Javanese Volcanic Allophane Adsorbent as Heavy Metal Adsorber to Improve the Quality of Drinking Water in Surakarta

Abstract

The present study is concern with the identification, characterization and activation of natural allophane as an adsorbent of heavy metal ions Cr, Fe, Cd, Cu, Pb and Mn. The purposes of this study were to identify and characterize the natural allophane of Javanese volcanoes (Papandayan, Arjuna and Wilis), and to determine the optimum conditions of adsorption and adsorption isotherms that happened. The identification of natural allophane was performed by using NaF, pH, FTIR, and XRD. The characterization of the acidity of allophane was analyzed by using ammonia adsorption. The activation was done in the NaOH solution of 1 N and 3 N, and in the soaking time of 1, 3, and 5 hours. The adsorption was done according to batch method with the variations of contact time of 30, 60, 90 and 120 minutes. The adsorption isotherms performed by using the variations of the amount of adsorbate. Atomic Absorption Spectroscopy (AAS) was used in the analysis to determine the concentration of heavy metal ions in solution. The results show that the analysis of NaF, pH, FTIR and XRD indicate the presence of  allophane in the volcanic samples. The optimum conditions of activation and adsorption of the metal ions of Cr and Cd are in  the activation of NaOH 3N for 3 hours within 120 minutes contact time, those of metal ions of Fe are in the activation of NaOH 3N for 1 hour within 30 minutes contact time, those of the metal ions of Pb and Mn are in the activation of NaOH 3N for 5 hours within 90 minutes contact time, and those of  metal ions of Cu are in the activation of NaOH 3N for 5 hours within 60 minutes contact time. The adsorption isotherms performed to all kinds of metals follow Freundlich equation which suggests that physical interactions occur. Thus, an activation with NaOH can increase the acidity ??of allophane causing to improve adsorption capacity to the metals by about 50-100%..

Keywords: allophane, heavy metals, adsorption