Preparation Of Modified Straw Adsorbent And Study On Its Adsorption Of Surfactants

With the continuous promotion of the concept of sustainable development of water resources,the treatment and reuse of greywater in rural areas has gradually become a new model for countryside water conservation pathways based on the concept of fractionated collection.Typical pollutants in greywater,anionic surfactants,pose a certain threat to both ecological environment and human health,and the enhancement of anionic surfactants removal method is of great practical significance to promote environmental green development.The adsorption method has significant advantages for the treatment of rural greywater.In this study,a bio-inspired polyethyleneimine-tannic acid(PEI-TA)complex was innovatively used for the coating of corn straw(CS),and the prepared modified straw(PEI-TA@CS)was used for the adsorptive removal of anionic surfactants sodium dodecylbenzene sulfonate(SDBS).The main research content and experimental results of the thesis are as follows:(1)The results of life cycle assessment showed that the method of PEI-TA coating modification caused the least environmental impact compared to the preparation of straw-based biochar,alkali modification and etherification treatment,and is an environmentally friendly method;(2)The optimal preparation conditions of PEI-TA@CS: TA concentration of 0.5g/L,PEI molecular weight of 3000 Da,PEI concentration of 5 g/L and modification time of 3 h.The removal of SDBS by PEI-TA@CS prepared under optimal conditions was 94.95%,which was much higher than the 8.81% of the raw straw.Adsorbent morphology and surface element characterization results showed that the PEI-TA coating was successfully coated on the surface of the corn straw.(3)At pH ≤ 7,the adsorption of SDBS on PEI-TA@CS was almost independent of pH,and the adsorption process reached equilibrium at about 3 h.The pseudo-secondorder and Freundlich model fitted the kinetic and isotherm data well,respectively,and the adsorption of SDBS on PEI-TA@CS was exothermic and spontaneous.The adsorption process was dominated by hydrophobic interactions,electrostatic and π-πinteractions were also contributing to the adsorption process;(4)Compared to the 94.95% removal rate in aqueous solution,the removal of SDBS in synthetic greywater by PEI-TA@CS was reduced to 81.99%.Due to the competitive adsorption of inorganic salt anions and lactic acid,the removal of SDBS from inorganic and organic solutions was reduced to 78.88% and 85.53%,respectively.In general,organic matter inhibited SDBS adsorption less than inorganic salts.