SYNTHESIS AND ADSORBENT APPLICATION BASED ON SILICA FROM VULCANIC ASH SINABUNG FOR HEAVY METAL ADSORPTION ON Cd (II)

Synthesis of silica gel has been done by utilizing the volcanic ash Sinabung Mountain taken Berastepu Village, Simpang Empat, Karo within 1.5 km from the top of the Sinabung Mountain. Volcanic ash is one of the biggest source of silica, potentially as materials for synthesis of silica gel. Synthesis of silica gel in this study conducted by sol-gel method. Volcanic ash in the destruction carried out with NaOH 4M solution and establishment of gel with HCl 3M solution. The result of synthesis of silica was characterized with AAS, FTIR, and XRD. The levels of silica obtained in this study amounted to 17,85%. Based on the results of analysis by FTIR pointed to the existence of the siloxane (Si-O-Si) and silanol (Si-OH) functional groups stating that the silica adsorbent was successfully formed. The XRD analysis showed amorphorus structure of silica. The silica gel was result of synthesis used as adsorbent to adsorps heavy metal Cd(II). The method used in interaction adsorbent with a solution is batch method. The determination of the optimum mass of silica adsorbent was carried out on variations (0.1, 0.15, 0.2, 0.25, 0.3) g. Data obtained using AAS showed that optimum absorption was obtained at 0.1 gram of silica with adsorption capacity of 17.95 mg/g.