绿茶生物炭负载纳米零价铁对地下水中五价钒的去除效果及机理研究

钒(V)作为一种重要的工业原料被广泛应用于各个领域，但同时造成了一定程度的地下水污染。为了去除地下水中的五价钒V(Ⅴ)，利用常见的生产废料绿茶渣为生物质原料制备了活性炭(BC)，并在其表面负载零价铁(nZVI)，得到一种环境友好的可渗透反应墙(PRB)活性填料nZVI@BC；优化了nZVI@BC的制备条件，考察了溶液pH和竞争离子对V(Ⅴ)去除效果的影响；通过等温吸附试验判断其吸附模型，进行了吸附动力学分析，并探究了其反应机理。结果表明：FeSO₄溶液的最佳反应浓度为1.0 mol/L，热解温度为300 ℃，在该条件下制备的nZVI@BC在吸附19 h后对V(Ⅴ)的去除量达71.6 mg/g；当溶液pH>3.0时，随着pH的升高，nZVI@BC对V(Ⅴ)的去除率逐渐降低；地下水中的共存阴离子与V(Ⅴ)发生竞争吸附，使V(Ⅴ)去除率降低；nZVI@BC的等温吸附过程符合Sips模型，吸附动力学符合Elovich模型，nZVI@BC去除V(Ⅴ)的机理为：BC吸附V(Ⅴ)后，表面Fe⁰与V(Ⅴ)发生氧化还原反应，生成Fe₂VO₄，V(Ⅴ)被还原为V(Ⅳ)。

Removal and mechanism of pentavalent vanadium in groundwater by green tea biochar loaded with nano-zero-valent iron

Pentavalent vanadium (Ⅴ) is widely used in industry but causes certain groundwater pollution. In order to remove V (Ⅴ) in groundwater, activated carbon (BC) was prepared using readily available waste green tea residue as a raw material. Zero-valent iron (nZVI) was loaded on its surface to afford an environmentally friendly permeable reactive wall (PRB) active filler nZVI@BC. The preparation conditions of nZVI@BC were optimized, and the effects of varying solution pH and the presence of competing ions on V (Ⅴ) removal efficiency were investigated. The adsorption model was determined by isothermal adsorption tests, the adsorption kinetics was analyzed, and the reaction mechanism was explored. The results showed that the optimal reaction concentration of FeSO₄ solution was 1.0 mol/L, and the optimum pyrolysis temperature was 300 ℃. The nZVI@BC prepared under these conditions could remove 71.6 mg/g of V (Ⅴ) after 19 h of adsorption. For a solution pH>3.0, the removal rate of V(Ⅴ) by nZVI@BC gradually decreased with increasing pH. The competitive adsorption of coexisting anions in groundwater reduces the removal rate of V (Ⅴ). The isothermal adsorption process of nZVI@BC conforms to the Sips model, and the adsorption kinetics conforms to the Elovich model. The mechanism of V (Ⅴ) removal by nZVI@BC is that after BC adsorbs V (Ⅴ), the Fe⁰ on the surface undergoes a redox reaction with V(Ⅴ) to generate Fe₂VO₄, and V (Ⅴ) is thus reduced to V (Ⅳ).