Potentials of NaOH modified agricultural waste of sorghum bagasse for lead (II) removal from aqueous solution: kinetics, isotherm and thermodynamic studies

Abstract

ABSTRACT The removal of lead from water and wastewater is a serious term for protecting the public and the environmental. Herein, an agriculture waste of sorghum bagasse modified with NaOH was used to adsorb Pb(II) from an aqueous solution. The modified sorghum bagasse (MSB) was characterised by field emission scanning electron microscopy (FESEM), Brunauer–Emmett–Teller (BET) method and Fourier transform infrared spectroscopy (FTIR). MSB with NaOH shows smoother, increasing porosity and pore size (mesopore). In a batch system, the parameter adsorption was investigated. The adsorption of Pb(II) by the adsorbents was optimum at pH 5.0, contact time: 15 min, adsorbent dosage: 6 g L−1 and initial concentration: 80 mg L−1. The pseudo second-order model was suitable to describe the kinetic of the process with the diffusion model of the Elovich model. Meanwhile, the adsorption isotherm model was suitable with the Langmuir model and gives a maximum adsorption capacity (qmax) 12.29 mg g−1. The Gibbs free energy was negative, and the enthalpy was negative, indicating the adsorption was a spontaneous and exothermic process. These results indicated that the MSB had potentially become an efficient, sustainable and low-cost adsorbent for Pb(II) uptake from an aqueous solution.