Stabilization of ferric arsenate sludge with ZVI intensive corrosion and enhancement of long-term arsenic immobilization via resin encapsulation

Abstract

In this study, a novel stabilization/solidification (S/S) method, achieved by mechanochemically activated zero-valent iron (ZVI) intensive corrosion and resin encapsulation, was investigated for arsenic sludge disposal. The results showed that arsenic stabilization was enhanced by intensive corrosion process, with arsenic leaching concentration decreasing from 128.75 mg/L to 0.35 mg/L after stabilization treatment under optimized conditions. The residual state arsenic was increased from 96.32 wt% to 99.13 wt% after stabilization. The subsequent resin encapsulation solidification scheme has a significant effect on the low arsenic leachability of the stabilized sludge. The arsenic concentration of resin solidification matrix was 0.47 mg/L, which was significantly lower than that of cement solidification matrix (1.77 mg/L), as a control group. It also can be seen that resin curing showed much lower cumulative release rate (0.009 wt%) than cement curing (0.54 wt%) at the end of leaching test, under a 60-day long-term leaching test, indicating that resin curing has higher long-term arsenic stability. Resin curing can maintain the structure of the stabilized As-Fe phase by resin encapsulation, while the traditional cement curing would destroy the original stable As-Fe phase, and produce unstable As-Ca phase, resulting in the risk of arsenic pollution. Moreover, the matrix based on ZVI intensive corrosion and resin encapsulation scheme has great advantages in low compatibilization ratio and resistance to pH impact.