TERMODINAMIKA DAN KINETIKA ADSORPSI [AuCl4]- OLEH ASAM HUMAT TERETERIFIKASI; THERMODYNAMICS AND KINETICS OF THE ADSORPTION OF [AuCl4]- BY ETHERIFIED HUMIC ACID

Ruhama, Luqman Hilmi, Sri Sudiono

2016 | Skripsi | FMIPA

Isolation, purification, etherification, and characterization of humic acid and study of thermodynamics and kinetics of the adsorption of [AuCl4]- have been conducted. Humic acid was isolated from Rawa Pening peat soil, Ambarawa, Jawa Tengah by dissolving the humic acid in NaOH 0.1 M and precipitated with HCl 1 M to pH 2. The isolation result of humic acid was purified by 0.1 M HCl : 0.3 M HF (1:1 v/v). Etherification of humic acid was performed by reacting humic acid with dimethyl sulfate and K2CO3 in methanol solvent. Isotherm models and entalphy values were determined by interacting etherified humic acid with [AuCl4]- solution at various of concentrations and temperatures. Kinetics models and activation energy were determined by interacting etherified humic acid with [AuCl4]- solution at various of times and temperatures. The concentration of [AuCl4]- before and after interactions were analyzed by UV-visible spectrophotometer while that of etherified humic acid before and after interaction were characterized using FTIR and XRD spectrophotometer. The results showed that adsorption of [AuCl4]- by etherified humic acid thermodynamically followed Langmuir isotherm models. The adsorption process occured more spontaneous as temperature increased, and the maximum adsorption capacity (q max) obtained was 315 mg.g-1, enthalpy (?H°) value was 38.1 kJ.mol-1 and entropy (?S°) value was 195 J.mol-1.K-1. The adsorption kinetics of [AuCl4]- by etherified humic acid followed Lagergren kinetics model. The adsorption rate constant (k) increased as temperature increased and activation energy (Ea) value was 39,8 kJ.mol-1.

Kata Kunci : etherified humic acid, adsorption thermodynamics, adsorption kinetics, enthalpy, activation energy, [AuCl4]-