Research On The Treatment Of Dye Wastewater With Highly Regenerated Three-dimensional Hollow Nano-sorbent

With the development and advancement of China's modern industrialization,the discharge of dye wastewater increases.While the chemical structure of dyes is stable,most of them are harmful substances,which increases the difficulty of wastewater treatment.It is urgent to develop a hollow nano material,which can effectively solve the problem of dye wastewater.At present,Many physical and chemical methods have been applied to dye wastewater treatment,among which adsorption method is the most widely used because of its convenience and low energy consumption,and the preparation of adsorption materials determines the effect of adsorption method.In order to cut cost and improve efficiency,it is a research hotspot in the field of water treatment to prepare a new adsorbent with high efficiency and environmental protection.Hollow nanomaterials have broad prospects in water protection due to their high specific surface area,porous structure and good stability.In this paper,three-dimensional hollow nano-materials were prepared by using sacrificial template method through different reaction systems,and were used as adsorbents to remove Congo red(CR).The optimum adsorption conditions,adsorption performance,recycling performance and adsorption reaction mechanism were studied.The main research contents are as follows:(1)NiFe-LDH was synthesized by using Ni precursor prepared by solvothermal method as template.The characterization results show that the synthesized NiFe-LDH is a hollow prismatic structure with uniform size,with a specific surface area of 162.21 m2/g and a large number of mesopores in it.The adsorption results of Congo red showed that the saturated adsorption capacity of NiFe-LDH for Congo red was 674.56 mg/g at 288 K,and reached 1088.76 mg/g when the temperature was raised to 308 K.The fitting of Langmuir isotherm model and quasi-first-order kinetics accords with the adsorption behavior of NiFe-LDH on Congo red dye.The adsorption mode is mainly physical adsorption,and the process is endothermic reaction.The removal rate is 64%after three regeneration.(2)Carbon doped cobaltosic oxide composites(Co3O4/C)were prepared by using sucrose as carbon source and C2CoO4·2H2O as precursor.The microstructure,elemental valence and specific surface area of Co3O4/C were examined by characterization test.The results showed that Co3O4/C was hollow spherical structure with specific surface area of 43.85 m2/g,pore size distribution in the range of 41.02-232.18 A and carbon content of 9.8%.The adsorption properties of Co3O4/C were studied with Congo red as the treatment object.The effects of temperature,pH and adsorbent addition on the adsorption of Congo red by Co3O4/C were investigated.After 6 h,the saturated adsorption capacity of Co3O4/C was 432.06 mg/g,and the removal rate was 97%.Chemical adsorption was the main process,accompanied by intra-particle diffusion,and the removal rate was 76%after regeneration by Fenton method for four times.(3)Carbon-based Fe3O4/C composites with hexamethylenetetramine(HMT)as carbon source were synthesized by sacrificial template method.The results show that Fe3O4/C is a flower-like hollow nanospheres with an average grain size of about 14 nm and a specific surface area of 78.48 m2/g,which is a typical mesoporous material.With the increase from 303 K to 323 K,the saturated adsorption capacity of Fe3O4/C for Congo red increases by 3.5 times to 1625.38 mg/g.The adsorption data of Congo red by Fe3O4/C accords with Langmuir isotherm model,and the fitting of quasi-second-order kinetics accords with the adsorption behavior of Fe3O4/C for Congo red dye.Because the material is magnetic,it can be quickly separated from the solution.Fe3O4/C is regenerated by Fenton method at low temperature.After four times of regeneration,the removal rate of Congo red still reached 76%.It has excellent regeneration performance and can be used as a new adsorbent for dye wastewater treatment.