High adsorption capacities of rhodamine B dye by activated carbon synthesized from cotton stalks agricultural waste by chemical activation

The worldwide water issue had been made worse by water contamination. The development of sustainable techniques to reduce water pollution was urgently needed because dye effluents constituted a major hazard to both the environment and human health. This paper described a simple process for producing cotton stalk-activated carbon (CSAC) using H₃PO₄ activation and agricultural waste (cotton stalks). The CS impregnation ratios of 1:1 and 1:2 were prepared, and they were named CSAC1 and CSAC2, respectively. Using a range of analytical methods, the produced materials' physical-chemical characteristics were examined. The prepared CSAC2 had a BET specific surface area of 461 m²g⁻¹. Additionally, CSAC2 material was employed for the adsorption of Rhodamine B (RhB) dye from aqueous solutions. However, the parameters of time, pH, dose, and dye concentration on the removal efficiency of dye were assessed. The isotherm modeling of the adsorption data over the concentration range (20–100 mg/L) was performed using non-linear regression analysis. In addition, it was shown to have >99.5 % removal efficiency and the adsorption isotherms of dye were significantly described by the Langmuir model with maximum adsorption capacities of 144.36 mgg⁻¹ for RhB. The kinetic modeling revealed that the experimental data followed the pseudo-first order and pseudo-second order rate equations for CSAC2. The negative ΔG° and positive ΔH° values indicated spontaneous and endothermic adsorption process. The work's findings demonstrate that CSAC2, which can be produced quickly, is a great environmentally friendly adsorbent for removing dye from contaminated water.