Functionalized locust bean pod (Parkia biglobosa) activated carbon for rhodamine B dye removal

Activated carbon prepared fromlocust beanhusk was modified using ortho-phosphoric acid (ALBP) and used toscavenge Rhodamine B (RhB) dye from aqueous solutions. Characteristic features of the adsorbents were inves-tigated using SEM, FTIR, pHpzcand Boehm Titration (BT) techniques respectively. Batch studies were used todetermine the influences of contact time, temperature and initial Rh–B dye concentrations. Adsorption data wereanalysed using four different isotherm models. The maximum monolayer adsorption capacity of 1111.1 mgg-1wasobtained for RhB dye adsorption. The kinetics of the adsorption process was studied using pseudo-first-order,pseudo-second-order Elovich and intraparticle diffusion models respectively. The experimental data was bestdescribed by pseudo-second-order kinetic model. Favourability of the process of adsorption was also establishedby the separator factor (RL) value ranging from 0 and 1, while the mean energy of adsorption (Ea) was 1.12 kJmol-1suggesting that the removal of Rh–B dye from aqueous solution followed a physisorption process. For thethermodynamic investigations, the positive values ofΔS (280.956 Jmol�1K�1) indicates the affinity of adsorbentfor the Rh–B dye uptake and increase randomness at the solid–solution interface during adsorption of Rh–B dyeonto the surface of the active sites of ALBP. The negative value ofΔG (-31.892 to -26.355 kJmol-1) depicts thespontaneity and feasibility of the adsorption process. The cost analysis provides a simple proof that ALBP (42.52USD per kg) is approximately six times cheaper than Commercial Activated Carbon, CAC (259.5 USD per kg). Thepresent study therefore established the suitability of ALBP for effective removal of Rh–B dye from aqueoussolutions