Ultrasonic-assisted photocatalytic degradation of various organic contaminants using ZnO supported on a natural polymer of sporopollenin

Water resource pollution by organic contaminants is an environmental issue of increasing concern. Here, sporopollenin/zinc oxide (SP/ZnO) was used as an environmentally friendly and durable catalyst for sonophotocatalytic treatment of three organic compounds: direct blue 25 (DB 25), levofloxacin (LEV), and dimethylphtalate (DMPh). The resulting catalyst had a 2.65 eV bandgap value and 9.81 m²/g surface area. The crystalline structure and functional groups of SP/ZnO were confirmed by X-ray diffraction (XRD) and Fourier transforms infrared spectroscopy (FTIR) analyses. After 120 min of the sonophotocatalysis, the degradation efficiencies of DB 25, LEV, and DMPh by SP/ZnO were 86.41, 75.88, and 62.54%, respectively, which were higher than that of the other investigated processes. The role of reactive oxygen species were investigated using various scavengers, enhancers, photoluminescence, and o-phenylenediamine. Owing to its stability, the catalyst exhibited good reusability after four consecutive cycles. In addition, the high integrity of the catalyst was confirmed by scanning electron microscopy (SEM), XRD, and FTIR analyses. After four consecutive examinations, the leaching of zinc in the aqueous phase was < 3 mg/L. Moreover, gas chromatography-mass spectrometry (GC-MS) analyses indicated that the contaminants were initially converted into cyclic compounds and then into aliphatic compounds, including carboxylic acids and animated products. Thus, this study synthesized an environmentally friendly and reusable SP/ZnO composite for the degradation of various organic pollutants using a sonophotocatalytic process.

Catalytic activation of hydrogen peroxide by Cr2AlC MAX phase under ultrasound waves for a treatment of water contaminated with organic pollutants

This study aims to investigate the sonocatalytic activation of hydrogen peroxide (H₂O₂) using Cr₂AlC MAX phase prepared by the reactive sintering process. The hexagonal structure of the crystalline MAX phase was confirmed by X-ray diffraction. Moreover, the compacted layered structure of the MAX phase was observed via scanning electron microscopy and high-resolution transmission electron microscopy. Under the desired operating conditions, Cr₂AlC MAX phase (0.75 g/L) showed suitable potential to activate H₂O₂ (1 mmol/L) under sonication, thereby allowing a considerable removal efficiency for various organic pollutants, including dimethyl phthalate (69.1%), rifampin (94.5%), hydroxychloroquine (100%), and acid blue 7 (91.5%) with initial concentration of 15 mg/L within 120 min of treatment. Kinetic analysis proved that the degradation reaction followed pseudo-first-order kinetics. Scavenging tests demonstrated that hydroxyl radicals and singlet oxygen were effective species during degradation. Furthermore, a probable mechanism for dimethyl phthalate degradation was suggested according to gas chromatography-mass spectroscopy and nuclear magnetic resonance analyses. The obtained results confirmed the capability of the triple Cr₂AlC/H₂O₂/US process as a promising method for treating contaminated water.

Titanium-based MAX-phase with sonocatalytic activity for degradation of oxytetracycline antibiotic

In light of growing environmental concerns over emerging contaminants in aquatic environments, antibiotics in particular, have prompted the development of a new generation of effective sonocatalytic systems. In this study, a new type of nano-laminated material, Ti₂SnC MAX phase, is prepared, characterized, and evaluated for the sonocatalytic degradation of oxytetracycline (OTC) antibiotic. A variety of identification analyses, including X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectrometry, Brunauer-Emmett-Teller, and diffuse reflectance spectroscopy, were conducted to determine the physicochemical properties of the synthesized catalyst. By optimizing the operating factors, total degradation of OTC occurs within 120 min with 1 g L^-1 catalyst, 10 mg L^-1 OTC, at natural pH of 7.1 and 150 W ultrasonic power. The scavenger studies conclude that the singlet oxygen and superoxide ions are the most active species during the sonocatalytic reaction. Based on the obtained data and GC-MS analysis, a possible sonocatalytic mechanism for the OTC degradation in the presence of Ti₂SnC is proposed. The catalyst reusability within eight consecutive runs reveals the proper stability of Ti₂SnC MAX phase. The results indicate the prospect for MAX phase-based materials to be developed as efficient sonocatalysts in the treatment of antibiotics, suggesting a bright future for the field.

Synthesis of N-Doped Magnetic WO3-x@Mesoporous Carbon Using a Diatom Template and Plasma Modification: Visible-Light-Driven Photocatalytic Activities

Synthesis of three-dimensional photocatalysts offers great potential for chemical conversion and hydrogen generation as appropriate solutions for environmental protection and energy shortage challenges. In this study, the magnetic WO_3-x@mesoporous carbon (M-WO_3-x@MC) was synthesized through the evaporation-induced self-assembly method applying diatom frustules as a natural template. Then, plasma modification was used to prepare the N-doped M-WO_3-x@MC (NM-WO_3-x@MC) with enhanced photocatalytic activity and durable performance. The WO_3-x was embedded in the conductive MC, which was also partially reduced by the carbon precursor within the heat-treatment procedure. The obtained M-WO_3-x@MC was treated by the plasma under an N₂ atmosphere for the production of the final photocatalyst containing both the N-doped WO_3-x and MC. As a result, the NM-WO_3-x@MC had larger surface area (208.4 m² g^-1), narrower band gap (2.3 eV), more visible light harvesting, and confined electron-hole pairs recombination. The H₂ generation rates of net WO₃ nanorods and NM-WO_3-x@MC nanocomposite were estimated as 532 and 2765 μmol g^-1 h^-1, respectively. Additionally, more than 90% of antibiotics (cephalexin, cefazolin and cephradine) degradation and 76% of total organic carbon elimination were obtained after 120 and 240 min of photocatalytic process under visible light irradiation. Eventually, more than eight intermediates were detected for each antibiotic degradation using the gas chromatography-mass spectrometer method, and based on the obtained results, the possible degradation pathways were suggested.

Mesoporous MIP-capped luminescent MOF as specific and sensitive analytical probe: application for chlorpyrifos

Specific recognition of organophosphate pesticides (OPs) is a significant challenge for analytical researchers. Herein, surface imprinted terbium-based luminescent metal-organic framework (MOF-76) are presented as a highly specific probe for the measurement of chlorpyrifos (CP). A mesoporous molecular imprinted polymer (mMIP) layer was generated on the surface of nano-sized MOF-76 using CP, as template. The resulting mMIP-capped MOF-76 (mMIP@MOF-76) contained specific sites for adsorption of CP molecules, guaranteeing the selectivity of the designed probe. The high porosity of rod-shape MOF-76, as well as the mesoporous structure of the MIP layer improved the diffusion process and caused the high sensitivity of the probe. The detection process is based on the remarkable quenching effect of CP on the fluorescence emission of mMIP@MOF-76. Plotting the CP concentration against the fluorescence intensity (λ_ex = 285 nm and λ_em = 544 nm) gave a linear curve in the concentration range 10-1000 ng mL^-1 CP, with 3.41 ng mL^-1 limit of detection. The designed probe was utilized for CP determination in fruit juice and environmental samples. The combination of the stable MOF-based support, as well as its remarkable fluorescence features and specific MIP sites, led to a highly selective and ultrasensitive detection system.Graphical abstract.

Scrutinizing the vital role of various ultraviolet irradiations on the comparative photocatalytic ozonation of albendazole and metronidazole: Integration and synergistic reactions mechanism

Herein, TiO₂ nanoparticles were immobilized on the ceramic surface using the sol-gel dip-coating method, which confirmed by scanning electron microscopy (SEM) and atomic force microscopy (AFM). Then, a semi-batch reactor containing the prepared ceramic plates, which irradiated by the various UV lights was used for the degradation of the albendazole (ALZ) and metronidazole (MTZ) pharmaceuticals by the photocatalytic ozonation process. The control experiments were performed to compare the photocatalysis, ozonation, photo-ozonation and photocatalytic ozonation processes under the same operational conditions with the UV-A, UV-B and UV-C irradiations. The synergistic effect of photocatalysis and ozonation was observed; moreover, the results revealed that the UV-A/TiO₂/O₃ had the highest efficiency for the ALZ and MTZ degradation owing to the synergistic heterogeneous reactions (SHRs), which led to more reactive oxygen species (ROS). The MTZ and ALZ degradation were probed by monitoring the dissolved ozone, oxygen and hydrogen peroxide concentrations during the various processes including the UV-A/TiO₂/O₃ process. The obtained results disclose that the ALZ degradation is lower than the MTZ due to its resistant nature with more direct attacks of the ozone in the bulk solution compared to the MTZ. Furthermore, the various compounds as the holes (h⁺) and ROS scavengers or ozone solubility enhancers were added to the reaction bulk to investigate the exact mechanism of the photocatalytic-ozonation. Eventually, the degradation intermediates of the pharmaceuticals generated in the photocatalytic-ozonation process were successfully recognized by the Gas chromatography-mass spectrometry (GC-MS) and the possible degradation paths were suggested for the degradation of pollutants considering the responsible ROS in each case.

Mg and La Co-doped ZnO Nanoparticles Prepared by Sol–gel Method: Synthesis, Characterization and Photocatalytic Activity

In this study, La and Mg doped, and co-doped ZnO nanoparticles were prepared using the sol-gel method. The prepared samples were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), UV-Vis diffuse reflectance spectroscopy (DRS), and N2 physisorption techniques. The XRD results indicated that the prepared nanoparticles can be well adopted by the hexagonal wurtzite structure crystal and there are no second impurity peaks. Studies of the FESEM, EDX and TEM have shown that the samples have uniform spherical-like morphology with a homogenous distribution. The incorporation of La and Mg into the ZnO lattice had no effect on the morphology of the nanoparticles, but a reduction in the size of the grains (≈ 14 nm to ≈ 7 nm) was observed due to the insertion of these ions. The results of N2 physisorption indicated that there was an increase in BET surface area and pore volume for doped and co-doped samples. The results of DRS showed an increase in band gap energy and a blue shift at the absorption edge for doped and co-doped samples. The photocatalytic activity of the prepared catalysts was evaluated in the removal of RhB under UVA irradiation. The results showed that Mg5%-La5%/ZnO had the highest photoactivity (91.18 %) among all samples.

CdSe quantum dots-sensitized chemiluminescence system and quenching effect of gold nanoclusters for cyanide detection

An efficient chemiluminescence resonance energy transfer (CRET) induced chemiluminescence (CL) system was developed for the sensitive determination of cyanide ion (CN^-) in environmental and biological samples. The selected CL reaction was hydrogen peroxide (H₂O₂)-bicarbonate (HCO₃^-) system with an ultra-weak emission at about 470 nm. It was found that glutathione-stabilized CdSe quantum dots (CdSe QDs) superbly increase the obtained CL intensity. The high performance CRET between the CL emitters and CdSe QDs with a broad absorption was mainly responsible for the observed improving effect. The absorption spectrum of QDs completely overlaps with the CL emission wavelength of H₂O₂-HCO₃^- system. Besides, CdSe QDs could also catalyze the CL reaction of H₂O₂-HCO₃^-, efficiently. On the other hand, it was observed that the gold nanoclusters (Au NCs) could prohibit the CRET system and turn off the CL emission. This diminishing effect can be useful for the analytical application. Herein, it was successfully exploited for the selective recognition of CN^-, using its leaching effect on Au NCs. After efficient dissolution of NCs, the CRET to CdSe QDs restored and the CL emission was again turned on. This strategy resulted in a high sensitive and reliable measurement of CN^- in the concentration range of 2-225 nM, with a detection limit of 0.46 nM.

Heterogeneous sonocatalytic degradation of anazolene sodium by synthesized dysprosium doped CdSe nanostructures

Undoped and Dy-doped CdSe nanoparticles are synthesized and then characterized by the SEM, XRD, FT-IR, XPS and BET methods, which verify successful preparation of the doped catalyst. The sonocatalytic degradation of anazolene sodium as a model azo dye is higher than sonolysis process and the 2% Dy-doped CdSe with band gap of 1.42eV exhibits the greatest sonocatalytic performance. The decolorization efficiency (DE%) of sonocatalysis with 2% Dy-doped CdSe, undoped CdSe and sonolysis after 90min of the process is 91.32%, 56.13% and 39.14%, respectively. In addition, the sonocatalytic degradation of anazolene sodium increases with enhancement of the dopant, catalyst dosage, ultrasonic power, dissolved gasses and decreasing of initial anazolene sodium concentration. Furthermore, with addition of chloroform, sulfate, chloride and ethanol as the radical scavengers, the DE% decreases indicating the controlling mechanism of free radicals for the dye degradation. Besides, the results reveal the appropriate reusability of the catalyst and various degradation by-products are identified using the GC-MS technique. Eventually, the empirical kinetic model is expanded by nonlinear regression analysis for prediction of pseudo first-order constants in various operational conditions.

Optimization of a textile dye degradation in a recirculating fluidized-bed reactor using magnetite/S2O82- process

Optimization of Acid Orange 7 (AO7) treatment using heterogeneous Fenton-like method in a recirculating fluidized-bed reactor (FBR) was investigated by using central composite design (CCD). Natural magnetite (NM) as Fenton-like catalyst was characterized using scanning electron microscopy. A nonlinear CCD model was obtained for the prediction of dye degradation as a function of experimental variables such as peroxydisulfate concentration (0.1-0.5 mmol/L), initial AO7 concentration (5-25 mg/L), pH (3-9) and NM dosage (0.25-1.25 g/L) after 105 min of treatment. The calculated results by the model were consistent with the experimental results (R² = 0.959). Furthermore, the model is suitable to estimate the optimum operational conditions and determine the effects of the parameters for maximum AO7 degradation. Eventually, gas chromatography-mass spectroscopy was used for the recognition of the dye degradation by-products.

One-step preparation of nanostructured martite catalyst and graphite electrode by glow discharge plasma for heterogeneous electro-Fenton like process

Natural Martite ore particles and graphite were modified by alternating current (AC) glow discharge plasma to form nanostructured catalyst and cathode electrode for using in the heterogeneous-electro Fenton-like (Het-EF-like) process. The performance of the plasma-treated martite (PTM) and graphite electrode (PTGE) was studied for the treatment of paraquat herbicide in a batch system. 85.78% degradation efficiency for 20 mg L^-1 paraquat was achieved in the modified process under desired operational conditions (i.e. current intensity of 300 mA, catalyst amount of 1 g L^-1, pH = 6, and background electrolyte (Na₂SO₄) concentration of 0.05 mol L^-1) which was higher than the 41.03% for the unmodified one after 150 min of treatment. The ecofriendly modification of the martite particles and the graphite electrode, no chemical needed, low leached iron and milder operational pH were the main privileges of plasma utilization. Moreover, the degradation efficiency through the process was not declined after five repeated cycles at the optimized conditions, which proved the stability of the nanostructured PTM and PTGE in the long-term usage. The archived results exhibit this method is the first example of high efficient, cost-effective, and environment-friendly method for generation of nanostructured samples.

Heterogeneous sono-Fenton-like process using martite nanocatalyst prepared by high energy planetary ball milling for treatment of a textile dye

High energy planetary ball milling was applied to prepare sono-Fenton nanocatalyst from natural martite (NM). The NM samples were milled for 2-6h at the speed of 320rpm for production of various ball milled martite (BMM) samples. The catalytic performance of the BMMs was greater than the NM for treatment of Acid Blue 92 (AB92) in heterogeneous sono-Fenton-like process. The NM and the BMM samples were characterized by XRD, FT-IR, SEM, EDX and BET analyses. The particle size distribution of the 6h-milled martite (BMM₃) was in the range of 10-90nm, which had the highest surface area compared to the other samples. Then, the impact of main operational parameters was investigated on the process. Complete removal of the dye was obtained at the desired conditions including initial pH 7, 2.5g/L BMM₃ dosage, 10mg/L AB92 concentration, and 150W ultrasonic power after 30min of treatment. The treatment process followed pseudo-first order kinetic. Environmentally-friendly modification of the NM, low leached iron amount and repeated application at milder pH were the significant benefits of the BMM₃. The GC-MS was successfully used to identify the generated intermediates. Eventually, an artificial neural network (ANN) was applied to predict the AB92 removal efficiency based upon the experimental data with a proper correlation coefficient (R²=0.9836).

Kinetic modeling of sonocatalytic degradation of reactive orange 29 in the presence of lanthanide-doped ZnO nanoparticles

The sonocatalytic degradation of reactive orange 29 (RO29) was examined from the reaction kinetics point of view. Sonochemically synthesized lanthanides (Ho³⁺ and Er³⁺)-doped ZnO nanoparticles were utilized as catalyst during the sonocatalytic process. The prepared nanoparticles were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The aqueous RO29 solution was irradiated with a 36kHz ultrasonic bath (150W) for investigation of the degradation kinetics by varying of the initial dye concentration (10-30mg/L) and catalyst dosage (0.25-1g/L). A novel kinetic model was developed and validated for prediction of the RO29 sonocatalytic degradation efficiency using generally accepted intrinsic elementary reactions. The proposed kinetic model clearly demonstrates the dependence of the apparent first-order rate constant on the mentioned operational parameters. The predicted values of degradation efficiency and experimental results were in good agreement with appropriate correlation coefficient (R²>0.945).

Preparation of zeolite nanorods by corona discharge plasma for degradation of phenazopyridine by heterogeneous sono-Fenton-like process

The plasma-modified clinoptilolite (PMC) nanorods were prepared from natural clinoptilolite (NC) utilizing environmentally-friendly corona discharge plasma. The PMC and NC were characterized by XRD, FT-IR, SEM, EDX, XPS and BET, which confirmed the nanocatalyst formation. The catalytic performance of the PMC in the heterogeneous sono-Fenton-like process was greater than the NC for treatment of phenazopyridine (PhP). The desired amounts were obtained for experimental parameters including initial pH (5), PMC dosage (2g/L), K2S2O8 concentration (2mmol/L), ultrasonic power (300W) and PhP concentration (10mg/L). Reactive oxygen species scavengers decreased the removal efficiency of the PhP. The treatment process followed pseudo-first order kinetic and seven degradation intermediates were identified by the GC-MS technique.

Central composite design optimization of pilot plant fluidized-bed heterogeneous Fenton process for degradation of an azo dye

Optimization of Acid Yellow 36 (AY36) degradation by heterogeneous Fenton process in a recirculated fluidized-bed reactor was studied using central composite design (CCD). Natural pyrite was applied as the catalyst characterized by X-ray diffraction and scanning electron microscopy. The CCD model was developed for the estimation of degradation efficiency as a function of independent operational parameters including hydrogen peroxide concentration (0.5-2.5 mmol/L), initial AY36 concentration (5-25 mg/L), pH (3-9) and catalyst dosage (0.4-1.2 mg/L). The obtained data from the model are in good agreement with the experimental data (R(2 )= 0.964). Moreover, this model is applicable not only to determine the optimized experimental conditions for maximum AY36 degradation, but also to find individual and interactive effects of the mentioned parameters. Finally, gas chromatography-mass spectroscopy (GC-MS) was utilized for the identification of some degradation intermediates and a plausible degradation pathway was proposed.

Heterogeneous sono-Fenton process using pyrite nanorods prepared by non-thermal plasma for degradation of an anthraquinone dye

Natural pyrite (NP) was treated using oxygen and nitrogen non-thermal plasmas to form modified catalysts. Cleaning effect of the O2 plasma by chemical etching leads to removal of impurities from catalyst surface and sputtering effect of the N2 plasma results in formation of pyrite nanorods. The mentioned plasmas were applied separately or in the order of first O2 and then N2, respectively. The catalytic performance of the plasma-modified pyrites (PMPs) is better than the NP for treatment of Reactive Blue 69 (RB69) in heterogeneous sono-Fenton process (US/H2O2/PMP). The NP and the most effective modified pyrite (PMP4) samples were characterized by XRD, FT-IR, SEM, EDX, XPS and BET analyses. The desired amounts were chosen for operational parameters including initial pH (5), H2O2 concentration (1mM), PMP4 dosage (0.6g/L), dye concentration (20mg/L), and ultrasonic power (300W). Moreover, the effects of peroxydisulfate and inorganic salts on the degradation efficiency were investigated. Gas chromatography-mass spectrometry (GC-MS) method was applied to identify the generated intermediates and a plausible pathway was proposed for RB69 degradation. Environmentally-friendly modification of the NP, low amount of leached iron and repeated reusability at milder pH are the significant privileges of the PMP4. The phytotoxicity test using Spirodela polyrrhiza verified the remarkable toxicity removal of the RB69 solution after the treatment process.

Heterogeneous sono-Fenton-like process using nanostructured pyrite prepared by Ar glow discharge plasma for treatment of a textile dye

The plasma-treated pyrite (PTP) nanostructures were prepared from natural pyrite (NP) utilizing argon plasma due to its sputtering and cleaning effects resulting in more active surface area. The NP and PTP were characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Brunauer-Emmett-Teller (BET) and scanning electron microscopy (SEM) methods. The performance of the PTP was greater than NP for treatment of Reactive Red 84 (RR84) by the heterogeneous sono-Fenton process. The optimum amounts of main operational parameters were obtained as PTP of 4 g/L, initial dye concentration of 10 mg/L, pH of 5, and ultrasonic power of 300 W after 120 min of reaction time. Also, the effects of enhancers, and inorganic salts and t-butanol as hydroxyl radical scavengers on the degradation efficiency were investigated. Gas chromatography-mass spectroscopy analysis (GC-MS) was applied for detection of some degradation intermediates. Environmentally friendly plasma modification of the NP, in situ production of H2O2 and OH radicals, low leached iron concentration and repeated reusability at the milder pH are the significant benefits of the PTP utilization.

Development of an empirical kinetic model for sonocatalytic process using neodymium doped zinc oxide nanoparticles

The degradation of Acid Blue 92 (AB92) solution was investigated using a sonocatalytic process with pure and neodymium (Nd)-doped ZnO nanoparticles. The nanoparticles were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). The 1% Nd-doped ZnO nanoparticles demonstrated the highest sonocatalytic activity for the treatment of AB92 (10 mg/L) with a degradation efficiency (DE%) of 86.20% compared to pure ZnO (62.92%) and sonication (45.73%) after 150 min. The results reveal that the sonocatalytic degradation followed pseudo-first order kinetics. An empirical kinetic model was developed using nonlinear regression analysis to estimate the pseudo-first-order rate constant (kapp) as a function of the operational parameters, including the initial dye concentration (5-25 mg/L), doped-catalyst dosage (0.25-1 g/L), ultrasonic power (150-400 W), and dopant content (1-6% mol). The results from the kinetic model were consistent with the experimental results (R(2)=0.990). Moreover, DE% increases with addition of potassium periodate, peroxydisulfate, and hydrogen peroxide as radical enhancers by generating more free radicals. However, the addition of chloride, carbonate, sulfate, and t-butanol as radical scavengers declines DE%. Suitable reusability of the doped sonocatalyst was proven for several consecutive runs. Some of the produced intermediates were also detected by GC-MS analysis. The phytotoxicity test using Lemna minor (L. minor) plant confirmed the considerable toxicity removal of the AB92 solution after treatment process.

Sonocatalytic degradation of Acid Blue 92 using sonochemically prepared samarium doped zinc oxide nanostructures

Pure and Sm-doped ZnO nanoparticles were synthesized applying a simple sonochemical method. The nanocatalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS) techniques which confirmed the successful synthesis of the doped sonocatalyst. The sonocatalytic degradation of Acid Blue 92 (AB92), a model azo dye, was more than that with sonolysis alone. The 6% Sm-doped ZnO nanoparticles had a band gap of 2.8 eV and demonstrated the highest activity. The degradation efficiency (DE%) of sonolysis and sonocatalysis with undoped ZnO and 6% Sm-doped ZnO was 45.73%, 63.9%, and 90.10%, after 150 min of treatment, respectively. Sonocatalytic degradation of AB92 is enhanced with increasing the dopant amount and catalyst dosage and with decreasing the initial AB29 concentration. DE% declines with the addition of radical scavengers such as chloride, carbonate, sulfate, and tert-butanol. However, the addition of enhancers including potassium periodates, peroxydisulfate, and hydrogen peroxide improves DE% by producing more free radicals. The results show adequate reusability of the doped sonocatalyst. Degradation intermediates were recognized by gas chromatography-mass spectrometry (GC-MS). Using nonlinear regression analysis, an empirical kinetic model was developed to estimate the pseudo-first-order constants (kapp) as a function of the main operational parameters, including the initial dye concentration, sonocatalyst dosage, and ultrasonic power.

Production of martite nanoparticles with high energy planetary ball milling for heterogeneous Fenton-like process

Natural martite microparticles (NMMs) were prepared with a high energy planetary ball mill to form a nanocatalyst for a Fenton-like process.

Degrading a mixture of three textile dyes using photo-assisted electrochemical process with BDD anode and O₂-diffusion cathode

In this paper, degradation of a mixture of three azo dyes was studied by the photo-assisted electrochemical process using an O₂-diffusion cathode containing carbon nanotubes and boron-doped diamond (BDD) anode. The concentration of three textile dyes (C.I. Acid Orange 8 (AO8), C.I. Acid Orange 10 (AO10), and C.I. Acid Orange 12 (AO12)) was determined simultaneously despite the severe overlap of their spectra. For this purpose, partial least square (PLS), as a multivariate calibration method, was utilized based on recording UV-Vis spectra during the decolorization process. Moreover, the central composite design was used for the modeling of photo-assisted electrochemical decolorization of the aqueous solutions containing three dyes. The investigated parameters were the initial concentration of three dyes, applied current and reaction time. Analysis of variance (ANOVA) revealed that the obtained regression models match the experimental results well with R (Khataee et al. 2010, Clean-Soil Air Water 38 (1):96-103, 2010) of 0.972, 0.971, and 0.957 for AO8, AO10, and AO12, respectively. Three-dimensional surface and contour plots were applied to describe the relation between experimental conditions and the observed response. The results of TOC analysis confirmed good ability of proposed photo-assisted electrochemical process for degradation and mineralization of textile industry wastewater.

Design equation with mathematical kinetic modeling for photooxidative degradation of C.I. Acid Orange 7 in an annular continuous-flow photoreactor

The decolorization of C.I. Acid Orange 7 (AO7), an anionic monoazo dye of acid class was investigated using UV/H(2)O(2) process in an annular continuous-flow photoreactor (ACFP) as a function of oxidant, dye concentrations, reactor length and volumetric flow rate. The removal efficiency of AO7 was a function of operational parameters and increased with increasing initial concentration of H(2)O(2) but it was low at high flow rate and initial concentration of AO7. Results indicated that the decolorization rate was pseudo-first order kinetic with respect to the dye concentration. A rate equation for decolorization of AO7 was obtained by kinetic modeling. Design equation for ACFP reactor was obtained with combination of kinetic model and rearranged tubular reactor design equation. Design equation was used for predicting concentration of AO7 and also electrical energy per order (E(EO)) at different conditions. The calculated results obtained from design equation and kinetic model were in good agreement with experimental data.

Increasing photoactivity of titanium dioxide immobilized on glass plate with optimization of heat attachment method parameters

In the present work the optimization of heat attachment method for increasing photoactivity of immobilized TiO2 on glass plate was investigated. Results show that sonication time, TiO2 suspension dosage, immobilization temperature, solvent type and immobilization replications are very effective on the photoactivity of immobilized TiO2 on glass plate on the removal of C.I. Acid Red 88 (AR88) and optimizing these parameters increases the photoactivity of immobilized catalyst. In other step, the effect of operational parameters such as light intensity and initial concentration of AR88 on the removal of AR88 was investigated with four times immobilized TiO2 on glass plate. Results show that removal rate decreases with increasing initial concentration of AR88 but increases with increasing UV-light intensity.

Effect of operational parameters on degradation of Malachite Green by ultrasonic irradiation

The aim of the present study was to apply ultrasonic technique to remove Malachite Oxalate Green (MG) from aqueous solution. An ultrasonic bath with frequency of 35 kHz was used to investigate the effect of different operational parameters such as MG concentration, power density, temperature, mechanical agitation and addition of EtOH, 2-PrOH and iso-BuOH. Decolorization of MG follows a first order kinetics and hydroxyl radicals have an important role in degradation of MG. The apparent reaction rate constant (k(ap)) was influenced by variation of operational parameters. The activation energy was 30.95 kJ/mol in temperature range of 21-34 degrees C, suggesting a diffusion-controlled reaction. Alcohols act as hydroxyl radicals scavengers having undesirable contribution. UV-vis spectral change of MG showed hypsochromic shift occurred with increasing sonication time, proposing N-demethylation process of MG.