title: Solidification/stabilisation of arsenic bearing fly ash from the metallurgical industry. Immobilisation mechanism of arsenic.
abstract: When a fly ash waste material from a copper refining process containing large amounts of As2O3 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 concentration in the leachate, mainly of As(III), is due to the formation of insoluble CaHAsO3 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 H2O2. The arsenic concentration in the leachate of the extraction test of an oxidised S/S sample was lowered to ca. 0.5 mg/l, a factor of 10 below the one for a non-oxidised sample. It is shown that the decrease of the concentration in the leachate mainly of As(V) is due to the formation of insoluble Ca3(AsO4)2 in the presence of Ca(OH)2. Extensive use was made of the speciation program MINTEQA2, to clarify the immobilisation of arsenic.
authors: Department of Chemical Engineering, University of Leuven, Heverlee, Belgium. carlo.vandecasteele@cit.kuleuven.ac.be
authors: Carlo
authors: C
authors: Vandecasteele
authors: Veroniek
authors: V
authors: Dutré
authors: Daneel
authors: D
authors: Geysen
authors: Guido
authors: G
authors: Wauters
mesh_terms: D001151:Arsenic / Q000737:chemistry*; D003300:Copper; D004784:Environmental Monitoring; D017745:Incineration; D007221:Industry; D008669:Metallurgy; D010084:Oxidation-Reduction; D012037:Refuse Disposal; D012995:Solubility
chemical_list: D003300:Copper; D001151:Arsenic