D removal surged from 33 % to 99 % at varying adsorbent amounts. Model validation was carried out utilizing the kinetic models (PFO, PSO) and isotherm models (Langmuir, Redlich-Peterson). The PFO kinetic model and Langmuir isotherm model proved more suitability for Cu adsorption, whereas PFO and PSO kinetic models, along with Redlich-Peterson isotherm models, were more prominent for MB and 2,4-D adsorption. Thermodynamic analysis revealed that the adsorption of Cu and 2,4-D was exothermic, while MB adsorption was endothermic. By optimization of experimental conditions, the maximum adsorption capacities were attained at 30.34 °C and 297.65 mg L-1 for KOSAC-Cu, 48.62 °C and 269.37 mg L-1 for ZOSAC-MB, and 30.31 °C and 299.02 mg L-1 for ZOSAC-2,4-D sorption. This research highlights ZOSAC's potential as a cost-effective, eco-friendly solution for water treatment, contributing to environmental sustainability and economical feasibility.

Mechanisms of adsorption and functionalization of biochar for pesticides: A review

Agricultural production relies heavily on pesticides. However, factors like inefficient application, pesticide resistance, and environmental conditions reduce their effective utilization in agriculture. Subsequently, pesticides transfer into the soil, adversely affecting its physicochemical properties, microbial populations, and enzyme activities. Different pesticides interacting can lead to combined toxicity, posing risks to non-target organisms, biodiversity, and organism-environment interactions. Pesticide exposure may cause both acute and chronic effects on human health. Biochar, with its high specific surface area and porosity, offers numerous adsorption sites. Its stability, eco-friendliness, and superior adsorption capabilities render it an excellent choice. As a versatile material, biochar finds use in agriculture, environmental management, industry, energy, and medicine. Added to soil, biochar helps absorb or degrade pesticides in contaminated areas, enhancing soil microbial activity. Current research primarily focuses on biochar produced via direct pyrolysis for pesticide adsorption. Studies on functionalized biochar for this purpose are relatively scarce. This review examines biochar's pesticide absorption properties, its characteristics, formation mechanisms, environmental impact, and delves into adsorption mechanisms, functionalization methods, and their prospects and limitations.

Effect of lignocellulosic corn stalk on mechanical, physical, and thermal properties of injection moulded low density polyethylene composites: An approach towards a circular economy

Escalating concern over global warming, which is mostly associated with deforestation, has led to the development of new classes of materials that can replace wood and better utilise natural resources. Presently, waste is a significant factor in recycling. In this regard, one of the leading contributors to waste is agricultural waste, which includes dried branches, leaves of trees, plants, and other organic materials. In the current study, waste from corn agriculture was utilised as a potential reinforcement for the fabrication of corn stalk-low density polyethylene (CS-LDPE) composites via an injection moulding technique at 170 °C. The different parameters were assessed to develop composites using CS, including physico-chemical, macromolecular, mineralogical, elemental, and morphological analysis. The amount of corn stalk (CS) was varied from 10 to 50 wt% with respect to the polymer. The mechanical, physical and thermal performance of the composites was examined. The density and water absorption of the composites were found to remain within the ranges of 1.00-1.11 g/cm3 and 0.22-1.01 %, respectively, whereas these parameters increased as the proportion of CS increased. The thermal conductivity decreases with the addition of CS from 0.36964 ± 0.020 to 0.22388 ± 0.002 W/mK. It was observed that adding CS to the composites increased their tensile and flexural properties, but decreased their impact strength. The maximum flexural strength of 14.40 ± 1.558 MPa, flexural modulus of 752.53 ± 180.409 MPa, tensile strength of 10.49 ± 0.946 MPa and tensile modulus of 539.79 ± 91.044 MPa were observed with a 50 % CS content. The results suggest that these materials have considerable potential to serve as a cost-effective substitute for the conventional lignocellulosic fillers in the manufacturing of wood-plastic composites.

Efficient Adsorption and Removal of the Herbicide 2,4-Dichlorophenylacetic Acid from Aqueous Solutions Using MIL-88(Fe)-NH2

Metal-organic frameworks (MOFs), a material known for its multifunctionality, chemical stability, and high surface area, are now commonly utilized as an adsorbent for water treatment. The MOF (MIL-88(Fe)-NH2) was synthesized and used to remove the commonly used toxic herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) from water. The MIL-88(Fe)-NH2 MOF was fully characterized using multiple techniques. A systematic investigation was conducted to evaluate the key parameters that impact the adsorption process, which include coexisting anions, adsorbent dosage, and solution pH. The adsorption isotherm was fitted using the Langmuir model, while the kinetics were fitted using pseudo-second-order. The adsorption process was both chemisorption and endothermic. The capacity for adsorption increased with rising temperatures. The MIL-88(Fe)-NH2 adsorbent has a maximum adsorption capacity of 345.25 mg g-1 for removing 2,4-D, significantly higher than previous adsorbents used for this purpose. The adsorption mechanism could be ascribed to hydrogen bonding, pore filling, π-π conjugations between the 2,4-D molecules and the MIL-88(Fe)-NH2 adsorbent, and electrostatic interactions. Furthermore, the adsorption capacity of MIL-88(Fe)-NH2 adsorbent showed only a slight decrease after five successive recycles, and it could be easily regenerated through solvent washing. When used in environmental water samples, especially those containing electronic wastes, the MIL-88(Fe)-NH2 adsorbent demonstrated satisfactory adsorption capacity and reusability. The MIL-88(Fe)-NH2 adsorbent is more practical and reusable and has better adsorption capacity and shorter equilibrium time compared to previously reported adsorbents.

Control Efficiency of Biochar Loaded with Bacillus subtilis Tpb55 against Tobacco Black Shank

Black shank caused by Phytophthora nicotianae has become a destructive soil-borne disease to different flue-cured tobacco cultivars in Southwest China. The use of biochar amendments for microorganism synergy is a promising effective strategy for P. nicotianae development control. In this study, biochar samples were prepared from tamarisk with different pyrolization temperatures (300–500 °C). The effect of pyrolytic temperatures on the bacteria immobilization efficiency of biochar was investigated. B. subtilis Tpb55 was successfully loaded on different biochars as biocontrol composites. The survival investigation of the inoculum suggested that biochar pyrolized at 300 °C (BC300), with a large pore opening diameter; a greater pore volume exhibited a better Tpb55 immobilization. A pot experiment indicated that Tpb55-loaded BC300 had a more pronounced decrease in the disease severity index of black shank disease and an increase in the soil pH, alkali-hydrolyzable nitrogen, soil-available phosphorus, and available potassium. BC300 inoculated with Tpb55 showed the highest control effect (79.60%) against tobacco black shank in the pot experiments, with the lowest copy number of P. nicotianae DNA. In conclusion, biochar-immobilized Tpb55 may provide a new strategy for preventing and controlling tobacco black shank.

Adsorption of 2,4-D and MCPA Herbicides on Carbon Black Modified with Hydrogen Peroxide and Aminopropyltriethoxysilane

The carbon black N-220 surface was subjected to modification through H2O2 oxidation and deposition of aminopropyltriethoxysilane. The pristine (CB-NM) and modified materials (CB-Ox and CB-APTES) were characterized by N2 adsorption−desorption isotherms, scanning electron microscopy, energy-dispersive X-ray spectroscopy (SEM-EDS), thermogravimetry, and FTIR spectroscopy. Carbon black samples were applied as adsorbents for the removal of 2,4-dichlorophenoxyacetic acid (2,4-D) and 2-methyl-4-chlorophenoxyacetic acid (MCPA) herbicides from aqueous solutions. The influence of their surface properties on adsorption efficiency was analyzed and discussed. The results showed that the adsorption of the herbicides was pH-dependent, and the most favorable adsorption was observed in an acidic environment. The experimental data best fit pseudo-second-order and Langmuir models for kinetic and equilibrium data, respectively. The adsorption rate of both the herbicides increased in the order of CB-APTES < CB-Ox < CB-NM and was closely correlated with the mesopore volume of the carbon blacks. The monolayer adsorption capacities were found to be 0.138, 0.340, and 0.124 mmol/g for the adsorption of 2,4-D and 0.181, 0.348, and 0.139 mmol/g for the adsorption of MCPA on CB-NM, CB-APTES, and CB-Ox, respectively. The results showed that the surface chemistry of the adsorbent plays a more important role than its porous structure. Both herbicides were preferably adsorbed on APTES-modified carbon black and were adsorbed the worst on oxidized carbon black (CB-APTES > CB-NM > CB-Ox).

Effects of different modifiers on the sorption and structural properties of biochar derived from wheat stalk

Nitrobenzene is a widespread contaminant in water. Biochar (BC) is a promising material for removing organic pollutants, but the adsorption capacity of pristine BC is low. Chemical modification is often used to improve the adsorption performance, but information on the sorption of nitrobenzene by modified BC is rare. In this study, BCs pyrolyzed at 300, 500, and 700 °C were modified by hydrochloric acid (HCl), sulfuric acid (H2SO4), sodium hydroxide (NaOH), hydrogen peroxide (H2O2), and nitric acid (HNO3), respectively. The properties, nitrobenzene sorption behaviors, and sorption mechanisms of different BCs were analyzed. The results showed that chemical modification decreased the sorption of nitrobenzene on BCs pyrolyzed at 300 °C, possibly due to the loss of the partition phase and the increase in polarity after modification. Regarding BCs pyrolyzed at 500 and 700 °C, the NaOH and HCl modifications significantly increased the sorption capacity by 19% and 60%, 18%, and 41%, respectively, possibly due to the increase in surface area, available pores, and aromaticity, while HNO3 modification decreased the sorption capacity by 41% and 31%. Two reasons were probably responsible for the decrease: one was the decrease in surface area after HNO3 modification due to the destruction of pore walls and the continuity of holes; the other was the strong repulsion between the nitro groups formed on the surface of BC and the nitro groups of nitrobenzene that drove nitrobenzene molecules away from the surface. A principal component-based comprehensive evaluation of the BC properties, which were significantly correlated with the sorption isotherm parameters, was used to evaluate the nitrobenzene sorption performance of the modified BC. Overall, BC pyrolyzed at 700 °C modified with NaOH or HCl were proposed as effective sorption materials for the removal of nitrobenzene in environment, which also provided a chemical modified method of biochar derived from agricultural waste.

Reviewing variables and their implications affecting adsorption of Cr(VI) onto activated carbon: an in-depth statistical case study

Removal of Cr(VI) from the aqueous phase using numerous activated carbons (AC) has been broadly studied in the last decades. Nevertheless, the diversity of activation methods, AC properties, and adsorption conditions precludes the standardization of specific characteristics required to achieve better adsorption results. This work reviewed the pertinent literature on Cr(VI) adsorption onto AC published over the past four decades. Pearson's correlation matrix and principal component analysis (PCA) assisted in identifying the parameters and AC characteristics that have the greatest influence on the maximum adsorption capacity (q_m). Two hundred thirty-six adsorption assays were found reporting data on 110 ACs and different parameters. Of these, 39.8% of the studies contemplated the variables q_m, pH, temperature (T), surface area (S_BET), micropore volume (V_micro), and mesopore volume (V_meso), and only 19.5% reported the point of zero charge (pH_PZC). Statistical analysis disclosed that S_BET and V_micro have a strong positive correlation with q_m, while V_meso, T, and pH show little or no correlation. The difference between pH and pH_PZC (PZC_diff) indicated a significant anticorrelation with q_m, thus evidencing that lower PZC_diff values enhance adsorption. The findings are useful for all researchers that work with Cr(VI) adsorption on AC since they provide a start point concerning the required adsorbent characteristics and process conditions to be employed.

Preparation, characterization, and application of modified magnetic biochar for the removal of benzotriazole: process optimization, isotherm and kinetic studies, and adsorbent regeneration

The adsorption of benzotriazole (BTA) by chemically modified magnetic biochar (MMBC) as a cheap and abundant biosorbent was investigated and optimized using response surface methodology (RSM). Initially, the MMBC composite was synthesized and characterized by scanning electron microscopy (SEM) energy dispersive X-ray spectroscopy (EDX), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, and Brunauer-Emmett-Teller (BET) techniques. The characterization results confirmed the existence of Fe₃O₄ in the composite structure, which had uniformly dispersed over biochar (BC) with porous texture. Moreover, the presence of Zn and Cl elements in EDX analysis indicated that the magnetic biochar (MBC) had been modified successfully. The effects of chemical modification methods on the adsorption capacity of magnetic biochar were investigated. Maximum BTA removal efficiency was demonstrated by MMBC, modifying using ZnCl₂ (>99%). Optimization was carried out based on reaction time, BTA concentration and the concentration of adsorbent. Optimum experimental conditions for the removal of BTA from aqueous solutions were found to be 35 min of reaction time, 0.55 g/L of adsorbent, and 50 mg/L of initial BTA concentration. At these optimal conditions, the predicted BTA adsorption efficiency was 92.6%. The adsorption process followed the Avrami fractional-order reaction kinetic and the Langmuir adsorption isotherm with the maximum adsorption capacity of 563.1 mg/g. The values of thermodynamic parameters demonstrated that the adsorption of BTA on ZnCl₂-MBC is endothermic and spontaneous. Under optimum usage of MMBC, the adsorptive removal efficiency of BTA non-significantly decreased from 99.2 to 93.9% after the 5th cycle. Thus, MMBC can be recommended as an environmentally friendly and cost-effective adsorbent to remove micropollutants from water.

The electro-Fenton regeneration of Granular Activated Carbons: Degradation of organic contaminants and the relationship to the carbon surface

Electrochemical regeneration of Granular Activated Carbon is an emerging treatment option to restore adsorption capacity in systems designed to remove organic contaminants from aqueous solutions. The electro-Fenton process is one such electrochemical process and it is reviewed along with other members of its family including Photoelectro-Fenton and Heterogeneous electro-Fenton and electro-Fenton like reactions, for its ability to regenerate Granular Activated Carbons contaminated with organics. The behaviour of critical operating parameter such as pH, current, catalyst concentration and initial contaminant concentration are reviewed to find optimal operating conditions. The relationship between electro-Fenton regeneration and the chemical and physical surface of the carbon is also explored. Understanding regeneration mechanisms and the optimal operating conditions enables these technologies to be used commercially and to be scaled-up and treat contaminated waters more efficiently.

Green synthesis of ZnO coated hybrid biochar for the synchronous removal of ciprofloxacin and tetracycline in wastewater

Preparation of biochar from kaolinite and coconut husk (KCB) and further activated with HCl (KCB-A) and KOH (KCB-B) via a microwave technique for the remediation of ciprofloxacin (CIP) and tetracycline (TET) from water was carried out. Characterization using scanning electron microscopy, energy dispersive X-ray, Fourier transform infrared spectroscopy and X-ray diffraction showed the successful synthesis of functionalized biochars. Batch adsorption experiments demonstrated the potential of the adsorbents for fast and efficient removal of CIP and TET from solution. The adsorption capacities were found to be 71, 140 and 229 mg g⁻¹ for CIP and 118, 117 and 232 mg g⁻¹ for TET removal on KCB, KCB-A and KCB-B, respectively. For KCB, KCB-B and KCB-B, CIP adsorption best followed the pseudo second order kinetic model (PSOM), pseudo first order kinetic model (PFOM) and intraparticle diffusion (IDP) respectively. TET adsorption followed PSOM for KCB, IPD for KCB-B and PFOM for KCB-A. CIP adsorption on KCB, KCB-A and KCB-B best fit the Temkin, Langmuir and Brouers–Sotolongo isotherms, respectively, and TET adsorption on KCB best fit Brouers–Sotolongo while KCB-A and KCB-B best fit Langmuir–Freundlich. Adsorption of both contaminants was thermodynamically feasible showing that these materials are excellent adsorbents for the treatment of pharmaceuticals in water.

Preparation of biochar from kaolinite and coconut husk (KCB) and further activated with HCl (KCB-A) and KOH (KCB-B) via a microwave technique for the remediation of ciprofloxacin (CIP) and tetracycline (TET) from water was carried out.

Microscopic mechanism about the selective adsorption of Cr(VI) from salt solution on O-rich and N-rich biochars

The adsorption of Cr(VI) on biochars can be suppressed by coexisting anions, but the roles of O-containing functional groups and in particular N-containing functional groups are unclear. In this study, we combined spectroscopic and molecular simulation approaches to investigate the selective adsorption of Cr(VI) on the O-rich (PB, UB1) and N-rich (UB3, UB5) biochars under strong competition of anions. The elemental analysis and pyrolysis-gas chromatography/mass spectrometry indicated that the structures of PB and UB1 were similar, and so were the UB3 and UB5. Quantification of functional groups showed that for UB1, 75.3% of Cr(VI) removal was attributed to O-containing groups, while 53.3-72.7% of that was mediated by N-containing groups in UB3 and UB5. X-ray photoelectron spectra and density functional theory calculations confirmed that for O-rich biochars, surface complexation and strong H-bonds between carboxyl/hydroxyl and HCrO₄^- improved Cr(VI) removal in the presence of anions, while for N-rich biochars, Cr(VI) adsorption was depressed by coexisting anions in the order of Cl^->NO₃^- >SO₄^2- because of the weaker H-bond between protonated amino groups and HCrO₄^-. This study presents a novel approach for quantitative, molecular-level evaluation of the roles of biochar functional groups in the Cr(VI) removal from complex environmental systems.

Preparation of UiO-66-NH2 and UiO-66-NH2/sponge for adsorption of 2,4-dichlorophenoxyacetic acid in water

MOFs are usually used as efficient adsorbents to remove specific pollutants in water. However, because of their poor water stability relatively small particle size, their application in adsorbing and removing pollutants from water is limited. In this paper, with nitrile rubber sponge as the substrate, UiO-66-NH₂/sponge composites were firstly in-situ synthesized and systematically evaluated UiO-66-NH₂ as an adsorbent to remove 2,4-dichlorophenoxyacetic acid from water. This composite could not only remain the adsorption capacity for 2,4-dichlorophenoxyacetic acid of UiO-66-NH₂, but also was much more convenient for separation after the adsorption compared to UiO-66-NH₂. In addition, the mechanism of the adsorption of UiO-66-NH₂ for 2,4-dichlorophenoxyacetic acid were discussed in detail. Electrostatic interaction between UiO-66-NH₂ and 2,4-dichlorophenoxyacetic acid was the main adsorption mechanism. The adsorption was mainly suitable for Langmuir isotherm models, and its maximum adsorption capacity of 2,4-dichlorophenoxyacetic acid was 72.99 mg g^-1.

Key factors and microscopic mechanisms controlling adsorption of cadmium by surface oxidized and aminated biochars

Modified biochar has great potential for adsorbing cadmium (Cd) in the aquatic environment, but the micro-immobilization mechanisms, driven by surface modifications, remain unclear. There has been no attempt to determine the key adsorption factors by integrating the numerous physiochemical indicators. In this study, surface oxidized biochar (OPBC) and surface aminated biochar (APBC) were prepared from porous biochar (PBC), and the Cd adsorption mechanisms by the modified biochars at the molecular and electronic scales were investigated. The adsorption capacity of APBC and OPBC for Cd was 23.54 and 19.04 mg g^-1, respectively, which was about three times higher than that of PBC. Macroscopically, physicochemical adsorption and intraparticle diffusion dominated the Cd adsorption, and surface properties, such as functional groups, were identified as key factors controlling adsorption. Microscopically, the adsorption of Cd mainly occurred in regions rich in π electrons, lone pair electrons and electron donor groups. The interaction between carboxyl and Cd dominated the adsorption performance of OPBC, while the Cd²⁺-π interaction was weakened by increasing the π electron electrostatic potential of aromatic rings. The lone pair electrons of the amino groups dominated the complexation of APBC with Cd, and the π electron electrostatic potential was almost unaffected.

A Review of Non-Soil Biochar Applications

Biochar is the solid residue that is recovered after the thermal cracking of biomasses in an oxygen-free atmosphere. Biochar has been used for many years as a soil amendment and in general soil applications. Nonetheless, biochar is far more than a mere soil amendment. In this review, we report all the non-soil applications of biochar including environmental remediation, energy storage, composites, and catalyst production. We provide a general overview of the recent uses of biochar in material science, thus presenting this cheap and waste-derived material as a high value-added and carbonaceous source.

Activated Carbon from Yam Peels Modified with Fe3O4 for Removal of 2,4-Dichlorophenoxyacetic Acid in Aqueous Solution

The removal of organic pollutants from water sources can be enhanced using suitable adsorbents. The aim of this research was to study the adsorption capacity and potential reuse of a magnetic adsorbent prepared from agricultural wastes of yam peels (Dioscorea rotundata) for 2,4-dichlorophenoxyacetic (2,4-D) acid removal. The procedure was performed through carbonization and activation at 400 and 500 °C, respectively. Then, the as-prepared activated carbon (AC) was chemically modified using magnetite (Fe3O4) nanoparticles. The AC and magnetic activated carbon (MAC) were characterized and then used for batch adsorption and regeneration tests at different pH, initial concentrations of 2,4-D, and temperature. AC and MAC were showed to have microporous structures with surface areas of 715 and 325 m2/g, respectively. Superparamagnetic behavior was observed for MAC with a saturation magnetization of 6 emu/g. The results from the batch experiments showed higher adsorption capacity at high initial concentration of 2,4-D, low pH, and room temperature. The thermodynamic parameters indicated that the experiments proceeded as exothermic and spontaneous adsorption. Our findings also showed that MAC can be separated from the water medium through a facile magnetic procedure, and from regeneration experiments, MAC showed better results with 60% of its initial adsorption capacity after five cycles. Hence, MAC was found to be a promising alternative adsorbent of pesticides in water.

A simple method to improve the adsorption properties of drinking water treatment residue by lanthanum modification

The loading of La can substantially enhance the adsorption capability of drinking water treatment residue (DWTR) for better recycling. Normally, the modification was based on incubation of DWTR and La solution at a certain ratio, following by solid-liquid separation and drying processes. This study attempted to simplify La loading procedures by adopting high ratio of DWTR and La solution to eliminate the solid-liquid separation, aiming to promote the potential actual production. According to the results of the short- (2 d) and long-term (30 d) P adsorption tests, the N₂ gas sorption and desorption analysis, the X-ray photoelectron spectroscopy analysis, and the metal fractionation, the substantial enhanced adsorption capability of the modified DWTR was maintained and the La loading mechanisms to DWTR changed little after eliminating solid-liquid separation processes during modification; typically, La loading increased the initial P adsorption rates from 1.00 (raw DWTR) to 6.08 and 6.03 mg g^-1 d^-1 for the modified DWTR with and without the separation processes. Furthermore, the DWTR before and after modification had little unfavorable effect on the survival of snail Bellamya aeruginosa, while eliminating the separation processes tended to reduce the bioavailability of Al, Fe, and La in the modified DWTR. These results demonstrated that solid-liquid separation was not the key step for DWTR modification and that the developed simple modification method was feasible for La loading to DWTR, promoting the beneficial recycling in environmental remediation.

Coupling interaction between porous biochar and nano zero valent iron/nano α-hydroxyl iron oxide improves the remediation efficiency of cadmium in aqueous solution

Based on the interaction between mesoscopic biochar materials and nanomaterials, the synergistic mechanism of the two materials in the process of cadmium remediation was studied. K₂CO₃ activated porous biochar (KBC) loaded with nano-zero-valent iron (nZVI)/nano-α-hydroxy-iron oxide (nHIO) was studied. Macroscopically, batch adsorption experiments were carried out to describe the adsorption properties of the composites. Microscopically, the changes of surface chemical states were characterized by electron microscopy, XRD, FTIR and XPS. Combining the macroscopic and microscopic characteristics, the synergistic mechanism between biochar and nZVI/nHIO was comprehensively analyzed. The strong synergistic effects between biochar and nano-zero-valent iron (nZVI)/nano-α-hydroxy-iron oxide (nHIO) were found, which improved the removal efficiency of cadmium (Cd) in aqueous solution. The results showed that the loading of nZVI/nHIO reduced the specific surface area to 178.6 m² g^-1 and 272.2 m² g^-1, respectively, but the adsorption capacity of Cd increased to 22.37 mg g^-1 and 26.43 mg g^-1, respectively, which was more than three times that of KBC (7.02 mg g^-1). The interaction between nZVI/nHIO and Cd was enhanced by the complexation of surface functional groups, but the coupling effects were different. The coupling mechanism of Cd on nZVI@KBC was complexation - reduction. Cd was partly reduced in the removal process. While for nHIO@KBC, the existence of Fe (III) on the surface of biochar increased the number and species of oxygen-containing functional groups and enhanced complexation. The existence of synergistic mechanism will provide theoretical basis for the preparation of high efficient nanocomposites and expand the application of nanomaterials in the field of environment.

High-efficiency removal of Pb(II) and humate by a CeO2-MoS2 hybrid magnetic biochar

This work prepares a novel CeO₂-MoS₂ hybrid magnetic biochar (CMMB) for the adsorptive removal of Pb(II) and humate from aqueous solution. The CMMB was evaluated against magnetic biochar (MB). The results showed that CMMB exhibited strong magnetic separation ability. Hybridization of CMMB greatly improved Pb(II) and humate removal compared to MB, with >99% Pb(II) and humate removed within 6 h. Pb(II) and humate removal capacities of CMMB were 263.6 mg/g and 218.0 mg/g, respectively, with negligible influence of ion strength in the range of 0-0.1 mol/L NaNO₃. Pb(II) removal mechanism involved predominately with electrostatic attraction, Cπ-Pb(II) bond interaction, and surface adsorption and complexation combined processes; while pore-filling, partition effect and π-π interaction contributed to the adsorption of humate. Overall, the introduction of graphene-like MoS₂ materials into biochar benefits both of the biomass resources recovery and environmental protection.