[en] A system of image processing on an IBM PC microcomputer has been developed. It is used in image processing of radionuclide scanings. The system has the ability of two-dimentional fast Fourier transformation, including over twenty methods of image enhancement and restoration. Tests of scanning phantom and clinical application demonstrated that it has greatly improved the imaging quality. In this paper, its implementation method, processing results and its principal features are presented

[en] The catalytic activity of natural vanadium-titanium magnetite was investigated in the decolorization of Acid Orange II by non-homogeneous Fenton process. The natural catalysts purified by magnetic separation were characterized using X-ray diffraction (XRD), polarizing microscope, X-ray absorption fine structure (XAFS) analysis and Moessbauer spectroscopy. The obtained results show that the natural samples after magnetic separation mainly contain titanomagnetite, with a small amount of ilmenite and chlorite. Titanomagnetite is doped with vanadium, whose the valency is mainly +3 and occupies the octahedral site. Batch decolorization studies were performed to evaluate the influences of various experimental parameters like initial pH, the amount of catalyst and initial concentration of hydrogen peroxide on the decolorization efficiency of Acid Orange II. The decolorization of the dye mainly relied on degradation. The degradation efficiency was strongly dependent on pH of the medium where it increased as the pH decreased in acid range. The increase of catalyst and hydrogen peroxide could accelerate the degradation. The catalytic property of natural vanadium-titanium magnetite in the degradation of Acid Orange II was stronger than that of synthetic magnetite (Fe₃O₄). The catalytic activity of the natural samples was greatly related to the titanomagnetite content. The degradation process was dominated by heterogeneous Fenton reaction, complying with pseudo-first-order rate law. The natural catalyst has a good catalytic stability.

[en] Diatomite-supported/unsupported magnetite nanoparticles were prepared by co-precipitation and hydrosol methods, and characterized by X-ray diffraction, nitrogen adsorption, elemental analysis, differential scanning calorimetry, transmission electron microscopy and X-ray photoelectron spectroscopy. The average sizes of the unsupported and supported magnetite nanoparticles are around 25 and 15 nm, respectively. The supported magnetite nanoparticles exist on the surface or inside the pores of diatom shells, with better dispersing and less coaggregation than the unsupported ones. The uptake of hexavalent chromium [Cr(VI)] on the synthesized magnetite nanoparticles was mainly governed by a physico-chemical process, which included an electrostatic attraction followed by a redox process in which Cr(VI) was reduced into trivalent chromium [Cr(III)]. The adsorption of Cr(VI) was highly pH-dependent and the kinetics of the adsorption followed a pseudo-second-order model. The adsorption data of diatomite-supported/unsupported magnetite fit well with the Langmuir isotherm equation. The supported magnetite showed a better adsorption capacity per unit mass of magnetite than unsupported magnetite, and was more thermally stable than their unsupported counterparts. These results indicate that the diatomite-supported/unsupported magnetite nanoparticles are readily prepared, enabling promising applications for the removal of Cr(VI) from aqueous solution.

[en] A new route for synthesis of Mg/Al layered double hydroxide (Mg₆Al₂(OH)₁₆(CO₃).4H₂O) has been introduced, which can be considered as a modified calcination-rehydration method. Under the hydrothermal conditions, LDHs with a high aspect ratio were synthesized and characterized by inductively coupled plasma-atom emission spectrometer (ICP-AES), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), thermal measurement (TG-DTG) and scanning electron microscopy (SEM). XRD patterns display the crystalline enhanced with the increase of hydrothermal temperature and aging time. TG-DTG curves show the more stable LDHs were synthesized at higher temperature. SEM images indicate the lateral size of the synthesized LDHs locates at ca. 1-6 μm and the thickness at ca. 35-60 nm. And the particle size depends strongly on the treatment temperature and aging time. A buffer solution consisted of HCO₃^- and CO₃^2- keeps the pH of reaction system in a certain range and offers a low supersaturated reaction circumstance. This is of high importance for the formation of LDHs with a high aspect ratio

[en] Hexavalent chromium (Cr(VI)) and dyes are of particular environmental concern and need to be removed from water urgently due to their high toxicity. Herein, we explored the possibility of electron transferring from dye Orange II (OII) to Cr(VI) under UV and simulated solar light irradiation, expecting to simultaneously decolorize dyes and reduce Cr(VI). Experimental results show that light irradiation can partially decolorize OII but has no ability to reduce Cr(VI) in solution only with OII or Cr(VI). However, both dyes and Cr(VI) can effectively and simultaneously be decolorized and reduced in the solution containing both OII and Cr(VI) under light irradiation, and a low pH level and high OII/Cr(VI) concentration ratio significantly favor the co-removal. Additionally, insoluble organo–Cr(III) complexes identified by FTIR and XPS characterization were generated during the reaction. These complexes are beneficial to the removal of chromium and total organic carbon from water. The possible degradation pathway of OII is further proposed based on the detection of degraded products by GC-MS analysis. The results of this work offer an approach for simultaneously removing multiple contaminants.

[en] Highlights: • Structural Fe(II) was found to reveal high sequestration potential in various chelated copper. • Chelated copper was reduced to Cu(0) and Cu_2O by =Fe(II), whcih was oxidized to Fe_2O_3·H_2O. • Both electron transfer and surface =Fe(II) were found to be crucial during chelated copper reduction. • The indispensible role of reductive decomplexation was identified in chelated copper sequestration. - Abstract: Chelated coppers, such as Cu"I"I-EDTA, are characteristically refractory and difficult to break down because of their high stability and solubility. Cu"I"I–EDTA sequestration by structural Fe(II) (=Fe(II)) was investigated intensively in this study. Up to 101.21 mgCu(II)/gFe(II) was obtained by =Fe(II) in chelated copper sequestration under near neutral pH condition (pH 7.70). The mechanism of Cu"I"I-EDTA sequestration by =Fe(II) was concluded as follows: 3Cu"I"I–EDTA + 7=Fe(II) + 9H_2O → Cu(0) ↓ + Cu_2O ↓ (the major product) + 2Fe_2O_3·H_2O ↓ + 3Fe"I"I–EDTA +14H"+ Novel results strongly indicate that Cu"I"I reductive transformation induced by surface =Fe(II) was mainly responsible for chelated copper sequestration. Cu(0) generation was initially facilitated, and subsequent reduction of Cu(II) into Cu(I) was closely combined with the gradual increase of ORP (Oxidation-Reduction Potential). Cu-containing products were inherently stable, but Cu_2O would be reoxidized to Cu(II) with extra-aeration, resulting in the release of copper, which was beneficial to Cu reclamation. Concentration diminution of Cu"I"I–EDTA within the electric double layer and competitive adsorption were responsible for the negative effects of Ca"2"+, Mg"2"+. By generating vivianite, PO_4"3"− was found to decrease surface =Fe(II) content. This study is among the first ones to identify the indispensible role of reductive decomplexation in chelated copper sequestration. Given the high feasibility and reactivity, =Fe(II) may provide a potential alternative in chelated metals pollution controlling.

[en] A class of nanomaterials based upon the surface modification of layered double hydroxides (LDHs) have been synthesized by grafting silanes onto the surfaces of the LDH. By in situ coprecipitation, the surfaces of a LDH have been modified through grafting of 3-aminopropyltriethoxysilane (APTS) using the anionic surfactant Na-dodecylsulfonate (SDS). The synthesized nanomaterials were characterized by X-ray diffraction (XRD), attenuated total reflection Fourier-transform infrared spectroscopy (ATR FTIR), thermogravimetry (TG) and transmission electron microscopy (TEM). The grafted LDH (LDH-G) displays distinct XRD patterns proving the obtained materials are a new and different phase. The FTIR spectra of the silylated hydrotalcite show bands attributed to Si-O-M (M = Mg and Al) vibration at 996 cm^-1, suggesting that APTS has successfully been grafted onto the LDH layers. The TG curves prove the grafted sample has less M-OH concentration and less interlayer water molecules, as indicated by the M-OH consumption during the condensation reaction between Si-OH and M-OH on the LDH surface. The grafted sample displays a ribbon-like thin sheet in the TEM images, with the lateral thickness estimated as 2.5 nm.

[en] Montmorillonite-supported magnetite nanoparticles were prepared by co-precipitation and hydrosol method. The obtained materials were characterized by X-ray diffraction, nitrogen adsorption, elemental analysis, differential scanning calorimetry, transmission electron microscopy and X-ray photoelectron spectroscopy. The average sizes of the magnetite nanoparticles without and with montmorillonite support are around 25 and 15 nm, respectively. The montmorillonite-supported magnetite nanoparticles exist on the surface or inside the interparticle pores of clays, with better dispersing and less coaggregation than the ones without montmorillonite support. Batch tests were carried out to investigate the removal mechanism of hexavalent chromium [Cr(VI)] by these synthesized magnetite nanoparticles. The Cr(VI) uptake was mainly governed by a physico-chemical process, which included an electrostatic attraction followed by a redox process in which Cr(VI) was reduced into trivalent chromium. The adsorption of Cr(VI) was highly pH-dependent and the kinetics of the adsorption followed the Pseudo-second-order model. The adsorption data of unsupported and clay-supported magnetite nanoparticles fit well with the Langmuir and Freundlich isotherm equations. The montmorillonite-supported magnetite nanoparticles showed a much better adsorption capacity per unit mass of magnetite (15.3 mg/g) than unsupported magnetite (10.6 mg/g), and were more thermally stable than their unsupported counterparts. These fundamental results demonstrate that the montmorillonite-supported magnetite nanoparticles are readily prepared, enabling promising applications for the removal of Cr(VI) from aqueous solution.

[en] Highlights: ► Ti-V co-doped magnetite has strong catalytic activity in UV-Fenton reaction. ► Ti⁴⁺ is more positive to adsorption and catalytic activity of magnetite than V³⁺. ► Mechanism of substitution increasing the adsorption and catalytic activity. ► The obtained results are benefit for application of magnetite in treating wastewater. - Abstract: This study investigated the methylene blue (MB) decolorization through heterogeneous UV-Fenton reaction catalyzed by V-Ti co-doped magnetites, with emphasis on comparing the contribution of V and Ti cations on improving the adsorption and catalytic activity of magnetite. In the well crystallized spinel structure, both Ti⁴⁺ and V³⁺ occupied the octahedral sites. Ti⁴⁺ showed a more obvious effect on increasing specific surface area and superficial hydroxyl amount than V³⁺ did, resulting in a significant improvement of the adsorption ability of magnetite to MB. The UV introduction greatly accelerated MB degradation. And magnetite with more Ti and less V displayed better catalytic activity in MB degradation through heterogeneous UV-Fenton reaction. The transformation of degradation products and individual contribution from vanadium and titanium on improving adsorption and catalytic activity of magnetite were also investigated. These new insights are of high importance for well understanding the interface interaction between contaminants and metal doped magnetites, and the environmental application of natural and synthetic magnetites.

[en] Iron nanoparticles have been successfully synthesized using sodium borohydride solution reduction of ferric trichloride hexahydrate in the presence of montmorillonite as an effective protective reagent and support as well. A combination of characterizations reveals the well disperse of these obtained iron nanoparticles supported on the external surface of clay with roughly spherical morphology and mean diameter of 55 nm. The particles are oxidation resistant well with iron core-iron oxide shell structure. The shell thickness of 3 nm remains almost invariable under ambient conditions. Discernable hysteresis loop reveals ferromagnetic behavior of the iron nanoparticles, which make them easy for magnetic separation and potential in some practical applications.