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Galvanic sludge is classified as a hazardous waste and incineration is one of the techniques used for its treatment. The aim of this work is to study the thermal behavior of a galvanic sludge which contains only chromium as a restriction metal. Simultaneous DTA/TG coupled with mass spectrometer tests were performed to characterize the thermal behavior of the sludge. Besides thermal analysis, sludge samples were heated in a specially designed furnace and these samples were submitted to X-ray diffraction. Vapor from the heated sludge was condensed and the particles were analyzed by EDS microprobe coupled in a scanning electron microscope. The slag formed after the calcination of the galvanic sludge was mainly composed of a mixture of calcium phosphate and fluoride. and minor concentrations of metals. A total weight loss of 34% was observed. The greatest part of this weight loss corresponds to CO2, H2O and SO2. H2O is liberated in the temperature range of 500-1,250 degrees C. CO2 in the range of 500-750 degrees C and SO2 near 1,000 degrees C. Chromium evaporation was not observed in relevant quantities, about 99.6% of the Cr remained incorporated in the slag.
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PMID:Thermal behaviour of chromium electroplating sludge. 1130 May 40

Germanium nanowires, ranging from 10 to 150 nm in diameter, were grown several micrometers in length in cyclohexane heated and pressurized above its critical point. Alkanethiol-protected gold nanocrystals, either 2.5 or 6.5 nm in diameter, were used to seed wire formation. Growth proceeded through a solution-liquid-solid mechanism at growth temperatures ranging from 300 to 450 degrees C. At temperatures exceeding 500 degrees C, large Ge particulates formed due to unfavorable growth kinetics. Temperature, the nature of the precursor, precursor concentration, and the Au:Ge ratio were determining factors in nanowire morphology. The Ge nanowires were characterized using a range of techniques, including XPS, XRD, high-resolution TEM and SEM, nanometer-scale EDS mapping, and DTA.
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PMID:Nucleation and growth of germanium nanowires seeded by organic monolayer-coated gold nanocrystals. 1184 11

Fine composite powders of yttria (3 mol%) stabilized zirconia (Z, 10 wt%) and hydroxyapatite (HA), denoted as HAZ, were prepared by the co-precipitation method. The resulting powders were characterized by XRF, TEM, EDS, XRD, FTIR, TG-DTA, and BET surface area techniques. AES and FTIR were employed to determine the surface properties of the HAZ suspensions in the presence of NH4PAA as a dispersant, which confirmed that the surfaces of both HA and Z were affected by the adsorbed polymers. The mechanism of NH4PAA adsorption on the particles was discussed. Zeta potential measurements showed that the addition of NH4PAA resulted in a dramatic increase in the absolute value of zeta potential. NH4PAA considerably enhanced the stability of the HAZ suspension via electrosteric barrier mechanisms. TEM micrographs confirmed that particles were well dispersed in the suspension. The adsorption density of the dispersant was found to decrease with an increase in pH value.
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PMID:Fabrication and surface characterization of NH4PAA-stabilized HAZ suspensions. 1625 23

Highly ordered silver sulfide nanorods conjugated with the Bovine Serum Albumin (BSA) protein have been successfully achieved at ambient temperature. Such a process is very simple and controllable, directly using silver nitrate and thioacetamide (TAA) as the reactants in the aqueous solution of BSA. The products have been characterized by XRD, HRTEM-SAED, SEM-EDS, TG-DTA, FT-IR, and CD spectroscopy. The results of the research show that the as-prepared Ag2S nanorods are monodispersed with sizes about 40 nm in diameter and 220 nm in length, and exhibit a high degree of crystallinity and good photoluminescence. Furthermore, an interesting mechanism is discussed for the formation of the Ag2S nanorods.
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PMID:Fabrication of protein-conjugated silver sulfide nanorods in the bovine serum albumin solution. 1672 64

In order to investigate the effect of sintering temperature on the characteristics of sludge ceramsite and find an optimal sintering temperature, dried sewage sludge, clay, and water glass were mixed at ratios of dried sewage sludge/clay=33% and water glass/clay=15%. Then these mixtures were heated to 850, 900, 950, 1000, 1100, and 1200 degrees C for production of sludge ceramsite. The sludge ceramsite were characterized by DTA-TGA, SEM-EDS, XRD, and XRF. The results indicate that the differences in thermal behaviours are caused by the compositional and structural variations; the ceramsite sintered at 1000 degrees C has more uniformly distributed finer pores (0.5 microm<pore size<10.0 microm), while the ceramsite sintered at other temperatures has less pores and rougher surfaces. The main crystalline phases of ceramsite are quartz and kyanite below 1000 degrees C; kyanite is the main crystalline phase at 1000 and 1100 degrees C, and most of the crystalline phases are mullite at 1200 degrees C. It is therefore concluded that sintering temperature has a significant effect on the characteristics of sludge ceramsite, and that 1000 degrees C is the optimal sintering temperature.
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PMID:Effect of sintering temperature on the characteristics of sludge ceramsite. 1756 41

A novel class of orange-red phosphors based on Eu(3+)-activated LaNbTiO(6) was successfully fabricated by a wet chemical method, called a modified combustion approach. XRD, TG-DTA, SEM, and EDS results show that the heat-treatment of the powders above 1000 degrees C is enough to obtain highly crystallized and phase-pure LaNbTiO(6) and Eu(3+)-doped samples, which is of prime importance in investigating the optical properties of the novel phosphors using LaNbTiO(6) as the host material. UV-vis diffuse reflectance spectroscopy reveals that the direct band gap of LaNbTiO(6) with large grains (above 200 nm) is calculated to be 3.27 eV, while the absorption edge of the small particles shows an obvious blue-shift. Two blue emission bands centered at 440 and 470 nm ascribed to the self-trapped exciton emission of the distorted NbO(6) and TiO(6) groups for the pure LaNbTiO(6) can be obtained. Photoluminescence spectra of the Eu(3+)-doped phosphor particles illuminated the simultaneous occurrence of several intense orange-red band emissions due to the characteristic transitions of (5)D(0,1) --> (7)F(J) (J = 0, 1, 2, 3, 4) of Eu(3+) under 395 nm excitation. The mechanism of these multiplets possibly arising from the odd-parity distortions of the Eu(3+) ion environment and the effect of crystallanity of the compounds on luminescence were discussed, respectively. The highly bright and color-uniform fluorescence images of the doped samples with short luminescence decay times (nanosecond magnitude) confirmed the potential applications of the phosphors in luminescence and display devices.
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PMID:Novel class of aeschynite structure LaNbTiO6-based orange-red phosphors via a modified combustion approach. 1793 5

Adsorption-based processes are widely used in the treatment of dilute metal-bearing wastewaters. The development of versatile, low-cost adsorbents is the subject of continuing interest. This paper examines the preparation, characterization and performance of a micro-scale composite adsorbent composed of silica gel (15.9 w/w%), calcium silicate hydrate gel (8.2 w/w%) and calcite (75.9 w/w%), produced by the accelerated carbonation of tricalcium silicate (C(3)S, Ca(3)SiO(5)). The Ca/Si ratio of calcium silicate hydrate gel (C-S-H) was determined at 0.12 (DTA/TG), 0.17 ((29)Si solid-state MAS/NMR) and 0.18 (SEM/EDS). The metals-retention capacity for selected Cu(II), Pb(II), Zn(II) and Cr(III) was determined by batch and column sorption experiments utilizing nitrate solutions. The effects of metal ion concentration, pH and contact time on binding ability was investigated by kinetic and equilibrium adsorption isotherm studies. The adsorption capacity for Pb(II), Cr(III), Zn(II) and Cu(II) was found to be 94.4 mg/g, 83.0 mg/g, 52.1 mg/g and 31.4 mg/g, respectively. It is concluded that the composite adsorbent has considerable potential for the treatment of industrial wastewater containing heavy metals.
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PMID:Characterization of carbonated tricalcium silicate and its sorption capacity for heavy metals: a micron-scale composite adsorbent of active silicate gel and calcite. 1795 Sep 99

Adsorption of aflatoxin B(1) (AFB1) by natural montmorillonite (MONT) and montmorillonite modified with copper ions (Cu-MONT) was investigated. Both MONTs were characterized using the X-ray powder diffraction (XRPD) analysis, thermal analysis (DTA/TGA) and scanning electron miscroscopy/electron dispersive spectroscopy (SEM/EDS). The results of XRPD and SEM/EDS analyses of Cu-MONT suggested partial ion exchange of native inorganic cations in MONT with copper occurred. Investigation of AFB1 adsorption by MONT and Cu-MONT, at pH 3, 7 or 9, showed that adsorption of this toxin by both MONTs was high (over 93%). Since AFB1 is nonionizable, no differences in AFB1 adsorption by both MONTs, at different pHs, were observed, as expected. Futhermore, it was determined that adsorption of AFB1 by both MONTs followed a non-linear (Langmuir) type of isotherm, at pH 3. The calculated maximum adsorbed amounts of AFB1 by MONT (40.982mg/g) and Cu-MONT (66.225mg/g), derived from Langmuir plots of isotherms, indicate that Cu-MONT was much effective in adsorbing AFB1. Since, the main cation in an exchangeable position in MONT is calcium, and in Cu-MONT both calcium and copper, the fact that ion exchange of inorganic cations in MONT with copper increases adsorption of AFB1 suggests that additional interactions between AFB1 and copper ions in Cu-MONT caused greater adsorption.
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PMID:Aflatoxin B(1) adsorption by natural and copper modified montmorillonite. 1858 10

This experimental research was to investigate the possibility of incorporating red mud and coal gangue as raw materials for the production of red mud-coal gangue cementitious material, abbreviated as RGC, including analyses of its chemical composition, physical properties, mechanical properties and hydration products. The red mud and coal gangue (at a ratio of 3:2) were mixed together and shaped in small spheres with a water to solid ratio of 0.30 and then calcined at 600 degrees C for 2h. Subsequently, the RGC was prepared by blending 50% the resultant red mud-coal gangue mixtures, 24% blast-furnace slag, 20% clinker and 6% gypsum. The hydration products of RGC were characterized by XRD, TG-DTA and SEM-EDS. The results showed that it is feasible to use red mud and coal gangue to replace up to 50% of the raw materials to produce cementitious material, which can be called as silica-alumina based cementitious material. The hydration products of RGC are mostly ettringite, calcium hydroxide and C-S-H gel. As the dominant products, C-S-H gel and ettringite are principally responsible for the strength development of RGC in early hydration process. The content of Ca(OH)(2) initially increased but later was depleted after reaching the peak value at 21 days. Moreover, it is found that the composition of the C-S-H gel shifted towards higher Si, Al and Na contents with the increase of hydration age, whereas that of Ca shifted towards lower content.
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PMID:Early-age characteristics of red mud-coal gangue cementitious material. 1923 41

MnCuO(x)/TiO(2) supported catalyst was synthesized by the incipient wetness impregnation method. The catalyst was then tested for the oxidation of chlorobenzene (CB) used as a Cl-VOC model. The results showed that MnCuO(x)/TiO(2) is very active for CB oxidation since a total conversion (exclusively into H(2)O, CO(2) and Cl(2)) was reached at 350 degrees C without formation of any other harmful organic compounds and no catalyst deactivation was observed. This performance was attributed to the formation Mn(1.6)Cu(1.4)O(4) spinel phase. However, at lower temperatures, some deactivation occurred before a steady-state is reached. At 300 degrees C, the CB conversion decreased and stabilised at 75% after 5h and a small amount of HCl and traces of CO were detected. The reason why HCl was not detected at temperatures higher than 350 degrees C was explained by Deacon reaction. SEM/EDS analysis revealed the presence of chlorine uniformly dispersed on the catalyst surface. The formation of chlorinated compound (MnCuO(x-a)Cl(2a)/TiO(2)), which is presumed to be responsible of the catalyst partial deactivation, was confirmed by other analysis experiments (TG/DTA, TPR). The catalyst regeneration under air at 350 degrees C allowed the system to recover the initial activity in spite of the fact that the chlorine was not completely removed from the catalyst.
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PMID:Removal of hazardous chlorinated VOCs over Mn-Cu mixed oxide based catalyst. 1941 Nov 36


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