Removal of decabromodiphenyl ether （BDE-209） by sepiolite-supported nanoscale zerovalent iron

Nanoscale zerovalent iron （nZVI） synthesized using sepiolite as a supporter was used to investigate the removal kinetics and mechanisms of decabromodiphenyl ether （BDE-209）. BDE-209 was rapidly removed by the prepared sepiolite-supported nZVI with a reaction rate that was 5 times greater than that of the conventionally prepared nZVI because of its high surface area and reactivity. The degradation of BDE-209 occurred in a stepwise debromination manner, which followed pseudo- first-order kinetics. The removal efficiency of BDE-209 increased with increasing dosage of sepiolite-supported nZVI particles and decreasing pH, and the efficiency decreased with increasing initial BDE-209 concentrations. The presence of tetrahydrofuran （THF） as a cosolvent at certain volume fractions in water influenced the degrada- tion rate of sepiolite-supported nZVI. Debromination pathways of BDE-209 with sepiolite-supported nZVI were proposed based on the identified reaction intermedi- ates, which ranged from nona- to mono-brominated diphenylethers （BDEs） under acidic conditions and nonato penta-BDEs under alkaline conditions. Adsorption on sepiolite-supported nZVI particles also played a role in the removal of BDE-209. Our findings indicate that the particles have potential applications in removing environ- mental pollutants, such as halogenated organic contami- nants.

Biochar-supported nano-scale zerovalent iron activated persulfate for remediation of aromatic hydrocarbon-contaminated soil:an in-situ pilot-scale study

Biochar supported nano-scale zerovalent iron(nZVI/BC)for persulfate(PS)activation has been studied extensively for the degradation of pollutants on the lab scale,but it was rarely applied in practical soil remediation in the field.In this research,we developed a facile ball-milling method for the mass production of nZVI/BC,which was successfully applied to activate persulfate for the remediation of organic polluted soil on an in-situ pilot scale.In-situ high-pressure injection device was developed to inject nZVI/BC suspension and PS solution into the soil with a depth of 0-70 cm.The removal efficiency of target pollutants such as 2-ethylnitrobenzene(ENB,1.47-1.56 mg/kg),biphenyl(BP,0.19-0.21 mg/kg),4-(methylsulfonyl)toluene(MST,0.32-0.43 mg/kg),and 4-phenylphenol(PP,1.70-2.46 mg/kg)at different soil depths was 99.7%,99.1%,99.9%and 99.7%,respectively,after 360 days of remediation.The application of nZVI/BC significantly increased the degradation rates of contaminants by 11-322%,ascribed to its relatively higher efficiency of free radical generation than that of control groups.In addition,it was found that nZVI/BC-PS inhibited soil urease and sucrase enzyme activities by 1-61%within 55 days due to the oxidative stress for microbes induced by free radicals,while these inhibition effects disappeared with remediation time prolonged(>127 days).Our research provides a useful implementation case of remediation with nZVI/BC-PS activation and verifies its feasibility in practical contaminated soil remediation.

Highly stable carbon-coated nZVI composite Fe0@RF-C for efficient degradation of emerging contaminants

Nanoscale zerovalent iron(nZVI)has garnered significant attention as an efficient advanced oxidation activator,but its practical application is hindered by aggregation and oxidation.Coating nZVI with carbon can effectively addresses these issues.A simple and scalable production method for carbon-coated nZVI composite is highly desirable.The anti-oxidation and catalytic performance of carbon-coated nZVI composite merit in-depth research.In this study,a highly stable carbon-coated core-shell nZVI composite(Fe0@RF-C)was successfully prepared using a simple method combining phenolic resin embedding and carbothermal reduction.Fe0@RF-C was employed as a heterogeneous persulfate(PS)activator for degrading 2,4-dihydroxybenzophenone(BP-1),an emerging contaminant.Compared to commercial nZVI,Fe0@RF-C exhibited superior PS activation performance and oxidation resistance.Nearly 95%of BP-1 was removed within 10 min in the Fe0@RF-C/PS system.The carbon layer promotes the enrichment of BP-1 and accelerates its degradation through singlet oxygen oxidation and direct electron transfer processes.This study provides a straightforward approach for designing highly stable carbon-coated nZVI composite and elucidates the enhanced catalytic performance mechanism by carbon layers.

Removing polybrominated diphenyl ethers in pure water using Fe/Pd bimetallic nanoparticles

Polybrominated diphenyl ethers （PBDEs） have been widely used as fire-retardants. Due to their high production volume, widespread usage, and environmental persistence, PBDEs have become ubiquitous contaminants in various environments.Nanoscale zero-valent iron （ZVI） is an effective reductant for many halogenated organic compounds. To enhance the degradation efficiency, ZVI/ Palladium bimetallic nanoparticles （nZVI/Pd） were synthe- sized in this study to degrade decabromodiphenyl ether （BDE209） in water. Approximately 90% of BDE209 was rapidly removed by nZVI/Pd within 80 min, whereas about 25% of BDE209 was removed by nZVL Degradation of BDE209 by nZVI/Pd fits pseudo-first-order kinetics. An increase in pH led to sharply decrease the rate of BDE209 degradation. The degradation rate constant in the treatment with initial pH at 9.0 was more than 6.8 x higher than that under pH 5.0. The degradation intermediates of BDE209 by nZVI/Pd were identified and the degradation pathways were hypothesized. Results from this study suggest that nZV//Pd may be an effective tool for treating polybromi- nated diphenyl ethers （PBDEs） in water.

Effect of humic acid and metal ions on the debromination of BDE209 by nZVM prepared from steel pickling waste liquor

As a promising in situ remediation technology, nanoscale zero-valent iron （nZVI） can remove polybromi- nated diphenyl ethers such as decabromodiphenyl ether （BDE209） effectively, However its use is limited by its high production cost. Using steel pickling waste liquor as a raw material to prepare nanoscale zero-valent metal （nZVM） can overcome this deficiency. It has been shown that humic acid and metal ions have the greatest influence on remediation. The results showed that nZVM and nZVI both can effectively remove BDE209 with little difference in their removal efficiencies, and humic acid inhibited the removal efficiency, whereas metal ions promoted it. The promoting effects followed the order Ni2＋ 〉 Cu2＋ 〉 Co2＋ and the cumulative effect of the two factors was a combination of the promoting and inhibitory individual effects. The major difference between nZVM and nZVI lies in their crystal form, as nZVI was found to be amorphous while that of nZVM was crystal. However, it was found that both nZVM and nZVI removed BDE209 with similar removal efficiencies. The effects and cumu- lative effects of humic acid and metal ions on nZVM and nZVI were very similar in terms of the efficiency of the BDE209 removal.