Removal of anions from water - by anion exchange using yellow bismuth hydroxide

摘要

Removal of anions from water is effected by anion exchange with yellow bismuth hydroxide (I) produced by pptn. from a Bi salt soln. with excess alkali. The treatment is effected by (a) passing the water through a column of (I) supported on or mixed with an inert carrier, e.g. Al2O3, or (b) suspending (I) in the water and then sepg. the solids. The selectivity with which anions are removed is varied by the pH of the soln. USE/ADVANTAGE - The process is esp. useful for removing nitrate from drinking water or waste water. (I) is capable of reducing nitrate levels by at least 93%, also removes phosphate, sulphate and chloride, is practically insoluble in water (traces can be removed by heavy metal pptn.), and has relatively low toxicity.