Comparative study of the adsorption on chitosan beads of phthalate esters and their degradation products

The adsorption behavior of phthalate esters (PAEs) and their degraded products such as phthalate monoesters (MPEs) and phthalic acid (PA) in aqueous solution on chitosan beads was studied. The results of kinetic experiments showed that dibutyl phthalate (DBP) was adsorbed more than di-(2-ethylhexyl) phthalate (DEHP) and dimethyl phthalate (DMP). MPEs exhibited less adsorption than PAEs. Monobutyl phthalate (MBP) had higher adsorption capacity than monomethyl phthalate (MMP) and monoethylhexyl phthalate (MEHP). PA showed the highest adsorption capacity compared to MPEs and PAEs. Fourier transform infrared spectroscopy (FT-IR) was used to characterise the interaction between chitosan and PAEs, MPEs, and PA molecules. Results showed that chitosan adsorbed PAEs mainly due to hydrophobic interactions, and interacted with PA mainly due to interactions between polar active groups. For the monoesters, especially MMP and MEHP, lower hydrophobicity than PAEs and higher hydrophilicity than PA made them less adsorbable.