Optimization for enhanced electrokinetic treatment of air pollution control residues using response surface methodology focusing on heavy metals leaching risk and extractability

Waste like air pollution control (APC) residues from incineration are potentially valuable resources. This paper reports the application of enhanced electrokinetic (EK) treatment processing to APC residues using an approaching anode coupled with a permeable reactive barrier (PRB). The changes of heavy metals (HMs) leaching risk and the effect of EK on metals extractability were explored for the possibilities of treated APC residues and metals recovery. The impact of various factors on HMs leaching was evaluated through response surface experiments. The adsorption ability of PRB and H + provided by approaching anode could alleviate HMs accumulation during treatment caused by high pH and buffer capacity. Compared with conventional EK treatment, the HMs extraction and leaching reduction improved significantly, with more than 30% energy saved after enhanced EK treatment. The best HMs leaching reduction was obtained after 16 days treatment at 1.97 V/cm of voltage gradient with 14.64 g modified activated carbon used as PRB while the anode was moved after 6.35 days. The results showed fraction conversions could increase the extractability of HMs with the electric field application, and the environmental risk of remaining HMs was reduced through the effective removal of HMs with potential risk after enhanced EK treatment.