The description relates to production of fly ash with properties suitable for use in Portland cement. The fly ash compositions will contain coal ash, water-insoluble copper compositions and metallic mercury adsorbed onto ash particles. In one aspect, the coal ash composition will have a total mercury content of from 0.1 to 2.0 ppm and the water-soluble mercury is less than 20% of the total mercury content. The process entails combusting coal to produce hot combustion gases containing fly ash, CO2, chlorine, and mercury, cooling the combustion gases and introducing into the combustion gases at a temperature of less than 1000° F., preferably within the range of from about 250° to about 900° F., a copper-based chloride remediator (CBCR), and collecting the fly ash which comprises insoluble copper compositions and water insoluble mercury compositions.