The effect of deproteinization temperature on chitosan extraction for iron metal ions adsorption: Case study in Bangka post tin mining water

This study aims to analyze the effect of deproteination temperature on the chitosan adsorption for iron metal ions in Bangka post tin mining water. Extraction of chitosan was carried out in four steps: deproteinization, demineralization, decolorization and deacetylation of chitin. The effect of deproteinization temperature on deacetylation process was studied. The results shown that the increase of deproteinization from 30°C to 90°C causes the decrease of chitosan deacetylation degree (DD): 65.72%; 64.31% and 63.75% respectively. The increase of deproteinization temperature triggers excess depolymerization which damages the chitin structure so that it has a negative effect on the chitosan DD. The metal content of iron in post tin mining water sample this study reached 6.1 ppm. Adsorption of chitosan on iron metal ions reduced the dissolved levels reaching an average of 99.67% from the initial content. The adsorption of iron lead by chelation mechanism. The reaction of chitosan with iron metal ion lead the formation of complex compounds with chitosan as a ligand and metal ions as the central ion. Based on the ligand strength series in spectrochemistry, the hydroxyl functional group is to the left of the amine group, so that the amine group is stronger than the hydroxyl group in adsorbing metal ions. It is more likely to predict that the valency forces through the sharing of electrons between transition metal cations and adsorbent are the adsorption behaviour may involve. (paper)