Immobilization of humic acid on chitin has been conducted and applied to the adsorption of Cr(III). The humic acid was isolated from Ambarawa-Central of Java soil by using NaOH 0.1 M, while chitin was isolated by deproteination of crab shells by using NaOH 3.5 % (w/v) and followed by demineralization using HCl 1 M. Chitin obtained from ambient-temperature-dried crab shell is named as chitin I, and that from crab shell washed by HOCl solution and followed by drying at ambient temperature is

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... chitin II. The result of acidity determination showed that total acidity of the humic acid was 230.95 cmol/kg, and it was distributed into the acidity of COOH 168.75 cmol/kg, and phenolic-OH 62.20 cmol/kg. The immobilization of humic acid on chitin has been successfully done, adsorbent A with chitin I as the main material and adsorbent B with chitin II as the main material, resulted the adsorbed humic acid of 9.25 and 1.68% (w/w), respectively. Humic acid immobilization on both adsorbent A and adsorbent B was stable up to pH 11. Adsorption of Cr(III) was maximum at pH 5, with rate of constants was in the orde of chitin II>adsorbent B>adsorbent A>chitin I, i.e. 0.3509; ; 0.2488; 0.1553; 0.0568 minute-1, respectively. The capacity of adsorption was in the orde of chitin I>adsorbent B>chitin II>adsorbent A, i.e. 944.77; 912.53; 895.37; 893.81 mg/g, respectively. The energy of adsorption of Cr(III) was in orde of chitin II>chitin I>adsorbent A>adsorbent B, i.e. 22.932; 20,945; 20.312; 19.615 kJ/mol, respectively.