جستجوی مقالات مرتبط با کلیدواژه "calcination" در نشریات گروه "شیمی"

The extraction of gold in any part of the world is left in the hands of artisanal local miners who do this with the use of mercury which is considered to be a very hazardous chemical to humans and the biophysical environment. This research investigated the use of borax as a replacement for mercury in the extraction of gold from its ore. The sample used for the study was collected from Chanchaga mining site in Niger State. Calcination of the sulphide ore was done at a temperature of 600 oC in order to oxidize the sulphur content of the ore. The Borax in its modified form was used as a metal flux in the extraction process and this was optimized through Box-Behnken experimental design method using Design Expert 7.0 software. The effect of temperature, the mole ratio of heavy mineral concentrate to borax, and time were studied at 800 – 1000 oC, 0.8 – 3.5, and 15-30 min respectively. Sieve, X-Ray Fluorescence (XRF), and carat analysis of the samples were carried out. The percentage yield of gold extract was 70.2 % at 900 oC, 30 min, and 0.8 mole ratio of heavy mineral concentrate to modified borax. The sieve analysis shows that visible gold liberation was achieved between 0.3 and 0.15 mm, and the X-Ray Fluorescence showed 88.7 % extract gold purity with 22 carats. This method can be a replacement for the current toxic method of gold extraction using mercury.

In this study, Copper oxide (CuO) nanoparticles (NPs) were prepared using the chemical co-precipitation method and treated at different calcination temperatures. The synthesized CuO NPs have been calcinated at 300 °C, 500 °C, and 700 °C. The X-Ray Diffraction (XRD) results exhibited a decrease in the width of the principle diffraction peak with the temperature rise. Crystallite size was determined by Scherrer’s formula, whereas, the Williamson-Hall method presented drastic variation in size indicating the creation of lattice strain with the rise in calcination temperature. Scanning Electron Microscopy (SEM) images showed an increase in grain size and vary from 170 nm – 430 nm. X-ray Energy Dispersive Spectroscopy (EDS) results indicate the formation of CuO NPs and relative Cu contents increased (52.9 to 72.5 Atomic percentage) with temperature. Optical properties are also affected by the calcination temperature and a reduction in bandgap is observed with the increase in temperature. Fourier Transform Infra-Red (FT-IR) spectroscopy spectra of different samples showed identical bonding behavior and no apparent change in bonding was observed. Photo-degradation of Congo Red dye was performed with CuO NPs treated at different temperatures and NPs treated at 500 °C, have shown maximum degradation efficiency in 75 min under visible light.

This study endeavors to investigate the influence of calcination temperatures (650, 750 & 850°C) on the strontium ferrite (SrFe2O4) nanoparticles synthesized by the co-precipitation method. The prepared powder samples were characterized by various measurement techniques such as X-ray diffractometer (XRD), scanning electron microscopy (SEM), thermo gravimetric analysis (TGA), and vibrating sample magnetometer (VSM). Initially, the XRD patterns were confirmed the presence of spinel SrFe2O4 phases. Overall, the number of diffraction peaks increased due to the enhancement of calcination temperature. The SEM morphological features are shown the spherical-shaped nanoparticles with less agglomeration. Considerably, the agglomeration between the nanoparticles increased due to the higher calcination temperatures. However, the structural and morphological investigation was helpful and carried out for the TGA and VSM investigation. At 850°C calcination temperature, TGA revealed 5.8% of weight loss and VSM endorsed the magnetic properties such as high saturation magnetization (Ms), remanent magnetization (Mr) and coercivity (Hc) come out to be 37.26 emu/g, 19.788 emu/g and 6188.4 Oe, respectively.

Two dimensional silver(I) coordination polymer, [Ag(μ5-T4S)]n (1), (T4S- = toluene-4-sulfonate), has been synthesized and characterized by Inductively Coupled Plasma (ICP) and elemental analyses, IR spectroscopy and powder X-ray diffraction. This compound was calcined at 450, 500 and 700 °C in a furnace and static atmosphere of air. The resulting compound from 1 at 450 °C is a spongy nanostructure which could not be characterized due to its partial calcination process. At 500 and 700 °C, the compound is a mixture of silver and silver sulfate compacted nanosheets and microstructures. By increasing the temperature  from 500 to 700 °C, the tendency for the formation of agglomerated mixture of silver and silver sulfate was increased. In addition, a number of one-step techniques including electrochemical deposition method, electroless deposition method, direct deposition method, redox reaction, mirror reaction, coating technique, self-seeding or self-assembling process and wet chemical method have been reviewed for the synthesis of two-dimensional nano silver.