Hydrodynamic Cavitation Process Research Articles

A comprehensive study of hole-to-hole interaction for multi-hole orifice (MHO) in hydrodynamic cavitation process

The hydrodynamic cavitation (HC) as an influential advanced oxidation technology is commonly used for treating organic wastewater. In the present research, a CFD model is used to study the hydrodynamic cavitation in multi-hole orifice (MHO). Accordingly, the effect of hole-to-hole interaction in MHO and its influence on the bubble generation and the flow turbulence downstream of the orifice are analyzed. During the cavitation, the central hole exhibits the highest flow rate, i.e., strong jet, over other jets for the dimensionless hole's pitch circle, δ, equal to 50 and 75%. This causes the occurrence of the pitchfork bifurcation phenomenon, and thereby a high level of turbulence intensity behind MHO especially for δ=50%. The value of δ also affects the streamlines curvature at the hole entrance. This curvature influences on the bubble generation due to a reduction in the pressure gradient. The bubble distribution is not uniform at the entrance of each holes because of non-uniform flow separation at the tip holes. The minimum cavitation number and pressure loss are obtained at δ equal to 50%. The MHO thickness, tD=0.5, provides more guidance to the outlet jet and thereby a decrease of the jet's interaction. Also, the results show the significant impact of MHO thickness on the issued jet, which in turn affects the turbulence intensity (i.e., bubble life). Alternatively, increasing the number of holes rather than using larger holes leads to more bubble formation from each hole when the opening area ratio remains constant. Finally, the change in operating conditions of the inlet pressure and the working temperature is studied and the results are discussed.

Bioaccessibility of carotenoids (β-carotene and lutein) from intact and disrupted microalgae (Chlamydomonas reinhardtii)

Chlamydomonas reinhardtii (C. reinhardtii) has a potential as a novel source for food/feed because it contains several constituents including bioactive compounds. However, its multilayer cell wall (hydroxyproline-rich glycoprotein [HRPGs]) may restrict the bioaccessibility of its nutrients. Therefore, using disruption techniques such as hydrodynamic cavitation (HDC) can be useful for assessing single cell compounds. This work aims to evaluate the impact of HDC on the bioaccessibility of carotenoids (β-carotene and lutein) from C. reinhardtii. Our results illustrated that digestive enzymes cannot fully break down the cell walls beside HDC process generates their significant change. The intact C. reinhardtii (ICR) and disrupted C. reinhardtii (DCR) have a comparable lutein bioaccessibility, in contrast, DCR decreased the biocessibility of β-carotene. HDC decreased the biocessibility of β-carotene in the small intestine although 37% of total carotenoids from DRC were absorbed.

Remediation of Toxic Heavy Metal Contaminated Soil by Combining a Washing Ejector Based on Hydrodynamic Cavitation and Soil Washing Process.

Based on the features of hydrodynamic cavitation, in this study, we developed a washing ejector that utilizes a high-pressure water jet. The cavitating flow was utilized to remove fine particles from contaminated soil. The volume of the contaminants and total metal concentration could be correlated to the fine-particle distribution in the contaminated soil. These particles can combine with a variety of pollutants. In this study, physical separation and soil washing as a two-step soil remediation strategy were performed to remediate contaminated soils from the smelter. A washing ejector was employed for physical separation, whereas phosphoric acid was used as the washing agent. The particles containing toxic heavy metals were composed of metal phase encapsulated in phyllosilicates, and metal phase weakly bound to phyllosilicate surfaces. The washing ejector involves the removal of fine particles bound to coarse particles and the dispersion of soil aggregates. From these results we determined that physical separation using a washing ejector was effective for the treatment of contaminated soil. Phosphoric acid (H3PO4) was effective in extracting arsenic from contaminated soil in which arsenic was associated with amorphous iron oxides. Thus, the obtained results can provide useful information and technical support for field soil washing for the remediation of soil contaminated by toxic heavy metals through emissions from the mining and ore processing industries.

The hydroxyl radical yield prediction of cavitation bubble clouds during the hydrodynamic cavitation process for chitosan degradation

In order to measure the influence of chemical effects in the process of hydrodynamic cavitation (HC) degradation of chitosan, a prediction model for the hydroxyl radical (˙OH) yields of cavitation bubble clouds (CBCs) was developed based on a single-hole orifice plate cavitator.

Analysis of Toc Values of Mixed Sewage Sludge Following the Hydrodynamic Treatment, in Course of Pilot Experiment in the Framework of R&D Ginop Ongoing Project

The primary and secondary stages in wastewater treatment generate a large amount of sewage sludge consisting of 90% water, mineral components, nutrients and also a variety of organic and inorganic contaminants. The contaminants do not degrade completely during these processes, thus an additional degradation is needed to stabilize the sewage sludge. The innovative technology is proposed consisting of hydrodynamic cavitation process along with the addition of Bakony brown coal as adsorbent. Hydrodynamic cavitation is known as an effective tool improving sewage sludge stabilization via aerobic degradation, while adsorbent, besides the adsorption ability, has microbial cells disintegration ability as well, further enhancing the biodegradation process. The changes in total organic carbon (TOC) values of sewage sludge after hydrodynamic treatment for various retention times (0, 5, 10, 15, and 25 minutes) was traced and interpreted.

Non-thermal hydrodynamic cavitation processing of tomato juice for physicochemical, bioactive, and enzyme stability: Effect of process conditions, kinetics, and shelf-life extension

Fresh tomato juice was processed by hydrodynamic cavitation (HC) at 5 to 15 psi pressures for 5–30 min. A full factorial design was applied to optimize the HC treatment of tomato juice quality. Optimal conditions were recorded at 10 psi for 10 min, which showed no significant (p < 0.05) change in lycopene content to that of freshly obtained unprocessed tomato juice (control). After processing, the retention of 93% ascorbic acid and 96.6% of total phenolic compounds (TPC) was observed. Similarly, sedimentation and viscosity were mildly affected by HC processing (89.2 and 94.4% of values in the treated sample, respectively). While pH, total soluble solids (TSS), titratable acidity (TA) of HC treated sample remained unchanged (p < 0.05). The results were also compared with the conventional thermally processed tomato juice (90 °C for 90 s). Although thermal treatment resulted in the inactivation of 92.2% of pectin methylesterase and a 5 log reduction in total plate counts, it also showed significant reductions in ascorbic acid (61.4%), TPC (72.3%), and physical properties (37.7% of SI and 83.2% viscosity). However, HC processing could achieve a maximum of 4.9% inactivation of PME and 1 log reduction at high treatment conditions, respectively (15 psi for 30 min). The shelf-life study showed more retention of bioactives and better physicochemical properties in tomato juice samples stored at 4 °C for 15 days than the control. Sensory evaluation revealed that the overall acceptability of the optimized HC treated (0.714) sample was better than the thermally treated sample (0.591). The observed results concluded that HC-treated tomato juice was comparatively better than thermally-treated tomato juice in retaining bioactive compounds. Consequently, HC constitutes a promising approach in food processing to improve and retain the beneficial properties of tomato juice.

Coumarin as a chemical probe to evaluate efficiency of vortex – based hydrodynamic cavitation process

Direct quantification of hydroxyl radicals (OH•), the major driver for advanced oxidation process (AOPs), is difficult due to its high reactivity and extremely low half-life. Given that the effectiveness of AOPs is usually determined by its ability to generate hydroxyl or peroxyl radicals, a quantitative measurement of these radicals is essential to assess the performance of the process. In this study, for the first time, the performance of a vortex-based hydrodynamic cavitation (HC) system is evaluated via an indirect method using coumarin as a chemical probe. The hydroxylation of coumarin – an indirect indicator of OH• - to 7-OHC served as a measure of the efficiency of the HC system. The inception of cavitation was observed at ΔP > 100 kPa, and maximum coumarin hydroxylation occurred at ΔP = 250 kPa, pH < pKa and in non-isothermal conditions. The maximum observed coumarin conversion with HC alone was 6%, with the cavitation yield of 3.87 × 10−4 mg/W-min. The use of persulfate oxidant along with HC is the most effective in maximizing OH• generation with a cavitation yield of 15.30 × 10−4 mg/W-min. This study shows that simpler chemical probes such as coumarin can be used to identify the best-operating conditions across cavitating devices and can be used in their scale-up and comparison.

Safe water and technology initiative for water disinfection: Application of natural plant derived materials

Safe drinking water is the necessity of life. The present study reveals use of natural resources such as plant extracts and natural oils for water disinfection. Differences between oil and water soluble additives were highlighted for plant extracts and insoluble natural oils. A hybrid hydrodynamic cavitation process was quite effective in both the cases and high rates of disinfection were achieved. Studies were reported using oils (ginger, turmeric, lavender, tulsi) and rhizome derived plant extracts such as ginger, turmeric and mango ginger, as additives in process intensification (0.1% v/V). A vortex based cavitation device (vortex diode, nominal capacity 1 m3/h) was used with pressure drop of 1 bar. A high disinfection of 96% and 88% was obtained in 15 min for ginger oil and mango ginger extract respectively as compared to 44% using cavitation alone. Acoustic cavitation gave 94% and 30% disinfection with and without additive-mango ginger extract. The FTIR analyses before and after cavitation, with ginger additive, showed no by-products formation and indicated gingerol as active component in disinfection. The per-pass disinfection values were also higher, up to 5 times than cavitation alone. Hybrid hydrodynamic cavitation using natural plant derived materials can offer a promising technology alternative in water disinfection.

Effect of thermally assisted hydrodynamic cavitation (HC) processing on physical, nutritional, microbial quality, and pectin methyl esterase (PME) inactivation kinetics in orange juice at different time and temperatures

Orange juice is the second most commonly consumed juice worldwide. However, its quality is deteriorated because pectin methyl esterase (PME), a thermostable enzyme. In this study, orange juice was processed by hydrodynamic cavitation (HC) at 4 bar pressure with varying temperatures (40℃–70℃) and process time (0–8 min). pH and TSS of the juice remained stable during HC processing. A decreased flow behavior index and increased flow consistency index was observed along with sedimentation index, indicating the effectiveness of HC in modifying the physical stability of juice. More retention of vitamin-C, phenolics, and antioxidants was observed in HC-processed juice compared with unprocessed; however, degradation was recorded at higher temperature. Maximum PME inactivation (65%) was observed at 70℃ for 8 min. Microbial inactivation at lower temperatures and time was achieved. Based on this research, it can be concluded that HC could be used as a potential liquid food-processing technique for improving the physicochemical and nutritional quality of orange juice. Practical applications Hydrodynamic cavitation (HC) is an upcoming novel nonthermal processing used for improving the physicochemical, nutritional, and microbial quality of fruit juices. HC is advantageous over other methods because of its low capital cost, reduced time, high efficiency, and lower temperature that help in retention of bioactives in foods. HC also causes inactivation of enzymes and microorganisms, thus improving quality and safety of final product. This novel processing is not yet being explored much and there is huge scope for its application in preservation and processing of different fruit juices and other liquid foods (milk, cereal drinks etc.)

Estimation of chemical and physical effects of cavitation by analysis of cavitating single bubble dynamics

Cavitation events create extreme conditions in a localized ‘bubble collapse’ region, leading to the formation of hydroxyl radicals, shockwaves and microscopic high-speed jets, which are useful for many chemical and physical transformation processes. Single bubble dynamics equations have been used previously to investigate the chemical and physical effects of cavitation. In the present study, the state of the art of the single bubble dynamics equations was reviewed and certain noteworthy modifications were implemented. Simulations reaffirmed previously reported collapse temperatures of the order ~5,000 K and collapse pressures well over ~1,000 bar under varying operating conditions. The chemical effects were assessed in terms of the hydroxyl radical generation rate (OHG), calculated by applying the minimization of the Gibb’s Free Energy method using simulated collapse conditions. OHG values as high as 1x1012OH molecules per collapse event were found under certain operating conditions. A new equation was proposed to assess the physical effects, in terms of the impact pressure of the water jet - termed as the jet hammer pressure (JHP), formed due to the asymmetrical collapse of a bubble near a wall. The predicted JHP were found to be within a range of ~100 to 1000 bar under varying operating conditions. Important issues such as the onset of cavitation and chaotic solutions, for a cavitating single bubble dynamics were discussed. The Blake threshold pressure was found to be a sufficient criterion to capture the onset of cavitation. The impact of key operating parameters on the chemical and physical effects of cavitation were investigated exhaustively through simulations, over the parameter ranges relevant to acoustic and hydrodynamic cavitation processes. Presented methodology and results will be useful for optimisation and further investigations of a broad range of acoustic and hydrodynamic cavitation-based applications.

Effects of Silver Fir (Abies alba Mill.) Needle Extract Produced via Hydrodynamic Cavitation on Seed Germination.

This paper describes the antigerminant capacity of water extracts of silver fir needles created by means of hydrodynamic cavitation processes. Fir needles (2 kg fresh weight) collected in the winter were blended and crushed in ice, poured in water only (120 L) and processed in a controlled hydrodynamic cavitation device based on a fixed Venturi-shaped reactor. The A. alba water extract (AWE), comprising an oil-in-water emulsion of silver fir needles’ essential oil (100% AWE), was diluted in distilled water to 75% and 50% AWE, and all aqueous solutions were tested as antigerminant against four weeds and four horticultural species and compared to control (distilled water). This study shows the effective inhibitory effect of pure AWE on germination, which mainly contains limonene (15.99 ng/mL) and α-pinene (11.87 ng/mL). Seeds showed delayed germination and inhibition but also a reduction in radicle elongation in AWE treatments as compared to control. This combined effect was particularly evident in three weeds (C. canadensis, C. album and A. retrofllexus) while horticultural species showed mainly effects on the radicle elongation as found in L. sativa, P. crispum and S. lycospermum, which showed on average 58%, 32% and 28%, respectively, shorter radicles than in the control. P. sativum was not affected by AWE, thus raising the hypothesis that seed characteristics and nutrition reserve might play a role in the resistance to terpenes inhibitory effect.

Techno‐economic assessment and sensitivity analysis of biodiesel production intensified through hydrodynamic cavitation

AbstractSince the last two decades, hydrodynamic cavitation has been introduced as one of the most efficient approaches to intensify transesterification. However, the number of industrial biodiesel plants utilizing this process is still minimal. One primary reason is the lack of information on both its economic and environmental impacts. In this study, a simulation‐based model was developed using Aspen HYSYS V8.4 for comparing flow‐through hydrodynamic cavitation with conventional mechanical stirring in terms of total capital investment, total product cost, net present value, modified internal rate of return, materials, and energy consumption. The two plants operated 7920 hours per year and produced 100 tons of biodiesel per day from fresh sunflower oil. The results showed that total capital investment and total product cost for hydrodynamic cavitation were roughly 65% and 10% lower than those for the mechanical stirring process, respectively. While the net present value was negative for the mechanical stirring, a positive net present value and a modified internal rate of return of 25.61% were obtained in the hydrodynamic cavitation process. Performing sensitivity analysis using the Box‐Behnken design and response surface methodology revealed that net present value was most affected by the linear term of the sunflower oil price. It was also found that hydrodynamic cavitation could significantly reduce materials and energy consumption, owing to higher reactor yield and lower alcohol and catalyst consumption.

Remediation of contaminated dredged harbor sediments by combining hydrodynamic cavitation, hydrocyclone, and persulfate oxidation process

A pilot-scale hybrid treatment system consisting of hydrodynamic cavitation (HC), hydrocyclone separator (HS), and sodium persulfate (PS), was employed for removing polycyclic aromatic hydrocarbons (PAHs) from dredged harbor sediments. The effectiveness of PAH degradation was studied by varying the inlet pressure (0–2.0 bar), PS dosage (or Σ[PAH] to [PS] mole ratio of 1:1–1:103) at HS inflow velocity of 2.85 m/s, slurry concentration of 10%, and reaction time of 60 min. The degradation rate of PAH in the overflow (OF) sediment was significantly lower than that of the underflow (UF) sediment. After an inlet pressure increase of 0.5 bar and ΣPAH: [PS] molar ratio of 1: 10, the PAH removal was 87% and 55% in the UF and OF, respectively, by the combined HC–PS–HS unit. Without PS, the PAHs removal was 46% and 40% in the UF and OF, respectively. The removal efficiency for 6-, 5-, 4-, 3-, and 2-ring PAHs was 100%, 93%, 93%, 92%, and 82% in the UF and 55%, 61%, 67%, 47%, and 36% in the OF by the combined HC−PS−HS system. FEEM spectroscopy clarified that aromatic protein-based components (tryptophan- and tyrosine-like combined) were gradually degraded and transformed into soluble microbial metabolites when organic matter content declined during the combined HC−PS−HS treatment. This study provides new insights into the combined HC−PS−HS system for PAH degradation in dredged sediments.

P–nitrophenol degradation by hybrid advanced oxidation process of heterogeneous Fenton assisted hydrodynamic cavitation: Discernment of synergistic interactions and chemical mechanism

The present study has investigated p-nitrophenol (PNP) degradation by hybrid advanced oxidation process (AOP) of hydrodynamic cavitation with heterogenous Fe3O4 nanoparticles. 78.8 ± 1.2% of PNP degradation was obtained at optimum operational conditions: inlet pressure = 8 atm, pH = 3, initial concentration of PNP = 20 mg L−1, Fe3O4:H2O2 = 1:100. PNP degradation profiles were analyzed using a kinetic model based on the reaction network. The closest match between the simulated and experimental degradation profiles was obtained for the initial concertation of [H2O2] = 0.6 M, which was far higher than concentration of externally added H2O2. This was attributed to in-situ generation of H2O2 through transient cavitation. Intense shear and turbulence generated in cavitating flow caused surface leaching of Fe3O4 particles that released Fe2+/Fe3+ ions. The synergy in the hybrid AOP was in-situ Fenton reactions between leached Fe2+/Fe3+ ions and H2O2 present in the reaction mixture. The mechanism in •OH mediated oxidative degradation of PNP was further explored with Density Functional Theory (DFT) simulations. Both •OH addition on benzene ring and H–abstraction reactions were simulated to identify the possible pathways for the degradation. On the basis of activation free energy analysis, degradation pathways initiating with both •OH addition and H abstraction were determined to be feasible. The ortho−C of benzene ring was the most favourable site for •OH addition, while H atom of phenolic hydroxyl group was more susceptible (or more reactive) for H-atom abstraction route.

Intensified Hydrodynamic Cavitation-Based Process for the Production of Liquid Emulsion Membrane (LEM) for the Extraction of Chromium(VI) Ions

The present work deals with the production of liquid emulsion membrane (LEM) accomplished by applying hydrodynamic cavitation-based process for the extraction of Chromium(VI) from wastewater. Aliquat 336 was used as the carrier during membrane transport. Diesel and Span 80 were used as diluent and emulsifier, respectively. NaOH (as a stripping agent in the internal phase) was used in emulsion preparation with the use of orifice (1 mm diameter)-based hydrodynamic cavitation process. Chromium(VI) removal from heavy metal-containing water was examined with the influence of LEM production time, amount of carrier, surfactant concentration, treat ratio (which is the ratio of feed phase to emulsion membrane phase) and type of diluent. The LEM synthesized using hydrodynamic cavitation process showed the possibility of complete removal of Chromium(VI) from the feed phase containing heavy metals, i.e. Chromium(VI). The optimal conditions were observed to be 2 min emulsification time, 1.00% carrier concentration, 3% surfactant concentration and treat ratio of 1:05. Therefore, the application of hydrodynamic cavitation for the production of LEM with excellent stability can be considered as a novel process for the extraction of Chromium(VI) from wastewater.

Optimization of the novel hydrodynamic cavitation based waste cooking oil biodiesel production process parameters using integrated L9 Taguchi and RSM approach

The present work investigated the optimization of the production method of biodiesel from waste cooking oil (WCO) using hydrodynamic cavitation process. To achieve the maximum WCO biodiesel yield with a minimum number of experimental trials, one of the most popular optimization technique L9 Taguchi has been used for the validation of hydrodynamic cavitation (HC) process. In this HC experimental process, 260 mL of methanol were mixed with 0.5% of wt. KOH into a 500 mL conical flask. The mixture was later added to 1000 mL of warmed WCO, preheated to 35 °C in a storage tank of 30 L capacity. The HC reactor then ran for 30 min. The products were allowed to settle for 30 min and then the final sample of biodiesel were collected. The same process was repeated for all nine readings. The controllable features that were selected for the investigation, were the catalyst concentration (5 ≤ B ≤ 20 g), reaction temperature (35 ≤ C ≤ 55 °C), reaction time (30 ≤ D ≤ 50 min) and molar ratio (1:6 ≤ A ≤ 1:12). After the optimized setting, it was observed that at the molar ratio of 12:1, and other parameters such as catalyst concentration (5 g), reaction temperature (55 °C), and reaction time (40 min), 97% WCO biodiesel yield was observed. During the investigation, it was found that the reaction temperature has significant contribution on the WCO biodiesel yield. The value of coefficient of determination was found to be unity which shows the efficacy of the present investigation. The investigation has provided low cost feedstock for the WCO biodiesel production with maximum yield.

Biomass Pretreatment via Hydrodynamic Cavitation Process.

There are three essential steps involved in bioethanol production from lignocellulosic biomass feedstocks. They are pretreatment, hydrolysis, and fermentation process. Among them, biomass pretreatment is an expensive and energy-intensive process used to remove the lignin and make the feedstock amenable for bioethanol production. The hydrodynamic cavitation can also be used for biomass pretreatment process. In order to improve the effectiveness of biomass pretreatment, a combination of any two methods of physical, chemical, and biological pretreatment can be used. A combination of the hydrodynamic cavitation pretreatment of biomass with the chemical or biochemical catalyst can be performed better than the individual pretreatment method. In this chapter, a protocol is describes the biomass pretreatment via a combined hydrodynamic cavitation with biocatalyst process.

ANN based modelling of hydrodynamic cavitation processes: Biomass pre-treatment and wastewater treatment

We have developed artificial neural network (ANN) based models for simulating two application examples of hydrodynamic cavitation (HC) namely, biomass pre-treatment to enhance biogas and degradation of organic pollutants in water. The first case reports data on influence of number of passes through HC reactor on bio-methane generation from bagasse. The second case reports data on influence of HC reactor scale on degradation of dichloroaniline (DCA). Similar to most of the HC based applications, the availability of experimental data for these two applications is rather limited. In this work a systematic methodology for developing ANN model is presented. The models were shown to describe the experimental data very well. The ANN models were then evaluated for their ability to interpolate and extrapolate. Despite the limited data, the ANN models were able to simulate and interpolate the data for two very different and complex HC applications very well. The extrapolated results of biomethane generation in terms of number of passes were consistent with the intuitive understanding. The extrapolated results in terms of elapsed time were however not consistent with the intuitive understanding. The ANN model was able to generate intuitively consistent extrapolated results for degradation of DCA in terms of number of passes as well as scale of HC reactor. The results will be useful for developing quantitative models of complex HC applications.

Method for calculating the longitudinal dimensions of hydrodynamic cavitation devices with a pressure jump

Cavitation technologies are widely used in many industries: from heavy machine building to the food industry. Such a wide range of different industries testifies to the variety of tasks that can be solved using these technologies: to disinfect wastewater, carry out various processes of dispersion, mixing, homogenization and many other processes. Depending on the source-cause of cavitation, ultrasonic and hydrodynamic are distinguished. The working process of hydrodynamic cavitation is rather complicated, but the development of a correct closed mathematical model allows one to calculate the parameters of cavitation devices. The applied calculation method is important in this. The article describes the workflow of a hydrodynamic cavitation device with a pressure jump and proposes a method for calculating such devices. The calculation problem is solved by the method of successive approximations and allows one to determine the longitudinal dimensions of the device. The industrial approbation of the device, calculated by this method, showed good convergence of theoretical and experimental data.

Second Life Application of Automotive Catalysts: Hydrodynamic Cavitation Recovery and Photo Water Splitting

A hydrodynamic cavitation method was used to maximize the effect of destructuration of a honeycomb monolithic support of a spent Selective Catalyst Reduction (SCR) catalyst—V2O5-WO3/TiO2-type—for extracting crystalline titanium and tungsten oxides from the cordierite surface. A high relative inlet pressure of 40 MPa was applied to a divergent nozzle for obtaining high shear stresses of the submerged cavitating jets and intensive micro- and nano-jets and shock waves acting on the particle surface of the milled catalyst. Scanning Electron Microscopy (SEM) analysis indicated the compact morphology of the thin metal oxide layer at the surface of the cordierite support and the high content of Ti and W elements in the sample. Energy dispersive spectroscopy (EDAX) performed along with TEM investigations on different nano-zones from the sample established the elemental composition of WO3-TiO2 agglomerates separated after hydrodynamic cavitation processing and identified as independent nanocrystalline structures through Bright Field Transmission Electron Microscopy (BF-TEM) and High Resolution Transmission Electron Microscopy (HR-TEM) measurements. The tetragonal anatase phase of TiO2 and cubic phase of WO3 were established by both interplanar d spacing measurements and X-ray diffraction analysis. The photoelectrochemical results showed the possible second life application of automotive catalysts.