Heavy metal removal from aqueous solution using carbonaceousK2S-impregnated adsorbent

A novel carbonaceous adsorbent for heavy metal removal was prepared from raw coal by one-step simple sulfur impregnation usingK2S. Raw coal was mixed with K2S powder and then heated at 800°C for 30 min in nitrogen to produce K2S char. The sulfur contentand form in K2S char were determined, and the ability of K2S char to adsorb Zn2+, Cd2+ and Pb2+ was examined. The K2S impregnationwas e ective at impregnating sulfur into coal, especially in the form of elemental, thiophenic and sulfatic sulfur. The sulfur content ofK2S char was higher than those of raw coal and pyrolysis char. The Zn2+ removal in 2.4 mmol/L of Zn2+ solution by K2S char washigher than raw coal with the removal rate of 100%. K2S char adsorbed Pb2+ and Cd2+ in 24 mmol/L of Pb2+ and Cd2+ solution withthe removal rate of 97% and 35%, respectively. The elution extents of adsorbed Pb2+ and Cd2+ were zero in distilled water and 27%in 0.1 mol/L HCl solution. These results indicated that an e ective adsorbent for heavy metal ions was prepared from coal using K2Ssulfur impregnation, and that the adsorbed metals were strongly retained in K2S char.