The active deep blue K2R dye solution was scanned by UV-visible near-infrared spectrophotometer, and the maximum absorption wavelength of 569 nm was selected as the measurement wavelength of the solution. A high-pressure ultraviolet lamp is used as a light source, and a glass spring loaded with a TiO2 catalyst is filled between the ultraviolet lamp and the tube wall of the self-made cylindrical glass catalytic degradation bed. The active deep blue K2R aqueous solution is circulated by a water pump between the water tank and the reactor for photocatalytic degradation. The absorbance of the water sample was measured with a spectrophotometer at a wavelength of 569 nm, thereby performing a decolorization rate calculation. COD was measured by the CODCr method.
Results and Discussion The effect of calcination temperature on the TiO2 film mineral phase was the XRD diffraction pattern of the TiO2 film heat treated at 300 ° C, 400 ° C and 500 ° C. It can be seen that the film heat-treated at 400 ° C is partially anatase phase and partially amorphous. Most of them are anatase phase at 500 °C. Since the glass tends to soften at 550 ° C or higher, 510 ° C is selected as the baking temperature of the glass spring-loaded TiO 2 film.
Environmental Chemistry 26 volumes are SEM images of the sol 2 gel coated with Ti(OH)4 nanoparticles, and it can be seen that the doped Ti(OH)4 nanoparticles are uniformly formed after calcination. The nano-sized particles are embedded in the TiO2 film, the particle size is about 50 nm, the grain size distribution is uniform, and the specific surface area is obviously increased. The supported photocatalyst produced by the split coating method has a uniform film surface without cracks. It can also be seen from the side profile of the film that the formed film has a thickness of about 016 μm. The nano-sized TiO 2 particles can be embedded in the film, so that the particles are firmly bonded to the film.
Under the same conditions, after 3 hours of photocatalytic degradation, the solution with pH value of 3 had the highest decolorization rate of 53%, followed by pH11, the decolorization rate was 34191%, and the pH value was 7 when the decolorization rate was the lowest. The reason may be that when the increased H+ or OH- in the solution diffuses to the surface of the catalyst, the electrons of the holes 2 are separated, and active radicals are generated, which effectively oxidize and degrade the dye substances, thereby causing an accelerated rate of degradation. In addition, the active dark blue is a sulfonate of an aromatic nucleus. In the aqueous solution, the sulfonate is an anion, which is mutually exclusive with the negative electrons occupying the semiconductor surface; and when the H+ in the solution increases, the sulfonate of the negative ion becomes a sulfonate due to the ion effect. The acid is more likely to diffuse to the surface of the catalyst and directly undergo electron or hole oxidation to be degraded, so that at a pH of 3, the decolorization rate is the highest.
It can also be seen that the CODCr removal rate is consistent with the pH value and the decolorization rate, but the ratio of CODCr removal rate (C) to decolorization rate (T) is still different. When the decolorization rate is high, the degradation rate is also high, but when the decolorization rate is low, the degradation rate is lower, indicating that the double bond contained in the compound is more susceptible to breakage by the action of active radicals.
The nano-sized TiO2 particles can be embedded in the film, the particle size is about 50 nm, the grain size distribution is uniform, and the specific surface area is obviously increased. The effect of pH from low to high on the decolorization rate and COD removal rate is "V" type, and the effect of temperature on both increases with the increase of temperature. Under the same conditions, the ratio of pH value to COD removal rate and decolorization rate is consistent with the decolorization rate, while the effect of temperature is small. Compared with ordinary films, the nano-particle-encapsulated film has a decolorization efficiency of 916%.
Although there are many types of tapping screws, they all have the following similarities:
(1) are generally made of carbonized carbon steel (accounting for 99% of total production). It can also be made of stainless steel or non-ferrous metals.
(2) The product must be heat treated. Carbon steel tapping screws must be carbonized and stainless steel tapping screws must be solution hardened. In order to make tapping screws to meet the requirements of the standard of mechanical properties and performance.
(3) The product surface hardness is high, the core toughness is good. That is, "soft inside strong outside". This is a major feature of tapping Screw performance requirements. If the surface hardness is low, it can not be screwed into the matrix; If the core toughness is poor, a twist will break, can not be used. So "inside soft outside steel" is self-tapping screw to meet the use of performance, very important requirements.
(4) The surface of the product needs surface protection treatment, generally electroplating treatment. Some product surface must be treated by phosphate (photostatting), such as wall panel self - tapping screws for photostatting.
(5) Production by cold heading process. It is recommended to use high-speed cold heading machine and high-speed wire rolling machine or high-speed planetary wire rolling machine. High speed is emphasized here to ensure product quality. Only the head of tapping screw produced by high-speed machine is well formed and the thread quality is high.
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