Removal of ppb-level DDTs from aqueous solution using organo-diatomites

Abstract

Three modified organo-diatomites (ODs) were used for removal of o,p′ dichlorodiphenyldichloroethylene (o,p′-DDE), p,p′ dichlorodiphenyldichloroethylene (p,p′-DDE) and p,p′ dichlorodiphenyltrichloroethane (p,p′-DDT) from water. It was found that the adsorption of dichlorodiphenyltrichloroethane (DDT) and its metabolites (DDTs) depended greatly on the type and concentration of modifying agent, the concentration of adsorbent and the initial concentration of DDTs. The hydrophobic characteristics of ODs–DDTs interactions were verified by measuring the amounts of DDTs adsorbed on ODs. The analysis of contact angle and total organic carbon (TOC) measurements revealed that the hydrophilic tails on the ODs surface were replaced with hydrophobic ones by surfactants. The following conditions were strongly suggested to provide the optimum performance for adsorption of DDTs: raw diatomite is modified by cetyltrimethylammonium bromide (CTMAB); dosing quantity of OD is no more than 3.0 g/L. The removal efficiencies of the three pesticides on ODs followed the order: p,p′-DDT > o,p′-DDE > p,p′-DDE. The adsorption efficiencies of ODs for the pesticides followed the order: GZY > GZF > GZYI > GZN. This experiment showed that the fittest models for the experimental data were given by the Redlich–Peterson and homogeneous particle diffusion models.