| 摘要 |
Iron sulphide contaminates in silica sand are decreased by leaching with a solution of sodium, potassium or calcium hypochlorite, at an acid pH, e.g from 1-3. The hypochlorite may be obtained by the reaction of Cl2 on a solution of Ca(OH)2 or CaO, or of Cl2 on NaOH or KOH solutions. The hypochlorite may also be obtained by the elctrolysis of the respective brine solution, collection of the products and reacting as above sodium hypochlorite may be obtained by hydrolysis of a brine solution in a direct electrolytic cell. It is advantageous to remove coarse sulphides, e.g. by gravity tables, floatation, Humphrey Spirals etc., before leaching. It may be necessary to precondition the sand by vigorous attrition and/or acid leaching. The hypochlorite solution may have up to 1% available chlorine and the temperature may be in the range 45-75 DEG C. Leaching may be for up to 24 hours. Sand containing up to 0.04% Fe2O3 may be so treated. |
