Telah dilakukan imobilisasi asam humat pada kitin dan aplikasinya untuk adsorpsi Ag(I) dalam medium air. Sampel asam humat (HA) diisolasi dari tanah gambut Rawa Pening, Ambarawa, Jawa Tengah, serta sampel kitin (C) diperoleh dari cangkang kepiting laut. Analisis HA hasil isolasi dan C meliputi konfirmasi spektra FTIR dan penentuan kuantitatif gugus karboksilat dan -OH fenolat adsorben HA, serta derajat deasetilasi dan kandungan nitrogen adsorben C. Selanjutnya dilakukan studi imobilisasi HA pada C meliputi; (1) metode imobilisasi, (2) stabilitas HA terimobilsasi, (3) pengaruh keasaman pada adsorben, serta beberapa parameter adsorpsi, yaitu laju, kapasitas, energi dan mekanisme adsorpsi. Hasil penelitian menunjukkan bahwa HA dari tanah gambut Rawa Pening mempunyai keasaman total 642,5 cmol/kg yang terdistribusi ke dalam keasaman –COOH sebesar 342,5 cmol/kg dan –OH fenolat sebesar 300 cmol/kg. serta C mempunyai derajat deasetilasi 45,86% dan kandungan N 4,63%. Imobilisasai HA pada C menghasilkan adsorben asam humat-kitin (HAC) dengan kandung HA 1,9% yang stabil hingga pH 11. Imobilisasi diduga melalui pembentukan ikatan C-O-C dibuktikan dengan munculnya pita serapan pada bilangan gelombang 1031,1 cm-1. Adsorbsi Ag(I) pada adsorben maksimum pada pH 5-6 dengan konstansta laju sebesar 27 x10-4, 22 x10-4, 86 x10-4 menit-1 masing untuk HA, HAC, dan C. Kapasitas adsorpsi sesuai dengan urutan HA>HAC>C masing-masing sebesar 8,6 x10-5, 5,3 x10-5, 8,6 x10-5 mol/g, serta energi adsorpsinya sebesar 25,22, 26,29, dan 28,93 kJ/mol. Desorpsi skuensial menunjukkan bahwa C pada HAC lebih dominan dalam mengadsorpsi Ag(I) yaitu 0,011 mg Ag(I)/mg C, sementara HA sebanyak 0.0026 mg Ag(I)/mg HA. Desorpsi dengan menggunakan HNO3 0,1M, KSCN 1M, dan tiourea 1M, hanya mampu melepaskan masing-masing 19,8%, 25,0%, dan 24,0% Ag(I) dari adsorben HAC, sedangkan desorpsi menggunakan HNO3 0,1M dengan bantuan radiasi sinar UV mampu melepaskan 40,2% Ag(I) dari adsorben HAC, hal ini menunjukkan bahwa adsorpsi Ag(I) pada adsorben HAC terjadi melalui ikatan yang sangat kuat.

Immobilisation of humic acid on chitin has been conducted and applied for the adsorption of Ag(I) in aqueous medium. The humic acid sample was isolated from peat soil of Rawa Pening, Ambarawa, Central Java, while chitin sample gained from marine crab shells. The analysis of the isolated HA and C included the confirmation of FTIR spectra and quantitative determination for carboxyl and phenolic -OH group of adsorbent HA as well as the degree of deacetylation and nitrogen contain of adsorbent C. Moreover, it was also studied of immobilisation HA on C that covered (1) method of immobilisation, (2) stability of immobilized HA, (3) effect of acidity on adsorption as well as the adsorption parameter include rate, capacity, energy and mechanism of adsorption. The results showed that total acidity of the humic acid was 642.5 cmol/kg, and it was distributed into the acidity of –COOH 342.5 cmol/kg and phenolic –OH 300 cmol/kg as well as the degree of acetylation of C was 45.86% and contained N 4.63%. Immobilisation of HA on C produce adsorbent HAC with 1.9% HA contained that stable up to pH 11. Immobilize estimated pass through C-O-C bond formation that evidenced with appear wavenumber at 1031.1 cm-1. Adsorption of Ag(I) was maximum at pH 5-6, with rate of adsorption constants of 27 x10-4, 22 x10-4, 86 x10-4 minute-1 for HA, HAC, and C, respectively. The capacity of adsorption was in the order of HA>HAC>C, i.e. 8.6 x10-5, 5.3 x10-5, 8.6 x10-5 mol/g, respectively. The energy of adsorption of Ag(I) on HA, HAC, and C was 25.22, 26.29, and 28.93 kJ/mol, respectively. Sequential desorption showed that C on HAC was more dominant in adsorbing Ag(I) that was 0.011 mg Ag(I)/mg C while HA was 0.0026 mg Ag(I)/mg HA. Desorption using reagents HNO3 0.1M, KSCN 1M, and thiourea 1M can only results 19.8%, 25.0%, and 24.0%, Ag(I) released from the adsorbent HAC, respectively, while desorption using reagents HNO3 0.1M under UV radiation released 40.2% of Ag(I) from HAC adsorbent, its showed that adsorption of Ag(I) on adsorbent HAC has consisted strongly bonded.

Kata Kunci : Adsorpsi Ag(I),Imobilisasi Asam Humat,Kitin