TREATMENT OF METAL INDUSTRIAL WASTE-WATER BY FLY-ASH AND CEMENT FIXATION

A process for the treatment of industrial wastewater containing heavy metals, using fly ash adsorption and cement fixation of the metal-laden adsorbent, was investigated. Results show that the fly ash can be an effective metal adsorbent, at least for Zn(II) and Cd(II) in dilute industrial wastewaters. Fly ash adsorption capacities for Zn(II) and Cd(II) were 0.27 mg/g and 0.05 mg/g, respectively. A mortar specimen prepared with 10% metal-laden fly ash showed a 56-day strength, about the same or even greater than that of cement alone. Leachates from the fixed metal-laden fly ash, obtained by using both the ASTM and U.S. Environmental Protection Agency-extraction procedure (USEPA-EP) leaching tests, exhibit metal concentrations lower than the drinking water standards. Compressive strength and leaching test results suggest that metal-laden fly ash can be considered for use in secondary construction materials.