Study On Preparation Of 2D Boron Nitride Nanomaterials For The Application Of Heavy Metal Ions Removal Mechanism In Water

With the emphasis on the hazards caused by heavy metal pollution,the adsorption method has been widely applied to the treatment of heavy metal due to its wide range of raw materials and fast effect.The traditional adsorption materials mainly rely on the physical adsorption of dispersive force,electrostatic force and inducing force.While heavy metal ions have the characteristics of small ionic radius,strong migration ability and obvious accumulation effect,the removal of heavy metal ions by conventional adsorbents has limitations,especially the rapid and effective removal of low concentrations of heavy metal ions in water.In response to this problem,the development of new high-efficiency nano-adsorbents with large specific surface area,multiple active sites or active adsorption bonds has become an important issue in the field of environmental.Among the many new nano-adsorbents currently in development,layered nanomaterials have become one of the research hotspots of new high-efficiency nano-adsorbents due to their typical structure.Among them,layered nano-boron nitride with polar groups and multiple active sites on the surface is a representative layered nanomaterial,which has theoretically high adsorption capacity and excellent chemical stability.Therefore,it is expected to be applied to the treatment of heavy metal ions.Based on this,this thesis discusses the preparation process of 2D porous BN-550 nanosheets and porous BNNR nanobelts,and studied their adsorption properties and mechanisms for Pb2+,Cd2+ and Cu2+,respectively.The main research contents are as follows:(1)A novel few-layer boron nitride nanosheet(BN-550)was developed by low-temperature synthesis to rapidly and efficiently adsorb lead ions(Pb2+).The samples were characterized by XRD,FT-IR,EELS,SEM,TEM,AFM and XPS.The results showed that it has a large specific surface area(696 m2/g)and an ultra-thin layer structure(thickness 1.2 nm),which is rich.The chemical bond acts as an active adsorption site.The adsorption capacity for lead ions is higher(845 mg/g),which is less equilibrium time(15 minutes)than many of the currently reported adsorbents.The removal process of Pbro by BN-550 belongs to pseudo second order(chemical process)and Langmuir model(surface single phase).The recyclability and stability of BN-550 were verified by experimental regeneration and pH.Under the interference of other heavy metal ions such as Ni2+,Cu2+and Cd2+ions,the adsorbents have a strong afflnity for Pb2+(the capacities they adsorb in separate solutions are 201,402 and 312 mg/g,respectively).XPS and FT-IR analysis showed that the adsorbent has excellent adsorption performance for Pb2+due to chemical bonding reactions with many surface functional groups,such as strong B-O-Pb interaction and-NH2-Pb mutual attraction.When the filter column is 50 mg/L Pb2+,the Bn-550 nanosheet has a Pb2+removal threshold of 1080 mL/g.These exceptional and unique properties make the ultra-thin nanosheet BN-550 an ideal choice for the removal of lead ions.(2)The new porous boron nitride nanobelt(BNNR)was successfully developed as an excellent adsorbent to rapidly remove cadmium and copper ions from water.The resulting BNNR has a large specific surface area and a small average porosity(866 m2/g and 2.1 nm,respectively),and the width of a single nanoribbon is about 660 nm.The maximum adsorption capacity of the adsorbent for Cd2+and Cu2+ions is about 530 mg/g(C0=600 mg/L,pH=6,dose=1 g/L)and 331 mg/g(C0=500 mg/L,pH=5,dose=1 g/L).In addition,BNNRs have the ability to rapidly adsorb Cd2+and Cu2+and achieve adsorption equilibrium in 10 minutes and 20 minutes,respectively.Interference and regeneration experiments show that BNNR has excellent anti-interference and reusability,easy to recycle and sustainable.BNNR can stably remove Cd2+and Cu2+under the pH of 3-8 wastewater and drinking water.XPS and FTIR analysis indicated that the possible mechanism of adsorption is to chelate and attract metal ions through surface chemical bonds such as B-O and-NH2 bonds.For cadmium ion(1 mg/L)and copper ion(10 mg/L)to simulate real wastewater,BNNR(dose=1 g/L)adsorbed Cd2+and Cu2+in 10 minutes and 1 minute,respectively.Meet the WHO standard.Therefore,BNNR is an ideal candidate for water purification applications.