Solidification/stabilisation of arsenic bearing fly ash from the metalurgical industry. Immobilisation mechanism of arsenic

摘要

When a fly ash waste material from a copper refining process containing large amounts of As_2O_3 is solidified using cement and lime, the arsenic concentration in the leachate can be lowered to ca. 5 mg/l in a saturated solution of Ca(OH)_2. It is shown that the decrease of the conentration in the leachate, mainly of As(III), is due to the formation of insoluble CaHAsO_3 in the leachate in the presence of ca(OH)_2. This method is compared with a method whereby use is made of oxidation of the waste before solidification to oxidise As(III) to As(V) using H_2O_2.