Application of waste tyre-based activated carbon for the removal of heavy metals in wastewater

This study presents the preparation and characterization of chemically activated carbonaceous materials obtained from waste tyres and the prepared adsorbent was applied for the adsorptive removal of Cd(II) and Pb(II) in the domestic wastewater samples. The activation efficiency of phosphoric acid (H3PO4) and hydrogen peroxide (H2O2) were evaluated and H2O2 was chosen as the appropriate activating agent as compared to phosphoric acid. The developed adsorbent was characterized using the scanning electron microscope (SEM), Brunnuer Emmet Teller (BET) which helped to decide which adsorbent material is best in terms of the surface area and Fourier transform infrared spectroscopy (FT-IR). Two-level fractional factorial design was used for the optimization of parameters affecting the adsorptive removal of Cd(II) and Pb(II). The optimum conditions were found to be 6.5, 0.2 g, 32.5 min and 55 mg L−1, for sample pH, mass of adsorbent, contact time and initial concentration, respectively. Amongst every adsorption isotherms that were used, Langmuir model was preferred due to the highest value of the correlation coefficient (r2). Therefore, the adsorption capacities of Cd(II) and Pb(II) were 201 and 196 mg g−1, respectively. The regeneration studies were performed and the adsorbent was capable of been used ten times and the material was stable with only a slight decrease in the removal efficiency of Cd(II) and Pb(II). Furthermore, *Corresponding author: Philiswa N. Nomngongo, Department of Applied Chemistry, University of Johannesburg, Doornfontein Campus, P.O. Box 17011, Johannesburg 2028, South Africa E-mails:[email protected], [email protected] Reviewing editor: Xiaoliang Wei, Pacific Northwest National Laboratory, USA Additional information is available at the end of the article