Obtaining chitin from the shrimp (Litopenaeus vannamei) exoskeleton as coagulant - flocculant in waters of low turbidity

Abstract

Chitin was obtained from shrimp exoskeleton, with a yield of 27.5 %, identifying the average values for demineralization and deproteinization with a weight percentage of 97.80±3.13 % and 32.18±0.14 % respectively. The biopolymer obtained was characterized by infrared spectroscopy with the presence of link stretch bands –OH at 3386 cm^-1, –NH at 3124 cm^-1, –C = O at 1644 cm^-1 in addition to the characteristic absorptions of bonds –C_sp3H of the carbon chain, which match the structure of the repeating unit of the biopolymer. Chitin was obtained as a white solid in the form of sheets, insoluble in water and diluted acids, soluble in concentrated hydrochloric acid and with a molecular weight of 202.978 ± 1.235 g/mol. The polymer behaves as a coagulant-flocculant of solids suspended in water, producing a reduction of turbidity levels. In experimental concentrations between 0.15-0.45 ppm of chitin, decreases in turbidity are observed, which according to the corresponding theoretical calculations are between 7.55-50.27 %; obtaining the maximum value of 55.84 % in the decrease of turbidity with 0.37 ppm of chitin. Thus, this biopolymer behaves as coagulant-flocculant and produces reduction in turbidity levels; this characteristic makes it a valid alternative to reduce the use of compounds of proven toxicity in the treatment of surface waters for human consumption.