Comparison of Cd2+ adsorption onto amphoteric, amphoteric-cationic and amphoteric-anionic modified magnetic bentonites. (January 2020)

• Record Type: Journal Article
• Authors: Ren, Shuang; Meng, Zhaofu; Sun, Xiuxian; Lu, Haoyuan; Zhang, Mengfei; Lahori, Altaf Hussain; Bu, Shuaibin
• Is Part Of: Chemosphere. Volume 239(2020)
• Publication Date: 2020-01
• Subjects: Magnetic -- Bentonite -- Adsorption -- Cadmium ions -- Surfactants; Pollution -- Periodicals; Pollution -- Physiological effect -- Periodicals; Environmental sciences -- Periodicals; Atmospheric chemistry -- Periodicals; 551.511
• DOI: 10.1016/j.chemosphere.2019.124840
• Languages: English
• ISSNs: 0045-6535

Abstract

Abstract: Organic-magnetic bentonites (OMBts), i.e., amphoteric modified MBt (BS-MBt), amphoteric-cationic modified MBt (BS-CT-MBt) and amphoteric-anionic modified MBt (BS-SDS-MBt), obtained by modifying magnetic bentonite (MBt) with amphoteric surfactant (BS), cationic surfactant (CT) and anionic surfactant (SDS) were investigated with the aim to remove cadmium (Cd 2+ ). The modifier contents, surface charge and Cd 2+ adsorption performances of OMBts were compared, and the influences of pH, temperature and ionic strength on Cd 2+ removal were evaluated. Results showed that modifier contents of OMBts increased in the order: BS-CT-MBt > BS-MBt > BS-SDS-MBt. Although CEC of adsorbents increased in the order: MBt > BS-MBt > BS-SDS-MBt > BS-CT-MBt. The BS-MBt exhibited the highest Cd 2+ adsorption capacity (233.19 mmol kg −1 ) than other adsorbents. The adsorption isotherms could be well described by Langmuir model. The Cd 2+ adsorption capacities on MBt and OMBts increased with an increase in pH, temperature and with a decrease of ionic strength. According to characterizations (FT-IR and XPS) and experiments, Cd 2+ adsorption on MBt and OMBts most possibly involved electrostatic interaction, ion exchange, and surface complexation. Furthermore, the adsorption of Cd 2+ on BS-MBt was also attributed to the chelation. The amidocyanogen group of BS-CT-MBt inhibited adsorption of Cd 2+ due to electrostatic repulsion, while Cd 2+ was adsorbed on BS-SDS-MBt through electrostatic attraction induced by the sulfo group. Graphical abstract: Image 1 Highlights: Organic-magnetic bentonites (OMBts) were prepared and tested for Cd 2+ removal. The charge properties and Cd 2+ adsorption performances of OMBts were compared. The influence of temperature, concentration, pH and ionic strength was studied. Amphoteric modified magnetic bentonite showed the highest affinity for Cd 2+ . Modifying by different surfactants can affect adsorption mechanism.