Ecological and health risk assessments of heavy metals and their accumulation in a peanut-soil system.

Heavy metals pollution is a notable threat to environment and human health. This study evaluated the potential ecological and health risks of heavy metals (Cu, Cr, Cd, Pb, Zn, Ni, and As) and their accumulation in a peanut-soil system based on 34 soil and peanut kernel paired samples across China. Soil As and Cd posed the greatest pollution risk with 47.1% and 17.6% of soil samples exceeding the risk screen levels, respectively, with 26.5% and 20.6% of the soil sites at relatively strong potential ecological risk level, respectively, and with the geo-accumulation levels at several soil sites in the uncontaminated to moderately contaminated categories. About 35.29% and 2.94% of soil sites were moderately and severely polluted based on Nemerow comprehensive pollution index, respectively, and a total of 32.4% of samples were at moderate ecological hazard level based on comprehensive potential ecological risk index values. The Cd, Cr, Ni, and Cu contents exceeded the standard in 11.76, 8.82, 11.76 and 5.88% of the peanut kernel samples, respectively. Soil metals posed more health risks to children than adults in the order As > Ni > Cr > Cu > Pb > Zn > Cd for non-carcinogenic health risks and Ni > Cr â‰« Cd > As > Pb for carcinogenic health risks. The soil As non-cancer risk index for children was greater than the permitted limits at 14 sites, and soil Ni and Cr posed the greatest carcinogenic risk to adults and children at many soil sites. The metals in peanut did not pose a non-carcinogenic risk according to standard. Peanut kernels had strong enrichment ability for Cd with an average bio-concentration factor (BCF) of 1.62. Soil metals contents and significant soil properties accounted for 35-74% of the variation in the BCF values of metals based on empirical prediction models.

An Evaluation of the Corrosion Inhibition Performance of Chitosan Modified by Quaternary Ammonium Salt for Carbon Steel in Stone Processing Wastewater.

Chitosan was used as the raw material. A quaternization reaction was carried out between 2,3-epoxypropyltrimethylammonium chloride and water-soluble chitosan to prepare quaternary ammonium salt water-soluble chitosan (QWSC), and its corrosion inhibition performance against the corrosion of carbon steel in stone processing wastewater was evaluated. The corrosion inhibition efficiencies of QWSC on carbon steel in stone processing wastewater were investigated through weight loss, as well as electrochemical and surface morphology characterization techniques. The results show that QWSC has superior corrosion inhibition performance for A3 carbon steel. When an amount of 60 mL·L-1 is added, the corrosion inhibition efficiency can reach 59.51%. Electrochemical research has shown that a QWSC inhibitor is a mixed-type corrosion inhibitor. The inhibition mechanisms of the QWSC inhibitor revealed that the positive charge on the surface of carbon steel in stone wastewater was conducive to the adsorption of Cl- in the medium, which produced an excessive negative charge on the metal's surface. At the same time, the quaternary ammonium cation and amino cation formed in QWSC in stone processing wastewater can be physically absorbed on the surface of A3 carbon steel, forming a thin-film inhibitor to prevent metal corrosion.

Effect of biochar and iron ore tailing waste amendments on cadmium bioavailability in a soil and peanut seedling system.

Biochar and iron ore tailing waste have been widely separately applied for remediation of various contaminants, but the remediation effect of their combination on cadmium (Cd) pollution is unclear. In this study, the peanut biochar (BC), thermally activated iron ore tailing waste (TS), and the products of the co-pyrolysis of peanut shell and iron ore tailing waste (TSBC) were prepared for stabilizing Cd and reducing its bio-accessibility in soil and peanut seedling system. Present amendments enhanced soil pH, cation exchange capacity, electrical conductivity, and organic carbon content. The application of BC, TS, and TSBC led to decreases in acid-extractable Cd proportion of 2.2-8.81%, 2.43-7.20%, and 7.84-11.57%, respectively, and increases in the residual Cd proportion of 3.48-8.33%, 3.27-11.50%, and 9.02-13.45%, respectively. There were no significant differences in Cd accumulation in peanut roots due to three amendments treatments, especially at low Cd concentrations (i.e., Cd concentration of 0, 1, and 2 mg·kg-1), and with a relatively small reduction (2.16-9.05%) in root Cd accumulation under the high Cd treatments of 5 and 10 mg·kg-1. The Cd concentrations in seedling roots were significantly positively related to the acid-extractable Cd fraction, with a Pearson correlation coefficient of r = 0.999. The maximum toxicity mitigating effects were found in TSBC treatment, with increases in the ranges of 9.80-17.58% for fresh weight, 5.59-14.99% for dry weight, 5.16-10.17% for plant height, 5.96-10.34% for root length, 5.43-21.67% for chlorophyll a content, 17.17-71.28% for chlorophyll b content, and 13.11-39.60% for carotenoid content in peanut seedlings. Therefore, TSBC is a promising amendment for minimizing Cd contamination in peanut crops and utilizing industrial solid waste materials efficiently.

Study on the enhancement of citric acid chemical leaching of contaminated soil by modified nano zero-valent iron.

This study aimed to evaluate the effect of modified nanoscale zero-valent iron (SAS-nZVI) on chemical leaching of lead and cadmium composite contaminated soil by citric acid (CA). The synthesized SAS-nZVI was used as a leaching aid to improve the removal rate of soil heavy metals (HMs) by CA chemical leaching. The effects of various factors such as SAS-nZVI dosage, elution temperature and elution time were studied. At the same time, the effect of chemical leaching on the basic physical and chemical properties of soil and the morphology of HMs was evaluated. The results show that when the SAS-nZVI dosage is 2.0 g/L, the leaching temperature is 25 °C, and the leaching time is 720 min, the maximum removal rates of Pb and Cd in the soil are 77.64% and 97.15% respectively. The experimental results were evaluated using elution and desorption kinetic models (Elovich model, double constant model, diffusion model). The elution and desorption process of Pb and Cd in soil by SAS-nZVI-CA fitted well with the double-constant model, indicating that the desorption kinetic process of Pb and Cd is a heterogeneous diffusion process, and the elution process is controlled by diffusion factors. After leaching with SAS-nZVI-CA, the physical and chemical properties of the soil changed little, the mobility and toxicity of HMs in the soil were reduced, and the HMs content in the leaching waste liquid was reduced. It can be concluded that SAS-nZVI enhances the efficiency of CA in extracting Pb and Cd from soil, minimizes soil damage resulting from chemical leaching technology, and alleviates the challenges associated with treating leaching waste liquid.

Assessment soil cadmium and copper toxicity on barley growth and the influencing soil properties in subtropical agricultural soils.

Evaluation joint cadmium (Cd) and copper (Cu) phytotoxicity in wide range of subtropical agricultural soils is highly vital for phytoremediation of soils contaminated with Cd and Cu. In this study, barley root elongation assays were performed in 30 representative soils in response to single and combined Cd and Cu inhibition. The single Cd caused nearly 50% inhibition of barley root elongation, and Cu induced more than 50% inhibition in most soils. Mixed Cd + Cu caused significant inhibition on barley growth with average relative root elongation values of 20.0% and 30.4% in soil with a pH < 7 and pH > 7, respectively. An antagonistic interaction was evaluated in combined Cd + Cu toxicity, which was strong in soils containing low soluble Cu and Cd contents. Soil pH was the controlling factor in predicting single and mixed Cd and Cu phytotoxicity, which could explain 44% and 46% variation of single Cd and Cu toxicity, respectively. Soil organic carbon and effective cation exchange capacity were another important factor positively influencing metal toxicity, which further improved empirical prediction models accuracy, with determined coefficient (r2) values of 0.44-0.84. These results provide a theoretical basis for soils Cd and Cu pollution control.

Degradation of 2,4-DCP by immobilized laccase on modified biochar carrier.

Rape straw was used as the raw material for the biochar in this study, which was then changed using acid, alkali, and magnetic techniques. The laccase was attached using the adsorptions-crosslinking process, and the three modified biochars served as the carriers. The ideal circumstances for laccase immobilization were explored, and both biochar and immobilized laccase's characteristics were examined. The removal of 2,4-dichlorophenol (2,4-DCP) by immobilized laccase from modified biochar and its degradation products were researched. The main conclusions are as follows: the optimal concentration of glutaraldehyde (GLU) was 4%, and the pH was four, and the enzyme dosage was 1.75 mg/mL for the immobilized laccase of acid-modified biochar (SBC@LAC). The optimal concentration of GLU was 5%; the pH was four, and the enzyme dosage was 2 mg/mL for immobilized laccase from alkali-modified biochar (JBC@LAC). The optimal concentration of GLU was 5%; the pH was four, and the enzyme dosage was 1.75 mg/mL for immobilized laccase from magnetically modified biochar (CBC@LAC). SEM images could show the changes in the surface morphology of biochar caused by three modification methods. The BET results demonstrated that acid and magnetic modification increased the specific surface area of biochar, and alkali modification mainly expanded the pore size of biochar. FT-IR and XRD showed that modification and laccase loading had little effect on the structure of biochar. The stability of immobilized laccase was better than that of free laccase in acid-base, heat, and storage. Among the three modified biochar immobilized laccases, JBC@LAC showed the best acid-base stability and thermal stability, and the relative enzyme activity changed the least when pH and temperature conditions changed. The storage stability of SBC@LAC is the best. After 30 days of storage, the relative enzyme activity is still 83%. The removal rates of 2,4-DCP were 57, 99, and 63%, respectively, by SBC@LAC, JBC@LAC, and CBC@LAC. After five reuses, the removal rates of 2,4-DCP by SBC@LAC, JBC@LAC and CBC@LAC were 26, 42, and 27%, respectively. The intermediate products of 2,4-DCP degradation by immobilized laccase were p-phenol, p-benzoquinone and maleic acid.

Study on the removal of Pb(II) from water by coated sulfur-modified nanoscale zero-valent iron.

Being prepared by a liquid-phase reduction method, sulfur-modified nanoscale zero-valent iron (S-nZVI) was then coated with sodium alginate (SA) to form gel beads (SAS-nZVI) which are capable of removing Pb(II) from water. SAS-nZVI was characterized by SEM, EDS, FTIR, XRD, and BET, and its removal effect on Pb(II) in water, including the effects of pH, adsorbent dosage, shaking time, and initial concentration of lead, was also studied. The results demonstrated that the maximum removal efficiency of Pb(II) by SAS-nZVI was 97.89%, and the maximum uptake was 246.40 mg/g. In the Pb(II) removal behavior study, the pseudo-second-order kinetic model and the Langmuir isotherm model were found to fit the adsorption process well. SAS-nZVI was easier to recycle from the reaction system, and the removal efficiency of SAS-nZVI to Pb(II) in water was still able to reach 82.75% after five cycles. Therefore, this study suggests that SAS-nZVI has a high removal capacity for Pb(II) and great potential in water pollution treatment.

Ion exchange synthesis of copper-based hydroxyapatite for the catalytic degradation of phenol.

Hydroxyapatite (HAP) is a material renowned for its exceptional capabilities in adsorbing and exchanging heavy metal ions, making it a widely employed substance within the environmental domain. This study aims to present a novel material, namely copper-HAP (Cu-HAP), which was synthesized via an ion exchange method. The resulting material underwent comprehensive characterization using scanning electron microscopy, X-ray diffraction, Fourier-transform infrared spectroscopy, and Brunauer-Emmett-Teller (BET) analysis. Subsequently, based on the principle of the Fenton-like oxidation reaction, the material was used for the degradation of phenol. The outcomes of the investigation revealed that the optimal preparation conditions for the catalyst were achieved at a temperature of 40 °C, a pH value of 5, and a relative dosage of Cu-HAP at 100 mg/g. Under the reaction conditions of a catalyst dosage of 2 g/L, a 30% hydrogen peroxide concentration of 30 mM, a phenol concentration of 20 mg/L, a pH value of 6, a temperature of 40 °C, and the degradation rate of phenol impressively reached 98.12%. Furthermore, the degradation rate remained at 42.31% even after five consecutive cycles, indicating the promising potential of Cu-HAP in the treatment of recalcitrant organic compounds within this field.

Improved stability and promoted activity of laccase by One-Pot encapsulation with Cu (PABA) nanoarchitectonics and its application for removal of Azo dyes.

Immobilization of laccase helps protect the laccase and realizes repeated use. However, excessive encapsulation protection will also limit the release of laccase activity. This work introduces an effective one-pot method encapsulating laccase in the porous material of metal organic framework (MOF) containing specific metal ions, which provided a new way to solve the problem of limited laccase activity. The immobilization process was mathematically modeled. The morphological and encapsulated properties of the prepared materials were confirmed by the characterization results of SEM, FTIR, XRD, TGA, XPS and CLSM. The results showed that laccase was successfully encapsulated, and the Cu (PABA) with Cu2+ as the central structure promoted the laccase activity, the activity of immobilized laccase increased by 1.7 times. The prepared laccase@Cu (PABA) (Lac@Cu (PABA)) showed enhanced stability to extreme pH, high temperature and storage time. More importantly, the Lac@Cu (PABA) exhibited superior reusability, maintaining 70% removal rate of Direct Red 31 (DR31) even after 10 cycles. The dye removal rate of immobilized laccase reached 92% in 6 h under optimal conditions. This research improved the stability of laccase while releasing the activity of laccase, which not only broadened the applicable environment of laccase, but also increased the rate of degradation, and provided a new idea for the clean and efficient treatment of water pollution in textile industry.

Degradation of 2,4-DCP by the immobilized laccase on the carrier of sodium alginate-sodium carboxymethyl cellulose.

In this paper, sodium alginate-sodium carboxymethyl cellulose (SA-CMC) composite material was used as a carrier, and sodium alginate-embedded laccase (Lac@SC) was prepared by traditional embedding method. After that, ethylene glycol diglycidyl ether (EGDE) and glutaraldehyde (GLU) were used as cross-linking agents, two different cross-linking-embedded co-immobilized laccases (Lac@SCG and Lac@SCE) were innovatively prepared, respectively, and then these immobilized laccases were characterized by SEM, FT-IR and XRD, and the stability of the three immobilized laccases was explored. In addition, the effects of different factors on the removal of 2,4-DCP by immobilized laccase were studied, and the degradation kinetic models of three immobilized laccases on 2,4-DCP were summarized, the possible degradation pathways of pollutants were also given. Experimental results showed that compared to free laccase, the pH stability, thermal stability and storage stability of immobilized laccase were greatly improved. These immobilized laccases could maintain high activity at pH3~6, 45~55 °C. Lac@SCG had the best storage stability. After 30 days of storage, the relative enzyme activity was still more than 40%. Lac@SC had good reusability, the relative enzyme activity was still more than 50% after 5 uses. In the degradation of 2,4-DCP, all three immobilized laccases showed good performance, when Lac@SCE was at pH5, 35 °C, 25 h, the removal rate of 2,4-DCP could reach 95.2%; When at 45 °C, Lac@SC had the highest degradation rate which reach to 94%; At 45 °C, the degradation rate of Lac@SCG reached 83.2%.

A novel carbonized derivative of Fe-Cu bimetallic organic framework (Fe-Cu-MOF@C): preparation and optimization.

A carbon derivative with Fe-Cu bimetallic organic framework (Fe-Cu-MOF@C) was prepared by microwave synthesis and pyrolysis. Using potassium persulfate (PS) as oxidant and 2,4-dichlorophenol (2,4-DCP) as target pollutant, the optimal preparation conditions of Fe-Cu-MOF@C were studied. The factors affecting the synthesis of Fe-Cu-MOF include microwave power, microwave time, microwave temperature, the molar ratio of metal ions to organic ligands, the molar ratio of iron and copper, etc. In addition, the influence of pyrolysis temperature on the performance of Fe-Cu-MOF@C cannot be ignored. The results show that Fe-Cu-MOF@C has the best catalytic performance when the microwave time is 30 min, the microwave power is 600 W, the microwave temperature is 150 °C, the molar ratio of (Fe2+ + Cu2+)/H2BDC is 10:3, the molar ratio of Fe2+/Cu2+ is 10:1, and the pyrolysis temperature is 700 °C. After 90 min of reaction, 2,4-DCP was completely removed. Repeatable experiments show that Fe-Cu-MOF@C has good stability and its service life can be restored by heat treatment. In this study, a heterogeneous catalyst with strong catalytic capacity, high stability and easy recovery was prepared by a simple and efficient process, which is conducive to the development of advanced oxidation technology and the progress of water environmental protection.

Adsorption and removal of direct red 31 by Cu-MOF: optimization by response surface.

Cu(PABA) is a Cu-based MOF material assembled from Cu2+ and the organic ligand p-aminobenzoic acid (PABA). Cu (PABA) was synthesized by a solvothermal method, characterized and applied to the adsorption of direct red 31 dye (DR-31). The effects of pH, DR-31 concentration and temperature on the adsorption performance of Cu(PABA) were investigated. The adsorption kinetics were analyzed by pseudo-first-order, pseudo-second-order and intra-particle diffusion models, and the adsorption equilibrium data was fitted by Langmuir and Freundlich isotherm models. The pseudo-first-order kinetics and Langmuir model satisfactorily described the adsorption kinetics and adsorption equilibrium, respectively. The maximum adsorption capacity of Cu(PABA) for DR-31 dye at room temperature was 1,244.8 mg/g, as calculated using the Langmuir adsorption isotherm model. By response surface methodology (RSM), the optimal adsorption was found at pH value of 10.9, DR-31 dye concentration of 216.6 mg/L, and temperature of 27 °C, and the removal rate was as high as 99.4%. Therefore, Cu(PABA) can be used as an efficient adsorbent for removing DR-31 dye from aqueous solution.

The study of laccase immobilization optimization and stability improvement on CTAB-KOH modified biochar.

BACKGROUND: Although laccase has a good catalytic oxidation ability, free laccase shows a poor stability. Enzyme immobilization is a common method to improve enzyme stability and endow the enzyme with reusability. Adsorption is the simplest and common method. Modified biochar has attracted great attention due to its excellent performance. RESULTS: In this paper, cetyltrimethylammonium bromide (CTAB)-KOH modified biochar (CKMB) was used to immobilize laccase by adsorption method (laccase@CKMB). Based on the results of the single-factor experiments, the optimal loading conditions of laccase@CKMB were studied with the assistance of Design-Expert 12 and response surface methods. The predicted optimal experimental conditions were laccase dosage 1.78 mg/mL, pH 3.1 and 312 K. Under these conditions, the activity recovery of laccase@CKMB was the highest, reaching 61.78%. Then, the CKMB and laccase@CKMB were characterized by TGA, FT-IR, XRD, BET and SEM, and the results showed that laccase could be well immobilized on CKMB, the maximum enzyme loading could reach 57.5 mg/g. Compared to free laccase, the storage and pH stability of laccase@CKMB was improved greatly. The laccase@CKMB retained about 40% of relative activity (4 °C, 30 days) and more than 50% of relative activity at pH 2.0-6.0. In addition, the laccase@CKMB indicated the reusability up to 6 reaction cycles while retaining 45.1% of relative activity. Moreover, the thermal deactivation kinetic studies of laccase@CKMB showed a lower k value (0.00275 min- 1) and higher t1/2 values (252.0 min) than the k value (0.00573 min- 1) and t1/2 values (121.0 min) of free laccase. CONCLUSIONS: We explored scientific and reasonable immobilization conditions of laccase@CKMB, and the laccase@CKMB possessed relatively better stabilities, which gave the immobilization of laccase on this cheap and easily available carrier material the possibility of industrial applications.

Intrinsic soil property effects on Cd phytotoxicity to Ligustrum japonicum 'Howardii' expressed as different fractions of Cd in forest soils.

A better comprehensive understanding of the influence of soil/solution properties on cadmium (Cd) phytotoxicity is essential for soil Cd ecological risk assessment. The toxicity of soil spiked Cd to Ligustrum japonicum 'Howardii' seedling growth was conducted by the greenhouse pot experiments using 13 typical forest soils selected from mainland of China. The results showed that the ranges of Cd toxicity thresholds of 10% seedling growth inhibition (EC10) and 50% inhibition (EC50) followed the order: soil pore water Cd (EC10 on average 0.88 mg L-1 with the variation of 54.9 folds and EC50 on average 2.28 mg L-1 with variation of 41.8 folds), DTPA extractable Cd (EC10 on average 5.4 mg kg-1 with 20.9 folds variation and EC50 on average 17.86 mg kg-1 with 6.6 folds variation), total added Cd (EC10 on average 6.55 mg kg-1 with 16.7 folds variation and EC50 on average 22.11 mg kg-1 with 5.1 folds variation), which suggested that whatever the available Cd expressed, its toxicity is largely affected by soil properties. The empirical multiple equations were well developed between different fractions of Cd toxicity thresholds ECx (x = 10 or 50) and soil/solution. The results also showed that the pH inversely correlated with EC10 (r2 = 0.54, P < 0.01) and EC50 (r2 = 0.63, P < 0.001) based on soil pore water, indicating the ECx decreased with more toxicity as pH increased. No single significant soil solution properties were found for ECx in DTPA extractable Cd. For the ECx of DTPA extractable and total Cd, the content of aluminum oxides in soil and soil pH were the two significant factors inversely related with ECx, which explained 68%-79% of the inter-soil variation, respectively. Overall, soil or solution pH was the most important factor controlling Cd toxicity thresholds. Meanwhile, significant negative correlations existed between the soil solution pH and the slopes of parameter (b) of the dose-response curves for different fractions of Cd, implying that the growth of toxic effect enhanced as unit Cd dosage increased in low pH soils. These results will be helpful to evaluate the metal ecological risk in forest soils.

The study on adsorption behavior of 2,4-DCP in solution by biomass carbon modified with CTAB-KOH.

In this study, rice straw was used to prepare biomass carbon, which was modified with KOH and cetyltrimethylammonium bromide (CTAB) to obtain modified biomass carbon (MBC). The biomass carbon (BC) before and after modification was characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), thermogravimetric analysis (TGA) and Fourier transform infrared spectroscopy (FT-IR), and the surface morphology, crystal structure and surface group characteristic BC were explored. The specific surface area and micropores of the modified biomass carbon increased significantly, the crystallinity was higher, and the pore structure was more clearly found. The adsorption performance of MBC for 2,4-dichlorophenol (2,4-DCP) was investigated. The results showed that under the best adsorption conditions ((2,4-DCP concentration (200 mg/L), MBC dosage (50 mg), pH (5.5), and loading time (60 min), temperature (room temperature)), the removal rate of 2,4-DCP was up to 42.5%, and adsorption capacity was 85.13 mg/g. The adsorption of 2,4-DCP on MBC materials was better explained by the pseudo-second-order kinetic model and the Langmuir adsorption isotherm model. It was believed that the adsorption of 2,4-DCP by MBC was the monolayer adsorption process on the uniform surface of MBC at high concentration, and there was no interaction between the 2,4-DCP and MBC adsorbate during this process.

Migration of heavy metals and migration-degradation of phenanthrene in soil using electro kinetic-laccase combined remediation system.

In order to solve the problem of heavy metal-organic compound soil pollution, in this paper, we developed a highly efficient electro kinetic-laccase combined remediation (EKLCR) system. The results showed that the EKLCR system had an obvious migration effect on heavy metals (copper and cadmium) and good migration-degradation effect on phenanthrene. The migration rates of copper and cadmium were 48.3% and 40.3%, respectively. Especially, with the presence of laccase, the removal rate of phenanthrene on Cu2+-contaminated soil was higher than that of Cd2+-contaminated soil due to the significant effect of heavy metals on the enzymatic activity of laccase. The average migration-degradation rate of phenanthrene by EKLCR system was 45.4%. Finally, gas chromatography-mass spectrometry (GC/MS) was used to analyze the degradation intermediates of phenanthrene in the soil, which included 9,10-Phenanthrenequinone, phthalic acid, and 2,2-Biphenyldicarboxylic Acid. In addition, we give the possible degradation pathways of phenanthrene, 2,2-Biphenyldicarboxylic Acid is further degraded to produce phthalic acid. The products of the phthalic acid metabolic pathway are protocatechuic acid, pyruvic acid or succinic acid, the final products of these organic acids are carbon dioxide and water.

Effect of Direct-Current Electric Field on Enzymatic Activity and the Concentration of Laccase.

This work investigates the effect of direct-current electric field on the extracellular enzymatic activity, concentration and other experimental parameters of laccase from Trametes versicolor. The results showed that laccase could significantly contribute to the change of pH at the end of graphite electrode. In addition, it increased the electrical conductivity of the water. In the experiment, the optimum pH and catalytic pH range for laccase activity were 3.0 and pH 2.5-4.0. The application of 6 V direct current showed significant effects on the laccase enzyme activity. The activity of laccase was enhanced in the anodic region, but at the same time was strongly inhibited at the cathode. The electric charge characteristics of laccase were changed when exposed to electric field, and some laccases molecules moved to the anode, which produced a slight migration phenomenon. This study is the basis of combination of laccase and electrical technology, at the same time, providing a new direction of enhancing laccase activity. Compared to immobilization, using electric field is simple, no chemical additives, and great potential.

Effects of Ca2+ and Mg2+ on Cu binding in hydrophilic and hydrophobic dissolved organic matter fractions extracted from agricultural soil.

Dissolved organic matter (DOM) has significant effects on soil copper (Cu) bioavailability. However, little is known about Cu interactions and major cation binding toward hydrophilic and hydrophobic DOM components extracted from soil solutions. In this study, we investigated the influence of major cations (Ca2+/Mg2+) on Cu complexing characteristics on different hydrophilic and hydrophobic DOM fractions using absorbance spectroscopy at different Cu2+ concentrations in the absence/presence of Ca2+/Mg2+. Different compositional hydrophobic and hydrophilic DOM fraction proportions occurred at three agricultural soil sites, with the hydrophobic acid (HOA) fraction accounting for the highest proportion. The addition of Cu2+ generated distinct ultraviolet (UV) bands/peaks (processed by differential linear and differential logarithmic transformation) of three hydrophilic DOM fractions, whereas Cu2+ induced less and weak specific peaks in the differential spectra and differential logarithmic of the HOA fractions, indicating hydrophilic DOM fractions tend to have a higher density of Cu2+ complexation sites. In the presence of either Ca2+/Mg2+, increased depression caused by Cu2+ binding on different DOM fractions was observed with increasing 10, 100, and 1000 µM Ca2+/Mg2+ levels, with more significant variations in peaks/banks for hydrophilic base (HIB) and HOA fractions, and less for hydrophilic acid (HIA) and hydrophilic neutral (HIN) fractions. In our study, the spectral parameters ΔS225-275 and ΔS275-325 were successfully used to quantify Cu amounts bonded to HIA and HIB, respectively. They exhibited strong linear relationships with correlation coefficients (R2) of 0.96 for HIA and 0.87 for HIB, respectively. Furthermore, Mg2+ exhibited stronger competition with Cu for HIA and HIB binding sites when compared with Ca2+.

Effective immobilization of bisphenol A utilizing activated biochar incorporated into soil: combined with batch adsorption and fixed-bed column studies.

This study presented the mixture of biochar and soil for removal of bisphenol A (BPA) to assess environmental remediation ability. Using phoenix tree leaves as biomass and phosphoric acid as activator, after one-step hydrothermal and short-term activation, the eventual solid product was phosphoric acid hydrothermal activated carbon (HPC). The characterizations showed that HPC had the high specific surface (994.21 m2·g-1), and large unsaturated esters and hydroxyl groups. The saturated adsorption capacities of batch and column adsorption for the addition of 0.5% HPC to soil were 0.790 mg·g-1 and 67.23 mg·kg-1, while to the natural soil were 0.236 mg·g-1 and 8.75 mg·kg-1, respectively. The adsorption kinetics and thermodynamic analysis indicated that the adsorption process utilizing HPC incorporated into soil was a chemical reaction rate-controlled, physical-dominated multilayer adsorption, and spontaneous endothermic. Also, batch adsorption experiments and analysis were performed under different pH levels, HPC contents, organic acid concentrations, and cationic strengths. Successively, fixed-bed column experiments were carried out with and without the HPC; the results showed that the wide mass transfer zone led to the effective fixation of BPA, and the organic acid had no obvious effect on the fixation of BPA when the 1.0% HPC mixed with soil. Finally, through characterizations and data analysis, the enhanced adsorption of BPA by HPC mixed with soil mainly relied on π-π interaction, hydrogen bonding, followed by electrostatic attraction and pore filling.

Study on the migration behaviour of heavy metals at the improved mine soil-plant rhizosphere interface.

With the increasing shortage of land resources and the aggravation of soil pollution in mining areas, the remediation of soil in abandoned mining areas has gradually attracted people's attention. The remediation of heavy metal contaminated soil in mining areas is the key to reduce the harm of heavy metals to the environment and human health. In this study, municipal sludge and phytoremediation technology were combined to investigate the migration and transformation of heavy metals at the soil-plant interface in improved mining areas through indoor pot experiments. The results showed that heavy metals in non-rhizosphere soil entered the rhizosphere environment with the growth of plants, leading to the increase of heavy metal content in rhizosphere soil. The cumulative amounts of Cu, Zn, Pb and Cd were 1299.32, 832.10, 347.89 and 71.34 mg/kg, respectively. The content of oxidized Cu and Zn decreased with increasing planting days, while the oxidized Pb and Cd showed an increasing trend. Under acidic conditions, H+ is easy to compete with heavy metal ions for exchangeable positions in the clay mineral layer, so that the reducible heavy metals are easy to be converted into exchangeable states. In this paper, the effects of various factors on the distribution of heavy metals were discussed by adjusting soil pH, adding humic acid and root exudates, so as to analyse the migration and transformation mechanism of heavy metals at the soil-plant interface, and provide a reliable theoretical basis for soil remediation in mining areas.