Batch Sorption of Divalent Metal Ions onto Brown Coal

Brown coal, a relatively abundant and inexpensive material is currently being investigated as an adsorbent to remove some contaminants from aqueous solution. The adsorption of some heavy metals from aqueous solutions on the brown coals was studied as a function of pH, contact time, adsorbent dosage and concentration of metal solutions. A carboxyl, phenolic hydroxyl, and metoxyl functional group present on the coal surface was the adsorption site to remove metal ions from solution by means of ion exchange and hydrogen bonding. Effective removal of heavy metals was achieved at pH values of 4.0-5.0. The experimental data have been analyzed using the Langmuir on isotherm models. Under optimized conditions, the percentage of metal removal by brown coal adsorption was over 80%.