Emerging highly porous activated carbon by pyrolysis-KOH chemical simultaneous-CO2 physical activation of waste tires for Cr(VI) and Cd(II) removal

Abstract

Abstract In this work, waste tires (WTs) were carbonized under an N2 atmosphere, and then KOH/WTs-char with KOH assisted-CO2 activation was used to prepare activated carbon (AC) as an emerging highly porous carbon to remove Cr(VI) and Cd(II) from a water media. Several techniques, including elemental analysis, Fourier-transform infrared spectroscopy, scanning electron microscopy, and N2 adsorption/desorption techniques, were operated to explore the physical and chemical features of the as-prepared carbons. The WTs-char activated with KOH under CO2 displayed a microstructure with a high BET surface area and pore volume of 1841 m2/g and 0.869 cm3/g, respectively, that exhibited excellent adsorbent performance. Adsorption kinetics was well-matched with the pseudo-second-order equation, and all equilibria were well-matched with the Redlich-Peterson isotherm equation. The positive values of ∆Go confirmed that the uptake process of both ions was nonspontaneous and that feasibility increased with increasing temperatures. The negative values of ΔH° and ΔS° were attained for both ions on carbon, revealing the exothermic nature of the adsorption and disorder decrease. However, the small activation energy revealed that the adsorption was kinetically favored. This study demonstrated the preparation of emerging carbon by effectively high pore structures and the adsorption performance of the carbons on Cr(VI) and Cd(II) ions.