Chitosan and corn stover derivative bioadsorbent: characterization and application in hexavalent chromium adsorption processes

Abstract

Several studies related to effluents treatment containing heavy metals have been developed, especially those that enable the application of lignocellulosic residues and natural polymers as well as chitosan to obtain adsorbents. In this study, carboxymethylcellulose (CMC) was obtained from corn stover to react with chitosan (CH) and ferulic acid (F) to synthesize a bioadsorbent (CMCCHF). This biomaterial was characterized by Fourier transform infrared spectra, differential scanning calorimetry, thermogravimetric analysis, scanning electron microscopy, and nuclear magnetic resonance. The ideal application condition of CMCCHF in the hexavalent chromium adsorption process was established resulting in a pH of 3.0, 60 min of contact time, and 20 °C of temperature by a physisorption process, according to the pseudo-second order kinetic model and Langmuir isotherm model, respectively. The results showed a maximum adsorption capacity of 80.31 ± 0.67 mg g−1 for the bioadsorbent CMCCHF and 55.04 ± 0.84 mg g−1 for chitosan, which suggests an increase in the adsorption capacity of approximately 46%. A decrease in the solubilization of the adsorbent in acid medium was also observed when compared to chitosan, which favors its application in low pH adsorption processes.