Abstract
The relationship between the molecular structure of nonionic surfactants and their adsorptivities on activated carbons was investigated. The adsorption isotherms for all water-soluble nonionic surfactants used in this study were Langmuir type and the adsorptivities were higher than ordinary organic compounds. With the increase in the length of polyoxyethylene chain of polyoxyethylene nonylphenyl ether (NP), activated carbons were saturated by NP in lower concentrations, and both the adsorption rate and the amount of adsorbed NP at saturation decreased. For the surfactants with a fixed length of polyoxyethylene chain, the adsorption was favored by the increase in the length of the alkyl chain. An unsaturated bond in the alkyl chain depressed the adsorption. The carbon activated with zinc chloride had large surface area and pores, and was effective for the adsorption of nonionic surfactants. When an aqueous solution of NP was passed through the column of activated carbon under certain conditions, the adsorption efficiency was 90.6%. These results suggest that the use of activated carbon may be very effective for the treatment of wastewater containing nonionic surfactants.
