Study On Adsorption Of Cadmium Ion On Sepiolite Modified By Manganese And Magnesium Oxides

Xiangtan,with its rich sepiolite resources,has the title of the capital of sepiolite.In order to take advantage of the resources,There is a need to promote the industrialisation of sepiolite in environmental management.The use of sepiolite as a aubstrate for the preparation of environmentally friendly composite materials to solve environmental problems can not only promote the multi-faceted use of sepiolite resources,but also provide an efficient solution for environmental management.In this thesis,sepiolite form Xiangtan was uses sepiolite from Xiangtan as a substrate to prepare environmentally friendly composites to replace inorganic toxic pigments with heavy metal like Pb and Cr inorganic toxic pigments,as well as to adsorb sodium dodecylbenzene sulfonate（SDBS）from wastewater.The synthetic composite material is environmentally friendly,economical and efficient in dealing with all these environmental problems,accelerating the application of sepiolite in environmental management.In this paper,non-toxic pigment yellow 12（PY.12）was used to wrap chitosan（CTS）modified inorganic material sepiolite（CTS-Sep）to form a composite pigment（CTS-Sep/PY.12）and an outer layer of Si O₂ was wrapped to form an envelope composite pigment（CTS-Sep/PY.12@Si O₂）to improve stability.The synthesis conditions were optimised for a concentration of 1%acetic acid（HAc）2.5 g/L chitosan,20%pigment yellow 12 and 10 g/L ethyl orthosilicate（TEOS）at 10 g/L to obtain an encapsulated composite pigment with a similar colour to pigment yellow 12.The physical and chemical properties of the composite pigment and the coating pigment were tested for the resistance to acid,alkaline and anhydrous ethanol.The samples were also analysed by thermal analyser and UV spectrophotometer to test their thermal and photostability.The results show that the UV full wavelength spectral intensity of the encapsulated pigment is significantly lower than that of Pigment Yellow 12 in different environments,confirming that the encapsulated pigment has a higher stability than Pigment Yellow 12.In the thermogravimetric analysis,the mass loss of the composite pigment was reduced by 30.98%compared to pigment yellow 12 and the mass loss of the encapsulated composite pigment was reduced by 4.32%compared to the composite pigment,confirming the best stability of the synthesised encapsulated composite pigment.After characterisation analysis it was found that CTS-Sep and pigment yellow12 are synthetic composite pigments using electrostatic attraction and the Si O₂ layer is formed electrostatically by the hydrolysis of TEOS in the presence of cetyltrimethylammonium bromide（CTAB）.Next,sepiolite loaded with magnesium oxide（Mg O-Sep）is used as a substrate to adsorb sodium dodecyl benzene sulfonate（SDBS）from the wastewater.Among other things,the proportion of magnesium oxide,calcination temperature and calcination time for the Mg O-Sep preparation process as well as the Mg O-Sep concentration,solution p H and reaction time for the adsorption process were optimised.By fitting the adsorption data to the Langmuir isotherm model and the pseudo-second order kinetic model the fit to the adsorption process achieved 0.971 and 0.999.When the reaction temperature was 313 K,the adsorbent（0.8-Mg O-Sep）with 80%Mg O ratio reached675.67 mg/g of SDBS for 180 min at p H=2.Analysis of the thermodynamic data,it was shown that the process of Mg O-Sep adsorption of SDBS increases in entropy and enthalpy and is a spontaneous,heat-absorbing reaction.Characterisation of the physicochemical characteristics of sepiolite before and after modification reveals that the mechanism of the adsorption process is mainly derived from the electrostatic attraction between the two surfaces and the hydrogen bonding between the hydroxyl group and the sulphonic acid group.