STUDI ADSORPSI-DESORPSI ANION NITRAT, FOSFAT DAN SULFAT PADA BENTONIT TERMODIFIKASI CTAB; ADSORPTION-DESORPTION STUDIES OF NITRATE, PHOSPHATE AND SULPHATE ANIONS ON CTAB MODIFIED BENTONITE

ADAWIAH, SYARIFAH RABIATUL, Sutarno

2015 | Disertasi | FMIPA

Adsorption-desorption studies of nitrate, phosphate and sulphate on CTAB modified bentonite have been investigated. Research was begun with characterization of materials using FT-IR spectrometer to determine the functional groups in bentonite and X-ray diffractometer to determine the type of minerals in the bentonite. Adsorption was conducted by shaking 10 mg adsorbent in 5 mL adsorbate solution at optimum condition of pH, contact time and concentration. Furthermore, desorption studies was conducted on 5 mL medium of both water and citric acid 0.33 M and using 6.5 mg of adsorbent which has adsorbed nitrate, phosphate and sulphate. The results showed that the bentonite has been successfully modified with CTAB. Studies showed that the adsorption capacity was influenced by the charge and the size of anion. The smaller the charge and the size of anion, the larger the adsorption capacity. The adsorption capacity was in the order: nitrate (0.032 mmol g-1) > phosphate (0.028 mmol g-1) > sulphate (0.020 mmol g-1). The desorption study showed that the percentage of release also influenced by the charge and the size of anion, the bigger the charge and the size of anion, the easier desorption process. Desorption percentage in water at equilibrium time are: sulphate (71,33%) > phosphate (57.81%) > nitrate (50,71%) and in citric acid 0.33 M: sulphate (95,76%) > phosphate (73,33%) > nitrate (59.05%). The result showed that the solubility of the anion in citric acid 0.33 M is greater than in water, this is a requirement for slow-release fertilizer application.

Kata Kunci : CTAB modified bentonite; adsorption-desorption; nitrate; phosphate and sulphate