Study On The Phytotoxicity And Oxidative Detoxification Of Surfactants With Different Structure

In order to investigate the toxicity of surfactants with different structures and their photocatalytic degradation products in aqueous solution,three anionic surfactants（SDBS,SLS and SDS）and four cationic surfactants（1227,1427,2HEAC-12 and 1831）were selected as the model pollutants.The germination tests of radish（Raphanus sativus）and cucumber（Cucumis sativus）seeds were respectively carried out using aqueous solutions containing different concentration of surfactants as culture media,The root length,bud length,fresh weight and dry weight of the germinated seeds were determined and the corresponding inhibition rate and half inhibition concentration(IC₅₀)of the surfactants used in the seed germination tests to evaluate and compare their phytotoxicity.Acrylic acid-modified PP fiber iron complex（Fe-PAA-g-PP）were then used as a heterogeneous Fenton catalyst for the photocatalytic oxidative degradation treatment of both surfactants（SDBS and 1227）.UV-Vis and TOC measurements were applied to identify the degradation products during the photocatalytic treatment.Finally,The germination tests of the two kinds of seeds were carried out with the surfactant aqueous solutions after the photocatalytic oxidative degradation for different time as the culture medium,and the above parameters were measured and calculated to determine the photocatalytic oxidative degradation and detoxification performance of Fe-PAA-g-PP/H₂O₂system for both surfactants.The results showed that the root length,sprout length,fresh weight and dry weight of germinated seeds decreased significantly with the increase of surfactant concentration.Cationic surfactants showed much lower IC₅₀values than anionic surfactants in the germination tests of radish and cucumber seeds.This means that cationic surfactants had a significant toxic effect on both germinated seeds than anionic surfactants at the same conditions,which was mainly due to the presence of quaternary ammonium salts in the molecular structure of cationic surfactants.Under the same conditions,the IC₅₀values of different surfactants for radish seed was significantly lower than their correspond values for cucumber seeds.This proved that radish seeds are more sensitive than cucumber seeds to surfactants during the germination process.More importantly,Fe-PAA-g-PP could promote the oxidative degradation of surfactants in water by H₂O₂under light radiation conditions.In addition,increasing the Q_Fevalue of Fe-PAA-g-PP and the concentration of H₂O₂,introducing light irradiation or acidic medium could significantly enhance the degradation rate of surfactants.Prolongation of the photocatalytic oxidation degradation time could significantly reduce toxicity of both surfactants.The root length,bud length,fresh weight and dry weight of the germinated seeds after irradiation for 5 h were almost same as those of them in distilled water as culture medium.This is mainly due to the gradual degradation and mineralization of surfactants into inorganic substances during the reaction.