Preparation Of Modified Nano-materials And Their Liquid-phase Adsorption Properties Of Arsenic In Weak Acid Environment

With the development of the economy,arsenic pollution of groundwater has become an environmental pollution problem that needs to be solved urgently.Emerging nanomaterials have become a highly valuable adsorbent,and ionic liquids have become a research hotspot in the field of environmental protection due to their remarkab le extraction properties for metal ions.In this paper,nanomaterials were used as carriers to carry out ionic liquid loading on nanomaterials by physical impregnation and calcination.On the other hand,nanomaterials were modified with ferric nitrate to prepare two types of composite nanomaterials,and the adsorption properties of arsenic by composite nanomaterials are studied.The specific work is as follows:(1)Synthesis of ionic liquid:Synthesis of ionic liquid by a two-step method:(1)N-methylimidazole and chlorine-n-hexane are subjected to quaternization under constant temperature to obtain an intermediate[Hmim]Cl,that is,a halogen salt containing a target cation;(2)The intermediates and Na Sb F₆ were heated by constant temperature[Hmim]Sb F₆,that is,a hydrophobic ionic liquid 1-ethylhexyl-3-methyl imidazole antimony was prepared by replacing the Cl^-with the target Sb F₆^-.The structure of the ionic liquid was characterized by FT-IR analysis.Studies have shown that the prepared ionic liquids are consistent with the reported results.The ionic liquid is slightly soluble in ethanol,and is soluble in organic solvents such as carbon tetrachloride and dichloromethane,has a good surface tension.(2)Study on arsenic removal properties of ionic liquid loaded nanomaterials:The above-mentioned synthesized[Hmim]Sb F₆ ionic liquid was used as an active supporting reagent,and graphene,carbon nanotubes and nano-iron were used as carriers.Three ionic liquid loading types were prepared by physical impregnation and calcination.Surface morphology and elemental composition of the material were studied by means of transmission electron microscopy(TEM),specific surface area measurement(BET),Fourier transform infrared spectroscopy(FT-IR),X-ray photoelectron spectroscopy(XPS),Zeta potential and other characterization methods.The results show that the dispersion of nanomaterials in the liquid phase becomes better after loading the ionic liquid.For ionic liquid-loaded graphene and carbon nanotubes,ethanol is the best loading solvent,the dosage is 0.1 g/L,p H=6,adsorption at 35oC for 2 h,HA concentration is 10 mg/L,the best removal efficenicy of arsenic is achieved.And the maximum removal rate was 99.3%and 99.5%,respectively.For nano-iron loaded with ionic liquid,the dosage is 0.5 g/L,p H=5,adsorption at 35oC for 2 h,and when the concentration of HA is zero,the best arsenic removal effect is99.1%.By static adsorption isotherm fitting,the adsorption results of graphene and carbon nanotubes loaded by ionic liquid were consistent with Langmuir adsorption.The adsorption results of ionic liquid-loaded nano-irons were consistent with Freundlich adsorption.The maximum arsenic adsorption amounts were 137.95 mg/g,108.44 mg/g and 12.81 mg/g,respectively,higher than the same type of adsorbent materials have been reported.(3)Study on arsenic removal properties of iron nitrate modified nanomaterials:Two kinds of ferric nitrate modified nanomaterials were prepared by using equal volume impregnation method with ferric nitrate as active agent,graphene and carbon nanotubes as carriers.Surface morphology and elemental composition of the material were studied by means of transmission electron microscopy(TEM),specific surface area measurement(BET),Fourier transform infrared spectroscopy(FT-IR),X-ray photoelectron spectroscopy(XPS)and other characterization methods.When the dosage is 0.1 g/L,the p H is 5?6,at 35oC for 2 h,the maximum removal rates of arsenic are 99.2%and 99.1%,respectively.According to the static adsorption isotherm fitting,the adsorption results of iron nitrate modified graphene and carbon nanotubes are consistent with Langmuir adsorption.The adsorption behavior of arsenic belongs to single layer adsorption,and the maximum adsorption capacity were 127.02 mg/g and 101.90 mg/g,respectively,both of which are higher than the same type of adsorbent materials has been reported.