Fly Ash as a Potential Scrubber of Acidic Wastes from the Phosphate Industries in Israel

Fly ash (FA) is produced in Israeli utilities via bituminous coal combustion. It is used as a cement additive or in concrete production, and its economic value is low. The FA produced in Israel is very basic (defined as class F) owing to ambient air quality standards that impose low sulfur content in the imported coals. Because the lime content is high (in the South African coal, ,10 wt%), it is a good potential chemical scrubber to acidic wastes. The phosphate industry in Israel produces mainly phosphate fertilizers and water-treatment products as well as phosphoric acid. The production methods rely heavily on dissolution of phosphate rock in strong acids, either sulfuric acid (Rotem Amfart plant) or hydrochloric acid (Haifa Chemicals plant). Thus, large quantities of acidic wastes are produced. These wastes have to be treated and neutralized before final storage. The treatment is based upon the addition of lime or calcium carbonate to the liquid waste. Wehavecheckedthepossibility of using FA to neutralize the acidity and fix the trace elements contained within the wastes. The results show that FA isanexcellent scrubber and a veryefficient absorber to the trace elements from the waste. The final product is an aggregate substitute, and because it passes the California Waste Extraction Test leach test, it can be used as a partial substitute for aggregates in the concrete industry. Initial calculations show that the actual economic value of the ash is in the range of 3-5 times better than its present value in utilizing it as a building material (cement additive or as aggregate in the construction industry). Thus, using two wastes (FA and the acidic waste) can result in a green nonpolluting product with an appreciable economic value.