Mechanism of chlorpheniramine adsorption on Ca-montmorillonite

An increased detection of common pharmaceuticals and personal care products in surface water and wastewater has rekindled the interests of studying their interactions with solid surfaces. In this research, adsorption of chlorpheniramine (CP), an antihistamine medicine commonly used to treat allergy, onto a swelling clay mineral montmorillonite (MMT) was investigated under kinetic and different solution conditions via batch adsorption, XRD, TG–DTG, and FTIR analyses in order to elucidate the mechanism of CP adsorption on MMT, an important environmental solid matrix, and explore potential use of MMT to remove CP from water. Stoichiometric desorption of exchangeable cations suggested cation exchange as the dominant mechanism of CP adsorption on MMT. The over-balanced desorption of exchangeable cations against the amount of CP adsorption may be attributed to protonation of the two N atoms, thus resulting in a divalent cation adsorption, or adsorption of an extra H+ generated from the second deprotonation of maleic acid. Both external and internal surfaces were responsible for CP adsorption on MMT, resulting in a large CP adsorption capacity of 0.72 mmol g−1, or about 20% by weight. The fast CP adsorption, large CP adsorption capacity, and negligible pH effect make MMT a good sorbent to remove CP from wastewater on one hand and an important environmental sink on the other.