Removal of formaldehyde and methylene blue from aqueous solution by adsorption on cerium-doped activated carbon: a comparative study

Abstract

ABSTRACT The present study deals with the adsorption mechanisms of methylene blue (MB) and formaldehyde (FA) in aqueous solution using cerium-doped activated carbon (Ce/AC). Firstly, the cerium-doped carbon material was synthesised and characterised by scanning electron microscopy–energy dispersive spectrometry (SEM-EDS), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR). The experimental results obtained have shown that MB and FA molecules were adsorbed onto Ce/AC through various mechanisms. The resulting cation from the dissolution of MB was rapidly adsorbed during the first 5 min, and reached equilibrium after 15 min of contact time. Whereas, the rapid phase of methanediol adsorption, a molecule obtained by reaction of FA with water molecules in equilibrium with its anion, took place during the first 40 min and reached equilibrium within 150 min. The MB adsorption data fitted well Langmuir II isotherm model, while the FA adsorption equilibrium was non-linear. The covered surface by the both two molecules increased linearly with their initial concentration. Also, the FA molecules were more adsorbed compared to MB molecules onto Ce/AC. This result was consistent with the pseudo-second order kinetic model, showing the MB maximum chemisorbed elimination of 76% against 92% for FA. These findings clearly demonstrated the high ability of Ce/AC to adsorb dye and volatile molecules from aqueous environment. Therefore, the Ce/AC is promising material that can be used as an environmentally friendly adsorbent for wastewater treatment purpose.