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 used, which were 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 results showed that CAC had higher specific surface area (978.4 m2 g-1) than the other adsorbents. 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 the other adsorbents. Also, the Langmuir isotherm model was fitted better to the laboratory data due to the higher R2 value compared to the Freundlich model. Moreover, the experimental data followed the pseudo-second order kinetic model. The highest adsorption capacity of formaldehyde was 48.5 mg g-1. Study of the reusability of adsorbents showedthat the CAC had a remarkable recyclability and it could be used in seven cycles with high sorption efficiency (>90%).