Influence of anodization parameters on the morphology of TiO2 nanotube arrays
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Anodizing
Phosphoric acid
Morphology
The paper studies the thin film of TiO2 nanotube arrays about diameter of 40 μm, which grown by electrochemically second anodization using titanium foil. The structure and compositions of nanotube arrays were characterized by scanning electron microscopy (SEM). Use the same electrolytes solution can grown three samples of TiO2 nanotube arrays under different times. That will be accordingly economize on electrolytes, and save on the time.
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Anodizing
Phosphoric acid
Oxalic Acid
Nanopore
Microelectronics
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Anodizing
Phosphoric acid
Oxalic Acid
Tartaric acid
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Anodizing film was prepared on aluminum plate making use of anodizing at constant voltage in phosphoric acid. The Al plate coated with the anodizing film was then immersed in a diluted phosphoric acid (5%) for 6~8 min to allow the processing of pore-enlargement. The morphology and structure of the anodizing film after the processing of pore-enlargement were analyzed by means of scanning electron microscopy. It was found that, after being treated in diluted phosphoric acid, the tiny pores distributed uniformly in the anodizing film and the enlarged pores had a diameter about 150 nm, with the amount of the pores to be as much as 2.5×10 9/cm 2. Moreover, the pore-enlargement in the dilute phosphoric acid caused the original irregular spheric pores in the film to be transformed to regular spheric ones. The size of the pores almost linearly increased with increasing pore-enlargement duration, but at a certain pore-enlargement duration the pores lost their spheric shape and came into conjunction with each other. The proper pore-enlargement duration was suggested to be 6~7 min.
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In order to deeply understand the mechanism and dynamic characteristics under the extraction process,the extraction kinetics of phosphoric acid and sulfuric acid was investigated by using constant-interface cell in the composite system.The effects of specific interfacial area,the concentration of phosphoric acid in the optimum extraction conditions and the concentration of sulfuric acid in the optimum extraction conditions on the extraction rate of phosphoric acid and sulfuric acid were reviewed.The kinetic equation of the extraction of phosphoric acid and sulfuric acid was put forward in the sulfuric acid-phosphoric acid system at 60 ℃.The results show that the extraction rate of phosphoric acid and sulfuric acid decreases with the increase of specific interfacial area,and increases with the increase of the initial concentration of phosphate in the aqueous phase gradually.With increasing the initial concentration of sulfuric acid in the aqueous phase,the extraction rate of phosphate is improved.The raw industrial phosphoric acid was used to verify the acid extraction kinetics.The result reveals that the extraction rates of the calculated values agree with the measured values of sulfuric acid and phosphoric acid.
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In this study, we investigated the feasibility of using a solution of sulfuric acid and phosphoric acid as an extraction method for soil-washing to remove Cu, Pb, Zn, and As from contaminated soil. We treated various soil particles, including seven fraction sizes, using sulfuric acid. In addition, to improve Cu, Pb, Zn, and As removal efficiencies, washing agents were compared through batch experiments. The results showed that each agent behaved differently when reacting with heavy metals (Cu, Pb, and Zn) and As. Sulfuric acid was more effective in extracting heavy metals than in extracting As. However, phosphoric acid was not effective in extracting heavy metals. Compared with each inorganic acid, As removal from soil by washing agents increased in the order of sulfuric acid (35.81%) < phosphoric acid (62.96%). Therefore, an enhanced mixture solution using sulfuric acid and phosphoric acid to simultaneously remove heavy metals and As from contaminated soils was investigated. Sulfuric acid at 0.6 M was adopted to combine with 0.6 M phosphoric acid to obtain the mixture solution (1:1) that was used to determine the effect for the simultaneous removal of both heavy metals and As from the contaminated soil. The removal efficiencies of As, Cu, Pb, and Zn were 70.5%, 79.6%, 80.1%, and 71.2%, respectively. The combination of sulfuric acid with phosphoric acid increased the overall As and heavy metal extraction efficiencies from the contaminated soil samples. With the combined effect of dissolving oxides and ion exchange under combined washings, the removal efficiencies of heavy metals and As were higher than those of single washings.
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An experimental study of the effect of stepwise dosing of sulfuric acid in the process of decomposition of apatite with sulfuric acid has been performed. The process of decomposition of apatite in the apatite-H3PO4-H2SO4-H2O system was carried out with stepwise dosing of sulfuric acid. At the beginning of the process, the calculated amount of phosphoric acid and half of the stoichiometric amount of sulfuric acid required for the decomposition of the loaded amount of apatite was loaded into the batch reactor. It was experimentally shown that the pH of the reaction mixture at the beginning of the process increases to a pH value of 6.13, at the same time there is a decrease in the concentration of sulfuric acid and the formation of phosphoric acid, this is due to the decomposition of apatite in the reaction mixture. Already in the seventh minute, the concentration of sulfuric acid is zero, and the concentration of phosphoric acid has the first peak value, after which it begins to decrease. Thus, at the beginning of the process, the formation of phosphoric acid occurs due to the decomposition of apatite with sulfuric acid. Since sulfuric acid was added at the beginning of the process with a deficiency (0.5 mol) of sulfuric acid is not enough to decompose the charged apatite, a decrease in the concentration of phosphoric acid and the formation of monocalcium phosphate are observed after the peak. This is due to the consumption of phosphoric acid on the decomposition of the remaining apatite with the formation of monocalcium phosphate. At the 140th minute, the remaining stoichiometric amount of sulfuric acid was added to the reactor (0.5 mol), a sharp drop in pH to 5.48 and a simultaneous increase in the concentration of phosphoric acid were observed. Consequently, sulfuric acid is consumed for the decomposition of monocalcium phosphate. Thus, it was shown that with an insufficient amount of sulfuric acid, the resulting phosphoric acid is spent on the decomposition of apatite with the formation of monocalcium phosphate. Adding sulfuric acid makes it possible to extract production phosphoric acid from monocalcium phosphate.
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The anodizing process of aluminum in phosphoric acid solution has been investigated. The results indica ted that the thickness of the barrier layer,the diameter of the cell and pore in the porous alumina film all increase with the increase of applied voltage.The reason is associated with the migration of the ions in the film.
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Activation effect of bentonite from Wulanlinge ore,treated with phosphoric acid,sulfuric acid and hydrochloric acid,respectively,were investigated.Results showed clearly that activation effect with phosphoric acid was worse as a whole,namely,free acid of products prepared with phosphoric acid with range from 0.302% to 0.869% was much higher than that,ranging from 0.026% to 0.070%,of products prepared with sulfuric acid.However,the bleaching capability was lower than that of products prepared with sulfuric and hydrochloric acid.Furthermore,both acids activated bentonites prepared with 25% sulfuric acid and 30% hydrochloric acid possessed the highest bleaching capability.Sulfuric acid was more suitable for activation reagent by taking everything into account.With the increasing of acid addition amount,activity degree of products prepared with each acidification reagent had the same changing tendency with free acid.The addition amount of acid at the maximum of activity degree was lower than that at the maximum of bleaching capability,and loose density and bleaching capability of products had reverse change trends as a whole.
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Hydrochloric acid
Bentonite
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