Preparation of new biocoagulants by shrimp waste and its application in coagulation-flocculation processes

Abstract

Chitin is a natural biopolymer produced from shrimp waste. Chitin has low solubility in usual organic and inorganic solvents. In the present work, it was possible to solubilize the extracted raw materials (biomaterials) through the chemical treatment steps that comprise the chitin extraction process. These biomaterials were characterized and solubilized in green solvents, producing four biocoagulants that were used in surface water treatment. The characterization of biomaterials confirmed a reduction in ash content and an increase in crystallinity when passing through chemical treatment steps, increasing the content of chitin and reaching the purity of 82.3% dry basis. The absorptions in the infrared spectra indicated the presence of the characteristic functional groups of the chitin before and after solubilization. The scanning electron microscopy images revealed chitin fibers randomly distributed. The energy-dispersive X-ray spectroscopy pointed out the presence of elements C, O and N. Biocoagulants were applied to the coagulation/flocculation of surface water, and the performance was investigated by the percentages of turbidity and organic material removal at pH 6.0. The biocoagulant composed of demineralized shrimp waste (DMSW), with a dosage of 200 mgDW L−1, presented the best results for both removals; the turbidity reached more than 95% and the organic matter was 80%. Based on results, the processing and application of solubilized shrimp waste could promote environmental and economic benefits.