Comparative study of CO2 and steam activation on carbon-derived tire waste for effective arsenic removal from water

Abstract

In this research, char prepared through dry carbonization of tire waste was subjected to two physical activating agents (CO₂ and steam) to prepare effective adsorbent for arsenic ions removal from aqueous solution. The effect of activation temperatures (500, 700, 800 and 900 °C) and the concentration of acid washing (0.0, 0.1 and 1.0M HCl) was also examined for char, CO₂-activted char (C-AC) and steam-activated char (S-AC). Then the char and activated chars were tested for arsenic ion adsorption, considering all parameter of adsorption study such as dosage of adsorbent, pH solution, kinetic and isotherms. To characterize the obtained adsorbents, BET-BJH, FTIR, pH_pzc and XRD analyses were conducted. The results show that the activation temperature has a significant impact on the specific surface area, mass yield and adsorption performance of the adsorbent. The increasing the concentration of acid washing is not considerable effect on adsorption capacity. The mass yield of activation of C-AC is higher than of S-AC at the same temperature. However specific surface (S_BET), pore volume and As-adsorption capacity of S-AC was higher than C-AC. Therefore, the S-AC, with a S_BET of 580.6 m²/g and As-adsorption capacity of 25.1 mg/g (compared to 7.8 and 16.9 mg/g for char and C-AC, respectively), an amorphous and fine crystalline graphite structure was the best porous carbon obtained from tire waste. The optimal pH value for the adsorption process was found to be between 6 and 8. The Langmuir model exhibited a superior fit for C-AC, while the Freundlich model proved more suitable for char and S-AC.