Coal-based granular activated carbon loaded with MnO2 as an efficient adsorbent for removing formaldehyde from aqueous solution

In this study, coal-based granular activated carbon loaded with MnO2 (ACLM) was tested as adsorbent for the removal of formaldehyde from aqueous solution. The ACLM was characterized by scanning electron microscopy, energy dispersive X-ray spectrometry, Brunauer-Emmett-Teller, and Fourier transform infrared spectra. The optimized pH of formaldehyde adsorption was 7.0. The removal percentage increased from 21.8 to 72.1% by raising the ACLM dosage from 0.1 to 1.0g. The formaldehyde adsorption rate increased a little at initial formaldehyde concentrations from 0.6 to 1.8mg/L. The adsorption equilibrium time was 24h. The adsorption rate of formaldehyde increased from 58.1 to 61.2% with temperature rising from 298 to 308K and decreased from 61.2 to 54.0% when temperature from 308 to 318K. Isotherm modeling revealed that Langmuir equation could better describe the adsorption of formaldehyde onto the ACLM and the maximum adsorption capacity obtained was 4.53mg/g. Kinetic data efficiently fitted with the pseudo-second order. The decrease of G degrees from 298 to 308K suggested more favorable of formaldehyde adsorption onto the ACLM and increase of G degrees from 308 to 318K revealed that the sorption was more unfavorable. Results from this study suggest that ACLM is an effective adsorbent for the removal of formaldehyde from aqueous solution in drinking water treatment field.