Influence of Quaternary Ammonium on Sorption of Selected Metal Cations onto Clinoptilolite Zeolite

Abstract

Clay minerals and zeolites have large cation exchange capacities, which enable them to be modified by cationic surfactant to enhance their sorption of organic and anionic contaminants. In this study, the influence of quaternary ammonium surfactants on sorption of five metal cations (Cs+, Sr+, La3+, Pb2+, and Zn2+) onto a clinoptilolite zeolite was investigated. Generally, the metal cation sorption capacity and affinity for the zeolite decreased, indicating that presorbed cationic surfactants blocked sorption sites for metal cations, as the surfactant loading on the zeolite increased. Cesium and Pb2+ sorption was affected to a small extent, indicating that selective sorption for Cs+ and specific sorption for Pb2+ play an important role in addition to cation exchange. Sorption of cationic surfactants on zeolite preloaded with different metal cations showed a strong correlation with the chain length of the surfactant tail group, while the roles of the charges and types of the metal cations were minimal. As the chain length increases, the critical micelle concentration decreases and the surfactant molecules become more hydrophobic, resulting in progressive bilayer coverage. Desorption of presorbed metal cations by cationic surfactants was strongly affected by the surfactant chain length and metal type. More metal cations, particularly Sr2+ and Zn2+, desorbed with an increase in surfactant chain length. The results, in combination with those from organic and oxyanion sorption on surfactant-modified zeolite, may be used for future surfactant modification to target sorption and desorption of a specific type of contaminant or a mixture of different types of contaminants.

The concept of “capacity” in zeolite ion-exchange systems

“…The most important clay minerals related to zeolite ores are kaolinite (Al 2 Si 2 O 5 (OH) 4 ), smectites (vermiculite and montmorillonite-(Ca, Na, H)(Al, Mg, Fe, Zn) 2 (Si, Al) 4 O 10 (OH) 2 ·xH 2 O)), and illite ((K, H) Al 2 (Si, Al) 4 O 10 (OH) 2 ·xH 2 O). It is well known that clays exhibit high cation exchange capacities [16]. Several studies have been published on ion exchange of Cs + , U, NH + 4 , K + , Na + , Ca 2+ , and Mg 2+ on several clays such as montmorillonite, vermiculite, and illite [15,17,18].…”

“…From the quartz group, clinoptilolite is found along with quartz and cristobalite [16]. Quartz is a neutrally charged inert mineral.…”

Removal of Cr(VI) and As(V) from aqueous solutions by HDTMA-modified zeolite Y

“…Recently, the utilization of natural zeolites, particularly clinoptilolite modified with cationic surfactant (SMZ) with the purpose to remove multiple types of contaminants from water was studied by many researchers especially from Li and Bowman groups [9,10,11,12,13]. Recent study by Campos showed that the modification of mordenite by ethylhexadecyldimethyl ammonium (EHDDMA) and hexadecyltrimethyl ammonium (HDTMA) can remove hexavalent chromium [14].…”

Removal of chromate from wastewater using amine-based-surfactant-modified clinoptilolite

“…Accordingly, the adsorption of chromate was promoted in the order of increasing carbon number of organic modifier. The correlation between surfactant tail's chain length and metal ion adsorption was previously investigated by Li et al (2002) who concluded that higher chain length elevated the coverage of clinoptilolite surface due to increased hydrophobic interactions. More recently, Xie et al (2013) have highlighted the effect of ordered chain (all-trans zigzag) conformation, which was also shown to increase as the chain length increased.…”