Study On Modification Of Palygorskite Clay And Its Physical-chemical Properties

Attapulgite clay (APT) is a hydrous layer-ribbon Al–Mg silicate mineral withspecial nanometer fibrous crystal structure, its unique crystal structure give it hassome functions such as adsorption and colloid carrier, etc. So it is widely used inpetroleum, chemical industry, building materials, medicine, agriculture andenvironmental protection, etc. However, the fibrous crystals of natural APT prefer toexist as aggregates or crystal bundles because of van der Waals’ force and thehydrogen bonding interaction, APT does not give full play to its colloidal properties.So it becomes one of the study hotspots of APT that how to disaggregate APT crystalbundles and improve its added value. In this paper, in order to improve the viscosityof APT and enlarge its application in the composite materials for the purpose,through the methed of salt treatment, organic modification and high pressurehomogeneous to deal with APT, discussed different modifier and modificationconditions effect on the viscosity of APT, at the same time, applied the modifiedAPT to prepare PVA composite flims, The main research results are as follows:1. APT was modified by different concentration of magnesium acetate solution,the effects on the viscosity of the APT in distilled water and saturated sodiumchloride solution were investigated, such as the suspension concentration, pH value,reaction temperature, stirring time and ageing time, and the modified microstructuresof the APT were characterized and analysed by FTIR, XRD, SEM, BET, Zeta andXRF. Results obtained from this study show that the APT under optimal modifiedconditions with magnesium acetate concentration of10%, suspension concentrationof7.5%, pH value of8, reaction temperature of20℃, stirring time of14h and ageingtime of24h exhibit the highest viscosity. Compared with natural APT, the viscosityof modified APT in distilled wate and saturated sodium chloride solution increasedby63.4%and31.6%respectively.2. APT was modified by different concentration of sodium pyrophosphate, theeffects of sodium pyrophosphate concentration and high-pressure homogeneouspressure on the viscosity of the APT were investigated, the modified microstructuresof the attapulgite clay were characterized by FTIR, XRD, SEM, BET, Zeta and XRF.Results obtained from this study show that sodium pyrophosphate and high pressurehomogeneous process can significantly modified the physical and chemicalproperties of APT. The APT under optimal modified conditions with sodiumpyrophosphate concentration of0.5%and high-pressure homogeneous pressure at 20MPa exhibit the highest viscosity. Compared with the APT of not through highpressure homogeneous, high pressure homogeneous process maked the viscosity ofAPT increase by38.0%.3. On the basis of the APT modification by sodium pyrophosphate, it was dealtwith through high pressure homogeneous method and organic modified by differenttypes of surfactant, the effects of surfactant types and concentration on the viscosityof APT were investigated. Results obtained from this study show that high pressurehomogeneous process, the types and concentration of the surfactant had a significanteffect on the viscosity of APT. The APT under optimal modified conditions withOTAB concentration of0.5%and high-pressure homogeneous pressure of20MPaexhibit the highest viscosity. Compared with the APT of not througu high pressurehomogeneous and modified by0.5%sodium pyrophosphate, the viscosity of APTmodified by OTAB increased by95.5%.4. Appliedd the modified APT to PVA film to prepare PVA/APT nanocompositefilms by film-casting method, investigated the effects of the concentration of APT,the APT at high pressure homogeneous and the types of modified APT on themechanical property and water resistance of the PVA/APT nanocomposite films.Results obtained from this study show that compared with the pure PVA film, whenthe concentrations of APT at20MPa high pressure homogeneous was3%,nanocomposite films had optimal property, elongation at break and tensile strengthincreased by126.01%and69.26%respectively, water absorption reduced by31.20%.The order of different types surfactants modified APT effect on the property ofnanocomposite films was cationicsurfactant> anionicsurfactant> nonionic surfactant.Compared with the pure PVA film, add the APT modified by OTAB and at20MPahigh pressure homogeneous, the elongation at break and tensile strength ofnanocomposite films increased by178.95%and156.09%respectively, waterabsorption reduced by56.01%.