Study On The Preparation Of Inorganic Nanomaterials From The Solvent Extraction Systems And Their Related Applications

Due to the excellent optical, electrical, photochemical, electrochemical, mechanical and catalytic properties of nanomaterials, much more attention has been paid to their preparation and applications. It is still a great challenge to develop a new, facile, and convenient, low-energy and environment-friendly method for preparing and designing nanomaterials. Although there were many reports, many chemists, physicists and materials scientists are devoting themselves to the controllable size, morphology and distribution, surface-modification and expansion of their applied research.As an important separation technology, the solvent extraction and separation were extensively applied in the field of hydrometallurgy, atomic energy industry and rare earth element purification. In this paper, the main attention has been paid to explore the preparation of inorganic nanomaterials and organic nanofluids from a solvent extraction system or a system containing an industrial extractant, then the application of the prepared materials or fluids in the field of tribology, heat transmit and electrochemical properties. In this study, the theory and experience of solvent extraction were both developed and enriched in the field of preparation materials, a new idea for the preparation of nanomaterials was also provided. Moreover, it has very important significance in industry to carrying out the"separation, preparation and modification"at the same time.The main purpose of this paper is, based on the interfacial properties of extractants and interfacial phenomenon appeared in the extraction systems, several kinds of inorganic nanomaterials and organic nanofluids are firstly synthesized from a solvent extraction system or a system containing an industrial extractant, then their related application and properties researches, such as the tribological properties, thermal conduction properties and preliminary electrochemical properties, are studied systematically, finally, the tribological, thermal conductivity and electrochemical mechanism are also discussed briefly. The main contents of this paper are as follows:(1) Mono-dispersed molybdenum disulfide micro-spheres with the diameter of 1~3μm have been successfully synthesized via extraction-solvothermal method at 150℃in the system of Cyanex 301(di- (2, 4, 4- trimethylpentyl) dithiophosphinic acid) -gasoline/Na2MoO4-HCl. The influences of reaction conditions were discussed while a mechanism was proposed to explain the formation of the micro-spherical structure. Moreover, the tribological properties (Extreme-pressure (EP) properties, anti-wear (AW) and friction-reducing properties) of liquid paraffin (LP), 500 SN and gear oil GL-4 containing the above surface-modified MoS2 micro-spheres (MS-MoS2) were also evaluated on a four-ball tester and an optimol SRV oscillating friction and wear tester and compared with those of commercial colloidal MoS2 (CC-MoS2). Results showed that the extractant Cyanex 301 acted as phase transferring agent, reductant, sulfur source and morphology-controlling agent in the whole procedure, and MS-MoS2 was a much better EP additive and AW and friction-reducing additive in the above base oils than CC-MoS2 because of the well modifying effect. The lubrication mechanism could be attributed to the chemical adsorption film, reaction film, deposition film and the existence of the rolling friction under the boundary lubricating conditions.(2) Due to the special crystal structure and good application potential of MoS2 materials, a facile, low-energy and green route to the preparation of molybdenum disulfide is explored in this dissertation. Flower-like molybdenum disulfide micro-spheres with the diameter of 400 nm were synthesized successfully by a simple in-suit hydrothermal method from the chemical reaction among the sulfur source of commercial reagents CS2, NH2(CH2)2NH2 and the molybdenum source of Na2MoO4?2H2O at 150℃for 24 h. The obtained MoS2 products were characterized by XPS, XRD, EDX, SEM and TEM technique, indicating that the flower-like spheres were built up of MoS2 thin flakes having a thickness of several nanometers. The influences of reaction conditions, such as the amount of ethylenediamine, reaction temperature, reaction time, the ratio of S to Mo, surfactant (PVP, CTAB and SDBS), etc, on the MoS2 formation process were studied to explain the evolution of flower-like spheres. The whole reaction could be divided into two parts, one is reductive stage and the other is growth stage. With the help of the formed (-HN-CH2-CH2-NH-CS-)n compound, the new formed MoS2 particles were induced to grow in all directions to form nano-sheets under the hydrothermal conditions. This facile synthesis method may provide an idea to produce other transition metal sulfides.(3) In this dissertation, stable organic nanofluids containing ZnS nano-particles modified by Cyanex 302 (di- (2, 4, 4-trimethylpentyl) monothiophosphinic acid) are prepared directly in gasoline via solvent extraction-precipitation method in the system of Cyanex 302-gasoline/Zn(CH3COO)2-H2O. The obtained organic fluids were so stable that ZnS nano-particles did not precipitate after keeping at room condition for more than six months when the loading concentration of ZnS was as high as 24.4 g?L-1. The influences of reaction conditions on the structure, morphology, dispersion properties and the loading concentration of nanoparticles in organic solvent were discussed briefly while a stabilization mechanism was proposed. Results indicated that because of well modifying effect, the obtained ZnS nano-particles could be well dispersed into organic solvents again and the new-formed nano-fluids were also very stable. Moreover, the tribological properties of base oil LP and 500 SN containing the above ZnS nano-particles were also studied with four ball machine and Optimol SRV oscillating friction and wear tester and compared with those of ZnS nano-particles obtained in ethanol-water mixed medium, showing that such a nanofluid containing modified ZnS particles has a lower friction coefficient and wear volume loss. The action mechanism could be deduced as the effective surface composite film composed of chemical adsorption film, chemical reaction film and deposition film under boundary lubrication conditions.(4) It is very important to prepare organic nanofluids at large scale simply for the application in the fields of the tribology and thermal conductivity. In this dissertation, ethylene glycol nanofluids containing high loading concentration of Ag nanoparticles modified with poly-(vinylpyrrolidone) (PVP) were obtained by a facile chemical reduction method at room temperature. The influences of reaction conditions on the size, morphology, dispersion and the loading concentration of Ag nanoparticles in organic solvent were discussed briefly while a stabilization mechanism was proposed. The results showed that the obtained Ag nanoparticles were well modified by PVP and the highest loading concentration of the corresponding nanofluid was about 21 g·L-1 when the additive amount of PVP is 1.25 g?L-1. Moreover, the thermal conductivity of the nanofluids containing the above Ag nanoparticles were also measured by the transient hot-wire method and compared with the traditional Maxwell and Kumar model, showing that such a nanofluid has a higher thermal conductivity coefficient, i.e., compared with pure ethylene glycol, the thermal conduction coefficient of 0.06% PVP-Ag ethylene glycol increased about 36%. It is expected that this method can be extended to synthesize other metallic nanofluids or nanoparticles.(5) On the basis of the studies about the phase behavior of TOPO (tri-alkyl phosphinic oxide)-gasoline/HCl-ZrOCl2 extraction system, crystals mesoporous ZrO2 and SO42-/ZrO2 with porous honeycomb-type structure are obtained using the third phase loading Zr(IV) by precipitation with ammonium solution under low temperature. Then the polyaniline, polyaniline-ZrO2 and polyaniline-SO42-/ZrO2 composite materials modified with different surfactants (PVP, CTAB and SDBS) are successfully synthesized, respectively. The influences of reaction conditions on the size, morphology, surface-modification, conductivity and electrochemical properties of polyaniline-ZrO2 composite materials were investigated respectively, while a stabilization and action mechanism were proposed to explain the change of chemical properties. Results indicated that the"core-shell"structure of polyaniline-ZrO2 composite materials were formed under the co-action of PVP and aniline hydrochloride, which has coarse surface, good dispersion, higher exterior area and sensitive conductivity and electrochemical properties. The aniline monomer would be well-regulated and adsorbed on the surface of ZrO2 and growth along the given direction, so the obtained composites are of higher conductivity and excellent electrochemical properties. The polyaniline-ZrO2 composites could be used for the detection the DNA hybridization. DNA specific-sequence related to PAT promoter gene with a detection limit ranging from 1.0×10-13 to 1.0×10-6 mol·L-1 and a detection limit of 4.25×10-14 mol·L-1 (3σ). It is expected that this polyaniline-ZrO2 composite materials can be applied in the electrochemical field in the future.(6) Because of the high surface activity of extractant, it could not only increase the loading concentration of metal ions in solvent, but also has very important significance in industry to carrying out the"separation, preparation and modifying"simultaneously through the solvent extraction system.①ZnS inorganic nanoparticles are successfully synthesized via extraction solvothermal method, which is very simple and could be used for preparation of other sulfides in a large scale.②CdS, CuS, MoS2 and MoSe2 semiconductors are successfully synthesized at the aqueous-organic interfaces via the chemical synthesis method. The Cd2+, Cu2+ and MoO22+ ions were extracted into organic phase by the Cyanex 301, then organic phase containing complexes were reacted with S2- (Se2-) in the aqueous phase at the aqueous-organic interfaces to synthesize sulfide nanomaterials, respectively, and the possible formation mechanism is proposed.③Surface modified Fe2O3 nanoparticles were successfully synthesized via different thermal treatment of the Fe(OH)3–Cyanex 301 precursor, which was obtained by the extraction-precipitation route. The obtained Fe(OH)3–Cyanex 301 precursor was given different thermal treatment, such as solvothermal reaction at 180℃, an intense refluxing boiling tetralin and calcine at 600℃respectively. Results indicated that Fe2O3 products were well-modified by Cyanex 301 and could be dispersed well into organic solvents to form the stable fluids due to the high affinity with non-polar solvent.④As surface modifying agent, flake-like MoSe2 nanomaterials were successfully synthesized via a chemical reaction in the mixed medium of ethanol and water at 70oC using home-made NaHSe as Se source, Na2MoO4·2H2O as Mo source and NH2OH·HCl as reducing agent. Results indicated that the morphologies of MoSe2 nanomaterials could be well controlled by the different concentration of extractant in this system and well-dispersed, flake-like MoSe2 nanomaterials with diameter of about 70 nm were obtained when the addition amount of extractant was 0.75 g·L-1.Compared with other typical methods in extractant systems, the studied approach have the advantages of strong cooperation and high loading concentration for metal ions. The theory and experience of solvent extraction were both developed and enriched in the field of preparation materials and their related applications.