Phthalate-functionalized Sorghum bicolor L.; an effective biosorbent for the removal of Alizarin Red S and Bromophenol blue dyes from simulated wastewater

This study aims to modify the agricultural waste, that is, Sorghum bicolor L. by means of phthalic anhydride for the enhanced removal of reactive dyes. This modified Sorghum was characterized by means of using Fourier-transform infrared spectroscopy-spectra, scanning electron microscope, pHpzc, and by Boehm’s titration for the determination of acidic and basic groups. Alizarin Red S (ARS) and Bromophenol blue (BPB) were used as a substrate for removal. The observed optimum values were 0.1 g/50 ppm for ARS and 0.1 g/30 ppm for BPB at neutral pH within 25–30 min at room temperature. The equilibrium statistics fitted well in the Langmuir equilibrium model with maximum adsorption capacities of 285.71 and 65.78 mg g–1 for ARS and BPB, respectively. The kinetic data was followed by the pseudo-second-order rate equation. The thermodynamics study revealed that the process was exothermic and spontaneous.