REMOVAL OF MANGANESE IN CONTAMINATED GROUNDWATER BY PERMEABLE REACTIVE BARRIERS USING COMPOST AND ZERO VALENT IRON

Abstract

Sorption and precipitation of manganese in groundwater remediation using compost and zerovalent iron (ZVI) were investigated by batch and column experiments. In batch tests, compost is more effective than ZVI to immobilize manganese, with the maximum removal of 238.09 mmol Mn. kg^-1 of compost according to Langmuir equation. High efficiency of Mn removal onto compost is probably not only by physical sorption but also by surface complexation with carboxylic groups in the compost. This result was confirmed with FTIR data that shown new peaks at 675 cm^-1 after contacted with manganese solution. Manganese was also immobilized through sorption onto ZVI due to high surface area, and partly by precipitation as manganese oxide because of intense alkalization. In column materials, after introducing manganese solution for 36 pore volumes (pv), manganese was predominantly immobilized in upper part of the column. It is considered that compost was degraded and the surface of ZVI granules was already uniformed and corrosion products are the most accumulated on ZVI granules near the inlet because ZVI has been contacted with high concentrations of manganese for the longest time in the most bottom parts. This was also supported by XRF data from ZVI grains that manganese was the largest in the most bottom segment. The results of geochemical calculations along with the SEM image suggest that partly of manganese were also precipitated with carbonates. The result demonstrates that combination of compost and ZVI is more effective to remove manganese than using single material due to the different mechanism of removal from each material.