Physicochemical regeneration of industrial spent activated carbons using a green activating agent and their adsorption for methyl orange

Abstract

Thermal regeneration of spent activated carbons (SACs) is widely used in industry. However, low specific surface areas (SBET) of regenerated activated carbons (RACs) are achieved after thermal regeneration, constraining the adsorption of contaminants. Herein, a green chemical mixture of K2CO3 and KCl compared to conventional activating agents was used to regenerate SAC1 and SAC2, all prepared from plants and used to adsorb compounds in pharmaceutical and food factory respectively. Two kinds of RAC were used for the adsorption of methyl orange (MO). The SBET value of SAC1 after regeneration increased from 592 m2 g−1 to 1830 m2 g−1 with an abundance of micropores, and the SBET of SAC2 after regeneration increased from 3 m2 g−1 to 1802 m2 g−1 consisting of mesopores. A high carbon yield of 73% for RAC was achieved due to the presence of a KCl activating agent. A maximum MO adsorption capacity (Qm) of 733.73 mg g−1 and 755.73 mg g−1 was achieved for RAC1 and RAC2, respectively. After five cycles of adsorption-regeneration, the Qm of RAC1 and RAC2 was 577.66 mg g−1 and 567.63 mg g−1, and the SBET was 1122 m² g−1 and 1101 m² g−1, respectively. This work shows that the combination of K2CO3 and KCl can be used as an activating agent to achieve high specific surface area and carbon yield.