Remmoval Of Hexavalent Chromium From Industrial Waste Water By Chemical Treatment

Abstract

Chromium is one of the heavy metal coming from various industries having high toxicity. The compounds of chromium especially Cr (VI) are known to be detrimental to human beings and animals. Extensive chemical analysis was done to detoxify Cr (VI) by reducing it to Cr (III) by using reducing agents such as ferrous sulphate and sodium metabisulphite, and the precipitation of chromium hydroxide by addition of base. Also experiments were conducted to study the effect of reduction time and pH on the reduction of chromium for various reducing agents.  In this  work, hexavalent chromium is removed by reduction and precipitation reaction, by using Ferrous sulphate ( FeSO₄) and Sodium metabisulphite ( Na₂S₂O₅) as reducing agents to convert Cr(VI) to Cr(III) and Calcium hydroxide ( Ca(OH)₂), Sodium hydroxide ( NaOH) and combination of Calcium hydroxide, Sodium hydroxide are used as precipitating agents to precipitate Cr(III) as hydroxides. The reduction reaction is conducted at low pH (<3) and precipitation reaction is carried out high pH (>8). Because hexavalent chromium is stable under oxidizing conditions, whereas trivalent chromium is stable under reducing conditions. The purpose of this work is to compare the effect of chemicals in the reduction and precipitation reactions of waste water on pH values.