Functionalized sol-gel material for extraction of mercury (II)

1,5 Diphenylcarbazide (DPC) functionalized sol-gel silicas (DPCSG) were prepared and investigated for the solid phase extraction of Hg(II) from aqueous solution by a batch equilibrium technique. The metal sorption properties of DPCSG were examined to evaluate their performance toward metal extraction under different controlling factors, such as pH of solutions, equilibration shaking times, effect of foreign ions and complexing agents. The equilibration was fast and was achieved within 30 min. Maximum extraction capacity of Hg(II) ions onto the DPCSG from non-competitive solutions was 5.6 mg/g (0.028 mmol/g) at 28 ± 2 °C and the enhancement factor was found to be 560 at optimized pH 6 when compared with control and commercial silica gel. The adsorption data obtained as a function of mercury concentration were fitted to a Langmuir adsorption model. The stripping and regeneration of the sorbent were reported and it was further observed that extraction and regeneration were indicated by the dark violet colouration and decoloration of the extractant, respectively. It is concluded from the extraction data that DPCSG is a promising material for the extraction of mercury.