Abstract
In this study, a novel adsorbent was prepared by modifying rice husk biochar (RHB) with cinnamic acid (CA). CA introduces the carboxylic group to biochar which is favorable for the adsorption of cationic methylene blue dye (MB) from the aqueous solution. The mechanism of adsorption and characteristics were investigated with the help of experimental and Density Functional Theory (DFT). The adsorption capacity of modified biochar for MB was enhanced (Langmuir Qmax of 277.8 mg g−1, for MB when Co = 200 mg/L, pH = 11, T = 25 °C) respectively. The adsorption kinetics plots were consistent with the pseudo-second-order model, indicating chemical adsorption through electrostatic interactions. The adsorption isotherm curves were well matched with the Langmuir model indicating the monolayer mechanism of adsorption. Based on DFT calculations the reactive sites were predicted by the ways of Molecular Electrostatic Potential (MEP). The material properties of CA-RHB were investigated by different characterization techniques (SEM, EDS, XRD, and FTIR). The investigation of various parameters indicates that the adsorption process increases with increasing pH, contact time, and dosage. The study suggests that modified rice husk biochar can be a promising sorbent for the adsorption of Methylene Blue (MB) from aqueous mediums.
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•Rice husk based adsorbent modified with cinnamic acid was successfully synthesized.•R2 values of pseudo first and second order were 0.08342 and 0.999.•Adsorption mechanism is based on ion exchange, H·B, π-π, and ES interactions.•Maximum monolayer adsorption capacity (277.8 mg/g) was achieved.