Controllable Synthesis Of Mg-based LDHs As Superstable Mineralization Materials And For The Removal Of Pb2+ And Other Heavy Metal Ions

With the continuous development of electroplating,printing,production and manufacturing of lead batteries and other industries,industrial wastewater including lead ions and other heavy metal ions were discharged wantonly,causing extremely serious environmental pollution problems.Based on layered double hydroxides（LDHs）,it is of great significance to develop stable mineralizations for the efficient treatment of wastewater contaminated by heavy metal ions and realizing the recycle of heavy metal resources at the same time.In this manuscript,the material with high mineralization capacity for lead ions and other heavy metal ions was designed and synthesized based on LDHs,which can be used for the efficient treatment of industrial wastewater.The microstructure,fine structure,mineralized product structure and mineralized mechanism of the synthesized materials were researched by bonding experiments and theory calculation.The the mineralization process of heavy metal ions was tracked to help clarify mineralized mechanism.Main works and achievements are as follows:The fast development of mining industry makes the industrial wastewater contaminated by Pb²⁺.Lead is a kind of highly toxic metal that causes irreversible health problems to the human body.The treatment of wastewater containing Pb²⁺and the recycle of lead element resources have grabbed the attention of researchers.LDHs has been widely used in the field of heavy metal ions mineralization due to its environmental friendliness and high possibility of alteration.To solve the pollution caused by heavy metals,Mg Fe-MMO was synthesized by calcining Mg Fe-LDH to realize the efficient mineralization of Pb²⁺with the mineralization capacity of 2406 mg/g.In addition,Mg Fe-MMO obtained by calcining Mg Fe-LDH as stable mineralization material for Pb²⁺also has excellent acid resistance,duability and competitive ions selectivity of Pb²⁺.Element lead can also be obtained by electrolysis by mineralized products,realizing the recycle of heavy metal lead resources.Fine structure of ineralization products were revealed by means of X-ray powder diffraction（XRD）and advanced spectroscopy,it was found that Mg Fe-MMO was recovered to Mg Fe-LDH through the"memory effect"and then Pb²⁺were mineralized.DFT calculation further illustrated the specific phase transformation of lead during the mineralization process.In this work,the calcined products of Mg Fe-LDH were used to realize the efficient mineralization and recycle of lead,providing a new idea for the treatment of industrial wastewater.As mineralization materials,powdery LDHs has the disadvantage of being difficult to seperation recycling.In addition,powdery LDHs usually also agglomerate in solution,which greatly reduces its specific surface area and cannot provide more heavy metal mineralizing sites.In order to further optimize the performance of LDHs,it has been revealed that embedding LDHs microcrystals on an appropriate substrate can greatly improve the phenomenon of LDHs agglomeration and increase the specific surface area.It also can overcome the disadvantage of difficult to seperation recycling of traditional mineralizer in the field of heavy metal mineralization.Therefore,we choose Al sheet,Ni foam and Fe foam as the substrate to synthesize LDHs film materials.After screening,the structure and performance of Mg Fe-LDH/Fe foam was specifically studied.SEM proves that Mg Fe-LDH was deposited on the substrate in the form of array without agglomeration.Experimental data showed that Mg Fe-LDH/Fe foam played an excellent mineralization effect on Cu²⁺,Zn²⁺and other heavy metal ions without subsequent filtration and separation steps,provides a new view for the design of efficient heavy metal mineralization materials.