Adsorption and recovery of alkylphenol polyethoxylates from synthetic wastewater using hexagonal mesoporous silicate

A large amount of alkylphenol polyethoxylate (APnEOs), one of endocrine disrupters, is disposed of directly to biological wastewater treatment plants. But microbial oxidation processes cannot completely degrade these molecules to nontoxic forms. Adsorption and recovery efficiency of APnEOs was investigated using four different types of Hexagonal Mesoporous Silicate (HMSs) and powdered activated carbon (PAC). HMSs were synthesized by surfactant-templating methods, and two of them were subsequently grafted with surface functional groups. The two types of organic functional groups grafted on the surface were n-octyldimethyl- and 3-mercaptopropyl- groups. Titanium substituted HMS was also made in the same way as HMS. Adsorption of APnEOs on synthesized HMSs was higher than that on PAC. Larger pore sizes of HMS and Ti-HMS enhanced accessibility of APnEOs to active surface sites in mesopores, which realized higher adsorption capacities and L-shape (Langmuir) adsorption isotherms. Adsorption capacities of APnEOs are influenced by water solubility of APnEOs. APnEOs adsorbed on HMSs can be completely recovered by a mixture of alcohol and water at 5:5 ratio, which is more effective than the recovery from PAC.