Raw Rice Husk Biochar as a Potential Valuable Industrial Byproduct for the Removal of Rhodamine B from Water

Abstract

In this work, raw rice husk biochar (RRHB) was investigated for its potential as a valuable industrial byproduct for the decontamination of water using rhodamine B (RB) as a model pollutant. Specific functional chemical groups that were identified in the structure of the biochar using Fourier transform infrared (FTIR) spectra were determined to be responsible for the interaction between the biochar and the pollutant, explaining the sorption process. The interaction between the pollutant and biochar was also explained by the porosity of the sorbent, as demonstrated by scanning electron microscopy (SEM), and the specific surface area (Brunauer–Emmett–Teller analysis, BET). The ionic charge of the biochar structure was determined based on the point of zero charge (pHPCZ). The best kinetic fit for the sorption of the dye on/in the biochar was obtained with the nonlinear pseudo-second-order and Elovich models. The nonlinear Freundlich isotherm had the best fit to the experimental data, and it was determined that the maximum sorption capacity was ~40 mg g−1. The thermodynamic parameters indicated that the sorption of the RB on/in the RRHB was spontaneous. Overall, RRHB was demonstrated to be a potential biosorbent for cationic dyes such as RB. Finally, it is possible to recover the biosorbent, aggregating value to the byproduct and showing it to be an excellent option for use in water purification filters.