title: Sorption and retention of diclofenac on zeolite in the presence of cationic surfactant.
abstract: Diclofenac (DC) is one of the most widely prescribed non-steroidal anti-inflammatory drugs and one of the commonly found pharmaceuticals in aquatic environments and wastewater treatment plants. It possesses negative charges when solution pH is greater than its pKa value, while most of the soil components and sediment minerals bear negative charges, too, resulting in a net repulsion between the soil minerals and DC. Surfactant-modified zeolite (SMZ) has been studied extensively over the last 20 years for its effective removal of anionic contaminants tested under different experimental scales. However, its application for the removal of anionic drugs, such as DC, was less reported. This study focused on the sorption of DC by SMZ under different physic-chemical conditions, supplemented with instrumental analyses, in order to elucidate the mechanism of DC sorption by SMZ and to expand the SMZ application further. The results showed that the retention of DC was on the external surfaces of SMZ with extremely fast removal rate. Both anion exchange and partitioning of DC into the adsorbed surfactant micelles (admicelles) were responsible for the extended DC sorption. Interactions of DC with SMZ were facilitated with the benzene ring, the CO, and the CH2CH3functional groups.
authors.affiliation: School of Environmental and Municipal Engineering, North China University of Water Resources and Electric Power, Zhengzhou 450045, China. Electronic address: sysunken@126.com.
authors.forename: Ken
authors.initials: K
authors.lastname: Sun
authors.affiliation: School of Environmental and Municipal Engineering, North China University of Water Resources and Electric Power, Zhengzhou 450045, China.
authors.forename: Yan
authors.initials: Y
authors.lastname: Shi
authors.affiliation: School of Materials Science and Technology, China University of Geosciences, Beijing 100083, China.
authors.forename: Xiaoyu
authors.initials: X
authors.lastname: Wang
authors.affiliation: School of Materials Science and Technology, China University of Geosciences, Beijing 100083, China; Geosciences Department, University of Wisconsin-Parkside, Kenosha, WI 53144, USA. Electronic address: li@uwp.edu.
authors.forename: Zhaohui
authors.initials: Z
authors.lastname: Li
mesh_terms: D000327:Adsorption; D002412:Cations; D004008:Diclofenac / Q000737:chemistry* / Q000302:isolation & purification; D004350:Drug Residues / Q000737:chemistry / Q000302:isolation & purification; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008823:Micelles; D008958:Models, Molecular; D013501:Surface-Active Agents / Q000737:chemistry*; D013816:Thermodynamics; D017641:Zeolites / Q000737:chemistry*
chemical_list: D002412:Cations; D008823:Micelles; D013501:Surface-Active Agents; D017641:Zeolites; D004008:Diclofenac
keywords: Anion exchange; Diclofenac; Mechanism; Sorption; Surfactant-modified zeolite