Sorption of nonylphenol on Na-Montmorillonite

Sorption of nonylphenol on Na-montmorillonite was studied by batch experiment and compared with that on α-SiO2, α-Al2O3 and gibbsite. It was found that sorption of nonylphenol on Na-montmorillonite reached the equilibrium state within 24 h, and that the interlayer width of Na-montmorillonite did not change before and after the sorption. These suggest that nonylphenol was sorbed on the outer surface of Na-montmorillonite. Sorption isotherms of nonylphenol on Na-montmorillonite, α-SiO2, α-Al2O3 and gibbsite were studied. Sorption amount of nonylphenol on the surface of octahedral sheets of Na-montmorillonite was found to be identical to that of gibbsite. On the other hand, sorption amount on α-Al2O3 was smaller, and that on α-SiO2 was fairly few. Dependence of sorption onto Na-montmorillonite on pH and ionic strength was also examined. Sorption amount was found to increase monotonously with pH. Sorption amount decreased with ionic strength in the low ionic strength region, reached to a minimum and then increased with ionic strength. These results might suggest that nonylphenol was sorbed on the broken-edges of octahedral alumina sheets of Na-montmorillonite.