Kinetic, isothermal and thermodynamic studies of Reactive Black 5 removal using rice husk ashes and powdered activated carbon

The study aimed to evaluate the potential of rice husk ashes (RHA) as an adsorbent for removing Reactive Black 5 (RB5) dye from water by comparing its performance to that of a commercial activated carbon (PAC) through kinetic, isotherm, and thermodynamic studies. The optimal results were obtained at pH 2.0 using PAC and RHA dosages of 0.4 and 15 g L-1, respectively. The pseudo-second-order model best described the kinetic data, with equilibrium reaching 40 min for PAC and 120 min for RHA. Langmuir model best-described isotherm data, with a calculated maximum adsorption capacity of 154.17 for PAC and 8.49 mg g-1 for RHA. Although RHA presented less adsorption capacity than PAC, the results suggest this viable and cost-effective adsorbent is an alternative to commercially available activated carbons for RB5 removal.