The Removal Of Pollutants From Water By Mo(Ⅵ) Oxy Ion-imprinted Particle

With environmental awareness increasing, people are not only concerned about the pollution of the toxic heavy metal ions. Molybdenum is a growing concern in the field of environmental protection, as one of the main heavy metal ions in groundwater and industrial wastewater,is a growing concern in the field of environmental protection. While the development of molecular imprinting, the new functional material with high capacity and great selectivity has become a hot area. In order to synthetic the ideal adsorbent, we choose the molybdenum as the template molecule, TEOS as crosslinking agent, and isonicotinic acid was used as a functional monomer for preparing the Mo ion-imprinted particle (Mo-ⅡP) on the surface of the amino silica. It used the molecular imprinting technique with a sol-gel process. And Mo(VI) oxy ion non-imprinted particle (Mo-NIP) was prepared without the template molecule, in the same manner.In this paper, we optimized the ratio of raw materials. The prepared Mo-IIP was characterized by a standard Brunauer-Emett-Teller (BET),scanning electron microscopy(SEM), Transmission Electron Microscope (TEM), Energy Dispersive X-ray Spectroscopy(EDS),Fourier transform infrared spectrometer (FTIR) and thermogravimetric analysis (TGA)analysis. The capacity and selectivity were tested by static adsorption experiments, and put forward a possible selective mechanism.The best molar ratio of raw material was amino-group:isonicotinic acid:NaMoO4=2:5:1,and the elution method of Soxhlet extraction + acid elution method achieve the purpose of the template molecule elution successffully. Characterization show: Mo-IIP was spherical particles,the average particle size is 250-300 nm; Mo-IIP wrapped the silica surface with a layer of floccules thickness of 50 nm; the characterization of Mo-NIP is similar to Mo-ⅡP;the FTIR peak of skeleton vibration of pyridine ring was changed by imprinting effect;Mo-IIP has the better thermal stability and more surface groups; Mo-IIP and Mo-NIP were found to be uniform pore size of mesoporous materials; The specific surface area of Mo-ⅡP was found to be 48.94 m2.g-1, the total pore volume was 0.1349 cm3 g-1 and the average pore diameter was 11.02nm.The kinetics of Mo-ⅡP 和 Mo-NIP show that the binding process fitted well to the pseudo-second-order kinetic model and the Weber-Morris model. The results suggested that a multi-step with the film and intraparticle diffusion process might dominate this chemical sorption for Mo(Ⅵ) binding onto Mo-ⅡP. the Mo(Ⅵ) initial binding rates (k2qe2) were 116.87 and 14.93 μmol·g-1 min-1 for Mo-ⅡP and Mo-NIP,respectively. The binding process was a heterogeneous process, and the energy distribution and adsorption affinity of adsorbent surface are different.The binding process of Mo-ⅡP and Mo-NIP fitted well to the Langmuir model. The Mo-ⅡP exhibited selectivity for Mo(Ⅵ) with a remarkably high binding capacity 2171.46μmol g-1,which was 7.6 times higher than that of the Mo-NIP. The binding process of Mo-ⅡP was divided into two phases according to the binding energy. Thermodynamic properties of Mo-ⅡP show that △H <0, it illustrated the adsorption process is an exothermic process;△S <0, △G<0, it illustrated the adsorption process is an exothermic process can be spontaneous.The selective experiment show that Mo-ⅡP have a great exclusive selectivity for Mo(Ⅵ).The competitive strength order of compete ions was Cr(Ⅵ)>Cu(Ⅱ)>Cr(Ⅲ)>Zn(Ⅱ)>Ni(Ⅱ)>Mg(Ⅱ). The binding process of Mo-ⅡP for Cr(Ⅵ), Cu(Ⅱ), Zn(Ⅱ), Ni(Ⅱ), Mg(Ⅱ) and Cr(Ⅲ)fitted to the Langmuir model. The Mo-ⅡP show no recognition performance for Cr(Ⅵ),Cu(Ⅱ), Zn(Ⅱ), Ni(Ⅱ), Mg(Ⅱ) and Cr(Ⅲ).The high concentrations compete ions was a strong interference for adsorption isotherm,,but the binding process of Mo-ⅡP still fitted to the Langmuir model. The Na+, K+,Cl-,SO42-,NO3- and H2PO4 have no interference for the binding process,when their concentrations was under 300 μmol·L-1. The binding capacity of Mo-ⅡP for Mo(Ⅵ) was reduced by 50% in simulated seawater system. Mo-ⅡP still keep the good adsorption properties after regenerate, and only lost 6% adsorption capacity.The excellent affinity and exclusive selectivity make the Mo-ⅡP become an potential material for Mo(Ⅵ) removal and concentration from the water environment.