The effect of alkali treatment on some physico–chemical properties of Xilinhaote lignite

Studies of the simultaneous removal of minerals and acidic functional groups from Xilinhaote lignite were carried out using NaOH solution to identify how the alkali concentration affects some physico–chemical properties of Xilinhaote lignite. Changes in total acidity and carboxylic acid values measured by modified barium ion exchange were investigated along with the ash content. Pore size distribution in the lignite was determined by mercury intrusion porosimetry and N2 adsorption. Adsorption water content was measured by desiccator method. The results show that at low alkali concentrations, NaOH reacts primarily with the acidic functional groups in lignite samples, and the changes in pore volume and adsorption water content are small. At high alkali concentrations, NaOH reacts with the minerals and organic matter simultaneously. A large amount of the elimination of minerals and organic matter causes significant change in increasing macropore volume which may lead to an increase in adsorption water content.