Effect of alkyl properties and head groups of cationic surfactants on retention of cesium by organoclays.
Cationic surfactants modified clays exhibit high sorptive capability toward anionic radionuclides but retention of cationic radionuclides was concurrently reduced. In this study, organoclays were synthesized by intercalating a variety of primary/quaternary alkylammonium species (NH(2)R/(CH(3))(3)N(+)RBr(-), where R = benzyl, dodecyl, and octadecyl) into bentonite MX-80. The effect of surfactant's properties on enhancing or limiting cationic sorption capability was investigated by performing Cs sorption experiments. Experimental results were analyzed using the MINEQL+ software by considering Cs uptake by structural and edge sorption sites. Bentonites that were intercalated with primary alkylammonium surfactants had a higher sorptive capacity than those intercalated with quaternary alkylammonium surfactants. Samples intercalated with octadecyl-bearing surfactants had the lowest sorption rate. XRD and FTIR analyses revealed that each organoclay had a characteristic arrangement of alkyl chains. The cation retention of organoclays was dominated by the extent of hydrophobic interactions affected by the local distribution and arrangement of surfactants. The intercalated primary alkylammoniun surfactants tended to transform into local clusters with a high packing density, leaving more structural sites available for Cs uptake. In contrast, the NH(3)R(+)-surfactants tended to form a denser monolayer over clay surface, inhibiting the retention of Cs at structural sites.
Institute of Nuclear Engineering and Science, National Tsing Hua University, Hsinchu 300, Taiwan.
Tsing-Hai
TH
Wang
Chi-Jung
CJ
Hsieh
Shih-Min
SM
Lin
Ding-Chiang
DC
Wu
Ming-Hsu
MH
Li
Shi-Ping
SP
Teng
D000327:Adsorption; D000465:Algorithms; D000538:Aluminum Silicates; D002412:Cations; D002586:Cesium / Q000737:chemistry*; D000077215:Clay; D006863:Hydrogen-Ion Concentration; D057927:Hydrophobic and Hydrophilic Interactions; D008962:Models, Theoretical; D009930:Organic Chemicals / Q000737:chemistry*; D012984:Software; D017550:Spectroscopy, Fourier Transform Infrared; D013501:Surface-Active Agents / Q000737:chemistry*; D014961:X-Ray Diffraction
D000538:Aluminum Silicates; D002412:Cations; D009930:Organic Chemicals; D013501:Surface-Active Agents; D002586:Cesium; D000077215:Clay