Sodium salt promoted the generation of nano zero valent iron by carbothermal reduction: For activating peroxydisulfate to degrade antibiotic.

Carbothermal reduction is a promising method for the industrial preparation of nano-zero-valent iron. Preparing it also involves very high pyrolysis temperatures, which leads to a significant amount of energy consumption. The temperature required for the preparation of nano-zero-valent iron by carbothermal reduction was reduced by 200 °C by the addition of sodium salt. Carbon-loaded nano zero-valent iron (Fe0/CB-Na) was prepared by carbothermal reduction through the addition of sodium salt. The results showed that Fe0/CB-Na@700 had the same activation performance as Fe0/CB@900 and the newly prepared nano-zero-valent iron. The addition of sodium salt promoted the transfer of oxygen from the iron oxide to the carbon structure during the roasting process so that the iron oxide was reduced to as much Fe0 as possible. Thus, sodium salts were optimized for the preparation of nano-zero-valent iron by carbothermal reduction through interfacial amorphization and oxygen transfer, thus reducing the preparation cost.

Selective removal of oxytetracycline by molecularly imprinted magnetic biochar.

Molecularly imprinted magnetic biochar (MBC@MIPs) was synthesized through molecular imprinting precipitation polymerization. This material demonstrated a selective adsorption capacity of oxytetracycline (OTC) from water samples. Upon characterization of MBC@MIPs, results revealed the formation of a memory cavity shell layer on the magnetic biochar's surface, exhibiting a distinctive recognition effect alongside commendable magnetic and thermal stability. Analysis of the adsorption kinetics indicated that the OTC adsorption process aligned well with the pseudo-second-order rate equation, with chemisorption acting as the predominant mechanism for antibiotic adsorption onto MBC@MIPs. The data could be well described by the Langmuir isotherm model. At 299 K, MBC@MIPs showed a maximum binding capacity of 67.89 mg·g-1, surpassing that of MBC (38.84 mg·g-1) by 1.77 times. MBC@MIPs exhibited the highest selectivity towards OTC, with an imprinting factor (IF) of 5.64. Even amidst interference from antibiotics, MBC@MIPs maintained a significant adsorption capacity for OTC (6.10 mg·g-1), with IF of 6.70.

Effect and mechanism of norfloxacin removal by Eucalyptus leaf extract enhanced the ZVI/H2O2 process.

The conventional ZVI/H2O2 technology suffers from poor reagent utilization, excess iron sludge generation, and strong low pH dependence. Therefore, eucalyptus leaf extract (ELE) was introduced to improve ZVI/H2O2 technology, and the efficacy and mechanism of ELE promoting ZVI/H2O2 technology were deeply explored. The results showed that the norfloxacin (NOR) removal and kobs of the ZVI/H2O2/ELE process were enhanced by 35.64 % and 3.27 times, respectively, compared to the ZVI/H2O2 process. In the ZVI/H2O2 process, the production of three reactive oxygen species (ROS: 1O2，·O2-，·OH) was effectively promoted by ELE so that the reaction efficacy was significantly enhanced. Moreover, the attack and degradation of pollutants by ROS was the main way to remove pollutants. With the introduction of ELE, the reactive sites on the catalyst appearance were increased to some extent, and the Fe(III)/Fe(II) cycle was improved. The analysis showed that ELE is rich in titratable acids and the ZVI/H2O2 technology is promoted mainly by lowering the pH of the process. In addition, the chelation of ELE and the reduction in pH by the ELE synergistically enhanced the ZVI/H2O2 technology, which significantly improved the reagent utilization (4.70 times for ZVI and 3.03 times for H2O2), broadened the pH range of the technology (6-9) and was able to effectively reduce the iron sludge contamination (30.33 %) of the process. Therefore, the study offers an important value to study eucalyptus leaves in micron-scale ZVI-Fenton technology.

Rapid removal of decabromodiphenyl ether by mechanochemically prepared submicron zero-valent iron with FeC2O4·2 H2O layers: Kinetics, mechanisms and pathways.

The utilization of nano zero-valent iron (nZVI) in polybrominated diphenyl ethers remediation has been studied extensively. However, challenges in balancing cost and reactivity have been encountered. A submicron zero-valent iron coated with FeC2O4·2 H2O layers (OX-smZVI) was synthesized via a mechanochemical method, aiming to resolve this contradiction. Characterization via SEM, TEM, and XPS confirmed the structure as FeC2O4·2 H2O coated iron lamellate with a surface area 24-fold higher than ball-milled zero-valent iron (smZVI). XRD highlighted an Fe/C eutectic in OX-smZVI, boosting its electron transfer capacity. Decabromodiphenyl ether degradation by OX-smZVI follows a two-stage process, with initial degradation by FeC2O4·2 H2O and a subsequent phase dominated by electron transfer. OX-smZVI exhibits a 4.52-34.40 times faster BDE209 removal rate than nZVI and scaled-up OX-smZVI displayed superior reactivity with preparation costs only 1/680 of nZVI. Given its enhanced reactivity and cost-efficiency, OX-smZVI emerges as a promising replacement for nZVI.

Lanthanum-doped magnetic biochar activating persulfate in the degradation of florfenicol.

In this study, lanthanum-doped magnetic biochar (LaMBC) was synthesized from bagasse by co-doping iron salt and lanthanum salt, and it was characterized for its application in the activation of persulfate (PS) in the degradation of Florfenicol (FLO). The results indicated that the LaMBC/PS system consistently achieved a degradation efficiency of over 99.5 %, with a reaction rate constant 4.71 times as that of MBC. The mechanism of FLO degradation suggested that O2•- and •OH played dominant roles, contributing 40.92 % and 36.96 %, respectively, during FLO degradation. Through physicochemical characterization and quenching experiments, it can be concluded that the key reasons for the enhancement of MBC activation performance are as follows: (1) Lanthanum doping in magnetized biochar increased the Fe(II) content in MBC. (2) Lanthanum doping significantly improved the adsorption capacity of LaMBC, increased the concentration of pollutants on the catalyst surface and effectively enhancing the reaction rate. (3) Lanthanum doping effectively increased the surface Fe(II) content during the reaction process in LaMBC, promoted the generation of active oxygen species in PS. This study delves into synthesizing and applying LaMBC for PS activation and FLO removal. The emphasis is on comprehensively characterizing and experimenting to elucidate the mechanism, proposing an innovative approach for efficiently degrading antibiotic wastewater.

Double-edged effect of frequent freeze-thaw on the stability of zero-valent iron after heavy metal remediation.

Freeze-thaw cycles (FTCs) cause dynamic microscale changes in ions and solvents. During freezing, heavy metals adsorbed on zero-valent iron (M-ZVI) and protons are excluded by ice crystals and concentrated in the liquid-like grain boundary region. The high proton concentration in this region leads to the dissolution of the passivation layer of ZVI. To assess the environmental risks of M-ZVI during FTCs, this study evaluated the stability of M-ZVI in this scenario from both microscale and macroscale perspectives. The results showed that the dissolution of the passivation layer had a dual effect on the stability of M-ZVI, which depends on the by-products of M-ZVI. The dissolution of the passivation layer was accompanied by the leaching of heavy metals, such as Ni-ZVI, but it also enhanced the reactivity of ZVI, causing it to re-react with desorbed heavy metals. The stability of Cr-ZVI and Cd-ZVI was improved due to frequent FTCs. Furthermore, changes in the surrounding environment (water dipole moment, ion concentration, etc.) of ZVI affected the crystallization of Fe oxides, increasing the content of amorphous Fe oxide. As low-crystallinity Fe oxides could facilitate ion doping, Ni2+ was doped into Fe3O4 lattice during FTCs, which reduced the mobility of heavy metals. Contrary to traditional views that freezing temperatures slow chemical reactions, this study provides new insights into the application of iron-based materials in cold environments.

Nitrogen-rich magnetic biochar prepared by urea was used as an efficient catalyst to activate persulfate to degrade organic pollutants.

In order to fully exploit the potential of magnetic biochar-based persulfate (PS) systems, N was utilized to modify the magnetic biochar-based catalysts through impregnation-pyrolysis method. A typical antifungal drug, metronidazole (MNZ), is selected as the target pollutant to score the reactivity of as-synthetic nitrogen-rich magnetic biochar (NMBC) catalysts. In the modified system, 99.6% of MNZ was removed, 13.6 times of that in the unmodified system. Active radical verification experiments showed that 1O2 was the key active radical. Various characterization showed that the nitrogen-rich significantly improved the persistent free radical, defect degree, content of oxygen-containing groups, electrochemical conductivity and other catalytic activity related properties. Physicochemical characterization, Fe(II) semi-quantitative analysis and masking experiments confirmed that the doping of magnetic biochar with nitrogen increased its Fe(II) content (23.79 mg/g), approximately 2.6 times higher than that of pristine magnetic biochar. Moreover, N induces strong electron accretion of Fe atom through coordination bond, which leads to the increase of electron density on the Fe atom, which increases the content of Fe (II) in the material, thus improving the ability of the material to activate PS to generate 1O2, and promoting the degradation reaction of MNZ. This paper provides a method to improve the activation performance of magnetic biochar.

Single/co-adsorption and mechanism of methylene blue and lead by ß-cyclodextrin modified magnetic alginate/biochar.

Due to the high biological toxicity, the concurrent elimination of lead (Pb (II)) and methylene blue (MB) has become a challenging problem. Therefore, a newly ß-cyclodextrin (ß-CD) modified magnetic alginate/biochar (ß-CD@MBCP) material was developed. Comprehensive characterizations proved the successful coating of ß-CD onto MBCP surface by microwave-aided fabrication. The ß-CD@MBCP achieved high-efficiency uptake for contaminants under a wide pH scope. In the dual system, Pb (II) elimination was facilitated with the presence of MB, due to the active sites provided by MB. In the presence of Pb (II), MB uptake was inhibited due to the electrostatic repulsion between positively charged MB and Pb (II). Electrostatic attraction and complexation contributed to capturing Pb (II), while π-π interactions, host-guest effect, and H-bonding were important in MB elimination. After four cycles, ß-CD@MBCP maintained comparatively good renewability. Findings demonstrated that ß-CD@MBCP could be an effective remediation material for Pb (II)/MB adsorption from aqueous environments.

Simultaneous remediation of co-contaminated soil by ball-milled zero-valent iron coupled with persulfate oxidation.

The problem of co-contaminated soil at e-waste dismantling sites is serious and constitutes a critical threat to human health and the ecological environment. Zero-valent iron (ZVI) has been proven to be effective in the stabilization of heavy metals and the removal of halogenated organic compounds (HOCs) from soils. However, for the remediation of co-contamination of heavy metals with HOCs, ZVI has disadvantages such as high remediation cost and inability to take into account both pollutants, which limits its large-scale application. In this paper, boric acid and commercial zero-valent iron (cZVI) were used as raw materials to prepare boric acid-modified zero-valent iron (B-ZVIbm) through a high-energy ball milling strategy. B-ZVIbm coupled with persulfate (PS) to achieve simultaneous remediation of co-contaminated soil. The synergistic treatment of PS and B-ZVIbm resulted in the removal efficiency of 81.3% for decabromodiphenyl ether (BDE209) and the stabilization efficiencies of 96.5%, 99.8%, and 28.8% for Cu, Pb, and Cd respectively in the co-contaminated soil. A series of physical and chemical characterization methods showed that the oxide coat on the surface of B-ZVIbm could be replaced by borides during ball milling. The boride coat facilitated the exposure of the Fe0 core, promoted the corrosion of ZVI and the orderly release of Fe2+. The analysis of the morphological transformation of heavy metals in soils revealed that most of the heavy metals in the exchangeable, carbonate-bound state were transformed into the residue state, which was the key mechanism for the remediation of heavy metal-contaminated soils with B-ZVIbm. The analysis of BDE209 degradation products showed that BDE209 was degraded to lower brominated products and further mineralized by ZVI reduction and free radical oxidation. In general, B-ZVIbm coupled with PS is a good recipe for synergistic remediation of co-contaminated soils with heavy metals and HOCs.

Effect of Mn-based magnetic biochar /PS reaction system on oxidation of metronidazole.

In order to fully exploit the potential of magnetic biochar-based persulfate (PS) systems, Mn was utilized to modify the magnetic biochar-based catalysts through impregnation-pyrolysis method. Taking metronidazole (MNZ), a typical antifungal drug, as the target contaminant, the reactivity of the synthesized magnetic biochar (MMBC) catalyst was evaluated. The degradation efficiency of MNZ in MMBC/persulfate system was 95.6%, which was 13.0 times higher than that in MBC/PS system. The characterization experiments confirmed the degradation of metronidazole by surface binding free radicals, the ·OH and 1O2 played the key role in remove of MNZ in the system of MMBC/PS. Physicochemical characterization, Fe(II) semi-quantitative analysis and masking experiments confirmed that the doping of MBC with Mn increased its Fe(II) content (43.0 mg/g), approximately 7.8 times higher than that of pristine MBC. The increase of Fe(II) content in MBC is the key reason to improve the optimization of MBC modified with Mn. Simultaneously, both Fe(II) and Mn(II) were the key components of PS activation by magnetic biochar. This paper presents a method to optimize the high efficiency of PS activation by magnetic biochar.

Remediation of polybrominated diphenyl ethers contaminated soil in the e-waste disposal site by ball milling modified zero valent iron activated persulfate.

Hydrophobic organic compounds (HOCs) in e-waste disposal sites are difficult to remove effectively. There is little reported about zero valent iron (ZVI) coupled with persulfate (PS) to achieve the removal of decabromodiphenyl ether (BDE209) from soil. In this work, we have prepared the flake submicron zero valent iron by ball milling with boric acid (B-mZVIbm) at a low cost. Sacrifice experiments results showed that 56.6% of BDE209 was removed in 72 h with PS/B-mZVIbm, which was 2.12 times than that of micron zero valent iron (mZVI). The morphology, crystal form, atomic valence, composition, and functional group of B-mZVIbm were determined by SEM, XRD, XPS, and FTIR, and the results indicated that the oxide layer on the surface of mZVI is replaced by borides. The results of EPR indicated that hydroxyl radical and sulfate radical played the dominant role in the degradation of BDE209. The degradation products of BDE209 were determined by gas chromatography-mass spectrometry (GC-MS), accordingly, the possible degradation pathway was further proposed. The research suggested that ball milling with mZVI and boric acid is a low-cost means of preparing highly active zero valent iron materials. And the mZVIbm has promising applications in improving the activation efficiency of PS and enhancing the removal of the contaminant.

Effect and mechanism of norfloxacin removal by guava leaf extract in the ZVI/H2O2 system.

To overcome the bottlenecks of the conventional zero-valent iron Fenton-like (ZVI/H2O2) process, such as low reagent utilization, low applicable pH, and iron sludge contamination, guava leaf extract (GLE) was used as a green promoter to enhance ZVI/H2O2 process in this study. Compared with the ZVI/H2O2 system, the removal rate and kobs of norfloxacin by the ZVI/H2O2/GLE system were increased by 33.76% and 2.19 times, respectively. The experimental investigation of the mechanism showed that the attack of reactive oxygen species was the main pathway for the removal of pollutants, and three types of reactive oxygen species (1O2, O2-,·OH) generations in the ZVI/H2O2/GLE system were effectively promoted by the introduction of GLE. The reactivity improvement was mainly due to the decrease of pH. At the same time, the chelation of iron ions by GLE promoted the Fe(III)/Fe(II) cycle on the catalyst surface was also a minor mechanism to improve the reactivity. This study provides a crucial reference for the practical application of guava leaf to promote the ZVI/H2O2 process in environmental pollution control.

Effects of Pretreatment and Polarization Shielding on EK-PRB of Fe/Mn/C-LDH for Remediation of Arsenic Contaminated Soils.

In this study, coupling electrokinetic (EK) with the permeable reactive barriers (PRB) of Fe/Mn/C-LDH composite was applied for the remediation of arsenic-contaminated soils. By using self-made Fe/Mn/C-LDH materials as PRB filler, the effects of pretreatment and polarization shielding on EK-PRB of Fe/Mn/C-LDH for remediation of arsenic contaminated soils were investigated. For the pretreatment, phosphoric acid, phosphoric acid and water washing, and phosphate were adopted to reduce the influence of iron in soil. The addition of phosphate could effectively reduce the soil leaching toxicity concentration. The removal rate of the soil pretreated with phosphoric acid or phosphoric acid and water washing was better than with phosphate pretreatment. For the polarization shielding, circulating electrolyte, electrolyte type, anion and cation membranes, and the exchange of cathode and anode were investigated. The electrolyte circulates from the cathode chamber to the anode chamber through the peristaltic pump to control the pH value of the electrolyte, and the highest arsenic toxicity removal rate in the soil reaches 97.36%. The variation of total arsenic residue in soil using anion and cation membranes is the most regular. The total arsenic residue gradually decreases from cathode to anode. Electrode exchange can neutralize H+ and OH- produced by electrolyte, reduce the accumulation of soil cathode area, shield the reduction of repair efficiency caused by resistance polarization, enhance current, and improve the removal rate of arsenic in soil.

Sophorolipid modification enables high reactivity and electron selectivity of nanoscale zerovalent iron toward hexavalent chromium.

Nanoscale zero-valent iron is considered to be a promising nanostructure for environmental remediation, while increasing the electron selectivity of nanoscale zerovalent iron (nZVI) during target contaminant removal is still a challenge (electron selectivity, defined as the percentage of electrons transferred to the target contaminants over the number of electrons donated by nZVI). In this study, the strategy for increasing the reactivity and electron selectivity of nZVI via sophorolipid (SL-nZVI) modification was proposed. The results showed that the removal efficiency and electron selectivity of SL-nZVI toward Cr(VI) was 99.99% and 56.30%, which was higher than that of nZVI (61.16%, 25.91%). Meanwhile, the particles were well characterized and the mechanism for enhanced reactivity and electron selectivity was investigated. Specially, both the morphology and BET specific surface area characterization suggested that stability against aggregation was higher in SL-nZVI nanoparticles than in nZVI. Besides, X-ray photoelectron spectroscopy (XPS), Tafel polarization curves, and Electrochemical impedance spectroscopy also indicated that the introduction of sophorolipid successfully prevent the nanoparticles from oxidation and benefit the electron transferring. In addition, a water contact angle test revealed that SL-nZVI nanoparticles were less hydrophilic (contact angle = 34.8°) than nZVI (contact angle = 23.9°). Therefore, in terms of reactivity, sophorolipid modification inhibited the aggregation of the nanoparticles and enhanced the electrical conductivity. For electron selectivity, the introduction of sophorolipid not only benefited Cr(VI) adsorption and the electron transfer from Fe0 to the surface-adsorbed Cr(VI) that followed but also reduced the possibility of side reactions between Fe0 and H2O. This study demonstrates that the introduction of sophorolipid is an effective strategy for developing a highly efficient nZVI-based nanocomposite system and highlights the potential role of sophorolipid in improving the electron selectivity of nZVI.

Effective immobilization of Cd(II) in soil by biotic zero-valent iron and coexisting sulfate.

In this work, zero-valent iron (ZVI) combined with anaerobic bacteria was used in the remediation of Cd(II)-polluted soil under the mediation of sulfate (SO42-). Owing to hydrogen-autotrophic sulfate reduction, serious corrosion occurred on sulfate-mediated biotic ZVI in terms of solid phase characterization as massive corrosive products (e.g., goethite, magnetite and green rust) were formed, which were crucial in the immobilization of Cd(II). Thus, this integrated system achieved a 4.9-fold increase in aqueous Cd(II) removal and converted more than 53% of easily available Cd(II)-fractions (acid-extractable and reducible) to stable forms (oxidizable and residual) based on the sequential extraction results as compared to the sulfate-mediated ZVI system. Increasing SO42- concentration and ZVI dosage both demonstrated positive correlation to Cd(II) immobilization, which further reflected that hydrogenotrophic desulfuration acted an essential role in improving Cd(II) immobilization. It indicated that hydrogenotrophic desulfuration could accelerate iron corrosion and promote reactive mineral formation through biomineralization, as well as generate cadmium sulfide precipitates (CdS) to achieve excellent immobilization performance for Cd(II). Besides, this reaction was favorable under neutral pH condition. Our results highlighted the promoted effect of hydrogen-autotrophic desulfuration on ZVI corrosion to immobilize Cd(II) and offered a practicable technique in Cd(II)-polluted soil remediation.

Remediation of cadmium or arsenic contaminated water and soil by modified biochar: A review.

Biochar has a high specific surface area with abundant pore structure and functional groups, which has been widely used in remediation of cadmium or arsenic contaminated water and soil. However, the bottleneck problem of low-efficiency of pristine biochar in remediation of contaminated environments always occurs. Nowadays, the modification of biochar is a feasible way to enhance the performance of biochar. Based on the Web of science™, the research progress of modified biochar and its application in remediation of cadmium or arsenic contaminated water and soil have been systematically summarized in this paper. The main modification strategies of biochar were summarized, and the variation of physicochemical properties of biochar before and after modification were illustrated. The efficiency and key mechanisms of modified biochar for remediation of cadmium or arsenic contaminated water and soil were expounded in detail. Finally, some constructive suggestions were given for the future direction and challenges of modified biochar research.

Impacts of anions on activated persulfate oxidation of Fe(II) - Rich potassium doped magnetic biochar.

The potassium-doped magnetic biochar (KMBC) preparation was inevitably introduced the different anions in the process of modifying magnetic biochar (MBC) with different potassium salts, but the effect and mechanism of different anion on KMBC activation properties has not been reported. Therefore, in this paper, five different KMBCs were prepared using several common potassium salts under the same dosage of K+ and Fe2+, and then was added in the presence of persulfate (PS) for the removal of metronidazole (MNZ). The removal rate of metronidazole was ordered as KMBCK2SO4 (98.40%) > KMBCKNO3 (76.84%) > KMBCKCl (20.79%) > KMBCK2CO3 (19.02%) > KMBCK2C2O4 (14.23%). However, the semi-quantitative of Fe(II) experiments results confirmed that the effectively increase of Fe(II) content by potassium salts modification played the dominant role in improvement of KMBC activation performance. The Fe(II) content of KMBC were ordered as KMBCK2CO3 > KMBCK2SO4 > KMBCKNO3 > KMBCKCl > KMBCK2C2O4, with the Fe(II) content of KMBC of 36.74, 17.70, 8.79, 5.24 and 4.85 mg/g, respectively. The indicated that the introduction of different anions would lead to different optimal Fe(Ⅱ) content in KMBC modified with different potassium salts, which was most directly reflected in 1O2 content in different KMBC/PS systems, and account for the difference in MNZ degradation efficiency. Meanwhile, when the Fe(II) content in KMBC reached the range of 13.7-28.8 mg/g, KMBC had the better performance of activating PS.

Enhanced Cd(II) immobilization in sediment with zero-valent iron induced by hydrogenotrophic denitrification.

In this study, an integrated system of Fe0 and hydrogenotrophic microbes mediated by nitrate (nitrate-mediated bio-Fe0, NMB-Fe0) was established to remediate Cd(II)-contaminated sediment. Solid phase characterization confirmed that aqueous Cd(II) (Cd(II)aq) was successfully immobilized and enriched on iron surface due to promoted iron corrosion driven by hydrogenotrophic denitrification and subsequent greater biomineral production such as magnetite, lepidocrocite and green rust. Compared to a Cd(II)aq removal of 21.1% in overlying water of the nitrate-mediated Fe0 (NM-Fe0) system, the NMB-Fe0 system obtained a much higher Cd(II)aq removal of 83.1% after 7 d remediation. The leaching test and sequential extraction results also showed that the leachability of Cd(II) decreased by 75.9% while the residual fraction of Cd(II) increased by 185.7% in comparison with untreated sediment. Besides, the Cd(II)aq removal raised with the increase of nitrate concentration and Fe0 dosage, further revealing the promotion effect of nitrate on Cd(II) removal by bio-Fe0. This study highlighted the involvement of bio-denitrification in the remediation of Cd(II)-contaminated sediment by Fe0 and provided a new insight to enhance its reactivity and applicability for Cd(II) immobilization.

Constructing mesoporous Zr-doped SiO2 onto efficient Z-scheme TiO2/g-C3N4 heterojunction for antibiotic degradation via adsorption-photocatalysis and mechanism insight.

Novel modified-TiO2/Zr-doped SiO2/g-C3N4 ternary composite is fabricated via an in-situ grow of porous Zr-SiO2 layer to TiO2/g-C3N4 heterojunction, which exhibits well adsorption-photocatalytic performance under simulated solar light irradiation. The nano-size mesoporous TiO2 are dispersed on the lamellar g-C3N4, and the Zr-SiO2 is in-situ fabricated onto the surface of g-C3N4 sheets. The adsorption occurs on the SiO2 layers, and doping Zr element to SiO2 enhances the adsorption of pollutants, while the photocatalytic reaction occurs on the valence band (VB) of TiO2 and conduction band (CB) of g-C3N4, which gives reactive oxygen species of ∙O2-, h+, and ∙OH for high efficient decomposition of antibiotics, i.e. berberine hydrochloride (98.11%), tetracycline (80.76%), and oxytetracycline (84.84%). The excellent adsorption capacity and Z-scheme photoinduced charge carrier migration behavior endowed the novel material with enhanced berberine hydrochloride (BH) removal in water, which approximately 2.5 and 3.8 folds than that of pure g-C3N4 and sole TiO2, respectively. Three degradation pathways are unraveled by LC-MS and theoretical calculations. Furthermore, the toxicity of intermediates was evaluated by the Toxicity Estimation Software Tool (T.E.S.T.), the result demonstrated a good application potential of M-TiO2/Zr-SiO2/g-C3N4 as an novel adsorptive photocatalyst.

Nanoscale zero-valent iron immobilized by ZIF-8 metal-organic frameworks for enhanced removal of hexavalent chromium.

nZVI is considered to be a promising material for environmental remediation. However, the drawbacks of easy agglomeration and low activity severely limit its application. In this work, nZVI/ZIF-8 was obtained by in-situ reduction of nZVI in the presence of performed ZIF-8. The reactivity of the as-obtained nZVI/ZIF-8 nanocomposites was investigated by removing hexavalent chromium (Cr(VI)) from wastewater. The as-obtained nZVI/ZIF-8 nanocomposites showed a superior activity for Cr(VI) removal, with an optimum activity (91.27%) achieved over 0.25 nZVI/ZIF-8 (i e., the mass ratio of ZIF-8 to nZVI was 0.25), higher than that of nZVI (64.55%), and this could be owned to the excellent dispersion of nZVI in nZVI/ZIF-8 and the high specific surface area as compared with the bare nZVI. The results of XPS characterization, quenching experiment analysis and kinetics fitting indicated that the Cr(VI) elimination was a surface-dominated chemical reduction process. Besides, more than 99.00% Cd(II), Cu(II), Cr(VI) and Pb(II) was removed from wastewater over nZVI/ZIF-8 nanocomposites, and negligible zinc ion was detected in the aqueous solutions. The results of our finding demonstrate that the introduction of MOFs is an effective strategy in developing a highly efficient nZVI-based nanocomposites system, and also highlight the promising role of using nZVI/MOFs in heavy metal treatment for practical wastewater.