Design Of Super-stable Mineralized Materials And Treatment,Recovery And Reuse Of Wastewater Containing Heavy Metals

Heavy metal related industries occupy an extremely important proportion in the national economy.In mining and smelting,electroplating,and the production and processing of electronic devices,machinery,leather,pesticides and other products,a large amount of wastewater containing heavy metals is generated.Its illegal discharge not only spreads heavy metal pollution around the world,but also causes serious waste of heavy metal resources.Although various treatment technologies and materials have been continuously improved and upgraded,there are still some shortcomings that cannot be ignored.It is difficult to achieve a good balance in cost,efficiency,stability and sustainability,which limits the scale and marketization of treatment technologies.At present,it is urgent to develop an economic and efficient treatment technology to treat heavy metal pollutants and recover heavy metal resources,so as to provide a multi-dimensional solution for the sustainable development of society.Layered double hydroxides（LDHs）is a kind of two-dimensional layered material,controllable in composition,structure,and morphology.It can remove various inorganic or organic pollutants through surface adsorption,electrostatic attraction,ion exchange and,isomorphous substitution.In terms of heavy metal removal,LDHs can fix heavy metal ions in the structural lattice through isomorphous substitution,transform them into super-stable mineralized structures,greatly inhibit the movement of heavy metal ions,and achieve long-term stable removal of heavy metal pollutants in situ.LDHs shows outstanding advantages in efficiency,stability,cost,and other aspects.However,the capacity of LDHs for heavy metal ions needs to be further improved,the understanding of super-stable mineralization process is still shallow,the advantages of cost and solid product quantity are not prominent enough,and the reuse value of products is still low.As a result,the large-scale promotion of super-stable mineralization technology in the treatment of heavy metal contaminants in water is greatly limited.This paper focuses on the removal,recovery and utilization of heavy metals in heavy metal-contaminated water and soil,with LDHs super-stable mineralized materials as the research center.Through the detailed analysis of the super-stable mineralization process,the mineralization path of heavy metal ions with adsorption and isomorphous substitution is revealed.Through rational design of mineralized materials and coupling upgrading of various technologies,the recovery of heavy metal resources is realized,and the comprehensive advantages of super-stable mineralization are strengthened.Through the post-treatment and high-value application of mineralization products,the utilization value of waste heavy metal resources is improved,and a multi-pronged sustainable route is provided in environmental protection,energy regeneration,resource reuse,and fine chemical synthesis.The conclusions are as follows:1.Overall strengthening of properties and in-depth analysis of mechanism of ultra-stable mineralization.An ultrathin Mg Fe-LDH super-stable mineralization material is designed,which has been further improved in mineralization capacity and strengthened in the all-round advantages of acid resistance,anti-interference,environmental friendliness,and cost.Ultrathin Mg Fe-LDH can purify the actual copper plating wastewater with ultrahigh concentration to the standard,and can effectively solidify the heavy metals in the soil.It also has the effect of magnesium fertilizer to promote the growth of crops,showing the industrial and agricultural application potential.The super-stable mineralization process is characterized by the coupling mechanism of adsorption and isomorphous substitution,which provides theoretical guidance for the improvement of super-stable mineralization agent.The mineralized product Cu Mg Fe-LDH has a superior performance in sewage treatment,and the enriched copper can be recovered with high purity,which provides an important reference for the recovery and utilization of waste heavy metal resources.To further reduce the cost and hazardous waste amount,and improve the value of resource recovery and utilization,electrolytic reduction and ultra-stable mineralization are coupled and upgraded,which can remove and recover heavy metals in electroplating wastewater more economically and efficiently.The technical feasibility is greatly improved,and the industrial scale prospect is broad.2.Multistage coupling and practicability enhancement of super-stable mineralization.Based on the comprehensive treatment of tannery,electroplating and other industries,a multistage super-stable mineralized heavy metal treatment route was proposed.Firstly,the wastewater containing chromium was treated with calcium hydroxide to achieve the atomic economical synthesis of Ca Cr-LDH and the standard treatment of wastewater.Ca Cr-LDH was further applied to the super-stable mineralization of divalent heavy metal ions（Cu,Ni）in wastewater,and the efficient and stable removal of various heavy metal ions was realized.The multistage super-stable mineralization technology has the advantages of low cost,high stability,and less solid products,realizing waste treatment with waste,meeting the urgent needs of related industries,and greatly improving the industrialization potential.It has a prospective guiding significance for the joint treatment of complex wastewater across factories in the future.The multistage super-stable mineralization products not only can highly selective photocatalytic reduction of CO₂to CH₄and CO,but also can highly selective photocatalytic reduction of gold from the integrated circuit board leaching wastewater,which provides a sustainable solution for the mitigation of greenhouse effect,energy,and resource crisis.3.Structural modification and application value improvement of mineralized products.To solve the problem of low application value of mineralization products,Fe-based LDH,a kind of common mineralization products,was regulated by elemental composition and defect structure construction,and an Ni Fe-LDH ultrathin nanosheet photo-Fenton catalyst was determined.With the decrease of thickness,the hydroxyl defects and metal defects are more abundant in the ultrathin Ni Fe-LDH.The existence of defects changes the electronic structure of ultrathin Ni Fe-LDH,improves the separation and migration efficiency of photogenerated charges,enhances the adsorption capacity of H₂O₂,promotes the transfer of photogenerated charges to H₂O₂and the production of·OH,and improves the performance of selective hydroxylation of phenol to synthesis of dihydroxybenzenes.Ultrathin Ni Fe-LDH can achieve a phenol conversion efficiency of about 70%and a dihydroxybenzene selectivity of more than 99%in the photocatalytic phenol hydroxylation reaction,and its performance can still be maintained under monochromic light of 550 nm wavelength or LED light of 460 nm wavelength,which enhances the application potential of photocatalytic technology and improves the application value of mineralization products.In this paper,the recovery and reuse of heavy metal resources in wastewater were systematically studied with the super-stable mineralized material LDHs as the center.In theory,the specific process of super-stable mineralization is revealed.In terms of performance,it achieves a comprehensive breakthrough in the multiple attributes of LDHs.In terms of technology,the electrolysis-super-stable mineralization coupling route and multistage super-stable mineralization route are designed.In the aspect of application,the application scope and value of mineralized products are deeply explored.This paper is of great significance to the improvement and popularization of super-stable mineralized materials.