Oualid Hamdaoui

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• Professor
• Professor (Full) and Academician at King Saud University

This review provides a comprehensive examination of strategies aimed at advancing low-temperature electrolysis for sustainable hydrogen production. It begins by exploring the significance and challenges associated with water splitting, followed by an in-depth discussion on the fundamentals of electrochemical water splitting and crucial performance...

Reactive oxygen species (ROS) and reactive chlorine species (RCS) and their involvement in the degradation process are explored in this work by thorough kinetic modeling of the solar-activated hypochlorite degradation of Rhodamine B (RhB) dye. The kinetic modeling enabled the determination of rate constants for both radical and non-radical pathways...

Endocrine disrupting compounds (EDCs) need to be removed by efficient treatment methods as they are a major concern for both human and environmental health. To reduce the impact of EDCs in water, this review examines the use of ultrasonic degradation processes. Following an overview of EDCs and their origins, the basic concepts of sonochemistry are...

This study investigates the effectiveness of ultrasonic (US) treatment in removing and mineralizing surfactants in wastewater. It examines the complex mechanisms and variables (acoustic conditions, solution temperature, initial dose, etc.) that affect sonolytic processes. The effect of water matrix components (such as salts and the presence of seco...

This chapter provides a comprehensive exploration of bubble sonochemistry utilizing a simplified model of a single acoustic bubble. The model encompasses various aspects of bubble collapse, evolution of reaction, and generation of radicals, offering valuable insights into the characteristics of acoustic cavitation such as temperature, size, and num...

The synergistic combination of ultrasound irradiation and chlorine has emerged as a promising advanced oxidation process (AOP). This unique approach harnesses the advantages of both ultrasonication and chlorination to enhance oxidant production and promote efficient pollutant degradation. Despite its potential, research on the ultrasound/chlorine A...

This chapter delves into the contemporary developments in utilizing ultrasound, specifically the sonochemical process, for the degradation of textile dyes in aqueous solutions. It begins by elucidating the principles of the sonochemical process. Subsequently, it provides a comprehensive summary of noteworthy studies in the field, highlighting their...

The impact of hydrostatic pressure, commonly known as ambient or external pressure, on the phenomenon of sonochemistry and/or sonoluminescence has been extensively investigated through a multitude of experimental and computational studies, all of which have emphasized the crucial role played by this particular parameter. Numerous previous studies h...

Due to the complex physical and chemical interactions taking place in the sonicated medium, various methods have been proposed in the literature for a better understanding of the sonochemical system. In the present paper, the performance of calorimetry, iodometry, Fricke, 4-nitrophenol, H2O2, and ascorbic acid dosimetry techniques have been evaluat...

The pseudo-first and pseudo-second order equations have been the most commonly used models to characterize the sonolytic disappearance kinetics of nonvolatile pollutants in aqueous media. In this work, the general rate law model, i.e., pseudo-nth order kinetics equation, was applied for the first time to the sono-decomposition of different nonvolat...

Ultrasonic systems must be able to produce an acoustic field with the highest possible energy concentration in sonochemical reactors to accomplish maximum efficacy in the sonolytic degradation of water contaminants. In the present study, the impact of cylindrical and conical stainless-steel reflectors placed on the liquid surface on the sonochemica...

Detailed kinetic studies of the ultrasonic decomposition of contaminants in water are scarce. Most of the work has used a pseudo-first order kinetics law, which is unrealistic. The model based on a Langmuir-type mechanism has been shown to fit the sonolytic decomposition data well, especially by using the non-linear technique. To avoid unrealistic...

There is a lack of literature on peroxynitrite formation due to sonolysis of aerated water. In this work, the impact of sonication parameters, frequency and power, on ultrasonic peroxynitrite production in aerated alkaline water was investigated. Peroxynitrite formation was clearly established with undeniable evidence at all the tested frequencies...

As an alternative to a water-based cooling system for a sonoreactor, the present work presents for the first time the use of a phase change material for the management and storage of the dissipated heat within the sonicated water. The performance of the PCM is analyzed as a function of liquid height (LH = 5.1, 10.2, 15.3, and 20.4 cm) at a frequenc...

In recent years, there has been growing interest in the application of UV/chlorine advanced oxidation processes for wastewater treatment. However, few studies have investigated this process in a strongly basic medium (pH > 10), which is a common characteristic of many industrial effluents. In addition, the use of artificial UV lamps in these proces...

This study includes the characterization and exploitation of an abundant agricultural waste in Algeria, Alfa (Stipa tenacissima L.) leaf powder (ALP) as a biosorbent for the removal of hazardous triphenylmethane dyes, malachite green (basic green 4) and crystal violet (basic violet 3), from aqueous media under various operating conditions in batch...

Ultrasound as a clean, efficient, and cheap technique gains special attention in wastewater treatment. Ultrasound alone or coupled with hybrid processes have been widely studied for the treatment of pollutants in wastewater. Thus, it is essential to conduct a review about the research development and trends on this emerging technique. This work pre...

The intensive consumption of pharmaceuticals and drugs in the last decades has led to their increased concentrations in wastewaters from industrial sources. The present paper deals, for the first time, with the sonochemical degradation and mineralization of furosemide (FSM) in water. FSM is a potent loop diuretic used to treat fluid build-up due to...

This study aims principally to assess numerically the impact of methanol mass transport (i.e., evaporation/condensation across the acoustic bubble wall) on the thermodynamics and chemical effects (methanol conversion, hydrogen and oxygenated reactive species production) of acoustic cavitation in sono-irradiated aqueous solution. This effect was rev...

In the present paper, the influence of iodate (IO3−) ions on the photocatalytic process using titanium dioxide (UV/TiO2) was systematically examined. The innovative studied system (UV/TiO2/IO3−) demonstrated high performance in the elimination of safranin O (SO), a model dye, from water due to the implication of iodine radicals (IO3•, IO2•, IO•, et...

Acoustic cavitation-induced sonochemistry is employed for a variety of industrial and laboratory-scale physical and chemical applications, including cleaning, nanomaterial synthesis, and destruction of water contaminants. In acoustic bubbles, CCl4 pyrolysis can totally alter the bubble sonochemistry as well as the active bubble-size population. The...

Hybrid advanced oxidation processes employed to degrade recalcitrant organic pollutants in water have been widely examined in recent years. In the present work, the potential of TiO2- mediated photocatalysis in the presence of the periodate anion (IO4−) toward Safranin O (SO) removal from aqueous solutions was investigated. The findings revealed a...

Herein, we present an original report on chlorine activation by ultrasound (US: 600 kHz, 120 W) for intensifying the sonochemical treatment of hazardous organic materials. The coupling of US/chlorine produced synergy via the involvement of reactive chlorine species (RCSs: Cl•, ClO• and Cl2•−), resulting from the sono-activation of chlorine. The deg...

Abrupt change in local pressure within a liquid medium is susceptible to break the liquid molecules cohesion, particularly when a gas is dissolved in the liquid. The created “cavity”, filled of gaseous/vaporous content is known as Cavitation. When the pressure perturbation is induced by an acoustic source, namely ultrasound, the phenomenon is then...

Power ultrasonics (> 100 kHz), through acoustic cavitation, efficiently splits water to generate reactive oxygen species (ROS: ·OH, O, HO2·, O3 and H2O2). As a result, water sonolysis is considered as an alternative advanced oxidation process for water treatment. In this process, the type of dissolved gases plays a crucial role in controlling the r...

An alternative semi-empirical technique is developed to determine the number density of active cavitation bubbles (N) formed in sonicated solutions. This was achieved by relating the acoustic power supplied to the solution (i.e. determined experimentally) to the released heat by a single bubble. The energy dissipation via heat exchange is obtained...

In the last decades, great interest has been focused on developing innovative, efficient and eco-friendly methods for the reduction of carbon dioxide (CO2). The use of ultrasound (sonochemistry) has appeared as one of these techniques, thanks to its operational simplicity (working at ambient conditions), safety and being environ- mentally benign...

This research aims at optimizing the effects of processing conditions, salts, natural organic materials, and water matrices quality on the effectiveness of the Fe(II)/K2S2O8(KPS)/hydroxylamine process in the degradation of pararosaniline, a toxic and carcinogenic dye. Assisting the Fe(II)/KPS treatment with protonated hydroxylamine (H3NOH+) increas...

A comprehensive numerical investigation was conducted to analyze the effect of ultrasound frequency (213-1000 kHz), ultrasonic intensity (0.7-1.5 W/cm 2) and medium temperature (293.15-333.15 K) on the production of hydrogen from methanol decomposition inside acoustic bubbles (methanol sono-conversion). The adopted model was firstly compared with s...

The present study combines, for the first time, experimental degradation findings and numerical simulation results of CCl4 sonochemistry for (i) understanding the right mechanism by which CCl4 improves Safranin O (SO) sono-bleaching (1.7 MHz, 15 W) and (ii) stating the impact of operational conditions on reactive species dis- tribution toward the...

To anticipate emulsion breakdown in the ELM process, the Box–Behnken design was used with an artificial neural network (ANN) and a metaheuristic approach, namely particle swarm optimization (PSO) and response surface methodology (RSM). Membrane stability testing began with an experimental component to collect data. The following parameters were use...

With the objective of establishing an overview of the limits of hydroxylamine-induced acceleration of the Fenton process, the impact of a wide range of processing conditions and water matrix compositions (water quality) on the degradation of persistent textile dyes is revealed in this study. The co-use of Fenton reagents and hydroxylamine in its pr...

Power ultrasonic (> 100 kHz) splits water into free radicals and hydrogen. As a result, water sonochemistry is considered as an alternative clean and fossil-fuel-free hydrogen production technique. In this research work, the impact of rare gases (Xe, Ar, and He) on the sonochemical production of hydrogen as well as the population of active bubbl...

In this work, after exploring the first report on the synergism of combining ultrasound (US: 600 kHz) and chlorine toward the degradation of Allura Red AC (ARAC) textile dye, as a contaminant model, the impact of various mineral water constituents (Cl–, SO42–, NO3–, HCO3– and NO2–) and natural organic matter, i.e., humic acid (HA), on the performan...

The assessment and control of energy efficiency of the sonochemical and ultrasound assisted processes requires a solid understanding of the chain of energy conversion at the different point of the studied device. The present chapter invokes the various technologies of high-power ultrasound systems and decorticates the ultrasound devices into power...

An energetic assessment of the impacts of the different internal bubble energy parameters, namely PV work, heat transfer, mass transport, and reaction heat, is performed for various acoustical conditions using different cavitation process scenarios. Through analyzing the two phases of the bubble lifetime, that is, rarefaction and collapse cycles, i...

Crystallization is an essential separation process that refines fluids by generating solids. Crystals are also formed by which molecules in solution or vapor are transformed into a solid phase. Acoustic cavitation leads to several physical effects. Collisions between the particles are the result of the shockwave generated by the acoustic cavitation...

In present chapter, a brief discussion was conducted in order to reveal the energetic effect of the different energy parameters (PV work, mass transport, reaction heat and heat exchange) in a multibubble system. Additionally, the overall energetic variation of this bubble's population was visualized. Interesting observations have been inferred from...

The present paper introduces a novel semi-empirical technique for the determination of active bubbles’ number in sonicated solutions. This method links the chemistry of a single bubble to that taking place over the whole sonochemical reactor (solution). The probe compound is CCl4, where its eliminated amount within a single bubble (though pyrolysis...

A number of theoretical and experimental works showed the possibility of increasing the sonochemical production of hydrogen through the pyrolysis of methanol within the acoustic cavitation (i.e. sonolysis of aqueous methanol solution). In this study, numerical simulations have been conducted in order to reveal, for the first time, the effect of met...

Carbon Tetrachloride (CCl 4 ) has a versatile role in sonochemistry, e.g., self�degradation, accelerator of ● OH radical production, and reactive chorine radical generator. These example aspects arise from the pyrolysis of CCl 4 inside acoustic bubbles. A model of CCl 4 sono-pyrolysis inside an acoustic bubble is used to provide a novel mechanistic...

In this paper, the degradation of the diazo dye naphthol blue black (NBB) using the Galvano-Fenton process is studied experimentally and numerically. The simulations are carried out based on the anodic, cathodic, and 34 elementary reactions evolving in the electrolyte, in addition to the oxidative attack of NBB by HO• at a constant rate of 3.35×107...

In addition to bubble number density, bubble size distribution is an important population parameter governing the activity of acoustic cavitation bubbles. In the present paper, an iterative numerical method for equilibrium size distribution is proposed and combined to a model for bubble counting, in order to approach the number density within a pop...

The present paper investigates the potential of the Galvano-Fenton process as an advanced technique in terms of the simultaneous oxidation of a model pollutant, phenol, and the energy release and saving as compared to conventional electrochemical techniques, namely, Fenton, Fenton-like, and Electro-Fenton. A numerical model describing the electroch...

A novel approach allowing the production of electrical energy by an advanced oxidation process is proposed to eliminate organic micropollutants (MPs) in wastewaters. This approach is based on associating the Galvano–Fenton process to the generation of electrical power. In the previous studies describing the Galvano–Fenton (GF) process, iron was dir...

UV/periodate (IO ⁻ 4 ) process is one of the recent advanced oxidation processes (AOPs) that have been efficiently applied to degrade various persistent organic pollutants and lower chemical oxygen demand in industrial wastewater. The photo-irradiation of periodate (λ < 400 nm) in aqueous solutions can produce several reactive radicals and non-radi...

The present chapter addresses the place of ultrasound and sonochemistry in water remediation applications, the panoply of effects generated by ultrasound travelling across wastewater are discussed in regards to their nature, i.e. physical and chemical, and impact, water disinfection and chemical oxidation. The mechanisms of action of ultrasound ran...

The cationic dye safranin-O was removed from an aqueous solution using the Emulsion Liquid membrane (ELM) method. The ELM system consists of a diluent (hexane) and a surfactant (Span 80). Sulfuric acid (H2SO4) solution was used as an internal aqueous phase. The key parameters regulating the safranin-O dye removal were investigated. Twenty-nine (29)...

The cationic dye safranin-O was removed from an aqueous solution using the Emulsion Liquid membrane (ELM) method. The ELM system consists of a diluent (hexane) and a surfactant (Span 80). Sulfuric acid (H2SO4) solution was used as an internal aqueous phase. The key parameters regulating the safranin-O dye removal were investigated. Twenty-nine (29)...

Sonochemistry is considered as one of the cleaner pathways for hydrogen production. The present paper investigates the potential of this technique based upon mass, mass to energy and energy conversion metrics, using modelling and experimental approaches. Four scenarios are examined assuming four saturating gases, namely O2, air, N2 and Ar, four aco...

It is known that the evaporation of carbon tetrachloride (CCl4) into the acoustic cavitation during water sonolysis results in the generation of many reactive species (e.g. chlorinated elements), probable reduction of bubble temperature and the scavenging of hydrogen atom by its reaction with CCl4. Consequently, the chemistry of bubbles (sono-activ...

In spite of the great number of experimental works conducted on CCl4 sono-degradation, several controversies are observed, these including the main species generated upon CCl4 decomposition and the mechanism by which CCl4 accelerated the sonolytic removal of nonvolatile contaminates. In this paper, a new mechanism of carbon tetrachloride pyrolysis...

Several experimental and computational works have been focused on the production of hydrogen by using ultrasonic irradiation. However, the effects of the different ultrasonic conditions have been analyzed by considering a single value for the ambient bubble radius R0 (mean value), which is not the true case as the size of active bubbles in sonicati...

Numerical simulations have been performed on a range of ambient bubble radii, in order to reveal the effect of mass transport, heat exchange and chemical reactions heat on the chemical bubble yield of single acoustic bubble. The results of each of these energy mechanisms were compared to a normal model in which all these processes (mass transport,...

The effect of static pressure (P∞) on.bubble.sonochemistry (i.e. hydrogen and reactive species production) is investigated on a range of ambient bubble sizes (R0) for argon-saturated water. The used ambient pressure ranges from 0.3 to 2 atm, where its impact is shown for frequencies of 355, 500 and 1000.kHz. It is found that for each ambient pressu...

In the present study, the kinetics of degradation of acid orange 7 (AO7) by the Galvano-Fenton process is assessed experimentally and simulated numerically in order to figure out the mechanism of generation and consumption of free radicals with this novel advanced oxidation process. 10 mg/L of the azo dye are degraded during 20 min by combining a c...

The present study treats the effects of mass transport, heat transfer and chemical reactions heat on the bubble dynamics by spanning a range of ambient bubble radii. The thermodynamic behavior of the acoustic bubble was shown for three wave frequencies, 355, 515 and 1000 kHz. The used acoustic amplitude ranges from 1 to 3 atm. It has been demonstra...

The acoustic cavitation bubble as an open energetic system is the seat of conversion of various forms of energy accompanying the bubble oscillation. The energy conversion would explain specific dynamical, thermal and kinetical behaviors. In the present paper, the energy balance related to a stable bubble irradiated by dual-frequency field is simula...

The present paper reports a numerical investigation of the feasibility of a hybrid concept associating the 1-Butyl-3-methylimidazolium Acetate [C4mim][CH3COO] to sonication, in terms of cavitation formation and generated extreme conditions allowing cellulose decomposition in the second reactivity site. The results of the proposed model revealed an...

Owing to the stability and resistance to biodegradation of synthetic dyes, their elimination from industrial wastewater is a very difficult task. This problem has triggered environmental engineers and scientists to search for innovative solutions. Over the last two decades, considerable attention has been paid to the use of ultrasound as an alterna...

Sonolysis and ozonation are two advanced oxidation processes (AOPs) that are actually well documented and their mechanisms are well established. Recently, the combination of these two processes, that is sonolytic ozonation [ultrasound (US)/O3], has been successfully applied to improve the degradation of several water contaminants, as compared to ea...

Both sonolysis and heat-activated persulfate (HAPS) are effective advanced oxidation processes (AOPs) for the destruction of organic pollutants in wastewater. Although ultrasound can activate persulfate at ambient temperature, the synergy between ultrasound and HAPS was poorly investigated, especially when megahertz frequency ultrasound is used. Th...

Acoustic cavitation is the central event of the sonochemical process, which is one of the most recent advanced oxidation processes for water treatment. Even though the liquid compressibility effect on acoustic cavitation has already been investigated by certain studies, their results are still limited to the radial dynamics and the thermodynamic be...

Acoustic cavitation is the central event of water sonolysis, which generates several radical and nonradical species such as H•, •OH, H2, and H2O2. In addition to these species, production of HNO2 and HNO3 was demonstrated in N2-containing aqueous solutions. These species were usually liberated as nitrite and nitrate ions. The mechanism by which NO2...

Injecting of soluble gases in water under sonication is an important tool for improving the efficiency of the sonochemical treatment of water. Among several used gases, nitrous oxide (N2O) has shown a special effect. Instead other gases, dissolving pure N2O in solutions suppresses all sonochemical effects. However, when low amount of this gas is in...

The mechanism by which seawater salts affect the sonochemical activity is until now under debate. In this work, a theoretical approach based on single bubble sonochemistry model has been adopted for examining the effect of seawater salinity on the acoustic generation of free radicals. The model combines the fluctuation dynamics of single acoustic b...

In the present work, the Paracentrotus lividus spines (PLS) are proposed as a novel low-cost non-conventional adsorbent for the removal of malachite green (MG) from aqueous phases in the absence and presence of ultrasonic irradiation and by combining simultaneously ultrasound and mechanical agitation. The PLS was characterized by Fourier transform...

Photocatalysis and sonolysis are two advanced oxidation processes, which are actually well documented and their mechanisms are well established. Recently, the combination of these two processes, i.e., sonophotocatalysis, has shown a potential application for the degradation of persistent organic dyes. This hybrid process has mostly shown a synergis...