Increasing Catalyst Concentration Research Articles

Effect of Catalyst Concentration on Reaction Rate in Organic Synthesis in Kenya

Purpose: The aim of the study was to assess the effect of catalyst concentration on reaction rate in organic synthesis in Kenya. Methodology: This study adopted a desk methodology. A desk study research design is commonly known as secondary data collection. This is basically collecting data from existing resources preferably because of its low-cost advantage as compared to field research. Our current study looked into already published studies and reports as the data was easily accessed through online journals and libraries. Findings: Increased catalyst concentration typically enhances the reaction rate by providing more active sites for the reactants to interact, thereby accelerating the reaction process. This phenomenon follows the principles of collision theory, which states that a higher concentration of catalyst molecules leads to more frequent collisions with reactant molecules, thus increasing the likelihood of successful reactions. Studies have shown that in many organic syntheses, an optimal catalyst concentration exists where the reaction rate is maximized; beyond this point, further increases in catalyst concentration may result in negligible improvements or even adverse effects due to catalyst aggregation or inhibition. Additionally, the nature of the catalyst, its dispersion in the reaction medium, and the specific reaction mechanism all play significant roles in determining the overall impact of catalyst concentration on reaction kinetics. Consequently, fine-tuning the catalyst concentration is essential for optimizing reaction conditions, improving yields, and achieving desired product selectivity in organic synthesis. Implications to Theory, Practice and Policy: Transition state theory, collision theory and michaelis menten kinetics may be used to anchor future studies on assessing effect of catalyst concentration on reaction rate in organic synthesis in Kenya. Practical guidelines are crucial for optimizing catalyst concentration in specific reaction types and industrial settings. Establishing regulatory frameworks that incentivize efficient catalyst concentration practices within industries is imperative.

Influence of monomer structure and catalyst concentration on topological transition and dynamic properties of dicarboxylic acid‐epoxy vitrimers

AbstractThis study delineates the dependence of thermophysical behavior of acid‐epoxy vitrimers on their formulation. The stress relaxation due to the bond exchange reaction and the glass transition temperature of acid epoxy vitrimers are investigated, with respect to the influence of catalyst content and acid chain length. This is carried out for a range of dicarboxylic acids and catalyst concentrations formulated and characterized using calorimetry and dynamic mechanical analysis. The influence of acid chain length on the bond exchange rate, topological transition, and glass transition temperatures of the vitrimers is found to be significant. The activation energy of the exchange reaction varies over a wide range from 73 to 104 kJ/mol and the topology freezing temperature from 66 to 136°C with the behavior governed by the interplay between crosslinking density, network flexibility and density and distance of functional groups, with an increase of catalyst concentration leading to lower topological transition temperature and the dependence on chain length showing non‐monotonic behavior. The glass transition decreases by about 30°C as the carbon chain length increases from 6 to 14 carbons due to enhanced monomer flexibility and is not affected by the concentration of catalyst.

Photocatalytic Degradation of Losartan with BiOCl/Sepiolite Nanocomposites

Developing highly active and available, environmentally friendly, and low-cost photocatalytic materials is one of the most popular topics in photocatalytic degradation systems. In the present study, a series of BiOCl/Sepiolite composite photocatalysts were prepared (in the range of 5%BiOCl/Sepiolite–30%BiOCl/Sepiolite). Their characterization was conducted using X-ray diffraction, diffuse reflectance spectroscopy, scanning electron microscopy, nitrogen physical physisorption at the temperature of liquid nitrogen (77 K), and attenuated total reflectance-Fourier transform infrared spectroscopy. Results showed that composite photocatalysts possess superior efficiency than the parent materials for losartan, an antihypertensive agent, degradation in water, with the sample with only 10%wt. BiOCl shows the highest performance. The beneficial effect of the addition of sepiolite to BiOCl is derived from the increase in surface area, the prevention of particle aggregation, and the efficient separation of photogenerated species. Increasing catalyst concentration from 125 mg/L up to 500 mg/L was accompanied by an increase in the apparent kinetic constant from 0.077 min−1 to 0.197 min−1 while varying losartan concentration from 0.25 to 5.00 mg/L slowed down the removal efficiency. In addition, losartan degradation was only partially hampered in the case of bottled water, whereas it was practically stopped in a secondary wastewater effluent. Overall, this study serves as a useful guide for using geopolymers in photocatalytic applications.

Photocatalytic Hydrosilylation over Pt@UiO-66-NH2: Enhanced Activity and Polymerization Kinetics.

Metal-organic frameworks (MOFs) have shown great research and application value in various types of hydrosilylation reactions. However, studies on photocatalysis-induced hydrosilylation using MOFs are extremely rare. Metal nanoparticles (MNPs)@MOFs are extensively studied for their excellent structural tunability and photocatalytic activity, but there are few reports on their application in photocatalytic hydrosilylation. Here, a novel photocatalyst consisting of platinum (Pt) nanoparticles immobilized in a MOF framework is synthesized and used for photocatalytic hydrosilylation. The effects of various factors on hydrosilylation conversion are investigated, including catalyst concentration, substrate ratio, and irradiation intensity. Furthermore, the photoreactivity of the synthesized Pt catalyst is evaluated in the presence of different concentrations of 2-chlorothixanthone as a photosensitizer. It is noteworthy that the conversion of the reaction increases with increasing catalyst concentration or photosensitizer concentration, whereas increasing the polymethylhydrosiloxane content does not lead to a significant increase in conversion. This study demonstrates the potential of MNPs@MOFs as efficient photocatalysts for photoinduced hydrosilylation reactions and paves the way for future applications in this area.

Kinetic study on the reaction between CO2 and tertiary amine catalyzed by zinc(II) aza‐macrocyclic complexes

AbstractIn this work, the kinetics study on the reaction between CO2 and tertiary amine catalyzed by zinc(II)‐1,4,8,11‐tetraazacyclotetradecane complexes (CM) and zinc(II)‐1,4,7,10‐tetraazacyclododecane complexes (CN) was carried out in a stopped‐flow device. The effects of the catalyst concentration, type of tertiary amines, and temperature on the reaction rate (ν) and catalytic activity (φ) were studied. It was found that the catalyst concentration, tertiary amine with higher pKa, and temperature had positive effects on ν. ν in N‐methyl diethanolamine solution with 10.0 mol m−3 CM and CN were 16.62 and 26.05 folds than the uncatalyzed ν at 298 K, respectively. φ increased with increasing catalyst concentration, decreasing temperature and tertiary amine's pKa. In addition, the kinetics behavior of tertiary amine‐CM/CN‐CO2 systems conformed to the Michaelis–Menten model. The activation energies in catalytic systems were 4%–15% lower than that in the non‐catalytic systems.

Granular titanium dioxide and silicon‐doped titanium dioxide as reusable photocatalysts for dye removal

AbstractIn this study, photocatalytic oxidation of methylene blue (MB) and malachite green (MG) dyes was investigated using granular pure titanium dioxide and silicon‐doped granular titanium dioxide as photocatalysts. Both catalysts were used repeatedly throughout the photocatalytic oxidation experiments. The effect of initial dye and catalyst concentration on photocatalytic oxidation was investigated. The photocatalytic oxidation followed first‐order kinetics for both catalysts. The efficiency of photocatalytic oxidation increased with the increasing catalyst concentration and decreased with the increasing dye concentration. In a 60‐min reaction using granular titanium dioxide, removal efficiencies of MB and MG at 20 g/100 mL catalyst loading and 10 mg/L initial concentration were 83% and 93.3%, respectively. In a 60‐min reaction using granular silicon‐doped titanium dioxide, the removal efficiencies of MB and MG at 5 g/100 mL catalyst loading and 10 mg/L initial concentration were 90.2% and 91.6%, respectively.

Kinetics of bis(2‐methyl) butylene carbonate by transesterification of dimethyl carbonate with 1,4‐butanediol

AbstractThe kinetic behavior of bis(2‐methyl) butylene carbonate (BMBC) by the transesterification of dimethyl carbonate (DMC) with 1,4‐butanediol (BDO) was investigated experimentally and theoretically. The Fourier transform infrared spectroscopy (FTIRs) test confirmed that the BMBC was successfully synthesized. The optimum preparation process of BMBC was investigated at atmospheric pressure, where Zn(Ac)2∙2H2O was the best catalyst for this transesterification reaction, and the optimal concentration was 0.3 wt%. The conversion was determined by measuring the amount of methanol produced during the reaction by refractometric method. A kinetic model was proposed according to the experimental results. The results showed that the transesterification reaction was a pseudo‐first‐order reaction. The apparent activation energy (Ea) significantly decreased with the increase of catalyst concentration from 0.1 wt% to 0.5 wt%. The Ea of the reaction was 102.13, 84.36, and 70.18 kJ mol−1, respectively, when the catalyst concentration was 0.1 wt%, 0.3 wt%, and 0.5 wt%. Furthermore, the parameters of the optimal heating curve in the batch reactor was obtained according to the optimal model.

THE INFLUENCE OF THE CONCENTRATION OF CHLORINE-CONTAINING CONDENSING AGENTS IN THE SYNTHESIS OF CARBOXYLIC ACID ANILIDESТ

Chlorine-containing condensing agents (PCl3, TiCl4, SiCl4) are widely used in the synthesis of carboxylic acid arylamides by the reaction of arylamines with carboxylic acids in stoichiometric amounts, and often in excess (40–150 mol % relative to the latter). To find the optimal amount of the condensing agent used, the acylation of aniline with 3-hydroxy-2-naphthoic acid in boiling ortho-xylene was studied in the PCl3 concentration range of 0–10 mol % from 3-hydroxy-2-naphthoic acid. It has been established that phosphorus tri-chlorochloride plays the role of a condensing agent and a catalyst, while 3-hydroxy-2-naphthoic acid anilide is formed along two routes with different rates, which can be separated kinetically. The first route includes the rapid synthesis of acid chloride, its interaction with aniline to obtain the target product. The second route is implemented due to phosphorous acid, which is formed from phosphorus trichloride and is a true acylation catalyst.
 The maximum yield of anilide 3-hydroxy-2-naphthoic acid decreases with increasing catalyst concentration, approximately propor-tional to the amount of aniline phosphite formed from it in the mass, which, apparently, is not reactive when interacting with the starting acid.
 Similar patterns were also found in the acylation of aniline with benzoic and salicylic acids in the presence of phosphorus trichloride; benzoic acid in the presence of titanium tetrachloride; 3-hydroxy-2-naphthoic acid in the presence of silicon tetrachloride. They allow a new look at the role of these products (PCl3, TiCl4, SiCl4) as condensing agents and/or ca­talysts in the synthesis of amides of carboxylic acids.
 Taking into account the obtained results, in practice it is better to use PCl3 as a catalyst in an amount not exceeding 2–2.5%, or even to replace it with phosphorous acid. This allows to completely get rid of the release of hydrogen chloride, significantly reduce the consumption rates for raw materials, simplify the entire technological process, reduce the amount of waste, ensure the yield of 3-hydroxy-2-naphthoic acid anilide close to quantitative, create a direct catalytic amidation technology that fully meets the criteria «green» chemistry processes.

Influence of Zn2+ catalyst stoichiometry on curing dynamics and stress relaxation of polyester-based epoxy vitrimer

In the classical “covalent adaptive network” constructed by diglycidyl ether of bisphenol A (DGEBA) and crosslinking agent glutaric anhydride (GA), Zn-based catalyst greatly affects the curing crosslinking reaction and dynamic transesterification reaction. Herein, the crucial roles of Zn(Ac)2 catalyst in the curing dynamics and stress relaxation were studied. The results reveal that increasing the content of Zn(Ac)2 can significantly reduce the reaction activation energy (Eα) at initial stage, thus effectively promoting the curing crosslinking reaction. The analyses of dynamic properties suggest that although stress relation time (τ) can be shortened by increasing catalyst content, the high content of catalyst would lead a fast transesterification rate at relatively low temperature, which is adverse to the mechanical stability of vitrimer resin at operating temperature. By comparison, the vitrimer resin with modest catalyst content (mole ratio of 1:0.5:0.05) shows a highest viscous flow activation energy (Eτ), i.e., excellent dimensional stability and processability. Besides, the crosslinking density of resin was significantly affected by the content of catalyst. Since the competitive catalytic effects on curing cross-linking reaction and subsequent transesterification, the vitrimer resin of 1:0.5:0.05 exihits the highest crosslinking density (1855 mol/m3), so that it has highest Tg (79 °C) and tensile strength (72 MPa).

Thermomechanical analysis (TMA) of vitrimers

Vitrimers are an exciting class and new generation of polymer materials combining the strength of a traditional thermoset polymer with the reprocessability of a traditional thermoplastic polymer. However, a key debate in literature has surrounded the best method to identify the vitrimer topology freezing temperature (Tv), above which dynamic covalent bond exchange reactions occur, allowing for self-healing, recycling, and shape reconfigurability of vitrimers. While common methods in literature to identify the Tv include stress relaxation, creep, and fluorescence, we herein validate thermomechanical analysis (TMA) as a reliable method for Tv identification. TMA provides several clear advantages as it is less time and sample intensive than stress relaxation. Furthermore, it is performed in compression to match application conditions, provides more consistent results than creep, and identifies the coefficient of thermal expansion (α). We demonstrate that expansion TMA is a valuable tool in Tv identification by validating several clearly accepted trends in literature; TMA validates that the Tv increases with decreasing catalyst concentration and increasing heating rate while showing negligible variation with increasing applied force. Finally, we report an increasing α with increasing catalyst concentration for our vitrimer material. By taking advantage of such a fast and reliable method to identify Tv, we believe this fundamental study will support future vitrimer research.

A kinetic study of thermal degradation of non-metallic part of printed circuit boards for the combined effect of particle size and catalyst

ABSTRACT After the successful removal of metals from printed circuit boards either through a physical or chemical process, epoxy resins are thermosetting plastics left over for landfilling. To overcome landfilling, thermal degradation of this resin was done under different particle sizes with varying catalyst concentrations. A series of thermogravimetric experiments were carried out using ZSM-5 as the catalyst. To study kinetics parameters’ mass loss with temperature was divided into 3 zones 120–240°C, 240–360°C and 360–650°C. To determine activation energy and the order of reaction, the Coats and Redfern method was used. Experimental data in all three zones were found in agreement with the Coats and Redfern method. ZSM-5 was found to be reducing activation energy and the order of reaction in zone 2. The average activation energy was in the range of 150–200 kJ/mol and the order of reaction was 1.5–2 in zone 2 for different experiments. Coarser particles were found to have less decomposition than finer particles due to heat transfer limitation within the particle. However, the effect of increasing catalyst concentration was found ineffective in the mass transfer of more volatiles from PCB.

Insight on the Dependence of the Drug Delivery Applications of Mesoporous Silica Nanoparticles on Their Physical Properties

SummaryMesoporous silica nanoparticles (MSNs) are fascinating due to their interesting properties and applications.PurposeThe optimization of MSNs for drug delivery applications was achieved by preparing different formulations of MSNs using different concentrations of ammonium hydroxide (NH4OH) (0.7, 1.4, 2.8, 4.2, and 5.6 mg/ml for MSN1, MSN2, MSN3, MSN4, and MSN5, respectively).MethodsIn the synthesis of MSNs, NH4OH was used as a catalyst while tetraethyl orthosilicate were used as a source of silica. Transmission electron microscopy (TEM) image revealed a linear increase in the size of the formed MSNs with increase in catalyst concentration. TEM images showed that all investigated nanoparticles were dispersed and spherical (changed to oval on addition of higher concentration of NH4OH).ResultsThe hydrodynamic sizes of prepared MSNs were (64.18 ± 6.8, 90.46 ± 7.1, 118.98 ± 7.01, 152.7 ± 1.7, and 173.9 ± 9.36 nm for MSN1, MSN2, MSN3, MSN4, and MSN5, respectively) assessed using the dynamic light scattering (DLS) technique. The negative values of zeta potential indicated high surface stability of the formed MSNs. N2-isotherm revealed that the pore volume of MSNs decreased with increase in the size of MSNs. In vitro drug release showed that all MSNs exhibited high encapsulation efficiency of doxorubicin. The encapsulation efficiency were 92.2%, 82.8%, 72.2%, 72.1% and 71.9%for MSN1, MSN2, MSN3, MSN4, and MSN5, respectively. ConclusionMSN1 and MSN2, with sizes of 64.18 ± 6.8 and 90.46 ± 7.1 nm, pore volume of 0.89 and 0.356 cc/g, encapsulation efficiency of 92.2% and 82.8%, and adequate drug release profiles, were probably the best choices for a drug carrier in drug delivery applications.

Performance of NiMo-Al2O3 catalyst in biokerosene production via hydrocracking of dirty palm oil

Energy consumption in the transportation sector steadily rises each year, requiring an effective solution to meet the demands present. In this study, biokerosene was produced through the hydrocracking process using NiMo-Al2O3 as a catalyst and dirty palm oil as raw material. The synthesized catalyst was characterized by Scanning Electron Microscopy (SEM) and X-Ray Diffraction (XRD), while the biofuel product which was analyzed by Gas Chromatography-Mass Spectrometry (GCMS). The results showed that in the hydrocracking process, the decarboxylation and decarbonylation reactions were the dominant pathways. The conversion of biokerosene increased with increasing catalyst concentration, temperature, and reaction time. The highest biokerosene yield was found to be 56.38% with a catalyst concentration of 0.01 g-catalyst/g-oil, 3 h reaction time and 450oC reaction temperature. The optimum catalyst concentration was 0.04 g-catalyst/g-oil, while the optimum temperature was 550oC and the optimum reaction time was 3 h.

Silica hydrogel composites as a platform for soft drug formulations and cosmetic compositions

In this work, silica hydrogels are considered as potential basis for the development of new soft drug formulations and cosmetic products. For this purpose, the hydrogel drug-silica composites having pH ∼7 were synthesized by two-step sol-gel method under different synthesis conditions (concentration of acidic catalyst, addition of co-solvent (DMSO), drug loading). Lipoamide, a powerful antioxidant, was used as the drug. Since biomedical functionality of the hydrogel materials is largely determined by their mechanical properties, response of the hydrogels to deformation under compression, tension and shear was measured, and their thixotropic behavior was also studied. The release kinetics of the drug from the hydrogel composites was investigated in vitro. It was shown that the synthesis conditions influenced significantly on the indicated properties of the synthesized hydrogels. The compression Young's moduli and the thixotropic indexes decreased with increasing catalyst concentration and drug loading due to the destabilizing effect of these factors on microstructure of the hydrogels. However, DMSO promoted improvement of the mechanical properties of the hydrogels. The tensile properties of the hydrogels were very low. It was found that the drug release from the hydrogel composites followed zero order kinetic for two days due to mechanism of anomalous diffusion. The drug release from the hydrogel composites prepared using the highest catalyst concentration and high drug loading is characterized by higher rate constants.

Combustion synthesis of SiC/Al2O3 composite powders with SiC nanowires and their growth mechanism

SiC/Al2O3 composite powders with SiC nanowires were synthesized using a one-step combustion synthesis method taking silica fume (SiO2), aluminum powder (Al) and carbon black (CB) as raw materials, while ferrocene (C10H10Fe) was used as the catalyst. The calculated results for the relationship between the equilibrium phase and temperature of the Al–SiO2–C system show that SiC and Al2O3 are the only equilibrium phases in the system. In addition, the effects of C10H10Fe on the combustion synthesis process and products were studied. It was found that with increasing catalyst content, the amount of residual Si in the products first decreases and then increases, the combustion temperature first increases and then decreases, and the nanowire content continues to increase. For an optimal amount of C10H10Fe of 0.75 wt%, almost no residual Si is observed in the product, while the combustion temperature (Tc) is high (2104 K), the SiC nanowire content is relatively high, and the nanowire aspect ratio is large. In addition, two growth mechanism models for SiC nanowires: VS and VLS were validated.

Comparison the visible photocatalytic activity and kinetic performance of amino acids (non-metal doped) TiO2 for degradation of colored wastewater effluent

Different types of amino acids as sources of carbon, nitrogen and sulfur were doped on TiO2 lattice to study the photocatalytic activity of three synthesized photocatalysts for dye removal under visible light. The phase composition, functional groups, morphology, optical properties, band gap energy and recombination rate of nanostructures were studied by X-ray diffraction (XRD), fourier transform infrared (FT-IR), field emission scanning electron microscopy with Energy Dispersive X-Ray Spectroscopy (FESEM/EDX), diffuse reflectance spectra (DRS) and photoluminescence spectroscopy (PL). These analysis verified the successful synthesis of the catalysts and showed the type of catalyst significantly affected PL analysis as l-Arginine-TiO2 (C,N co-doped TiO2) had lower recombination rate and PL intensity compared to l-Proline-TiO2 (C,N co-doped TiO2) and l-Methionine-TiO2 (C,N,S tri-doped TiO2). The firs-order kinetic model described the photodegradation of methyl orange (MO) and direct red 16 (DR16) and the rate constant for DR16 photocatalytic removal using l-Arginine (1 wt %)-TiO2 was 2.9 and 4.3 times higher compared to those of l-Methionine (1.5 wt %.)-TiO2 and l-Proline (2 wt %.)-TiO2 respectively. The effect of five processing variables and their optimum values were determined using central composite design (CCD). The result confirmed that decreasing pollutant concentration and pH and increasing catalyst concentration, irradiation time and light intensity improved the removal efficiency. The catalyst showed reusable and stable structure as 93% and 84% of DR16 and MO removed after four times of reusing.

Photocatalytic Degradation of Valsartan by MoS2/BiOCl Heterojunctions

In the present study, the removal of valsartan (VLS), an antihypertensive agent, under simulated solar radiation with the use of molybdenum sulfide-bismuth oxychloride composites (MoS2/BiOCl), of variable MoS2 content (0.1–10.0 wt.%) was investigated. The physicochemical properties of the photocatalysts were examined by XRD, DRS, BET and TEM/HRTEM. Preliminary tests were conducted to examine the photocatalytic efficiency of the synthesized MoS2/BiOCl composites towards VLS degradation in ultrapure water (UPW). It was found that the activity of pure BiOCl is improved with the addition of MoS2. The degradation rate was maximized with the use of the catalyst containing 0.25 wt.% MoS2. It was also found that the increase in catalyst concentration (50–1000 mg/L) enhances VLS degradation. It was found that VLS removal decreased by increasing VLS concentration. The effect of the water matrix on VLS removal was studied by carrying out experiments in real and synthetic water matrices. VLS degradation in UPW was faster than in bottled water (BW) and wastewater (WW), mainly due to the existence of organic matter in real aqueous media. Lastly, 0.25 wt.% MoS2/BiOCl showed great stability after 360 min of irradiation, serving as a promising catalyst for water remediation of emerging contaminants under solar irradiation.

Potential of ammonium chloride-activated carbon for decomposition of penicillin G by catalytic ozonation process (COP)

Pharmaceutical compounds that enter the aqueous solution are classified as emerging pollutants. The aim of this study was to use a single adsorption process (adsorption/AC), single ozonation process (SOP), and catalytic ozonation processes (COPs) with activated carbon obtained from Calligonum comosum as novel advanced oxidation processes to decomposition and mineralization of penicillin G from pollutant waters. The influence of important parameters including solution pH (2, 4, 6, 8, and 10), contact time (5, 10, 15, 20, 25, 30, 35, and 40 min), catalyst dosage (0.025–0.1 g/L), and initial PG concentration (25–100 mg/L) was examined on the efficiency of COP in degradation and mineralization of penicillin G in aqueous solution. The BET results indicated that the surface area of the activated carbon catalyst was1473 m2/g. The efficiency of adsorption/AC, SOP, and COP/AC in penicillin G decomposition at a pH of 10 was 11.17%, 33.6%, and 85%, respectively. The efficiency of COP/AC increased to 100% with the increase in catalyst concentration up to 75 mg/L. The highest synergistic rate of the catalyst at this concentration and a pH of 10 was 46.6%. A maximum reduction of 100% of PG was achieved at a pH of 10, a concentration of 50 mg/L in 40 min. The results also indicated that the mineralization rate in COP/AC was 52%. Also, the results showed that the catalytic ozonation process can be used as an effective method for the oxidation of penicillin G from contaminated water.

Novel homogeneous catalyst assisted sonocatalytic degradation of dye Direct Blue 71

Industrial effluents, particularly from dye industry, is one of the major causes of serious concern as it contaminates the environmental water resources and affect human health. Treatment of such contaminants is a challenging area of interest to researchers. In this context, here, we have explored degradation and mineralization of Direct Blue (DB71) dye in aqueous solution by means of ultrasound irradiation at a frequency of 25 kHz and its combination with a novel homogenous sonocatalyst is investigated. The following experiments have been conducted to achieve complete degradation of the dye molecule. In-situ generation of the radicals under ultrasonic irradiation is measured by EPR technique. The effects of various operational parameters such as the effects of pH, dye concentration, catalyst dosage, electrolytes, energy input and kinetics of oxidation processes on the degradation efficiency are studied. COD measurements are also carried out in order to evaluate the mineralization efficiency of DB71. The effect of electrolytes on dye degradation is studied with different inorganic electrolytes. The rate constant decreases with increasing dye concentration. The degradation increases with increasing catalyst concentration and decreases with increasing dye concentration. Sonocatalytic degradation of the dye molecules are observed by UV-visible absorption and TOC measurements. The by-products formation of the sonocalytically degraded dye samples are analyzed by ESI-MS+ analysis. The catalyst is also tested for its efficiency in the degradation of real dye house effluents.

Photodegradation of Methylene Blue and Rhodamine B Using Laser-Synthesized ZnO Nanoparticles.

In this paper we examined the photocatalytic efficiency of a laser-synthesized colloidal solution of ZnO nanoparticles synthesized by laser ablation in water. The average size of the obtained colloidal ZnO nanoparticles is about 47 nm. As revealed by electron microscopy, other nanostructures were also present in the colloidal solution, especially nanosheets. A photocatalytic degradation of UV-irradiated Methylene Blue and Rhodamine B solutions of different concentration in the presence of different ZnO catalyst mass concentrations was studied in order to examine their influence on photodegradation rates. ZnO nanoparticles have shown high photocatalytic efficiency, which is limited due to different effects related to UV light transmittivity through the colloidal solution. Therefore, increasing catalyst concentration is effective way to increase photocatalytic efficiency up to some value where photodegradation rate saturation occurs. The photodegradation rate increases as the dye concentration decreases. These findings are important for water purification applications of laser-synthesized ZnO nanoparticles.