PENGARUH pH TERHADAP ADSORPSI [AuCl4]- OLEH ASAM HUMAT DAN ASAM HUMAT TEROKSIDASI;THE EFFECT OF pH ON THE ADSORPTION OF [AuCl4]- BY HUMIC ACID AND OXIDIZED HUMIC ACID

The effect of pH on the adsorption of [AuCl4]- by humic acid and oxidized humic acid has been conducted. Humic acid was isolated from peat soil Rawa Pening, Jawa Tengah. It was extracted by NaOH 0.1 M and was precipitated by HCl 1 M, then was purified with HCl 0.1 M : HF 0.3 M (1:1 v/v). Oxidation of humic acid was carried out by reacting humic acids with H2O2 3% on the temperature of 70 ?C during 5 hours. The effect of pH on the adsorption [AuCl4]- was determined by reacting humic acid and oxidised humic acid with [AuCl4]- solution on the pH variations of 1 to 6, then was characterized with spectophotometer UV-Visible, FTIR, XRD and microphotography. The ash content in humic acid was 18% and after purification it became 0.67%. FTIR spectra showed that humic acid and oxidized humic acid had functional groups, they were –COOH and –OH, X-Ray difractogram showed three characteristic peaks for gold. Adsorption by humic acid was optimum at pH 2, while oxidized humic acid was optimum at pH 3.