A comparative study on stabilization of available As in highly contaminated hazardous solid waste

The stabilization of available As was conducted by chemical fixation after Fenton process in a solid waste residual (SWR) from organic arsenic industry. Single as well as combined fixation treatments by using ferric sulfate (FS), magnesium chloride (MC) and calcium hydroxide (CH) were carried out to assess and to evaluate the fixation effect through toxicity characteristic leaching procedure (TCLP), synthetic precipitation leaching procedure (SPLP) and sequential extraction procedure (SEP). The effect of aging treatment on the fixation of available As in SWR was also investigated. Experimental result showed that the optimal molar ratios for Fe:As, Mg:As and Ca:As were 2:1, 3:1 and 2:1, respectively, and the combination fixation FS + MC + CH was found to be the optimal fixation treatment. With respect to the leaching behavior and the speciation migration of As in SWR after stabilization, TCLP, SPLP and SEP represent a pertinent and inseparable system for the fixation effect evaluation. The fixation treatment of available As in SWR could be evaluated directly after 3 days and the aging treatment is not needed though it can further enhance the fixation effect.