Study On Magnesium Based Adsorbent Planted On TiO₂ Nanotube Arrays

With the development of machinery,metallurgy,mining and other industries,heavy metal ions and organic dyes have directly been discharged into the water bodies.This discharge had led to water pollution,waste of water resource and serious harm to human health.We need to find a simple and efficient method to deal with water pollution.Owing to its time efficiency,low cost,high efficiency,and high treatment capacity,adsorption is one of the common methods for treating wastewater.Metal hydroxide adsorbent has attracted more and more attention attributing to environmental friendliness,excellent adsorption and low cost.As an adsorbent,Mg（OH）₂ has an extensive application in wastewater treatment or recycling because of its disadvantages,such as abundant reserves,non-toxicity,and absence of secondary pollution.Recently,scientific workers have focused on the microstructure of Mg（OH）₂ via controlling the synthesis method or adding other materials to prepare composite adsorbents.Nano-Mg（OH）₂ does not have internal diffusion resistance which can accelerates the adsorption rate.However it is difficult to separate from the water bodies when the adsorbent was finished.With the deepening of electrochemical deposition theory and experimental research,electrochemical deposition technology is widely used in the preparation and environmental protection of new materials with unconventional properties such as nanomaterials and oxide films.In order to solve the problem,we proposed to use the electrodeposition method to load a layer of Mg（OH）₂film on the surface of titanium dioxide nanotube carrier（TNA）.The composite structure（Mg（OH）₂/TNA）can retain impurities on it when the wastewater was completed.The impurities is taken out with the TNA after the adsorption is completed,without centrifugal filtration and reducing the complexity of the process.The main research is as follows:The TNA has a regular surface without impurities,uniform tube diameter and highly ordered uneven surface,which can be used as a carrier for subsequent experiments.The Mg（OH）₂/TNA film was made by pulse electrodeposition.We chose the Mg（OH）₂/TNA film with better performance by optimizing the amount of directing agent and deposition time,then we explored its adsorption performance for heavy metal ions(Pb²⁺)and organic dye methyl orange（MO）in wastewater.We found that the adsorption of Mg（OH）₂/TNA to Pb²⁺and MO conforms to the Langmuir model,and the maximum adsorption capacity for Pb²⁺and MO are 1468 mg/g and 868 mg/g respectively.We also found that Mg（OH）₂/TNA reacts with Pb²⁺to produce Pb₃（CO₃）₂（OH）₂in wastewater,and the generated material can also be fixed on the surface of TNA.After adsorption,it can be taken out directly,with TNA which reducing the complexity of the process.Cyclic voltammetry was used to make Mg（OH）₂/TNA film.We filtered the Mg（OH）₂/TNA structure with better performance by changing deposition rate and cycle number.We explored the adsorption performance of Mg（OH）₂/TNA film on heavy metal ions(Pb²⁺)and organic dye methyl orange（MO）in wastewater.After experimental analysis,we found that the adsorption of Mg（OH）₂/TNA to Pb²⁺and MO also fits the Langmuir model,and the maximum adsorption capacity for Pb²⁺and MO are 1858 mg/g and 1156 mg/g respectively.XPS analysis after adsorption of Pb²⁺shows that Mg（OH）₂/TNA adsorbed Pb²⁺is mainly chemical adsorption and generated Pb₃（CO）₃（OH）₂ and Pb O substances during the adsorption process,which also shows that the adsorbed substances can be retained on the TNA surface.The maximum adsorption capacity of the Mg（OH）₂/TNA structure prepared by cyclic voltammetry to Pb²⁺is 1.27 times higher than that of the Mg（OH）₂/TNA structure prepared by the pulse electrodeposition method,and the maximum adsorption amount to MO Increased by 1.33 times.In this test,a layer of porous magnesium hydroxide structure was deposited on the surface of the TNA by anodizing and electrochemical deposition.By exploring its performance,the structure of Mg（OH）₂/TNA prepared by cyclic voltammetry was found to be loose and porous,with high uniformity Compared with Mg（OH）₂/TNA prepared by pulse electrodeposition method,it has a higher specific surface area and therefore higher adsorption performance.