Degradation Of Recalcitrant Organic Pollutants Research Articles

Enhancement of the reactivity of sulfidized nanoscale zero-valent iron-persulfate by ligand addition for the oxidative degradation of water pollutants

The main objective of the study was to derive an appropriate ligand in sulfidized nanoscale zero-valent iron-persulfate (S-nZVI-PS) system for the efficient and rapid degradation of recalcitrant organic pollutants. In this aspect, we have compared the efficiency of three ligands (L) such as ethylenediaminetetraacetic acid (EDTA), oxalic acid (OA) and citric acid (CA) for the degradation of benzoic acid (BA). Complete degradation of BA was achieved within 10 min in S-nZVI-L-PS system. In order to investigate the controlling factors in ligand assisted degradation, Fe dissolution, the thermodynamic feasibility of Fenton reactions and adsorption of ligands on the material surface has been studied. It is found that CA and OA caused more Fe dissolution and there by a more feasible Fenton condition compared to other ligands. Whereas EDTA has high affinity for the Fe surface and it attracts the PS after adsorption. Thus, we confirmed that heterogeneous Fenton like reactions are more favorable in the presence of EDTA and homogeneous Fenton like reaction is more favorable in presence of CA and OA. All these reactions produce OH and SO4− (confirmed by electron spin resonance (EPR) measurements). However, for used S-nZVI the adsorption possibility is less and only CA is the choice in this case. Thus our study concluded that S-nZVI-CA-PS system would be the conclusive solution for field remediation.

Treatment of a Highly Concentrated Industrial Effluent with a Pre-Pilot Electrochemical Reactor – Approach to a Practical Application

Electrochemical advanced oxidation processes (EAOPs) rely on the non-selective and strong oxidant •OH to mineralize organic pollutants in contaminated effluents [1]. Among them, electro-Fenton (EF) has proven efficient and robust for the degradation of recalcitrant organic pollutants [2]. However, most of the studies on EF are limited to reactors with volumes below 1 L and synthetic effluents. Aiming at practical applications, a pre-pilot scale EF reactor is disclosed here with the highest working volume (50 L) among all reports to date. The reactor incorporated commercial BDD or DSA anodes, as well as our patented cathodes , made of carbon fibers coated with graphene. A local company provided us with real wastewater, originating from the fabrication of flat sheet membranes, with an initial TOC of 10,000 ppm and containing hexane, n, n-dimethylformamide (DMF), trimesoyl chloride (TMC), m-phenylene diamine (MPD) and isopropyl alcohol. One of the biggest challenges of scaling up the EF system was to maintain the same efficiency (in terms of mineralization and energy consumption) as in smaller scale laboratory setups. Figure 1A shows the main results at different stages of scaling up the process. The initial lab-scale stage consisted of beaker experiments with a mineralization efficiency of 98% in 24 h. The bench-scale stage, conducted in a specially-designed flow-through recirculated reactor, saw a decrease in mineralization efficiency (36.2%) and an increase in energy consumption (38.4 Wh g-1 of TOC ), which laid the foundations to improve the engineering design of the pre-pilot scale reactor, using a flow simulation CAD software (Fig. 1B). As a result, the energy consumption decreased to 12.8 Wh g-1 of TOC in that final setup and the 24-h mineralization yield attained 64.8%. In conclusion, we demonstrated the successful scale-up of EF for treatment of real industrial wastewater with high organic load, with good mineralization and energy consumption efficiencies.

Immobilization of green BiOX (X= Cl, Br and I) photocatalysts on ceramic fibers for enhanced photocatalytic degradation of recalcitrant organic pollutants and efficient regeneration process

Abstract Visible-light-driven photocatalysis using BiOX (Cl, Br and I) have gained tremendous interest due to their efficient performance, unique optical properties, and high chemical stability. In the present approach, the BiOX (X = Cl, Br and I) were synthesized by Azadirachta indica (A.I.) leaf extract assisted hydrolysis route followed by their immobilization on Alumina (Al2O3)-based ceramic fiber sheet as supporting material. The main objective of the present work was to eliminate the separation problem of the powder photocatalysts from the aqueous medium and evaluate their efficacy for the photocatalytic disintegration of organic contaminants in the long run. Furthermore, the as-prepared BiOX-ceramic fiber (CerF) samples i.e. BiOCl-CerF, BiOBr-CerF, and BiOI-CerF were characterized by scanning electron microscopy and BET-technique, which suggested that the BiOX were successfully embedded in the host matrix of ceramic fibers with an enhanced specific surface area. The photocatalytic activity of the BiOX-CerF samples was evaluated by varying operational parameters such as pH (2, 7 and 11), initial concentrations (20, 40 and 60 mg L−1) and in certain combinations. The results revealed that the higher pH value was more favorable for bisphenol A (BPA) and Ampicillin (AMP) degradation, while the MO was completely degraded at all pH range. Moreover, the stability test was performed and high stability of the immobilized samples was observed for five cycles without leaching out in the aqueous medium. The present study could offer new outcomes for advancing the large-scale applications of supported materials for environmental remediation.

Synthesis of MoS2/MnFe2O4 nanocomposite with highly efficient catalytic performance in visible light photo-Fenton-like process

The novel flower-like MoS2/MnFe2O4 nanocomposite was successfully prepared through a hydrothermal route using molybdenum disulfide nanospheres and magnetic spinel manganese ferrite as the raw materials. The synergistic effect of Fenton-like and visible light photocatalysis was observed through the degradation of a recalcitrant diazo dye, Acid Blue 113. Analysis of the process using response surface methodology (RSM) revealed that the data were well fitted to a quadratic model with R-squared close to unity. At the optimal conditions of pH 6.3, 0.6 ml H2O2, 6.59 mg catalyst and 42 min, >99% of the dye was removed. Degradation of the dye by visible light assisted Fenton-like process was well described by a pseudo-first-order kinetic model. Excellent catalytic performance, easy preparation and reusability of the fabricated nanocomposite makes it a highly efficient catalyst for the degradation of recalcitrant organic pollutants.

Biogenic manganese oxide: An efficient peroxymonosulfate activation catalyst for tetracycline and phenol degradation in water

From the view of environment and easy availability, to develop the most efficient manganese oxide for peroxymonosulfate (PMS) activation is of great importance for the degradation of recalcitrant organic pollutants. In this study, biogenic manganese oxide (BioMnOx) exhibited an unprecedented efficiency than the most efficient 3D α-Mn2O3 prepared by chemical method. 100% of phenol degradation at 40 min and 99.4% of tetracycline removal at 60 min were achieved over BioMnOx with PMS, which was 3-fold faster than 3D α-Mn2O3. BioMnOx also has an excellent long-term stability and good performance toward the pollutants degradation at a wide pH range of 3.0–9.0. Most importantly, 1O2 was identified as the primary reactive species in BioMnOx/PMS system based on the trapping experiment and EPR analysis. The PMS activation over BioMnOx should follow a self-decomposition and energy quenching mechanism instead of electron transfer process as confirmed by the XPS analysis. Finally, the degradation pathways of tetracycline and phenol by 1O2 over BioMnOx were proposed according to HPLC and HPLC-MS results, which are greatly different from that by OH oxidation in the literature.

PERFORMANCE OF TiO2 IN PHOTODEGRADATION SEAFOOD WASTEWATER

In this work, photocatalysts TiO2-HT prepared by hydrothermal method and TiO2-P25 Degussa were characterized by Energy Dispersive X-Ray analysis (EDX), X-ray powder diffraction analysis (XRD), Raman Spectroscopy, BET surface area measurements, scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared (FT-IR) and UV-Vis absorption spectroscopy and tested in degradation of recalcitrant organic pollutants in bio-treated seafood wastewater (COD > 80 mg/L). After 9 hours of photodegradation under UV-A irradiation, COD removal efficiency reached 85.6 % and 48.9 % on TiO2-P25 and TiO2 catalysts, respectively. COD values of seafood wastewater treated by photocatalysis met the standard discharge requirement - QCVN 11:2008 – level A (COD £ 50 mg/L).

Degradation of the chlorophenoxyacetic herbicide 2,4-D by plasma-ozonation system

A novel advanced oxidation process based on the combination of ozonation with non-thermal plasma generated in a pulsed corona discharge was developed for the oxidative degradation of recalcitrant organic pollutants in water. The pulsed corona discharge in contact with liquid, operated in oxygen, produced 3.5mgL−1 ozone, which was subsequently introduced in the ozonation reactor. The solution to be treated was continuously circulated between the plasma reactor and the ozonation reactor. The system was tested for the degradation of 2,4-dichlorophenoxyacetic acid (2,4-D) and considerably improved performance as compared to ozonation alone, both with respect to the removal of the target compound and to mineralization. The apparent reaction rate constant for 2,4-D removal was 0.195min−1, more than two times higher than the value obtained in ozonation experiments. The mineralization reached more than 90% after 60min treatment and the chlorine balance confirms the absence of quantifiable amounts of chlorinated by-products. The energy efficiency was considerably enhanced by shortening the duration of the discharge pulses, which opens the way for further optimization of the electrical circuit design.

Photocatalytic reactor, CVD technology of its preparation and water purification from pharmaceutical drugs and agricultural pesticides

A tubular photocatalytic reactor of the immersion type for water purification from organic pollutants has been developed. Few important principles were used in the construction of the reactor, namely, a symmetrical and uniform light distribution with direct incidence of UV irradiation on the photocatalyst surface, a highly active mixing of contaminated water as a result of an air bubbling flux, that simultaneously supplying oxygen that is necessary for a photocatalytic reaction. The implemented highly active thin film photocatalyst was prepared by the Chemical Vapor Deposition (CVD) technology using titanium(isopropoxide) (TTIP) as a precursor. The factor K=Surface/Volume of this reactor is about 255m−1. Together with an effective mixing, it creates excellent contacts between the contaminants and the photocatalyst which is very favorable for water purification. The efficiency of this reactor was proven by the decomposition of some pharmaceutical drugs (Ibuprofen, Acetylsalicylic acid, Sulphanilamide, Paracetamol, Caffeine) and of some pesticides (Dimethoate, Azoxystrobin, Iprodione, Propizamid, Isoproturon, Fenarimol). The relation between the kinetic constants of photocatalysis and of photolysis is Kphotcat./Kphotolysis=2÷18. These results demonstrate the feasibility of the developed photoreactor for the degradation of recalcitrant organic pollutants, such as pharmaceuticals and pesticides in water.

Formic acid enhanced effective degradation of methyl orange dye in aqueous solutions under UV–Vis irradiation

Developing efficient technologies to treat recalcitrant organic dye wastewater has long been of great research and practical interest. In this study, a small molecule, formic acid (FA), was applied as a process enhancer for the degradation of methyl orange (MO) dye as a model recalcitrant organic pollutant in aqueous solutions under the condition of UV–Vis light irradiation and air aeration at the ambient temperature of 25 °C. It was found that the decolouration of the dye solutions can be rapidly achieved, reducing the time, for example, from around 17.6 h without FA to mostly about less than 2 h with the presence of FA. The mineralization rate of MO dye reached as high as 81.8% in 1.5 h in the case of initial MO dye concentration at 25 mg L−1, which is in contrast to nearly no mineralization of the MO dye for a similar system without the FA added. The study revealed that the generation of the H2O2 species in the system was enhanced and the produced OH radicals effectively contributed to the degradation of the MO dye. Process parameters such as the initial concentration of MO dye, FA dosage and solution pH were all found to have some effect on the degradation efficiency under the same condition of UV–Vis light irradiation and air aeration. The MO dye degradation performance was found to follow a first-order reaction rate to the MO dye concentration in most cases and there existed a positive correlation between the reaction rate constant and the initial FA concentration. Compared to the traditional H2O2/UV–Vis oxidation system, the use of FA as a process-enhancing agent can have the advantages of low cost, easy availability, and safe to use. The study hence demonstrates a promising approach to use a readily available small molecule of FA to enhance the degradation of recalcitrant organic pollutants, such as MO dye, especially for their pre-treatment.

Photocatalytic degradation of recalcitrant organic pollutants in water using a novel cylindrical multi-column photoreactor packed with TiO2-coated silica gel beads

A novel cylindrical multi-column photocatalytic reactor (CMCPR) has been developed and successfully applied for the degradation of methyl orange (MO), amoxicillin (AMX) and 3-chlorophenol (3-CP) in water. Due to its higher adsorption capacity and simpler molecular structure, 3-CP compared with MO and AMX obtained the highest photodegradation (100%) and mineralization (78.1%) after 300-min photocatalytic reaction. Electrical energy consumption for photocatalytic degradation of MO, AMX and 3-CP using CMCPR was 5.79×104, 7.31×104 and 2.52×104kWhm−3 order−1, respectively, which were less than one-thousand of those by reported photoreactors. The higher flow rate (15mLmin−1), lower initial concentration (5mgL−1) and acidic condition (pH 3) were more favorable for the photocatalytic degradation of MO using CMCPR. Five repetitive operations of CMCPR achieved more than 97.0% photodegradation of MO in each cycle and gave a relative standard deviation of 0.72%. In comparison with reported slurry and thin-film photoreactors, CMCPR exhibited higher photocatalytic efficiency, lower energy consumption and better repetitive operation performance for the degradation of MO, AMX and 3-CP in water. The results demonstrated the feasibility of utilizing CMCPR for the degradation of recalcitrant organic pollutants in water.

Unraveling the photocatalytic mechanisms on TiO2 surfaces using the oxygen-18 isotopic label technique.

During the last several decades TiO2 photocatalytic oxidation using the molecular oxygen in air has emerged as a promising method for the degradation of recalcitrant organic pollutants and selective transformations of valuable organic chemicals. Despite extensive studies, the mechanisms of these photocatalytic reactions are still poorly understood due to their complexity. In this review, we will highlight how the oxygen-18 isotope labeling technique can be a powerful tool to elucidate complicated photocatalytic mechanisms taking place on the TiO2 surface. To this end, the application of the oxygen-18 isotopic-labeling method to three representative photocatalytic reactions is discussed: (1) the photocatalytic hydroxylation of aromatics; (2) oxidative cleavage of aryl rings on the TiO2 surface; and (3) photocatalytic decarboxylation of saturated carboxylic acids. The results show that the oxygen atoms of molecular oxygen can incorporate into the corresponding products in aqueous solution in all three of these reactions, but the detailed incorporation pathways are completely different in each case. For the hydroxylation process, the O atom in O2 is shown to be incorporated through activation of O2 by conduction band electrons. In the cleavage of aryl rings, O atoms are inserted into the aryl ring through the site-dependent coordination of reactants on the TiO2 surface. A new pathway for the decarboxylation of saturated carboxylic acids with pyruvic acid as an intermediate is identified, and the O2 is incorporated into the products through the further oxidation of pyruvic acid by active species from the activation of O2 by conduction band electrons.

Behavior of dihydroxybenzenes and gallic acid on the Fenton-based decolorization of dyes

Dihydroxybenzenes (DHBs) are used as mediators to increase the degradation of recalcitrant organic pollutants by Fenton reaction. DHBs regenerate Fe2+ ions, resulting in the formation of OH radicals in a more intense and continuous manner than the classical Fenton reaction. The present work investigates the behavior of different DHBs and gallic acid (a trihydroxybenzene) on the decolorization of dye solutions by Fenton systems (Fe2+/H2O2, Fe3+/H2O2). For the majority of DHBs and gallic acid, pro-oxidant properties were observed on the decolorization of methylene blue, chromotrope 2R, methyl orange, and phenol red. These properties were dependent on the hydroxyl position in the aromatic ring and were highly influenced by the structure and redox potential of the target pollutant. The dye decolorization by Fenton-like reaction (Fe3+/H2O2) in the presence of 2,5-dihydroxybenzoic acid as mediator was more efficient than classical Fenton reaction. For example, Fe3+/H2O2/2,5-dihydroxybenzoic acid system provided 60% of phenol red decolorization against 40% by Fe2+/H2O2 after 60 min of reaction. DHBs and gallic acid increased the decolorization of dyes, requiring the highest H2O2 consumption. However, H2O2 consumption occurred even when the dye solutions were not extensively decolorized, suggesting that part of the generated OH radicals reacted with either DHBs, H2O2 or other reactive species in solution.

One-step synthesis of metal@titania core-shell materials for visible-light photocatalysis and catalytic reduction reaction.

Metal@TiO2 composites with a core-shell structure possess multifunctional properties. The demonstrated protocols for synthesizing such materials involve multiple steps, requiring precise control over the particle uniformity of the core and shell thickness, as well as complex surface modification. A simple approach to synthesizing metal@TiO2 hybrid nanostructures remains a great challenge. Herein, we report on a one-step method for the preparation of metal@TiO2 core-shell nanospheres, which exhibited excellent performance in photocatalytic degradation of recalcitrant organic pollutants under visible light irradiation, and in catalytic reduction of nitrophenol in water. The simple method described here represents a sustainable approach to preparing core-shell materials at low cost, involving fewer chemicals, and requiring less energy, which will make a significant contribution toward large-scale synthesis of high-performance hybrid materials for photocatalytic applications.

Sonophotocatalytic Degradation Studies of Alizarin Reactive Red Dye

The photocatalytic oxidative degradation and discoloration of the reactive dye was investigated. Along with photochemical oxidation process, the sonochemical effect was also used. Experiments were performed in slurry mode in both UV and solar light at optimized conditions. Degradation observed was 88% under photocatalytic optimized conditions, i.e., pH 4.8, TiO2 = 0.3 g L−1 and oxidant dose of 0.3 g L−1 after 180 min. sonophotocatalytic treatment enhanced the degradation up to 94% with optimized parameters of photocatalytic treatment. The results obtained were quite appreciable as also confirmed from reduction in COD from 280 to 36 mg L−1. The results of sonophotocatalytic degradation of dye showed that it could be used as efficient and environmental friendly technique for the complete degradation of recalcitrant organic pollutants that will increase the chances for the reuse of wastewater.

Synthesis, characterization, photocatalytic evaluation, and toxicity studies of TiO2–Fe3+ nanocatalyst

Based on our previous work on the green preparation of Ag–TiO2 photocatalyst with bactericidal activity under visible light, we extended our studies to the synthesis of TiO2–Fe3+ materials with enhanced photocatalytic activity for the degradation of recalcitrant organic pollutants in water. TiO2–Fe3+ nanopowders were synthesized using a robust, environmentally friendly procedure. Established amounts of Fe(NO3)3·9H2O and titanium tetraisopropoxide (TTIP) were mixed using glacial acetic acid as solvent. Hydrolysis of TTIP–Fe3+ was accomplished using a 30 % (W/V) Arabic gum aqueous solution. TiO2–Fe3+ nanopowders were obtained by thermal treatment at 400 °C. In order to elucidate the structure of these photocatalysts, microscopic and spectroscopic characterization techniques were applied. The high resolution transmission electron microscopy (HRTEM) analysis indicated the presence of uniformly distributed particles with average particle size of about 9 nm. According to the HRTEM lattice fringes, ring pattern, and selected area electron diffraction pattern, the crystalline part of the samples consists of anatase (PDF 01-086-1157 with the lattice constant of 3.7852, 9.5139 A and 90°) as dominant phase. X-ray photoelectron spectroscopy (XPS) was applied to determine the oxidation state of iron. The XPS provides evidence for Fe3+ surface species in the TiO2–Fe3+ composite. Complete degradation of aqueous solutions (20 ppm) of methylene blue and/or methyl orange was accomplished after 4 h of treatment using 150 mg of TiO2–Fe3+/150 mL of dye solution. The in vitro toxicity of the materials was tested. The materials showed no toxicity against human red blood cells.

Investigations in Synergism of Hybrid Advanced Oxidation Processes with Combinations of Sonolysis + Fenton Process + UV for Degradation of Bisphenol A

Hybrid advanced oxidation processes (HAPOs) for degradation of recalcitrant organic pollutants have been extensively studied in recent literature. In this paper, we have presented a mechanistic investigation of hybrid advanced oxidation processes with combinations of sonolysis and Fenton process coupled with UV. Degradation of a ubiquitous pollutant, bisphenol A, discharged in environment with solid plastic waste has been used as the model reaction. Essentially, an attempt is made to explore synergy between the individual mechanisms of these processes. With conjectures of possible synergies, we have devised the experimental protocols with combination of sonolysis and Fenton process coupled with UV. It is revealed that techniques of sonolysis + Fe2+ and sono–Fenton have positive synergy while technique of Fenton process + UV has no synergy. The technique of sono–Fenton + UV has been found to have negative synergy. The rationales for positive synergy have been identified as conservation and/or regeneration of •OH radicals and increased probability of radical-pollutant interaction, while the absence of synergy is a consequence of low utilization of UV irradiation due to lesser fractional energy at absorption wavelength (254 nm) of H2O2. A probable cause for negative synergy is conjectured as hindrance to effective utilization of H2O2 through sonolysis and Fenton process route by UV irradiation. The highest mineralization, monitored through total organic carbon (TOC) of the solution, was obtained with the sono–Fenton process.

Mechanistic insight into sono-enzymatic degradation of organic pollutants with kinetic and thermodynamic analysis

In this paper, we have attempted to get a physical insight into process of sono-enzymatic treatment for degradation of recalcitrant organic pollutants. Decolourization of an azo dye has been used as model reaction with different experimental protocols that alter characteristics of ultrasound and cavitation phenomena in the system. Experimental data is analyzed to determine kinetic and thermodynamic parameters of decolorization process. The trends observed in kinetic and thermodynamic parameters of decolourization are essentially manifestations of the dominating mechanism of the decolorization of the textile dye (or nature of prevalent chemical reaction in the system), viz. either molecular reaction due to enzyme or radical reaction due to transient cavitation. The activation energy for sonochemical protocol is negative, which indicates instantaneity of the radical reactions. The frequency factor is also low, which is attributed to high instability of radicals. For enzymatic and sono-enzymatic protocols, activation energy is positive with higher frequency factor. Enthalpy change for sonochemical protocol is negative, while that for enzymatic and sono-enzymatic protocols is positive. The net entropy change for sonochemical protocol is more negative than enzymatic or sono-enzymatic protocol due to differences in prevalent chemical mechanism of dye decolorization. Due to inverse variations of frequency factor and activation energy, marginal rise in reaction kinetics is seen for sono-enzymatic protocol, as compared to enzymatic treatment alone. Due to inverse variations of enthalpy and entropy change, net Gibbs energy change in all experimental protocols shows little variation indicating synergism of the mechanism of ultrasound and enzyme.

Physical mechanism of sono‐Fenton process

Hybrid advanced oxidation processes (AOPs), where two or more AOPs are applied simultaneously, are known to give effective degradation of recalcitrant organic pollutants. This article attempts to discern the physical mechanism of the hybrid sono‐Fenton process with identification of links between individual mechanism of the sonolysis and Fenton process. An approach of coupling experimental results with simulations of cavitation bubble dynamics has been adopted for two textile dyes as model pollutants. Fenton process is revealed to have greater contribution than sonolysis in the overall decolorization of both dyes. H2O2 added to the liquid medium as a Fenton reagent scavenges radicals produced by cavitation bubbles. Addition of only H2O2 to the medium during sonolysis does not yield marked difference in decolorization. Elimination of transient cavitation with application of elevated static pressure to the medium does not alter the extent of decolorization. The synergy between sonolysis and Fenton process is, thus, revealed to be negative. The dissolved oxygen in the medium is found to play an important role in decolorization through conservation of oxidizing radicals. © 2013 American Institute of Chemical Engineers AIChE J, 59: 4303–4313, 2013

Photocatalytic, Sonolytic and Sonophotocatalytic Degradation of 4-Chloro-2-Nitro Phenol

Abstract The photocatalytic, sonolytic and sonophotocatalytic degradation of 4-chloro-2-nitrophenol (4C2NP) using heterogeneous (TiO2) was investigated in this study. Experiments were performed in slurry mode with artificial UV 125 watt medium pressure mercury lamp coupled with ultrasound (100 W, 33+3 KHz) for sonication of the slurry. The degradation of compound was studied in terms of first order kinetics. The catalyst concentration was optimized at 1.5 gL-1, pH at 7 and oxidant concentration at 1.5 gL-1. The results obtained were quite appreciable as 80% degradation was obtained for photocatalytic treatment in 120 minutes whereas, ultrasound imparting synergistic effect as degradation achieved 96% increase in 90 minutes during sonophotocatalysis. The degradation follows the trend sonophotocatalysis > photocatalysis > sonocatalytic > sonolysis. The results of sonophotocatalytic degradation of pharmaceutical compound showed that it could be used as efficient and environmentally friendly technique for the complete degradation of recalcitrant organic pollutants which will increase the chances for the reuse of wastewater.

Mechanistic Investigations on Sonophotocatalytic Degradation of Textile Dyes with Surface Active Solutes

In recent years, two advanced oxidation processes, namely, photocatalysis and sonolysis have been extensively investigated for the degradation of recalcitrant organic pollutants. Simultaneous application of these two techniques, known as sonophotocatalysis has been found to give synergistic enhancement in degradation under specific experimental conditions. The present study attempts to establish the physical mechanism of sonophotocatalytic process by finding the synergy between two techniques that gives enhancement in degradation. Transient collapse of cavitation bubbles gives rise to light emission (known as sonoluminescence), which could provide activation of the photocatalyst. To test this hypothesis, we have conducted experiments on the basis of known effects of surface active solutes on sonoluminescence. Three different textile dyes have been chosen as model pollutants. Experiments have been conducted in the presence of three different surface active solutes, namely, SDS, 2-propanol, and 1-butanol. The rate of degradation reduces drastically with the addition of surface active solutes. The reduction in the degradation process ranges from 5-fold (for Acid Red B) to ∼20% (for Direct Blue 6) for SDS, while for alcohols much higher (∼ 10-fold) reduction is seen for all three dyes. It is revealed that the interaction between photocatalyst and sonolysis is merely of physical nature. The sonoluminescence light from cavitation bubbles is not able to activate the photocatalyst. The role of TiO2 is revealed to be only that of an adsorbent for the dyes. The degradation is caused mostly due to the radicals generated by the cavitation bubble, with negligible role of the radical generation from photocatalyst.