Remediation of rhodamine B dye from aqueous solution by alkali and acid treated casuarina seed powder as low-cost adsorbent: adsorption dynamics, kinetic and thermodynamic studies

The purpose of the current study was to assess the sorptive properties of casuarina seed powder (CSP) to get rid of the dye rhodamine B (RhB). Activators' roles (acid and alkali) in modification of the sorbent characteristics were studied. CSP and activated CSP features were analyzed by the textural characteristic study, scanning electron microscope (SEM) analysis, FTIR (Fourier-transform infrared (FTIR) spectroscopy) spectrum study, elemental composition and thermal degradation study. Thermodynamic studies were performed and Delta G degrees, Delta H degrees and Delta S degrees were calculated. Batch adsorption studies were done to examine the effect of solution pH (4-12), temperature (25 to 45 degrees C), dosage (0.1 to 1.2 g/L) and dye concentration (50 to 200 mg/L) on removal of RhB. The findings indicate that alkali-treated CSP biomass achieves a maximum removal efficiency of 98.05% at an initial concentration of 200 mg/L, a temperature of 35 degrees C, a pH of 7 and a sorbent dosage of 0.6 g/L for the alkali-treated CSP. Langmuir isotherm shows good regression with a maximum uptake of 28.5, 25.8 and 32.57 mg/g using raw CSP, acid-treated CSP and alkali-treated CSP, respectively. The experimental data fits well with the pseudo-second-order model equation and was better governed. The adsorption is found to be endothermic and spontaneous at high temperature. The results suggest that modified CSP can be a suitable candidate for the removal of dyes.