Extraction of Nano Fraction from Volcanic Tuff of Mount Talagabodas, West Java and Its Phosphate-adsorption Characterization

Abstract

Allophane and imogolith, previously regarded as amorphous mineral and now known as crystalline with nano dimension (<5 nm) (Abidin, 2003 in Sugiarti et al., 2010), pose pH-dependent charge and high adsorption capacity of anion such as P. Indonesia is rich in volcanic soils that contain allophane and imogolith. However, research on the potential usage of natural nano materials from the volcanic soils of Indonesia in non-agricultural application has not been done. This study was aimed at to: (1) explore, select and extract positively-charged nano fraction from volcanic tuff materials of Central Java and West Java, (2) know the phosphate-adsorption characteristics of the selected nano fraction, and (3) study the prospects of the selected nano fraction to be used in processing (waste) water contaminated with phosphate. Based on geological maps, exploration and sampling of volcanic tuff materials was done in 15 points that spread from Tawangmangu, Central Java to Bogor, West Java in February 2010. The nano fraction sample preparation, extraction and amonium-adsorption characterization were carried out in the Lab. Soil Chemistry and Soil Fertility, Dep. Soil Science and Land Resource, IPB in March-July 2010. Based on dispersion test, nano fraction containing volcanic tuffs were selected and extracted with the following steps: dispersion in a 1 L-cylinder at pH-4 or pH-10 placed in an ultrasonic apparatus [15 min], sedimentation [20 hours], separation of the top 10 cm solution [containing nano and clay fractions], flocculation with NaCl, redispersion, separation of the nano fraction (which did not settled, <0.2 μm) from the clay fraction (which settled, <2 μm) by mean of centrifugation [3500 rpm, 15 min], flocculation and washing the excess NaCl using dialysis membrane, dilution with distilled water [250 cc] and gravimetrically determination of the amount of the nano and clay fractions. The Langmuir isothermal P-adsorption characterization was done by adding solutions containing 0, 0.5, 1, 2.5, 5, 10, 20, 30, 40 and 50 mg P/L. The P concentration at equilibrium was measured by UV-Vis spectrophotometer at λ 660 nm. From 1 g volcanic tuff of M. Talagabodas, Garut, West Java, it could be extracted 1.31 mg positively-charged nano fraction and 0.81 mg clay fractions only by applying simple principle of dispersion at pH-4 and flocculation. The clay fraction was more effective than the nano one in P-adsorption with an average of 18-30% and 30-49%, respectively, of the initial P concentration with a range up to 15.63 mg P/L. The effectiveness of P adsorption increased with the increasing ratio of fraction:solution or the weight of fraction used. The positively-charged nano fraction extracted from volcanic tuff of M. Talagabodas was prospective to be used in the field of environmental sanitation as a flocculant in P-contaminated (waste) water treatment.