| abstract |
PROCESS FOR PURIFYING WASTE ACID SOLUTIONS CONTAINING HEAVY METALS INCLUDING IN PARTICULAR ARSENIC, ANTIMONY, MERCURY AND TIN PRESENT IN CONSIDERABLE PROPORTION, BY CHEMICAL PRECIPITATION USING SULPHIDE IONS, PROCESS IN IN WHICH SULPHIDE IONS ARE CHARGED AT LEAST IN TWO SEPARATE INTERVALS OF ACIDITY AND THE ACIDITY BETWEEN THE INTERVALS ARE ADDED BY ADDING AN APPROPRIATE BASE, THEN THE PRECIPITES FROM THE SOLUTION ARE SUBJECTED; THE FIRST CHARGE OF SULPHIDE ION IS CARRIED OUT AT A PH LESS THAN 3.4, PREFERABLY FROM 1.0 TO 2.5 AND THE SECOND CHARGE AT A PH GREATER THAN 4.0 BUT ADVANTAGEOUSLY LESS THAN 4.3. |