Effective reuse of electroplating rinse wastewater by combining calcined oyster shell powder with H2O2/UV process

Abstract

In this study, the merits of combining the oyster shell powder (OSP) pre-treatment with H2O2/UV post-oxidation for the reuse of electroplating rinse wastewater were evaluated. The results showed that the calcined OSP was more effective in removing heavy metals than the original OSP. For the 1,000°C-calcined OSP of 0.6 g/L, the removals were 98, 94, and 99% for Fe, Ni, and Cr, respectively. That is, a small quantity of the calcined OSP could remove a large quantity of heavy metals due to the large specific surface area and the dramatically increased pH; the former resulted in a better adsorption capability and the latter induced buck precipitation. Further, after the post H2O2/UV process, the chemical oxygen demand and total organic carbon were reduced from 1,206 to 41.2 mg/L and from 252 to 12.6 mg/L, respectively, for pH of 8.0, H2O2 of 1,000 mg/L, UV of 52 W, and oxidation time of 240 min. That is, the combination of calcined OSP pre-treatment and H2O2/UV post-oxidation could not only treat the electroplating rinse wastewater to comply with the Taiwan’s effluent standard but could also satisfy the in-house water reuse criteria while resolving the issue of waste oyster shells simultaneously.