葡萄籽提取液还原制备生物炭负载纳米铁对水中As(Ⅲ)的去除性能及机理

Removal performance and mechanism of As(Ⅲ)from water by reduction preparation of biochar supported nano-iron from grape seed extract

利用植物提取液绿色合成的纳米铁,具有绿色环保、成本低廉等优点。本文采用葡萄籽提取液作为还原剂和稳定剂,风车草生物炭为载体,制备了生物炭负载纳米铁(CBC-nZVI),用于去除废水中的As(Ⅲ)。结果表明,纳米铁(nZVI)成功负载于生物炭表面,具有较大的比表面积和孔体积;随着反应时间的延长,溶液温度的升高,CBC-nZVI投加量的增加和溶液初始pH的增大,CBC-nZVI对As(Ⅲ)的吸附量不断增大;Langmuir等温吸附模型能更准确地描述CBC-nZVI对As(Ⅲ)吸附行为,CBC-nZVI对As(Ⅲ)去除过程符合准二级动力学模型,表明CBC-nZVI对As(Ⅲ)的吸附是单层吸附,以化学吸附为主。ESR表征结果表明CBC-nZVI在有氧反应体系中生成了·OH,反应过程中,As(Ⅲ)大部分被氧化为毒性较低的As(Ⅴ),通过吸附、氧化还原和共沉淀实现As(Ⅲ)的最终去除。

The green synthesis of iron nanoparticles using plant extracts has the advantages of green environment protection and low cost.In this study,biochar-loaded nano-iron(CBC-nZVI)was prepared for As(Ⅲ)removal from wastewater using grape seed extract as the stabilizer and reducing agent,and Cyperus alternifolius based-biochar as the carrier.The results showed that the nano-iron(nZVI)was successfully loaded on the surface of biochar,and had a large specific surface area and pore volume.The adsorption of As(Ⅲ)by CBC-nZVI increased continuously with the increase of reaction time,solution temperature,dosage and initial pH of the solution.Langmuir isothermal adsorption model could more accurately describe the adsorption behavior of CBC-nZVI on As(Ⅲ)than other ones.The removal of As(Ⅲ)by CBC-nZVI was in accordance with the quasi-secondary kinetic model,indicating that above adsorption process was a monolayer adsorption and was dominated by chemisorption.The characterization of ESR showed that CBC-nZVI produced·OH in the aerobic reaction system.During the reaction,most of As(Ⅲ)was oxidized to As(V)with lower toxicity,and the final removal of As(Ⅲ)was achieved by adsorption,redox and co-precipitation.