Construction Of The Integrated System Of Corrosion And Bacteriostasis Based On Layered Double Hydroxides And Its Performance Study

Layered double hydroxides(LDHs),commonly known as hydrotalcites,is a class of two-dimensional layered material with good adsorption and controlled release properties.The LDHs are mainly composed of metal cations and interlayer anions.The metal cations are adjustable and the interlayer anions can be exchanged,which greatly enriches the application range of LDHs.This study is based on the special structural characteristics of LDHs,to prepares the LDHs with dual functions of corrosion inhibition and antimicrobial activities by changing the metal cations and intercalation anions containing different functional groups of corrosion inhibitors,This research is carried out from the following three aspects:(1)First,Nitrate-type LDHs were synthesized as a precursor by co-precipitation method,and then vanillin(Vanillin,Van)with good corrosion inhibition effect was intercalated into LDHs by ion exchange method.Next,silver nanoparticles were deposited on the surface of LDHs by silver ammonia reaction to prepare Ag/Mg Al-Van-LDHs(N).Scanning electron microscopy(SEM),X-ray diffractometer(XRD),Fourier transform infrared spectrometer(FTIR),electrochemical impedance spectroscopy(EIS),bacterial growth curve and other test analysis were performed on Ag/Mg Al-Van-LDHs(N).The results showed that Mg Al-NO₃^--LDHs showed irregular lamellar shape by SEM observation.The diameter of the LDHs lamellar layer was about 1?m and the thickness was about tens of nanometers.After Van intercalation,there was no obvious change in the morphology of LDHs.However,the XRD characteristic peaks(003)and(006)of LDHs shifted to the left,and the interlayer spacing became larger.The EIS test shows that the LDHs have a good corrosion inhibition efficiency,which maintains above 86%within 24 hours.Bacteriostasis experiments show that Ag/Mg Al-Van-LDHs(N)has very good antibacterial performance,and the inhibition rates against E.coli and Staphylococcus aureus reach 99.65%and 99.79%,respectively.(2)Carbonate LDHs were prepared by the decomposition of urea,in order to prepare Ag/Mg Al-Van-LDHs(C).CO₃^2-as an interlayer anion is tightly bound to the LDHs plate layer,so it is difficult to intercalate corrosion inhibitor by ion exchange method.Therefore,it is necessary to calcinate Mg Al-CO₃^2--LDHs at high temperature to remove CO₃^2-,and then obtain mixed metal oxides(MMOs).Then Van intercalates by rehydration to obtain Mg Al-Van-LDHs(C),and finally nano-silver particles are deposited on the surface of Mg Al-Van-LDHs(C)by silver ammonia reaction,and the final product is Ag/Mg Al-Van-LDHs(C).Through the analysis of SEM,XRD,FT-IR,EIS,bacterial growth curve test and other characterization methods,it was observed that Mg Al-CO₃^2--LDHs showed a regular hexagonal structure under SEM,and the size of the sheet was large,up to 5?m.After calcination,the MMOs are still regular hexagons with cracks on the surface.At the same time,XRD results show that MMOs do not have the typical layered structure of LDHs.After intercalating Van by hydration,XRD characteristic peaks(003)and(006)were re-measured and shifted to the left,indicating that the layered structure of LDHs was restored and the interlayer spacing became larger.EIS results show that Ag/Mg Al-Van-LDHs(C)has good corrosion inhibition performance,and the corrosion inhibition efficiency is maintained at 97.63%at 24 h.In addition,the results of the antibacterial test showed that the antibacterial effect of Ag/Mg Al-Van-LDHs(C)was not obvious,and the inhibition rates against E.coli and Staphylococcus aureus were only 43.99%and 17.80%.(3)Zn Ti-LDHs are prepared by reverse phase microemulsion method,which can synthesize corrosion inhibitor intercalation LDHs in one step.First,the active agent is added to the organic solvent to prepare a mixed liquid containing a microemulsion mixing unit.Then the metal salt and corrosion inhibitor are gradually added to the mixed solution and fully dissolved.Then,the mixed solution reacts under high temperature and high pressure conditions.Finally,Zn Ti-LDH and Zn Ti-Vc-LDHs and Zn Ti-Van-LDHs intercalated with corrosion inhibitor were synthesized.Zn Ti-LDHs were tested by SEM,XRD,FT-IR,EIS,bacterial growth curve,etc.Zn Ti-Vc-LDHs and Zn Ti-Van-LDHs show irregularly shaped flakes under SEM,and the diameter of the flakes ranges from tens of nanometers to 1?m.XRD showed that the characteristic peaks(003)and(006)of LDHs shifted to the height after the corrosion inhibitor intercalation.Because the molecular weight of intercalated organics Van and Vitamin C(Vc)is less than the interlayer anion sodium lauryl sulfate(SDS)of Zn Ti-LDH,the interlayer spacing of LDHs becomes smaller after intercalation;At the same time,the EIS results show that the corrosion inhibition efficiency of Zn Ti-Vc-LDHs and Zn Ti-Van-LDHs is good,which are 90.47%and91.97%respectively at 24 h.After the bacteriostasis test,it was found that Zn Ti-Vc-LDHs and Zn Ti-Van-LDHs had good bacteriostasis,the inhibition rates against E.coli were 93.57%and 92.63%respectively,and the inhibition rates against Staphylococcus aureus were 91.34%and 97.23%.In addition,Zn Ti-LDH has a more excellent antibacterial effect,the inhibition rate of Escherichia coli and Staphylococcus aureus were 100.00%and 99.63%,respectively.