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Pure Appl. Chem., 2009, Vol. 81, No. 1, pp. 113-122

Prospects for processing wastes into products used in agriculture

Adam Pawełczyk and Bogdan Szczygieł

Department of Chemistry, Wroclaw University of Technology, Wyb. Wyspianskiego 27, 50-370 Wroclaw, Poland

Abstract: The authors have proposed their own newly developed universal procedure for assessing waste and selecting methods of processing the waste for agricultural purposes. Increasingly more rigorous environmental legal regulations, especially pertaining to sustainability in agricultural and chemical production, were the most convincing motivation for such approach. The procedure is based on technological and environmental safety criteria. Special attention is devoted to the chemical processing of hazardous wastes into fertilizer products and the underlying reasons for such methodology. As opposed to physical and biochemical processes, in chemical processes the agents used completely change the chemical structure of the waste materials or at least that of some of their components. As a result, new phases are formed and the harmful properties of the initial material are eliminated. Prospects for the chemical processing of hazardous wastes are demonstrated using as an example the utilization of asbestos wastes. There are vast amounts of asbestos materials installed in industrial, communal, and service facilities. Landfill asbestos waste disposal is the common practice, but this does not solve properly the problem of environmental hazard. The proposed utilization concept consists in destroying asbestos with a phosphoric acid solution in a two-stage process. The obtained suspension is then filtered, and the solution of phosphates containing an excess of phosphoric acid is subsequently neutralized with lime and processed into phosphate fertilizers of TSP (triple superphosphate) or DCP (dicalcium phosphate) type. Experiments showed that the process yielded asbestos-free products which did not contain any respirable fibers. Comparative immunological tests showed that the products did not cause any degeneration of human lung cells exposed to them, as opposed to the original asbestos, which had a highly damaging effect on the cells.