Preparation And Adsorption Mechanism Of Nanomaterials For Efficient Removal Of Organic Dyes And Fluoride From Wastewater

Chemical,pharmaceutical and printing and dyeing industries bring good economic benefits,but also accompanied by the production of a large number of industrial wastewater.For example,a large amount of azo dye wastewater produced by printing and dyeing process contains aromatic structure which is difficult to be degraded;And in non-ferrous metal smelting,aluminum electrolysis,glass,electronic industry and other industries will produce high concentration of fluoride wastewater.Fluorine and organic dye wastewater after initial treatment in their respective factories is difficult to reach the standard,and is collected to urban sewage treatment plants through municipal pipelines;Therefore,the sewage in the municipal sewage plant often contains a mixture of the above two wastewater.However,the mixed wastewater still contains residual organic dyes and fluorides after conventional treatment in sewage treatment plants.Therefore,the further treatment of organic dyes and fluorides in industrial wastewater is beneficial to the protection of environment and human health.The adsorption method has the advantages of wide adaptability,simple and quick operation,good adsorption effect and abundant sources of adsorbents,which has great potential advantages for industrial wastewater treatment.The key to the treatment of industrial wastewater by adsorption is to develop an economically effective,environmentally friendly and renewable adsorbent with abundant sources.Nanomaterials have a large active specific surface area and good adsorption performance,so the application of nanomaterials to adsorb harmful pollutants from industrial wastewater has a broad application prospect.In this paper,three kinds of nano-adsorbents for the removal of organic dyes and fluorine-containing wastewater produced in industry were prepared.The research contents and conclusions are summarized as follows:（1）Molybdenum disulfide（MoS₂）nano-adsorbent was prepared by one-step hydrothermal process using ammonium molybdate tetrahydrate and excess thiourea to treat methylene blue（MB）,an azo dye commonly used in industrial printing and dyeing wastewater.The materials were characterized by scanning electron microscopy（SEM）,X-ray diffraction（XRD）,energy dispersive spectroscopy（EDS）and Fourier transform infrared spectroscopy（FT-IR）.The effects of different preparation conditions on the morphology and crystallization properties of the products were discussed.The experimental results show that MoS₂adsorbent can selectively adsorb MB.The adsorption equilibrium data of MoS₂nano-adsorbent fit the Langmuir adsorption isotherm model,and the maximum adsorption capacity is 200 mg/g.The adsorption process follows a pseudo-second-order kinetic model.The p H value had little effect on the removal rate of methylene blue,with the removal rate above 93.47%,indicating that the MoS₂nano-adsorbent could maintain good adsorption performance under a wide p H condition.（2）Nickel trisulfide（Ni₃S₂/Mo）nanoparticles were prepared by one-step hydrothermal method,which showed good adsorption effect on the common azo dye Congo red（CR）in industry.The structure was characterized by SEM,XRD,EDS and FT-IR,and the effects of different nickel-molybdenum ratios on the adsorption of Congo red were studied.The experimental results show that the Ni₃S₂/Mo nanoparticle adsorbent can selectively adsorb CR.The adsorption equilibrium data of Ni₃S₂/Mo nano-adsorbents conform to the Freundlich adsorption isotherm model,and the maximum adsorption capacity fitted by the Langmuir adsorption isotherm model is 500 mg/g.The adsorption process follows a pseudo-second-order kinetic model.When the p H is close to neutral（6-8）,and the adsorption capacity is the largest when the p H is neutral,the removal rate of the adsorbent can be maintained above 90%.（3）In the laboratory,a nano-sized sorbent with layered structure of sodium magnesium carbonate（Na₂Mg（CO₃）₂）was successfully prepared by one-step hydrothermal method for simultaneous treatment of organic dyes and fluoride-containing wastewater.The structure was characterized by SEM,XRD,EDS and FT-IR.The adsorption capacity for industrial fluorine-containing wastewater was studied,and the adsorption mechanism was analyzed.The results showed that the adsorption equilibrium data of Na₂Mg（CO₃）₂was consistent with the Freundlich adsorption isotherm model,and the maximum adsorption capacity was 113.64 mg/g.The adsorption process follows a pseudo-second-order kinetic model.In a wide range of p H（3-10）,p H has little effect on the adsorption of Na₂Mg（CO₃）₂nanoparticles to fluorine.At the lower concentrations of 20 and 30 mg/L,the presence of phosphate,nitrate,sulfate,carbonate and chloride has little effect on the fluoride removal by Na₂Mg（CO₃）₂adsorbent.After 6 cycles of adsorption-desorption,the adsorbent can still maintain a high adsorption efficiency,indicating that the adsorbent has a promising application prospect in the treatment of fluoride containing wastewater.Na₂Mg（CO₃）₂ not only has a good removal effect on fluoride,but also has a good selective adsorption on CR.The adsorption data of CR solution by Na₂Mg（CO₃）₂accorded with Langmuir isotherm model,and the maximum adsorption capacity was 36.364mg/g.The adsorption kinetics follows a pseudo-second-order kinetics model.When the p H is close to neutral（6-8）,the removal rate of the adsorbent can maintain more than 90%,and the adsorption capacity is the largest when the pH is neutral.