Coal-derived mineral matter is used to capture or remove combustion gas emissions from flue gas or exhaust gas. The coal-derived mineral matter may be obtained by separating it from coal particles, such as by use of a flotation separation process. Coal-derived mineral matter may also be present in fine coal refuse. In the method of removing combustion gas emissions from flue gas, an aqueous suspension of coal-derived mineral matter particles is contacted with the combustion gas emissions for sufficient time to cause the combustion gas emissions to react with the aqueous suspension and form an enhanced aqueous suspension. The combustion gas emissions may comprise NOx, SOx, CO, or mixtures thereof. An aqueous suspension of coal-derived mineral matter particles containing enhanced amounts of soluble and insoluble sulfate, sulfite, nitrate, nitrite, or carbonate reaction compounds formed by reaction of the aqueous suspension of the coal-derived mineral matter particles with combustion gas emissions.