Abstract
Arsenic-containing precipitates obtained from waste water may be redissolved in accordance with their stockpiling condition and therefore, should be stabilized for stockpiling safely without contamination of the environment for a long time. The stabilization of precipitates as calcium arsenate, calcium arsenite and ferric arsenate has been examined. Calcium arsenate precipitate was formed very insoluble Ca3(AsO4)2 by calcining above 700°C without evaporation of arsenic. Calcium arsenite precipitate was changed to very insoluble Ca3(AsO4)2 by calcining in air above 700°C without evaporation of arsenic, too. Ferric arsenate precipitate was formed insoluble ferric arsenate by calcining above 600°C, but decomposed to form valatile arsenic trioxide above 900°C. The precipitate was formed very insoluble one with an increase in the Fe III/As (V) molar ratio in precipitate. Accordingly, it is better for stabilization to maintain the Fe (III)/As (V) molar ratio in precipitate more than 2.The flowsheet for removing arsenic from waste water with calcium hydroxide was proposed on the basis of our experimental results that arsenic was removed remarkably by adding a large excess of calcium hydroxide to waste water at a level of less than 10mg/l and that calcium arsenate and arsenite were formed very insoluble Ca3(AsO4)2 by calcining in air above 700°C. The flowsheet consists of two steps of nutralization for removing arsenic and calcination for stabilizing precipitates.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
