Evaporating crystallization effect of ammonium sulfate at atmospheric pressure under the action of ultrasound.

Ultrasound enhanced evaporating crystallization has been proposed to solve the problems of low crystallization yield and uneven particle size in the evaporating crystallization process of ammonium sulfate solution at atmospheric pressure. The effects of key operating parameters, including the ultrasound power, stirring speed, pH value, and ultrasound time, on the yield of ammonium sulfate product and the duration of solid-liquid transformation time are studied. The results show that the ultrasound crystallization can increase the ammonium sulfate yield by 52.9 %, reduce the solid-liquid transformation time of ammonium sulfate by 10 %, and obtain ammonium sulfate products with higher crystallinity and more uniform particle size. Ultrasound promotes the crystallization of ammonium sulfate by enhancing the transfer of heat in the solution and reducing the supersolubility of the ammonium sulfate solution from 937.5 g/L to 833.33 g/L. This study provides experimental justification for the use of ultrasound in atmospheric evaporative crystallization.

Efficient and eco-friendly cadmium ion recycling: Ultrasonic enhancement of aluminum powder replacement for low-temperature industrial applications.

Replacing cadmium ions in cadmium-containing solutions with aluminum powder is beneficial for cadmium resource recycling and environmental protection. However, the conventional aluminum powder replacement method requires harsh temperatures and prolonged conditions. In this study, the effect and mechanism of ultrasound on the replacement of cadmium with aluminum powder were investigated at low temperatures. Ultrasound has been proven to promote the etching of alumina films through the use of TEM and XPS, providing mechanistic support for the superiority of the new process. A degree of Cd replacement as high as 95.08 % is achieved at a low temperature (60 ℃) and in a short time (20 min) when using ultrasonicated aluminum powder replacement, which is 42.17 % higher than that of conventional aluminum powder. Compared with conventional aluminum powder replacement conditions with the same effect, the introduction of ultrasound can reduce the temperature by 30℃ and shorten the replacement time by 2/3, which has significant advantages in reaction efficiency and safety. The strengthening mechanism of ultrasound on the replacement effect of aluminum powder at low temperatures is revealed through detailed discussions on the corrosion of alumina films, agglomeration of aluminum powder, and adhesion of replacement products to the surface of aluminum powder, dissolved oxygen in the solution, and redissolution of cadmium. Therefore, a new approach for replacing aluminum powder in solutions with high Cd2+ concentrations at low temperatures is proposed in this work, which is expected to solve the existing harsh and dangerous problems of industrial aluminum powder replacement.

Effect and mechanism of ultrasound on acid loading in the preparation of silicon-based sulfonic solid acids.

Silicon-based sulfonic solid acids have the advantages of high catalytic activity and selectivity, easy separation from products, low equipment corrosion, and environmental protection, and sulfuric acid loading is the key to their preparation. To overcome the shortcomings of low acid loading and uneven distribution in the existing preparation methods of micron-sized silicon-based sulfonic solid acids, a method was proposed to prepare micron-sized silicon-based sulfonic solid acids using ultrasonic enhanced technology. The effect of different reaction parameters, such as time, power, and temperature of ultrasonication, sulfonation temperature and time, and sulfuric acid concentration, on acid loading in solid acid was investigated in this work. The results showed that a micron-sized mesoporous silica-based solid acid was successfully synthesized with a high acid content of 0.8633 mmol/g, uniform acid distribution, high specific surface area of 269.332 m2/g, and large average particle size of 172.142 µm in this work. The introduction of ultrasound was found to expand the carrier's pore volume and increase the carrier's specific surface area and the number of hydroxyl groups, thereby increasing the acid loading capacity and the specific surface area of the solid acid sample by 66.6 % and 10.97 % respectively, compared with the case without ultrasound.

Treatment of complex sulfur-containing solutions in ammonia desulfurization ammonium sulfate production by ultrasonic-assisted ozone technology.

In this work, the cause of abnormal color in ammonium sulfate products formed by flue gas desulfurization is revealed by investigating the conversion relationship between different sulfur-containing ions and their behavior in a sulfuric acid medium. Both thiosulfate (S2O32-) and sulfite (SO32- ＆ HSO3-) impurities affect the quality of ammonium sulfate. The S2O32- is the main reason for the yellowing of the product due to the formation of sulfur impurities in concentrated sulfuric acid. To address the yellowing of ammonium sulfate products, a unified technology (US/O3), using ozone (O3) and ultrasonic waves (US) simultaneously, is exploited to remove both thiosulfate and sulfite impurities from the mother liquor. The effect of different reaction parameters on the degree of removal of thiosulfate and sulfite is investigated. The synergistic effect of ultrasound and ozone on ion oxidation is further explored and demonstrated by the comparative experiments with O3 and US/O3. Under the optimized conditions, the thiosulfate and sulfite concentration in the solution is 2.07 and 5.93 g/L, respectively, and the degree of removal is 91.39 and 90.83%, respectively. The product obtained after evaporation and crystallization is pure white and meets the national standard requirements for ammonium sulfate products. Under the same conditions, the US/O3 process has apparent advantages, such as saving reaction time compared with the O3 process alone. Introducing an ultrasonically intensified field improves the generation of oxidation radicals ·OH, 1O2, and ·O2- in the solution. Furthermore, the effectiveness of different oxidation components in the decolorization process is studied by adding other radical shielding agents using the US/O3 process supplemented with EPR analysis. The order of the different oxidation components is O3(86.04%) > 1O2(6.53%) > â€¢OH(4.45%) > â€¢O2-(2.97%) for the oxidation of thiosulfate, and it is O3(86.28%) > â€¢OH(7.49%) > 1O2(4.99%) > â€¢O2-(1.25%) for the oxidation of sulfite.

Ultrasonic-assisted ozone degradation of organic pollutants in industrial sulfuric acid.

In this work, a combination of ozone (O3) and ultrasound (US) has been firstly used to decolorize black concentrated sulfuric acid with high organic content. The effect of different reaction factors on the transparency, extent of decolorization, H2SO4 mass fraction, and organic pollutants removal is studied. In addition, the systematic interaction between ultrasound and ozone on the decolorization process is reviewed through comparative experiments of O3, US and US/O3. A sulfuric acid product that meets the requirements for first-class products in national standards, with an extent of decolorization of 74.07%, transparency of 70 mm, and a mass fraction of 98.04%, is obtained under the optimized conditions. Under the same conditions, it has been established that the treatment time can be saved by 25% using the US/O3 process compared to using O3. Further, the production of oxidative free radicals (•OH) in a concentrated sulfuric acid system is enhanced using the US/O3 process compared with O3. In addition, the degree of effectiveness of different oxidizing components on the decolorization process is revealed by adding different free radical shielding agents when the US/O3 process is used.

Kinetics of Ni, V and Fe Leaching from a Spent Catalyst in Microwave-Assisted Acid Activation Process.

Ni, V and Fe are the main contaminant metals that lead to the deactivation of the spent fluid catalytic cracking (SFCC) catalyst. In this work, the properties and distribution of Ni, V and Fe in the SFCC catalyst are investigated by employing EPMA-EDX, SEM and XPS techniques. The kinetics of Ni, V, Fe and Al leaching in organic and inorganic acids are studied under microwave heating. The EPMA-EDX results show that Fe and Ni mainly accumulate near the particle surface, while V eventually distributes throughout the catalyst particle. The XPS result suggests that the phase speciations of Ni in the SFCC catalyst are Ni, Ni2SiO4 and NiAl2O4, while Fe is present in a mixture of Fe3O4, Fe2O3 and Fe2SiO4. V is in the forms of V2O5 and VO2. Compared with oxalic acid, sulfuric acid has a better removal effect of contaminant metals, especially for Ni. The leaching kinetics results indicate that using either sulfuric acid or oxalic acid, the apparent activation energy of V is obviously lower than that of Fe and Ni, and the priority of the three contaminant metals in the removal effect is V > Fe > Ni. In addition, the leaching kinetics of contaminant metals in the microwave-assisted acid activation process are controlled by the surface chemical reaction control model.