Study Of Removing Arsenic From Fluosilicic Acid By The Modified Activated Carbon

Fluosilicic acid is the byproduct coming into the producing process of wet process phosphoric acid.In the concentration process of wet process phosphoric acid,in wet process phosphoric acid fluorine is escaped in form with four fluorinating silicons.Then it is absorbed by water and turns into fluosilicic acid solution.In the procedure of production,arsenic,the impurity in the phosphorite,also enters wet process phosphoric acid,and is also escaped with four fluorinating silicons in the concentration process of wet process phosphoric acid,and consists in fluosilicic acid solution.For getting fluosilicic acid after-products with higher quality, the content of arsenic must be strictly controlled.Therefore,that arsenic impurity in the byproduct fluosilicic acid of wet process phosphoric acid is effectively eliminated has important significance and economic value.The paper imposes the activated carbon adsorption to eliminate arsenic impurity in fluosilicic acid,and mainly researches modify of activated carbons and eliminating arsenic of modified activated carbons.The orthogonal test was used to arrange experiments to study two different methods of modifying the activated carbon:one was modified by removing impurities using both acid and alkali treatments to modify the activated carbon to improve the adsorb ability.The other method was modification of the carbon with cation of ferric salt,and the adsorb ability on the activated carbon is improved through changing chemical environment on activated carbon surface.It showed that the removal rate of arsenic on the modified activated carbon using 5%acid and alkali treatment for 5 hours would be the best;the second method was based on the first method. The removal rate of arsenic on the modifed activated carbon that impregnated with 0.68mol/l ferric chloride solution for 24 hours showed the best result.The quadratic regression rotation design method was used to arrange experiments to study the modified activated carbon to improve the removal rate of arsenic and the dosage of the modified activated carbon,the temperature of reaction,the time of reaction.The results of experimentation show that the dosage of the modified activated carbon and the temperature of reaction have great effect on the removal rate of arsenic,and the time of reaction has less effect in the experimental scope of the study.The optimum conditions of removing arsenic are: Dosage of the modified activated carbon 0.232g/mL fluosilicic acid Time of reaction 4.5h Temperature of reaction 15℃The removal rate of arsenic on these conditions is over 77.6%.