Surface modification of date palm activated carbonaceous materials for heavy metal removal and CO2 adsorption

In this study, high surface area activated carbon (AC) was prepared from a local palm tree (Phoenix Dactylifera) using a variety of metal carbonates activators and finally achieved an excellent SBET of 2700 m2/g when Cs2CO3 was used as an activating agent at a temperature of 600 degrees C. Surface modification of AC was carried out using various nitrogen transporting agents, resulting in N-doped ACs with nitrogen content varying from 4.0 to 11.4 %, depending on the func-tionalizing agents and activators used. The bimodal (presence of micro-as well as meso-porosity) ACs with such excellent surface properties were studied for their CO2 uptake capacity at two dif-ferent temperatures (0 and 25 degrees C) by isotherms recorded at pressure 1 bar and showed a remarkable uptake ability of 3.52 mmol/g (at 25 degrees C) and 5.6 mmol/g (at 0 degrees C), respectively. Also, batch exper-iments with variable pH, contact time, adsorbate concentrations, adsorbent dose, and temperatures were evaluated to understand the mechanism of sorption phenomena of Cr(VI) and Pb(II) achieving > 99.9 % removal capacity by the prepared ACs. Depending on the heavy metal ions being investigated, it was revealed that the pH of the solution and the amount of adsorbent had a direct impact on the total adsorption ability. Nitrogen atoms doped into the carbon frameworks were found to enhance the adsorption in the case of Pb(II) while the removal of Cr(VI) appeared to be unaffected. Maximum adsorption for Cr(VI) was observed at pH 2 and was determined to follow Freundlich isotherm while that of Pb(II) was observed at pH 7 and follows Langmuir isotherm. Best adsorption was found at an adsorbate concentration of 10 ppm and an adsorbent dose of 10 g/L. Kinetic modeling parameters showed the applicability of pseudo-second-order model perfectly.(c) 2022 The Author(s). Published by Elsevier B.V. on behalf of King Saud University. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).