NaOH-modified mesoporous biochar derived from tea residue for methylene Blue and Orange II removal

Abstract

To enhance the adsorption capacity via increasing the pore filling, the exchangeable ions content and electrostatic interaction, a late-model NaOH modified tea biochar for MB and OR-II removal was prepared. The effects of pyrolysis temperature, mass ratio of NaOH/tea residue powder (TRP) and other operation parameters, such as initial pH of the solution, contact time, initial concentration of dyes and adsorbent dosage on OR-II and MB removal in aqueous solution were studied by batch adsorption experiment. The results showed that with 10% w/w NaOH/TRP and pyrolysis at 700℃, the maximum adsorption capacities of BH700-10 of 105.27 and 91.68 mg/g for 250 mg/L MB and OR-II at pH10 or 2, respectively, were observed at 60 min. The adsorption isotherms of MB were in accordance with Langmuir and Sips models while the adsorption of OR-II was better described by the Freundlich model. The pseudo-second-order kinetic model could better describe the adsorption process. The possible interactions involved in the adsorption process was proposed. The results of this study indicated that BH700-10 is a promising low-cost adsorbent in dye wastewater treatment.