Synthesis of Silica Based Sorbents and their Uses in Removal of Hg2+ Ions from Water

The mercury sorption properties of commercial silica (CS), activated carbon (AC) and a cation exchange resin (CER) were investigated by the batch process. Thiolfunctionalized silica (TFS), functionalized hexagonal mesoporous silica (FHMC), silylated malonamide silica (SMS), dithiocarbamate anchored silica gel (DASG) were synthesized. The mercury removal from water was estimated over a wide range of initial Hg2+ concentration 1-20 mg/L, contact time 1-12 h, sorbent dose 1-10 g/L, pH 2-7 at temperature 25 degrees C and rpm 190. The sorption increased with increasing contact time but the equilibrium was attained in 6 h. The order of metal removing capacities for these chemical sorbents was SMS > CER > DASG > TFS > FHMS > AC > CS. The sorption followed Freundlich as well as Langmuir isotherms. The present paper shows the possibility of using functionalized silica in designing treatment plants for industrial effluents having low levels of heavy metals.