Removal of Formaldehyde from Aqueous Solution Using Low-cost and Reusable Adsorbents

In this paper, activated carbon (AC) was utilized to eliminate formaldehyde from synthetic sewage. To this end, three kinds of activated carbon were utilized including commercial AC (CAC), AC derived from walnut shell (ACWS), and AC derived from lotus leaves (ACLL). Also, the influence of sorption time, formaldehyde concentration, and adsorbent dose on formaldehyde removal was investigated. The surface properties of the adsorbents were determined by SEM, FTIR and BET analyses. The outcomes showed that CAC has a higher specific surface area (978.4 m2/g) than other adsorbents. Also, the highest adsorption efficiency of formaldehyde using CAC, ACWS, and ACLL adsorbents was 99.2%, 88.2%, and 54%, respectively, indicating significant adsorption capacity of CAC compared to other adsorbents. Also, the Langmuir isotherm model was fitted better with the laboratory data due to the higher R2 compared to the Freundlich model. Moreover, the experimental data follows the pseudo-second order kinetic model. What is more, the utmost adsorption capacity of formaldehyde was 48.5 mg/g. The reusability of adsorbents displayed that CAC has a remarkable recyclability and can be utilized in seven cycles with high sorption efficiency (>90%).