A comprehensive new study on the removal of Pb (II) from aqueous solution by şırnak coal-derived char

Abstract

ABSTRACT In this study, char was prepared from the Şırnak coal derivative as a new adsorbent by the pyrolysis process and successfully applied for Pb (II) removal. Prepared char adsorbent was characterized by analysis techniques such as thermogravimetric (TG)/differential thermogravimetric (DTG), iodine number, scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), and Brunauer–Emmett–Teller (BET) surface area. In the experimental design of the Pb (II) removal process, the relationship between operating factors (contact time, initial Pb (II) concentration and temperature) and process responses (adsorption capacity and removal efficiency) was modelled by applying response surface methodology (RSM). After that, the operating factors for the maximum adsorption capacity and removal efficiency of Pb (II) by char were optimized. In the removal of Pb (II), pseudo-first order and pseudo-second order kinetic models were used to determine the process mechanism. In addition, adsorption isotherm models such as Langmuir, Freundlich, and Dubinin-Radushkevich were applied to the equilibrium data to explain the adsorption mechanism between the adsorbent and adsorbate molecules. According to the results obtained, it was determined that kinetic and equilibrium isotherm data were better defined with pseudo-second order kinetic and Dubinin-Radushkevich isotherm models, respectively. The optimum values of the contact time, initial Pb (II) concentration, and temperature for maximum adsorption capacity (124.64 mg/g) and removal efficiency (92.35%) of Pb (II) were found as 150.00 min, 144.81 ppm, and 35.06°C, respectively. This study indicated the application potential of Şırnak coal-derived char as a promising cost-effective adsorbent for the removal of heavy metals.