Dissertation for the degree of a candidate of technical sciences in specialty 21.06.01 – «Environmental safety» (21 - National Security). - National Technical University of Ukraine «Igor Sikorsky Kyiv Polytechnic Institute», Kyiv. National Aviation University, Kyiv, 2019.
The dissertation is devoted to the development of sorption technologies for protecting water against contamination by heavy metals and radionuclides using composite materials based on organomodified natural layered and layered belt silicates.
The physicochemical and technological peculiarities of obtaining sorbents on the basis of organomodified montmorillonite and malogorsk with a layer of nanosized zero-valent iron were considered. Their structure was investigated by means of X-ray diffraction, IR-spectra, microscopic research, thermal analysis and rheological research.
To modify the surface of clay minerals cationic surfactants - salts of quaternary ammonium with different length of the alkyl chain: hexadecyltrimethylammonium bromide (HDTMA), (C16H33)N(CH3)3Br; alkylbenzyldimethylammonium chloride (ABDMA), (C6H5)N(CH3)2(C14H29)Cl; dodecyltrimethylammonium bromide (DDТМА), (С12H25)N(CH3)3Br; tetramethylammonium chloride (TMA), N(CH3)4Cl. It is established that the largest degree of surface organofilization can be provided by HDTMA.
It was proved that the resulting composites contained stable, high dispersed particles of nanosized zero-valent iron in the size of 20-80 nm, having «core-shell» structure with shell shell thickness of 3 nm. It has been established that the surfactant monolayer formed on the surface of silicates promotes the formation of more dispersed particles of null valent iron in comparison with the natural silicate surface.
The sorption ability of the composites obtained in relation to heavy metal ions and radionuclides in solutions was studied. Significant increase in the sorption characteristics of the materials obtained for the compounds Cr (VI), Co (II) and U (VI) was found compared to the source minerals and iron-based composites on the basis of natural montmorillonite and palygrskite.
The optimal conditions for the modification of laminated and laminated tape silicates were established to obtain sorbents in the form of powder, as well as in the form of stable dispersions of iron containing composites. It is confirmed that the optimal content of zero-valent iron in the powdered composite is 1:10, the degree of modification of the surface of the minerals HDTMA amounts to S / CEC = 1.
It has been shown that sorption of iron-containing materials based on organometallic humor is about 23 mg / g for chromium (VI), 55 mg / g for cobalt (II) and 78 mg / g for uranium (VI). For iron-containing materials on the basis of organopaliguric acid, sorption values were about 18 mg / g for chromium (VI), 45 mg / g for cobalt (II) and 54 mg / g for uranium (VI). Such sorption values exceed the corresponding values for natural and organomodified minerals, as well as unstable iron and iron-based composites based on unmodified silicates.
The investigation of the rheological properties of iron-containing dispersions on the basis of organomotor morpholones has been carried out. It is proved that the aqueous suspensions of the obtained materials remain stable and sedimentation while modifying the S /CEC = 0.1 and the iron content in solid phase to 1%.
The stability of iron-containing materials was investigated and the rate of their oxidation significantly determined the storage conditions. Sorption characteristics of aliologically based samples based on organomodified minerals stored in anaerobic conditions without access to air have not changed significantly over a sufficiently long time (up to 500 hours). Significant decrease in sorption properties is recorded in samples stored in aerobic conditions, which can be explained by processes of oxidation of zero-valent iron. Partial reduction of characteristics (7.8%) is observed in samples that were stored as an initial water-alcohol suspension due to the sorption of organic molecules on the surface of iron nanoparticles with the formation of a protective layer. The efficiency of purification of groundwater from compounds of U (VI) using iron-based sorbents on the basis of organomodified silicates has been proved.
The technological scheme for obtaining iron-containing sorption materials with the use of montmorillonite and cationic surfactant hexadecyltrimethylammonium bromide is proposed. The direction of utilization of spent sorbents according to ceramic technology, by immobilizing heavy metals and radionuclides in the formed ceramic matrices is substantiated.
Key words: sorption, heavy metals, natural radionuclides, purification of natural waters, nZVI, cationic surfactants, silicate composite materials.
