Key Laboratory of Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University, Changsha, 410082, China.
Hunan Zihong Ecology Technology Co., Ltd, Changsha, 410082, China.
J Environ Manage. 2019 Nov 1;249:109322. doi: 10.1016/j.jenvman.2019.109322. Epub 2019 Sep 5.
Cr(IV) pollution in water leads to serious environmental contamination and health risks. Among various wastewater treating methods, electrocoagulation (EC) is widely applied because of its high efficiency. However, there is still a problem of high energy consumption that has to be solved by direct current coagulation (DCC). In this paper, a sinusoidal alternating current coagulation (SACC) technique was used to reduce energy consumption and improve the efficiency of Cr(VI) removal. The effects of pH value, current density, initial concentration of Cr(VI) and reaction time are studied on the removal of Cr(VI). The response surface methodology (RSM) was used to optimize the parameters of SACC process. Compared with pulse direct current coagulation (PDCC) and DCC, SACC can greatly reduce the concentration polarization and prevent Fe electrodes from passivation so as to reduce energy consumption and improve the efficiency of Cr(VI) removal. When pH 5.6 wastewater containing 33.1 mg⋅dm Cr(VI) was treated by applying 2.7 A⋅m density for 20.5 min, the removal rate of Cr(VI) reached 99.73%, and the residual Cr(VI) in the effluent was <0.1 mg⋅dm. The power consumption of SACC process decreases by 14.98% compared to DCC process and the electrode loss is about 16.4% less than that of the DCC. The coagulation produced by SACC has a large specific surface area and better adsorption performance through analysis of SEM and EDS as well as adsorption dynamic analysis. FTIR and XRD patterns verified the strong interaction between Cr(VI) and iron sol. The Cr(VI) on the electrode can be deposited as a form of insoluble Cr(III) compounds. Langmuir adsorption isotherm model and the second-order kinetic model in SACC are more suitable to explain the adsorption behavior and characteristics of Cr(VI) in SACC.
六价铬（Cr(VI)）污染会导致严重的环境污染和健康风险。在各种废水处理方法中，由于其高效性，电絮凝（EC）被广泛应用。然而，直流电凝聚（DCC）仍存在能耗高的问题。本文采用正弦交流电凝聚（SACC）技术降低能耗，提高 Cr(VI)去除效率。研究了 pH 值、电流密度、Cr(VI)初始浓度和反应时间对 Cr(VI)去除的影响。采用响应面法（RSM）优化了 SACC 工艺参数。与脉冲直流电凝聚（PDCC）和 DCC 相比，SACC 可以大大降低浓度极化，防止 Fe 电极钝化，从而降低能耗，提高 Cr(VI)去除效率。当处理 pH 为 5.6、Cr(VI)初始浓度为 33.1 mg⋅dm 的废水时，施加 2.7 A⋅m 的电流密度 20.5 min，Cr(VI)去除率可达 99.73%，出水中 Cr(VI)残留浓度<0.1 mg⋅dm。与 DCC 相比，SACC 工艺的能耗降低了 14.98%，电极损耗减少了约 16.4%。通过 SEM 和 EDS 分析以及吸附动力学分析，发现 SACC 产生的絮体具有较大的比表面积和更好的吸附性能。FTIR 和 XRD 图谱验证了 Cr(VI)与铁溶胶之间的强烈相互作用。电极上的 Cr(VI)可以以不溶性 Cr(III)化合物的形式沉积。SACC 中的 Langmuir 吸附等温线模型和二级动力学模型更适合解释 SACC 中 Cr(VI)的吸附行为和特征。
