Enhancement of ball-miling on pyrite/zero-valent iron for arsenic removal in water: A mechanistic study.

In this study, the effect of ball milling on pyrite (FeS) promoting arsenic (As) removal by zero-valent iron (Fe) was investigated. The influences of different mass ratios of ball-milled FeS/Fe, the dosage of ball-milled FeS/Fe used and initial pH value were evaluated by batch experiments. The results showed that the ball-milled FeS/Fe system had a higher total As removal efficiency than the mixed FeS-Fe system, ball-milled FeS and ball-milled Fe systems in equal mass. Higher As removal efficiency in ball-milled FeS/Fe system was primarily related to the accelerated corrosion of Fe, which was supported by the determination of total Fe release and electrochemical experiments. SEM-EDS and XPS characterizations revealed that there were iron sulfides (Fe(II)-S and Fe(III)-S) produced on the surface of Fe in ball-milled FeS/Fe, which could facilitate the electron transfer of Fe and enhanced the corrosion of it. BET test also indicated that ball-milled FeS/Fe possessed a higher specific surface area than ball-milled Fe. In addition, the results also showed the optimum mass ratio of FeS and Fe in ball-milled FeS/Fe to remove As ([As(III)] = 2 mg/L) was 1:1, and the optimum dosage was 0.5 g/L, thereby indicating the optimal As:Fe molar ratio was about 1:168. And the removal rate of As by ball-milled FeS/Fe was faster in acidic condition than that in alkaline condition. These findings suggest that Fe-based arsenic removal efficiency can be enhanced by ball-milling with FeS, making it more feasible for remediation of arsenic-polluted water.