A high grade of fluorite ore is necessary to produce hydrogen fluoride (HF) that is changed to fluoro-resin and then used in the semiconductor manufacturing. With the continues depletion of resources, novel technologies for processing low-grade fluorite ores are urgently needed, in order to lower the arsenic concentration to less than 100 mg/kg. In this study, a low-grade flotation concentrated fluorite ore, imported from Mexico, was upgraded by removing arsenic, which is difficult to be decreased by conventional method. The micro-bubble flotation, liquid-liquid separation and mechano-chemical leaching of fluorite ore were carried out to investigate the removal of arsenic from the low-grade fluorite. Experimental results showed that the arsenic concentration was reduced to less than 100 mg/kg.
Electroless nickel plating waste liquor contains a large amount of nickel ions, but nickel ions in waste liquor have not been recovered for technical and economic reasons. If the recovery of nickel ions is effectively carried out, nickel ions could be recycled as a nickel source for electroless plating liquor. The process to recover nickel ions from electroless plating waste liquor was investigated by using a solvent extraction method. The existence of various phosphate species and organic acids in the waste liquor causes the incomplete extraction of nickel ions with any single extractant due to the complex formation between nickel ions and them. The application of solvent extraction using a synergistic effect makes possible to separate and recover 90% or more of nickel ions in the waste liquor. The extractant mixtures of acidic extractant such as D2EHPA and PC-88A, and another extractants with electron-donating ability such as nicotinic acid dodecyl ester and iso-nicotinic acid dodecyl ester are used for this purpose.
We have proposed a new technique for recycling silicate glasses, removing metallic elements from them. This technique utilizes a liquid-phase deposition (LPD) method at lower temperatures than 40°C. In this LPD method, cathode ray tube (CRT) glasses are dissolved in hydrofluoric (HF) acid aqueous solution. An LPD-SiOF thin-film with thickness 1 μm was formed on a silicon (Si) substrate. The recycled LPD-SiOF film properties were compared with those for the high quality LPD-SiOF thin-film deposited using semiconductor grade hydrofluorosilicic acid (H2SiF6) aqueous solution. In the FTIR analysis, the chemical bonding structure for the recycled LPD-SiOF film is quite similar to high quality LPD-SiOF film. The refractive index at 632.8 nm for the recycled LPD-SiOF film is 1.43 and is the same as that for the high quality LPD-SiOF film. In order to separate metal oxides and metal ions from the H2SiF6 aqueous solution, we examined electrochemical analyses. The reactivity of various metal oxides with HF and H2SiF6 aqueous solutions was also evaluated. Undissolved metal oxides and precipitated metal fluorides can be separated by filtering. Some residual metal ions, such as Sb3+ and Fe3+, can be reduced to metals by electrolysis.
The use of exergetic efficiency rate of change to evaluate fuel cell performance is developed and explained. It is important to understand the maximum possible thermal efficiency a fuel cell system is capable of obtaining on a fuel and then what fraction of this efficiency it actually achieves. The exergetic efficiency rate of change is a natural and instantaneous measure of the change in fuel cell performance occurring at any time. There are three central performance measures for fuel cells. The first is exergetic efficiency which is measured by thermal efficiency. It permits the direct comparison of the performance of all fuel cell types operating on the same fuel, if desired. The second is exergetic efficiency rate of change which is useful in degradation and which is a broader, more inclusive concept than rate of change of ASR. The third is power or power density which can be related to the economic viability of the fuel cell or fuel cell system. Fuel cell system design and operation is ultimately the resolution of the tradeoffs between the three performance measures.