Selection And Toxicity Evaluation Of Hydrophobically Modified Chitosan/Surfactant Binary Systems For Oil Spill Remediation

HMC(Hydrophobically Modified Chitosan)is modified by chitosan which is a kind of resourceful natural macromolecular compound.In this thesis,the effect of HMC on improve the stability of oil-water emulsion dispersed by three kinds of surfactants which are anionic surfactant SDS(sodium dodecyl sulfate),cationic surfactant CTAB(Cetyltrimethyl Ammonium Bromide)and nonionic surfactant Tween80(polyoxyethylene sorbitan monooleate)were studied.And then the effect of HMC on the toxicity of surfactants was also explored.Oil spill for this experiment were gasoline,diesel and crude oil.The oil and water emulsions were prepared by surfactants and different concentrations of HMC solution.The effects of HMC on improve the stability of oil and water emulsions were obtained by direct observation.We can conclude through the direct observation that the stability of the oil and water emulsion dispersed by CTAB has no improvement after adding HMC.The stability of emulsions dispersed by Tween 80 can be improved when the concentration of HMC is high(≥0.8wt%).The stability of oil-water emulsion dispersed by SDS can be significantly improved when the HMC concentration is equal or greater than 0.2wt%.And the oil droplets in emulsion will flocculate when the HMC concentration is lower than 0.06wt%.Mechanism of this phenomenon is that there is charge attraction between HMC and SDS which make it easier for HMC to adsorb on the surface of the oil droplets and affect it’s stability.The bridging effect will cause the emulsion flocculate when the concentration of HMC in the emulsion is low,and HMC will form a polymer layer on the surface of oil droplet which will improve the emulsion’s stability when the HMC concentration is high.The comparison of the turbidity change rate of the emulsion showed that HMC could improve it’s stability,and the higher the HMC concentration,the more obvious the effect was.The Spinning drop interfacial tensiometer results show that the interfacial tension of oil and water in the emulsion added HMC is two order of magnitude lower than the original oil and water interface without any reagent,so the oil spill is still easily dispersed.The results of Zeta potential analyzer on the surface potential of oil droplets show that it can be affected by HMC.When the concentration of HMC in the emulsion is equal or greater than 0.2wt%,the surface potential of oil droplets increase from negative to positive which means HMC has absorb on the surface of oil droplet and affect emulsion’s stability.The acute toxicity test of the test of SDS and SDSH(the solution of SDS added HMC)showed that the LC50 of the two solutions on T.japonicus are respectively 4.254×10-4 wt% and 3.450×10-4wt%,its 95% confidence interval have overlap,indicating that their acute toxicity has no significant different.The IC50 of the two solutions on S.costatum were respectively 7.611 × 10-4wt% and 2.586 × 10-4wt%,indicating that the acute toxicity increased after adding HMC,but when the oil and water emulsion dispersed by the two solutions have same stability,the toxicity of the SDS solution is much greater than SDSH solution.