Processing of arsenic waste by precipitation and solidification

摘要

As a consequence of more stringent environmental legislation being applied in Slovakia, traditional ways of arsenic waste treatment no longer became acceptable. For that reason it has been necessary to develop a cheap and effective method for pro- cessing of arsenic sludge which is accumulating in the reaction tower during the carbon dioxide refining in the VETROCOKE technology. A substantial part of the problem is to reach a compromise between reasonable operation costs of technology and sufficient long-term stability of the disposable product. The proposed method of arsenic stabilisation together with the other toxic elements present is based on progressive reduction of their solubility by a series of precipitation and solidification agents. The key factor of successful arsenic fixation is embedding of calcium and ferric arsenates/arsenites in the cement matrix. It is possible to reduce original arsenic solubility of 6430 mg/1 from untreated waste to 0.823 mg/1 from final solidificate by this technique. Leaching tests were conducted in distilled water at 25℃, without pH value control, solid to liquid ratio was 1 : 10, mixing speed was 150 rpm.