生物炭负载纳米铁活化过硫酸盐去除土壤中的五氯联苯

Degradation of Pentachlorobiphenyl in Soil Using Persulfate Activated by Biochar-supported Nano Zero-valent Iron

以污染土壤中检出量较高的PCB118为目标污染物,采用银杏叶提取液绿色合成纳米铁材料(nZVI)、玉米秸秆制备生物炭(BC),将nZVI负载在BC表面合成生物炭负载纳米零价铁复合材料(BC-nZVI),利用制备的BC-nZVI复合材料催化活化过硫酸盐(PS)去除土壤中PCB118。主要探讨了在生物炭负载纳米零价铁活化过硫酸盐体系(BC-nZVI/PS)中复合材料BC-nZVI碳铁比及其投加量、PS浓度、pH值、温度等因素对PCB118去除速率的影响。结果表明,反应时间为24h时,碳铁比为2?1时BC-nZVI反应体系对土壤中PCB118去除效果优于其他3种比例。实验条件下,随着BC-nZVI的投加量由0.002 g增加到0.500 g,PS浓度由0.05 mol·L^(-1)增至0.35 mol·L^(-1),温度由15℃升高到45℃,土壤中PCB118的去除率分别增加了32.4%、10.6%及14.7%。随着溶液初始pH值由3升到9,土壤中PCB118的去除率降低了11.4%。单因素实验数据显示,在BC-nZVI的投加量为0.500 g,PS浓度为0.35 mol·L^(-1),pH值为3,温度为45℃的条件下,土壤中PCB118去除效果最佳。为分析不同因素及其交互作用对土壤中PCB118去除率的影响,采用Box-Behnken响应面法设计了三因素三水平试验,建立了PS浓度、温度和pH等3个变量的二次多项式回归模型,得到土壤中PCB118最佳去除条件为:PS浓度0.23 mol·L^(-1)、pH 3.11、温度45℃。在此条件下,土壤中的PCB118在BC-nZVI/PS体系中去除率为71.6%。实验验证结果与模型预测值的相对偏差<5%,表明可使用此模型对BC-nZVI/PS体系中PCB118的去除率进行预测。该研究可为土壤中PCB118污染治理提供一些基础数据,为绿色环保修复土壤中有机污染物提供理论参考。

The biochar-supported nano zero-valent iron composite materials(BC-nZVI),synthesized by loading nano zero-valent iron(nZVI)on the surface of biochar(BC),was used to remediate soil contaminated with polychlorinated biphenyls(PCBs).The green nZVI was prepared with the extraction solution from ginkgo leaves,and the BC was prepared with corn straw.The prepared BC-nZVI composite material was used to catalyze the activation reaction of persulfate(PS)to remove PCB118,which was highly detected in soil.Various factors affecting the removal rate of PCB118 in the activated persulfate system(BC-nZVI/PS)were mainly discussed,such as the iron-carbon ratio and its dosage in composite material BC-nZVI,PS concentration,pH value,and temperature.The results showed that when the reaction time was 24 h and the carbon-iron ratio was 2꞉1,the BC-nZVI reaction system had a better removal effect on PCB118 compared to the other three ratios.Under experimental conditions,as the dosage of BC-nZVI increased from 0.002 g to 0.500 g,the PS concentration increased from 0.05 mol·L^(-1) to 0.35 mol·L^(-1),and temperature increased from 15℃to 45℃,the removal rate of PCB118 increased by 32.4%,10.6%,and 14.7%,respectively.As the initial pH value of the solution increased from 3 to 9,the removal rate of PCB118 decreased by 11.4%.Experimental data of single factor showed that the removal effect of PCB118 in the soil was the best under conditions of BC-nZVI dosage of 0.500 g,PS concentration of 0.35 mol·L^(-1),pH value of 3,and temperature of 45℃.To analyze the impact of different factors and their interactions on the removal rate of PCB118 in soil,the Box Behnken response surface method was used to design a three-factor three-level experiment.A quadratic polynomial regression model was established for three variables:PS concentration,temperature,and pH.According to the model,the optimal removal conditions for PCB118 were as follows:PS concentration of 0.23 mol·L^(-1),pH of 3.11,temperature of 45℃.Under these conditions,the removal rate of PCB118 in the BC-nZVI/PS system was 71.6%.The relative deviation between the experimental verification results and the predicted values of the model was less than 5%,suggesting that this model could be used to predict the removal rate of PCB118 in the BC-nZVI/PS system.This study might provide some basic data for the control of PCB118 in soil and provide theoretical references for the green and environmentally friendly remediation of organic pollutants in soil.