Ultrasound-assisted oxidative process for sulfur removal from petroleum product feedstock

A procedure using ultrasonic irradiation is proposed for sulfur removal of a petroleum product feedstock. The procedure involves the combination of a peroxyacid and ultrasound-assisted treatment in order to comply with the required sulfur content recommended by the current regulations for fuels. The ultrasound-assisted oxidative desulfurization (UAOD) process was applied to a petroleum product feedstock using dibenzothiophene as a model sulfur compound. The influence of ultrasonic irradiation time, oxidizing reagents amount, kind of solvent for the extraction step and kind of organic acid were investigated. The use of ultrasonic irradiation allowed higher efficiency for sulfur removal in comparison to experiments performed without its application, under the same reactional conditions. Using the optimized conditions for UAOD, the sulfur removal was about 95% after 9 min of ultrasonic irradiation (20 kHz, 750 W, run at 40%), using hydrogen peroxide and acetic acid, followed by extraction with methanol.     

Study on ultrasound-assisted oxidative desulfurization for crude oil

The existence of sulfur compounds in crude oil will bring many problems such as corrosion, catalyst poisoning and pollution to the petroleum processing process. Therefore, how to reduce the sulfur content as much as possible in the process of crude oil processing has become an important research topic in the petroleum processing industry. In this paper, ultrasonic-oxidative desulfurization is studied. The effects of reaction temperature, reaction time, amount of oxidant and demulsifier on desulfurization rate are investigated. And the effect of oxidative desulfurization and single oxidative desulfurization under ultrasonic treatment are compared. It is found that the addition of ultrasonic treatment can enhance the desulfurization effect of desulfurizer, the desulfurization efficiency can be increased by about 10% under ultrasonic treatment (100 W, 70 kHz); ultrasonic wave plays an auxiliary role in the system, it can promote heterogeneous reactions, improve the activity of oxidants, and promote the degradation of macromolecular compounds. Finally, physical desulfurization, chemical desulfurization and biological desulfurization technologies are compared.     

Ultrasound assisted oxidative desulfurization of model diesel fuel

Very stringent environmental regulations have limited the level of sulfur in diesel, therefore deep desulfurization of fuels is required. For that purpose, the frequently used industrial process is hydrodesulfurization (HDS) which enables effective elimination of sulfur compounds such as mercaptanes, thiols, sulfides, disulfides from diesel oil, but removal of thiophene sulfur compounds (benzothiophene, dibenzothiophene, 4,6 dimethyldibenzothiophene) is insufficient. Ultrasound assisted oxidative desulfurization (UAOD) as one of several new technologies enables performance under mild conditions without use of explosive hydrogen. A higher reactivity of thiophene sulfur compounds during UAOD also provides conversion into highly polar sulfoxides and sulfones that are easily removed by adsorption or extraction. Nowadays, different catalyst/oxidants systems are being studied to improve oxidation reaction efficiency and enhance the mass transfer in the interfacial region. In this paper, the effect of reaction temperature (40–70 °C) and oxidation time (5–150 min) for UAOD of model diesel fuel with a catalyst/oxidants system (acetic acid/hydrogen peroxide) was investigated in a 70 ml batch reactor. Furthermore, the effects of different initial concentrations of dibenzothiophene (DBT) and of ultrasound amplitude were additionally examined to achieve efficient sulfur removal. The obtained results indicated that temperature and US amplitude of 70 °C and 80% respectively were efficient for conversion of DBT (sulfur concentration up to 3976.86 ppm). The results indicate a rise in the yield of sulfones at higher temperatures and subsequent extraction with N,N-dimethylformamide conducted after the process of oxidation at different solvent/oil ratio revealed sulfur removal efficiency of 98.35%.     

Removal of carbamazepine from aqueous solution using sono-activated persulfate process

This study investigated systematically the removal of carbamazepine (CBZ) in solution using the combination of ultrasound and persulfate anions to identify the factors affecting the kinetics of the process. The effects of reaction time, initial persulfate anion concentration, initial CBZ concentration, ultrasonic power input, solution pH and temperature on CBZ removal efficiency were examined. The sulfate radical oxidation of CBZ in the presence of ultrasonic irradiation showed a significant synergistic effect on CBZ removal. It is found that up to 89.4% CBZ removal efficiency was achieved after 120 min reaction. The removal process of CBZ in solution could be described using pseudo-first-order kinetics. In this system, sulfate radicals (SO₄⁻) were considered to be the mainly oxidant to remove CBZ while ultrasound power input could affect CBZ removal efficiency significantly. Changing solution pH influenced the CBZ removal efficiency and the best performance would be achieved at pH 5.0.     

Ultrasound-assisted oxidation of dibenzothiophene with phosphotungstic acid supported on activated carbon

Phosphotungstic acid (HPW) supported on activated carbon (AC) was applied to catalyze deep oxidation desulfurization of fuel oil with the assist of ultrasound. The sulfur-conversion rate was evaluated by measuring the concentration of dibenzothiophene (DBT) in n-octane before and after the oxidation. Supporting HPW on AC has been verified to play a positive role in UAOD process by a series of contrast tests, where only HPW, AC or a mixture of free HPW and AC was used. The influences of catalyst dose, ultrasound power, reaction temperature, H₂O₂:oil volume ratio and the reuse of catalyst on the catalytic oxidation desulfurization kinetics were investigated. The DBT conversion rate of the reaction catalyzed by supported HPW under ultrasound irradiation was higher than the summation of the reactions with HPW only and AC only as catalyst. With the increase of loading amount of HPW on AC, ultrasound power, H₂O₂:oil volume ratio and reaction temperature, the catalytic oxidation reactivity of DBT would be enhanced. The optimum loading amount of HPW was 10%, exceed which DBT conversion would no longer increase obviously. DBT could be completely converted under the optimized conditions (volume ratio of H₂O₂ to model oil: 1:10, mass ratio of the supported HPW to model oil: 1.25%, temperature: 70 °C) after 9 min of ultrasound irradiation.     

Ultrasonic desulfurization of amphiphilic magnetic-Janus nanosheets in oil-water mixture system

Fe₃O₄ was obtained by reacting FeCl₂ and FeCl₃ with polyethylene glycol, and labeled onto a amphiphilic Janus nanosheet. It was confirmed by infrared spectroscopy, SEM, AFM and EDS that the Fe₃O₄ nanoparticles changed from hydrophilic to amphiphilic. The oxidative desulfurization performance of amphiphilic iron oxide was studied. Results showed that the Janus nanosheets labeled with Fe₃O₄ could significantly improve the removal rate of thiophene sulfide in simulated oil synergistically with ultrasonic waves, and the desulfurization rate could reach 100%. Further, the effect of ultrasound on the sensing ability of the oil–water interface was studied and the ultrasonic attenuation coefficient was calculated. In addition to the desulfurization mechanism of Fe₃O₄, it was found that although the ultrasonic attenuation coefficient of the amphiphilic nanosheets was high, the number of hydroxyl radicals determined the desulfurization efficiency. The amphiphilic Fe ions were more favorable for the formation of hydroxyl radicals than the single hydrophilic ones.     

Dual-frequency (20/40 kHz) ultrasonic assisted photocatalysis for degradation of methylene blue effluent: synergistic effect and kinetic study

Dual-frequency ultrasonic assisted photocatalysis (DUAP) was proposed to enhance the degradation efficiency of methylene blue (MB) solution. The influence of operational parameters, i.e., irradiation time, ultrasonic arrangement, TiO₂ concentration and power density, was studied. The results implied that the rapid degradation of MB solution was achieved in 18 min under DUAP with the dual frequencies of 20/40 kHz. Kinetic investigation of MB degradation for the DUAP process was conducted on the basis of first-order kinetic equation and the synergistic effect was assessed by examination of the apparent rate constant. The effect of ultrasonic arrangement was analyzed by comparison of the pressure amplitude of ultrasonic superposition field. The evolvement of intermediate products and the role of active species during DUAP were distinguished by UV-Vis spectra and the free radical scavenging experiment.     

Theoretical and experimental investigation of desalting and dehydration of crude oil by assistance of ultrasonic irradiation

In this paper desalting/dehydration process of crude oil by ultrasonic irradiation in a novel batch standing-wave resonator reactor is studied both theoretically and experimentally. The effect of main parameters including ultrasonic irradiation parameters, namely irradiation input power and irradiation time, and also operating parameters, such as temperature and injected water, on the removal efficiencies of salt and water is examined. The obtained results demonstrate that finding the optimum values of the above mentioned parameters is important to prevent a significant decrease in the removal efficiencies of water and especially salt. Thus, crude oil was subjected to optimal ultrasonic irradiation with an input power of 57.7 W, and irradiation time of 6.2 min at temperature of 100 °C. The injected water to dissolve the salt of crude oil was 7 vol.%. Also, the applied settling time and dosage of chemical demulsifier were 60 min and 2 ppm, respectively. Under these optimum conditions the removal efficiencies of the desalting/dehydration process were 84% and 99.8%, respectively, which are suitable for refineries.Also, based on the optimal experimental data, two inferential estimators are developed to obtain the relationships between the salt and water removal efficiencies, and input energy density. These empirical relationships can offer a proper estimation for the salt and water removal efficiencies with irradiation input energy.     

Evaluation of ammonia–nitrogen removal efficiency from aqueous solutions by ultrasonic irradiation in short sonication periods

In this study, mechanisms and efficiency of ammonia–nitrogen removal from aqueous solutions by ultrasonic irradiation were investigated. Depending on the factors affecting the sonication (initial concentration, initial pH, ultrasonic power density and sonication period), sonication tests were carried out and ammonium–nitrogen removal efficiency by ultrasonic irradiation was determined. In these experiments, ammonia–nitrogen removal efficiency was achieved in the range of 8–64%. In short sonication periods, the best ammonia–nitrogen removal efficiency was achieved at pH 8.2–11. Lower ammonia–nitrogen removal efficiency was observed in high initial ammonia–nitrogen concentration of solutions. It was observed that high initial ammonia–nitrogen concentrations may led to decreased ammonia–nitrogen removal efficiency however quantity of ammonia–nitrogen removal was higher. Because high initial concentration had a negative impact on the sonochemical reactions the heat of cavitation bubbles was reduced. Ammonia–nitrogen removal efficiency was increased with ultrasonic density and sonication period. This study showed that effective ammonia–nitrogen removal could be achieved by the ultrasonic irradiation in short sonication periods (as 60–600 s). Specific cost of ammonia–nitrogen removal by the ultrasonic irradiation from simulated ground water, surface water, wastewater and landfill leachate was also calculated. The specific removal cost was varied between 0.01 and 0.25 $/g ammonia–nitrogen.     

Degradation of Acid Orange 7 in aqueous solution by zero-valent aluminum under ultrasonic irradiation

Degradation of azo dye Acid Orange 7 (AO7) by zero-valent aluminum (ZVAl) in combination with ultrasonic irradiation was investigated. The preliminary studies of optimal degradation methodology were conducted with sole ultrasonic, sole ZVAl/air system, ultrasonication + ZVAl/air system (US-ZVAl). In ZVAl/air system, the degradation of AO7 could almost not be observed within 30 min. The degradation of AO7 by ZVAl/air system was obviously enhanced under ultrasound irradiation, and the enhancement is mainly attributed to that the production of hydroxyl radicals in ultrasound-ZVAl process was much higher than that in sole ultrasonic or in sole ZVAl/air system. The variables considered for the effect of degradation were the power of ultrasound, the initial concentration of AO7, as well as the initial pH value and the dosage of zero-valent aluminum. The results showed that the decolorization rate increased with the increase of power density and the dosage of ZVAl, but decreased with the increase of initial pH value and initial concentration of AO7. More than 96% of AO7 removal was achieved within 30 min under optimum operational conditions (AO7: 20 mg/L, ZVAl: 2 g/L, pH: 2.5, ultrasound: 20 kHz, 300 W). This study demonstrates that ultrasound-ZVAl process can effectively decolorize the azo dye AO7 in wastewater.     

Ultrasonic-assisted synthesis of nano-sized metal-organic framework; a simple method to explore selective and fast Congo Red adsorption

A novel mixed linker Metal-organic Framework, [Co(NH₂IsoBDC)(bpfn)].DMF (TMU-69), with amide and amino functionalized spacers (bpfn = N,N'-(naphthalene-1,5-diyl)diisonicotinamide, NH₂IsoBDCH₂ = 5-Aminoisophthalic acid) was synthesized through both solvothermal and ultrasonic approaches. Applying sonochemical irradiation led to ultrafast formation of Flower-shaped nanoplates of TMU-69 within 15 min with high yield while, solvothermal method takes 3 days to form the framework. Control of size and morphology was also enhanced through applying ultrasonic irradiations. The implication of applied time and concentration of reagents on size and morphology of nano-structured TMU-69 have been optimized. Applying higher concentration of initial material with optimized 60-minute irradiation forms uniform smaller sized nanoplates of TMU-69. Also, the efficiency of TMU-69 bulk and nanoplates toward removal of pollutant dyes from water was investigated. The selective adsorption of Congo Red was observed among other dyes. Also, drastic enhancement in removal kinetic of Congo Red through using ultrasonic assisted nanoplates of TMU-69 was obtained.     

Multi-objective optimization of oxidative desulfurization in a sono-photochemical airlift reactor

Response surface methodology (RSM) was employed to optimize ultrasound/ultraviolet-assisted oxidative desulfurization in an airlift reactor. Ultrasonic waves were incorporated in a novel-geometry reactor to investigate the synergistic effects of sono-chemistry and enhanced gas-liquid mass transfer. Non-hydrotreated kerosene containing sulfur and aromatic compounds was chosen as a case study. Experimental runs were conducted based on a face-centered central composite design and analyzed using RSM. The effects of two categorical factors, i.e., ultrasound and ultraviolet irradiation and two numerical factors, i.e., superficial gas velocity and oxidation time were investigated on two responses, i.e., desulfurization and de-aromatization yields. Two-factor interaction (2FI) polynomial model was developed for the responses and the desirability function associate with overlay graphs was applied to find optimum conditions. The results showed enhancement in desulfurization ability corresponds to more reduction in aromatic content of kerosene in each combination. Based on desirability approach and certain criteria considered for desulfurization/de-aromatization, the optimal desulfurization and de-aromatization yields of 91.7% and 48% were obtained in US/UV/O₃/H₂O₂ combination, respectively.     

Ultrasound assisted oxidative deep-desulfurization of dimethyl disulphide from turpentine

A promising approach of ultrasound assisted oxidative desulfurization (UAOD) was studied for deep desulfurization of simulated sulphated turpentine containing dimethyl disulphide (DMDS) as model pollutant. The effect of ultrasound parameters such as power (80–120 W) and duty cycle (50–80%) as well as operating conditions as initial concentration (50–100 ppm), volume (100–300 ml) and temperature (28 °C as ambient condition, 50–70 °C) on the extent of desulfurization have been studied. The effect of addition of various oxidizing agents such as hydrogen peroxide over the range of 3–18 g/L, Fenton reagent by varying FeSO₄ loading from 0.75 g/L to 1.75 g/L at constant H₂O₂ loading and titanium dioxide (loading over the range 1–4 g/L) in the presence of ultrasonic horn have also been investigated at laboratory scale. The addition of oxidizing agents in presence of ultrasound enhanced the extent of DMDS removal. The extent of desulfurization was found to be remarkably low for individual approaches as compared to combination approaches of US/oxidizing agents. The kinetic analysis revealed that oxidation follows first order kinetics. A significant increase in cavitational yield was observed for combination approach of US/H₂O₂/TiO₂ (5.78 × 10⁻⁹ g/L) compared to individual ultrasound approach (2.04 × 10⁻⁹ g/L). Under best conditions of 120 W power, 70% duty cycle, 50 ppm initial concentration, 15 g/L H₂O₂ loading and 4 g/L TiO₂ loading, 100% desulfurization was obtained at 23.19 Rs/L as the treatment cost. Based on the obtained results it can be concluded that US/H₂O₂/TiO₂ approach is highly efficient desulfurization technique for deep desulfurization of simulated sulphated turpentine.     

Frequency and power dependence of ultrasonic degassing

We investigated the time variation of ultrasonic degassing for air-saturated water and degassed water with a sample volume of 100 mL at frequencies of 22, 43, 129, 209, 305, 400, 514, 1018, and 1960 kHz and ultrasonic power of 15 W. Ultrasonic degassing was evaluated by dissolved oxygen concentration. Ultrasonic degassing was also investigated at a frequency of 1018 kHz and ultrasonic powers of 5, 10, 15, and 20 W. The dissolved oxygen concentration varied with the ultrasonic irradiation time and became constant after prolonged ultrasonic irradiation. The constant dissolved oxygen concentration value depended on the frequency and ultrasonic power but not the initial dissolved oxygen concentration. The degassing rate at 101.3 kPa was higher in the frequency range of 200 kHz to 1 MHz. The frequency dependence of the degassing rate was almost the same as that of the sonochemical efficiency obtained by the potassium iodide (KI) method. Ultrasonic degassing in the frequency range of 22–1960 kHz was also investigated under reduced pressure of 5 kPa. Degassing was accelerated when ultrasonic irradiation was applied under reduced pressure. However, under a reduced pressure of 5 kPa, the lower the frequencies, the higher is the degassing rate. The sonochemical reaction rate was examined by the KI method for varying dissolved air concentrations before ultrasonic irradiation. Cavitation did not occur when the initial dissolved oxygen concentration was less than 2 mg·L⁻¹. Therefore, the lower limit of ultrasonic degassing under 101.3 kPa equals 2 mg·L⁻¹ dissolved oxygen concentration. A model equation for the time variation of dissolved oxygen concentration due to ultrasonic irradiation was developed, and the degassing mechanism was discussed.     

Ultrasound assisted two-stage biodiesel synthesis from non-edible Schleichera triguga oil using heterogeneous catalyst: Kinetics and thermodynamic analysis

Present work deals with the ultrasound-assisted biodiesel production from low cost, substantial acid value kusum (Schleichera triguga) oil using a two-step method of esterification in presence of acid (H₂SO₄) catalyst followed by transesterification using a basic heterogeneous barium hydroxide (Ba(OH)₂) catalyst. The initial acid value of kusum oil was reduced from 21.65 to 0.84 mg of KOH/g of oil, by acid catalyzed esterification with 4:1 methanol to oil molar ratio, catalyst concentration 1% (v/v), ultrasonic irradiation time 20 min at 40 °C. Then, Ba(OH)₂ concentration of 3% (w/w), methanol to oil molar ratio of 9:1, ultrasonic irradiation time of 80 min, and temperature of 50 °C was found to be the optimum conditions for transesterification step and triglyceride conversion of 96.8% (wt) was achieved. This paper also examined the kinetics as well as the evaluation of thermodynamic parameters for both esterification and transesterification reactions. The lower value of activation energy and higher values of kinetic constants indicated a fast rate of reaction, which could be attributed to the physical effect of emulsification, in which the microturbulence generated due to radial motion of bubbles, creates an intimate mixing of the immiscible reactants causing the increase in the interfacial area, giving faster reaction kinetics. The positive values of Gibbs-free energy (ΔG), enthalpy (ΔH) and negative value of entropy (ΔS) revealed that both the esterification and transesterification were non-spontaneous, endothermic and endergonic reactions. Therefore, the present work has not only established the escalation obtained due to ultrasonication but also exemplified the two-step approach for synthesis of biodiesel from non-edible kusum oil based on the use of heterogeneous catalyst for the transesterification step.     

A systematic study of the degradation of dimethyl phthalate using a high-frequency ultrasonic process

A comprehensive study of the sonochemical degradation of dimethyl phthalate (DMP) was carried out using high-frequency ultrasonic processes. The effects of various operating parameters were investigated, including ultrasonic frequency, power density, initial DMP concentration, solution pH and the presence of hydrogen peroxide. In general, a frequency of 400 kHz was the optimum for achieving the highest DMP degradation rate. The degradation rate was directly proportional to the power density and inversely related to the initial DMP concentration. It was interesting to find that faster removal rate was observed under weakly acidic condition, while hydrolysis effect dominated in extreme-basic condition. The addition of hydrogen peroxide can increase the radical generation to some extent. Furthermore, both hydroxylation of the aromatic ring and oxidation of the aliphatic chain appear to be the major mechanism of DMP degradation by sonolysis based on LC/ESI-MS analysis. Among the principle reaction intermediates identified, tri- and tetra-hydroxylated derivatives of DMP, as well as hydroxylated monomethyl phthalates and hydroxylated phthalic acid were reported for the first time in this study. Reaction pathways for DMP sonolysis are proposed based on the detected intermediates.     

Ultrasound-assisted oxidative desulfurization process of liquid fuel by phosphotungstic acid encapsulated in a interpenetrating amine-functionalized Zn(II)-based MOF as catalyst

In this work, ultrasound-assisted oxidative desulfurization (UAOD) of liquid fuels performed with a novel heterogeneous highly dispersed Keggin-type phosphotungstic acid (H₃PW₁₂O₄₀, PTA) catalyst that encapsulated into an amino-functionalized MOF (TMU-17-NH₂). The prepared composite exhibits high catalytic activity and reusability in oxidative desulfurization of model fuel. Ultrasound-assisted oxidative desulfurization (UAOD) is a new way to performed oxidation reaction of sulfur-contain compounds rapidly, economically, environment-friendly and safely, under mild conditions. Ultrasound waves can be apply as an efficient tool to decrease the reaction time and improves oxidative desulfurization system performance. PTA@TMU-17-NH₂ could be completely performed desulfurization of the model oil by 20 mg of catalyst, O/S molar ratio of 1:1 in presence of MeCN as extraction solvent. The obtained results indicated that the conversions of DBT to DBTO₂ achieve 98% after 15 min in ambient temperature. In this work, we prepared TMU-17-NH₂ and PTA/TMU-17-NH₂ composite by ultrasound irradiation for first time and employed in UAOD process. Prepared catalyst exhibit an excellent reusability without PTA leaching and loss of activity.     

Decolorization of azo dye Orange G by aluminum powder enhanced by ultrasonic irradiation

In this work, the decolorization of azo dye Orange G (OG) in aqueous solution by aluminum powder enhanced by ultrasonic irradiation (AlP-UI) was investigated. The effects of various operating operational parameters such as the initial pH, initial OG concentration, AlP dosage, ultrasound power and added hydrogen peroxide (H₂O₂) concentration were studied. The results showed that the decolorization rate was enhanced when the aqueous OG was irradiated simultaneously by ultrasound in the AlP-acid systems. The decolorization rate decreased with the increase of both initial pH values of 2.0–4.0 and OG initial concentrations of 10–80 mg/L, increased with the ultrasound power enhancing from 500 to 900 W. An optimum value was reached at 2.0 g/L of the AlP dosage in the range of 0.5–2.5 g/L. The decolorization rate enhanced significantly by the addition of hydrogen peroxide in the range of 10–100 mM to AlP-UI system reached an optimum value of 0.1491 min⁻¹. The decolorization of OG appears to involve primarily oxidative steps, the cleavage of NN bond, which were verificated by the intermediate products of OG under the optimal tested degradation system, aniline and 1-amino-2-naphthol-6,8-disulfonate detected by the LC–MS.     

Degradation of m-xylene solution using ultrasonic irradiation

This study is to apply ultrasound to remove m-xylene, a volatile compound from aqueous solutions which causes environmental damage. High frequency ultrasound was used to investigate the effect of different operational parameters, such as m-xylene initial concentration, ultrasonic frequency and ultrasonic power. The degradation rate of m-xylene was increased with decreasing initial concentration of m-xylene and increasing frequency and power. Optimal conditions include 26.07 mg/L, 806.3 kHz and 70±1 W, in which MnO(2), Cu(2+), Fe(2+), and H(2)O(2) had little or no effect on the degradation. Moreover, the effect of radical scavengers such as Na(2)CO(3) and t-butyl was not obvious, which indicates that direct pyrolysis inside the collapsing bubbles has an important role in m-xylene ultrasonic removal. In addition, the degradation of m-xylene was observed to behave under pseudo-first-order kinetics with different experimental conditions tested in the present work.     

Sulfur removal from bauxite water slurry (BWS) electrolysis intensified by ultrasonic

Effects of ultrasonic on desulfurization ratio from bauxite water slurry (BWS) electrolysis in NaOH solution were examined under constant current. The results indicated that ultrasonic improved the desulfurization ratio at high temperatures because of the diffusion and transfer of oxygen gas in electrolyte. However, due to the increase in oxygen gas emission, ultrasonic could not improve the desulfurization ratio obviously at low temperatures. Additionally, the particle size of bauxite became fine in the presence of ultrasonic, indicating that the mass transfer of FeS₂ phase was improved. According to the polarization curves, the current density increased in the presence of ultrasonic, indicating that the mass transfer of liquid phase was improved. The apparent activation energy (AAE) of electrode reaction revealed that ultrasonic did not change the pathway of water electrolysis. However, ultrasonic changed the pathway of BWS electrolysis, converting indirect oxidation into direct oxidation. The AAE of BWS electrolysis in the presence of ultrasonic was higher than that in the absence of ultrasonic. And the low AAEs (less than 20 kJ/mol) clearly indicated the diffusion control during BWS electrolysis reaction.