INFLUENCE OF ADDITIVES ON IMMOBILIZATION PROCESS OF HEAVY-METAL CONTAINING WASTE RESIDUES USING ELEMENTAL SULFUR

摘要

In this paper, three additives, namely sodium hydroxide, calcium hydroxide and sodium carbonate, were used to enhance the immobilization of cadmium and zine in sulfuration neutralization sludge using elemental sulfur. The results showed that the pH of the leachate increased as the addition rate of these three additives increased. Both NaOH and Ca(OH)_2 greatly improved the performance of immobilization. Na_2CO_3 also enhanced the immobilization of cadmium and zinc, however, to a less extent. After analyzing the products of metal oxides mixed with sulfur and additives or without any additive at 413K, the results revealed that metal sulfuration did not occur during the sulfur immobilization process without any additive. However, with the addition of NaOH, cadmium sulfide and zinc sulfide were produced. Other two additives could not promote metal sulfuration, while they enhanced the immobilization of cadmium and zinc simply by increasing the pH value of the leachate.