Quaternized Chitosan for Ecological Treatment of Bauxite Mining Effluents

One of the major concerns of mining companies is the safety of their tailing dams. Among the cares required to operate such a dam, a proper treatment of the effluent composing its waste stands out, since that, waste must be treated before returned to the environment. In the process of bauxite beneficiation, the effluent level of turbidity is the discard parameter that deserves attention. In this work, quaternized chitosan (TMCCl-) derivative with cationic charge was synthetized and investigated to be used as coagulant in bauxite treatment for tailing dam effluent. The chitosan (CHT) was quaternized by methylation reaction. The quaternized chitosan structure was characterized by the following techniques: FTIR Spectroscopy and H-1 nuclear magnetic resonance (NMR). Its thermal stability was analyzed by differential scanning calorimetry (DSC) and thermogravimetric analysis. After quaternized chitosan was obtained, analysis with aluminum sulfate, protonated and quaternized chitosan were executed in jar-test apparatus. The tests were conducted in order to find the optimum pH, velocity gradient, coagulant and alkalizer dosages, as well as coagulation, flocculation and decantation time. The studied coagulants showed good results and reduced the effluent turbidity to levels below determined by legislation. By comparing the coagulants, it was possible to state that quaternized chitosan presented higher reduction of effluent turbidity levels; the tests were performed in the same conditions.