Termodinamika dan Kinetika Adsorpsi [AuCl4]- oleh Asam Humat Tereterifikasi

LUQMAN HILMI RUHAMA, Sri Sudiono, S.Si., M.Si.

2016 | Skripsi | S1 KIMIA

Isolasi, pemurnian, eterifikasi dan karakterisasi asam humat serta studi tentang parameter termodinamika dan kinetika adsorpsi [AuCl4]- telah dilakukan. Asam humat diisolasi dari tanah gambut Rawa Pening, Ambarawa, Jawa Tengah dengan cara melarutkan asam humat dalam NaOH 0,1 M kemudian diendapkan dengan HCl 1 M hingga pH 2. Asam humat hasil isolasi dimurnikan dengan 0,1 M HCl : 0,3 M HF (1:1 v/v). Asam humat murni selanjutnya dieterifikasi dengan dimetil sulfat dan K2CO3 dalam pelarut metanol. Penentuan model isoterm dan nilai entalpi dilakukan dengan menginteraksikan asam humat tereterifikasi dengan larutan [AuCl4]- pada berbagai variasi konsentrasi dan temperatur. Penentuan model kinetika dan energi aktivasi dilakukan dengan menginteraksikan asam humat tereterifikasi dengan larutan [AuCl4]- pada berbagai variasi waktu dan temperatur. Konsentrasi [AuCl4]- sebelum dan sesudah interaksi dianalisis dengan spektrofotometer UV-visibel dan asam humat tereterifikasi sebelum dan sesudah interaksi dikarakterisasi menggunakan spektrofotometer FTIR dan XRD. Hasil yang diperoleh menunjukkan bahwa adsorpsi [AuCl4]- oleh asam humat tereterifikasi secara termodinamika mengikuti model isoterm Langmuir. Proses adsorpsi berlangsung semakin spontan seiring kenaikan temperatur, dan diperoleh kapasitas adsorpsi maksimum (q maks) sebesar 315 mg.g-1, nilai entalpi (∆H°) sebesar 38,1 kJ.mol-1 dan entropi (∆S°) sebesar 195 J.mol-1.K-1. Kinetika adsorpsi [AuCl4]- oleh asam humat tereterifikasi mengikuti model kinetika Lagergren. Nilai konstanta laju adsorpsi (k) meningkat seiring kenaikan temperatur, dan diperoleh nilai energi aktivasi (Ea) sebesar 39,8 kJ.mol-1.

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 (ΔH°) value was 38.1 kJ.mol-1 and entropy (ΔS°) 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 : asam humat tereterifikasi, termodinamika adsorpsi, kinetika adsorpsi, entalpi, energi aktivasi, [AuCl4]-