Peanut shell biochar for Rhodamine B removal: Efficiency, desorption, and reusability.

A high-performance and affordable peanut shell-derived biochar was employed for the efficient removal of Rhodamine B (RhB) from aqueous solutions. The properties of peanut shell biochar (PSB) were investigated through Fourier transform infrared (FTIR) spectroscopy and Brunauer-Emmett-Teller surface area measurements. The FTIR analysis revealed numerous active sites and functional groups for the binding of dye molecules, while the BET surface area was determined to be 351.11 mg. Four different isotherms and kinetic models were applied to determine the equilibrium adsorption of RhB, and the results indicated that the Freundlich isotherm was the most appropriate model. A maximum dye removal rate of 94.0% occurred at a pH of 3 with an adsorbent dose of 0.325 g L. The prepared adsorbent showed excellent sorbent behaviour and can be reused multiple times after regeneration, with the surface area decreasing from 351.11 mg to 140.13 mg after the third cycle. The negative Gibbs free energy ΔG at all applied temperatures suggested that spontaneous adsorption occurred and RhB adsorption on the PSB was found exothermic, as evidenced by the negative value of ΔH. The regenerated PSB can be utilized as an efficient, environmentally friendly, and cost-effective sorbent for the removal of dyes at temperatures lower than ambient temperature, providing both technical and financial advantages for sustainable environmental management.