Extraction of Silver Ions from Aqueous Solution by Sorbents Based on Carbonized Lignite

If porous carbon materials derived from lignite are modified by means of nitric acid, how does that affect the sorption of silver ions from aqueous solution? To answer that question, we study carbonized lignite produced by box coking at 800 and 1000°C. Oxidative modification by nitric acid is found to reduce the ash content of carbonized lignite. The O/C atomic ratio is increased, and the content of various oxygen-bearing functional groups rises. In addition, the specific surface and the total pore volume of the carbonized lignite increase. Experiments on the sorption of silver ions from aqueous solution by the initial and modified samples show that oxidation of the carbonized lignite does not improve their sorption.