Simultaneous removal of nitrate, phosphate, and fluoride using a ZVI- packed bed electrolytic cell

Abstract

The present study aims to treat wastewater containing anionic contaminants such as nitrate, phosphate, and fluoride generated by the etching process of the semiconductor industry. The ZVI-packed bed electrolytic cell was developed to treat the contaminants using reduction, adsorption, and precipitation by electrochemical reactions. The 1L reactor was operated with a voltage of 600V, a flow rate of 30mL/min (HRT: 12min, EBCT: 33min), and a packing ratio of 2:1 (v/v, silica sand to ZVI). Synthetic wastewater consisting of 30 mg/L as N, 10-50mg/L as PO4,3- and 5-30mg/L F- was used for the experiment. Different combinations of anionic contaminants were tested in the experimental setup. Results indicated that nitrate, phosphate, and fluoride were removed at greater than 90%. When the reactor was operated without nitrate to act as a support electrolyte, phosphate, and fluoride removal efficiencies dropped drastically. Ammonia was produced during nitrate reduction, which led to iron oxidation. The FESEM and EDX analyses were performed to further investigate the electrochemical behavior in the ZVI-packed bed electrolytic cell.