Removing of carmoisine dye pollutant from contaminated waters by photocatalytic method using a thin film fixed bed reactor.

Recently, the advanced oxidation processes have been used to treat wastewater containing various dye pollutants via various methods of purification. In this work, the removal of the Carmoisine dye from contaminated waters by a photocatalytic method in a recirculating thin-film fixed bed reactor (TFFBR) was investigated and was compared with photolysis. By the surface response method via Minitab software, the experiments were designed in such a way that the effects of different parameters on the process were studied. The effect of various parameters, for instance, pH of solution, reaction time, initial dye concentration, flow rate, hydrogen peroxide concentration on the dye removal efficiency has been investigated. By the screening and optimization stages in the response surface method, the optimal conditions for performing the process were as follows: 45 min of time, pH 2, 13.33 mM of H2O2 concentration, the flow rate of 0.25 Lmin-1, and 10 mg/L of dye concentration. The proficiency of removing color by advanced oxidation is more than 97% under optimum conditions.

Effect of Co60 irradiation on the degradation and mineralization of sulfonated aromatic compounds in aqueous solutions.

As sulfonated aromatic compounds are widely used in industry, they have frequently been detected in aquatic environments. This study evaluated the degradation and mineralization of 2,6-naphthalenedisulfonic acid disodium salt (2,6-NS), sodium 2-naphthalenesulfonate (2-NS), benzenesulfonic acid sodium salt (BS), and 4-vinylbenzene sulfonate sodium (4-VBS) by exposing aqueous solutions of these compounds to Co60 irradiation. The radiolytic degradation of these pollutants was found to follow pseudo-first-order kinetics. The dose required to achieve 90% degradation (D90) of these four sulfonated compounds was 0.480 (2,6-NS), 0.390 (2-NS), 0.194 (BS), and 0.280 kGy (4-VBS). The chemical radiolytic yield (Gvalue) decreased as the absorbed dose increased; moreover, the chemical structures of these compounds affected their radiolytic efficacy. No significant reduction in radiolytic degradation was observed in the presence of inorganic anions (SO42-, Cl-). The radiolytic degradation efficiency was higher when hydrogen peroxide (H2O2, a hydroxyl radical (OH) promoter) was added. The results also showed that combining H2O2, persulfate anions (S2O82-, a sulfate radical anion (SO4-) promoter), or N2O gas (a OH radical promoter) with the sulfonated compounds enhanced the radiolytic mineralization yield and process by reducing the required irradiation energy. In terms of the Co60/O2 system, at an absorbed dose of 12 kGy, the total organic carbon (TOC) removal efficiency was almost 70%, resulting in the observed release of SO42- anions. In addition, the concentration of dissolved oxygen decreased and the pH was lowered. Based on these results, irradiation with Co60 was found to be a useful tool to remedy wastewater containing sulfonated aromatic compounds.

Photocatalytic performance of TiO2/Clinoptilolite: Comparison study in suspension and hybrid photocatalytic membrane reactor.

Comparison studies in suspension and hybrid photocatalytic membrane reactor (HPMR) system was investigated by using Reactive Black 5 (RB5) as target pollutant under UVA light irradiation. To achieve this aim, hybrid TiO2/clinoptilolite (TCP) photocatalyst powder was prepared by solid-state dispersion (SSD) methods and embedded at the outer layer of dual layer hollow fiber (DLHF) membranes fabricated via single step co-spinning process. TiO2 and CP photocatalyst were also used as control samples. The samples were characterized by Scanning Electron Microscopy (SEM), Energy Dispersion of X-ray (EDX), X-ray diffraction (XRD) and Brunauer-Emmett-Teller (BET) analyses. The result shows that TCP was actively functioned as photocatalyst in suspension system and 86% of RB5 photocatalytic degradation achieved within 60 min; however the additional step is required to separate the catalyst with treated water. In the HPMR system, even though the RB5 photocatalytic degradation exhibits lower efficiency however the rejection of RB5 was achieved up to 95% under UV irradiation due to the properties of photocatalytic membranes. The well dispersed of TCP at the outer layer of DLHF membrane have improved the surface affinity of DL-TCP membrane towards water, exhibit the highest pure water flux of 41.72 L/m2.h compared to DL-TiO2 membrane. In general, CP can help on improving photocatalytic activity of TiO2 in suspension, increased the RB5 removal and the permeability of DLHF membrane in HPMR system as well.

Photosensitization of CuI - the role of visible light induced CuI→ CuII transition in photocatalytic degradation of organic pollutants and inactivation of microorganisms.

Bare and photosensitized copper iodides were tested in photocatalysed degradation of an organic dye (Acid Red 1) and inactivation of fungi (Saccharomyces cerevisiae). CuI, with the band gap energy slightly lower than that of TiO2, appeared to be highly efficient in these processes. Sensitization of copper iodide was achieved by surface modification with [Cu(SCN)2(phen)2]. The photosensitization mechanism encompasses a metal to metal charge transfer, CuI→ CuII. The applied photosensitizer binds to CuI through thiocyanate ligands resulting in the formation of an active CuII/CuI hybrid photocatalyst ([CuII(SCN)2(phen)2]@CuII). Its absorption edge is red shifted towards a lower energy when compared with bare CuI, resulting in enhanced visible light induced photocatalytic activity. The studied materials appeared to be photoactive in current generation, degradation of organic compounds and inactivation of fungi.

Enhanced photocatalytic hydrogen production from aqueous sulfide/sulfite solution by ZnO0.6S0.4 with simultaneous dye degradation under visible-light irradiation.

Photocatalytic hydrogen (H2) production was performed by visible-light-driven (VLD) ternary photocatalyst, zinc oxysulfide (ZnO0.6S0.4) in the presence of sulfide/sulfite (S22-/SO32-) sacrificing system, with simultaneous azo-dye Reactive Violet 5 (RV5) degradation. Enhancement in both RV5 degradation and H2 production was achieved, with the promotion of H2 production after decolorization of RV5. The effect of initial concentration of RV5 was found to be influential on the enhancement of H2 during the simultaneous processes, with a maximum of 110% increase of H2 produced. The mechanism of the simultaneous system was investigated by scavenger study and intermediate analysis, including Fourier transform-infrared (FTIR) spectroscopy and total organic carbon (TOC) analysis. It was confirmed that the partial degradation of RV5 and presence of dynamic organic intermediates contributed to the enhancement in H2 production. The present study revealed the feasibility of developing VLD photocatalysis as a sustainable and environmentally friendly technology for concurrent organic pollutant degradation with energy generation.

Adsorption and photocatalysis of nanocrystalline TiO2 particles for Reactive Red 195 removal: effect of humic acids, anions and scavengers.

In the present study, the coupling of adsorption capacity and photocatalytic efficiency of two different industrially produced titania catalysts was investigated and compared. The azo dye Reactive Red 195 was selected as a model compound. The tested catalysts, PK-10 and PK-180, exhibited different adsorption capacities due to their significant difference in their specific surface, but both have proven to be effective photocatalysts for photodegradation of the studied dye. PK-10 exhibited strong adsorption of the studied dye due to its high specific surface area, while the second studied catalyst, PK-180, demonstrated negligible adsorption of Reactive Red 195. The effect of the pH, the concentration of the catalyst and the initial concentration of the dye appear to affect the photocatalytic rate. The effect of the presence of humic acids and inorganic ions was also examined, while the contribution of various reactive species was indirectly evaluated through the addition of various scavengers. To evaluate the extent of mineralisation of the studied dye, total organic carbon (TOC) measurements during the experiment were also conducted. Besides total colour removal, evident reduction of TOC was also achieved using both catalysts.

Photocatalytic degradation of Reactive Red 195 using anatase/brookite TiO2 mesoporous nanoparticles: optimization using response surface methodology (RSM) and kinetics studies.

In the present study, the photocatalytic degradation of Reactive Red 195 (RR195) from aqueous samples under UV-A irradiation by using anatase/brookite TiO2 (A/B TiO2) mesoporous nanoparticles has been investigated. Batch experiments were conducted to study the effects of the main parameters affecting the photocatalytic process. The effects and interactions of most influenced parameters, such as substrate concentration and catalyst load, were evaluated and optimized by using a central composite design model and a response surface methodology. The results indicated that the dye degradation efficiency in the experimental domain investigated was mainly affected by the tested variables, as well as their interaction effects. Analysis of variance showed a high coefficient of determination value (R(2) = 0.9947), thus ensuring a satisfactory adjustment of the first-order regression model (2FI model) with the experimental data. The obtained results also indicate that catalyst loading plays an important role in determining the removal efficiency of RR195 attributable to both photodegradation and adsorption process. Under optimal conditions (initial dye concentration (50 mg/L) and catalyst loading (2,000 mg/L), A/B TiO2 showed similar removal efficiency compared to that of commercial titania (Degussa P25). Also, at these conditions, complete degradation of RR195 can be achieved by both catalysts within 15 min under UV-A irradiation. The experiments demonstrated that dye removal on the prepared A/B TiO2 was facilitated by the synergistic effects between adsorption and photocatalysis. Photocatalytic mineralization of RR195 was monitored by total organic carbon. The recycling experiments confirmed the stability of the catalyst.

Evaluation of the antifouling and photocatalytic properties of poly(vinylidene fluoride) plasma-grafted poly(acrylic acid) membrane with self-assembled TiO2.

Immobilization of TiO(2) is a promising approach that produces antifouling and photocatalytic membranes that could help advance wastewater treatment and re-use processes. In this study, poly(acrylic acid) (PAA) was plasma-grafted on commercial poly(vinylidene fluoride) (PVDF) to introduce functional groups on the membrane surface that can support the nanoparticles. It was found that plasma treatment at 100 W for 120 s followed by liquid grafting with 70% aqueous AA at 60°C for 2h maximized the number of TiO(2) binding sites. Membrane hydrophilicity was tremendously enhanced by the self-assembly of TiO(2), following a direct proportionality to TiO(2) loading. The membrane with 0.5% TiO(2) loading maintained the highest pure water flux and the best protein antifouling property. UV irradiation triggered the photodegradation of strongly bound foulants, but at least 1.5% TiO(2) and 30 min cumulative irradiation were necessary to completely recover the membrane's original performance. The TiO(2)-modified membranes removed 30-42% of 50mg/l aqueous Reactive Black 5 (RB5) dye. The fabricated membranes demonstrate huge potential for use in membrane reactors with high hydrophilicity, fouling mitigation, and photocatalytic capability.

Heterogeneous photo-catalysis system for the degradation of azo dye Reactive Black 5 (RB5).

This study investigated a heterogeneous photo-catalysis system by introducing a novel brick supported iron oxide (denoted as B1) for the heterogeneous photoassisted degradation of Reactive Black 5 (RB5) at pH value from 3 to 7 in a three-phase (gas-liquid-solid) fluidized bed reactor (3P-FBR). Scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray powder diffraction (XRD) and N(2) adsorption/desorption were used to characterize the B1 catalyst. The in situ formation of hydrogen peroxide and the depletion of oxalic acid by photochemical cycle of Fe(III)-oxalate complex under UVA light (λ = 365 nm) were studied. The effects of the solution pH and the concentration of oxalic acid on the degradation of RB5 are elucidated. About 90% decolourization was measured and 80% of the total organic carbon (TOC) was eliminated at pH 5.0 after 120 min for 20 mg/L RB5 in presence of 10 g/L B1 catalyst, 30 mg/L oxalic acid under 15 W UVA light. A mechanism for the photocatalytic degradation of RB5 over B1 catalyst is proposed.

Influence of operational parameters on photocatalytic degradation of a genotoxic azo dye Acid Violet 7 in aqueous ZnO suspensions.

The photocatalytic degradation of a genotoxic azo dye Acid Violet 7 (AV 7) using ZnO as a photocatalyst in aqueous solution has been investigated under UV irradiation. The degradation is higher with UV/ZnO process than with UV/TiO(2)-P25 process at pH 9. The effects of different parameters such as pH of the solution, amount of catalyst, initial dye concentration and the influence of cations, anions and oxidants on photodegradation of AV 7 were analyzed. Addition of oxidants except H(2)O(2) has no significant effect on degradation. The degradation of AV 7 follows pseudo-first order kinetics according to the Langmuir-Hinshelwood model. The degradation of AV 7 has also been confirmed by COD and CV measurements.

Decolorization of reactive dye using a photo-ferrioxalate system with brick grain-supported iron oxide.

The photocatalytic activity of a brick grain-supported iron oxide (denoted as B1) was tested for its activity to degrade Reactive Black 5 (RB5) in the presence of oxalic acid. B1 was obtained as a solid waste from a wastewater treatment plant, and characterized using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray powder diffraction (XRD) and N(2) adsorption/desorption isotherm analyses. The decolorization experiments were performed in a fluidized bed reactor with aeration under UV-A irradiation (λ = 365 nm). The effects of various factors such as solution pH, concentration of oxalic acid and dissolved oxygen on the decolorization of RB5 were evaluated considering the contributions of adsorption and photo-catalytic degradation. The role of dissolved iron in the removal of RB5 and the stability of B1 were also examined. In addition, the removal of TOC during the photo-catalytic reaction was monitored.

Investigation on solar photocatalytic degradation of various dyes in the presence of Er(3+):YAlO(3)/ZnO-TiO(2) composite.

In this work, Er(3+):YAlO(3)/ZnO-TiO(2) and ZnO-TiO(2) composites were prepared by the ultrasonic dispersion and liquid boiling method. In succession, they were then characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Acid red B as a model dye compound was degraded under solar light irradiation to evaluate the photocatalytic activities of the Er(3+):YAlO(3)/ZnO-TiO(2) and ZnO-TiO(2) composites. We found that the photocatalytic activity of ZnO-TiO(2) composite can be enhanced by adding an appropriate amount of Er(3+):YAlO(3). We reviewed influencing factors, such as Er(3+):YAlO(3) content, heat-treated temperature and heat-treated time on the photocatalytic activity of the Er(3+):YAlO(3)/ZnO-TiO(2) composites. In addition, the effects of solar light irradiation time, dye initial concentration, Er(3+):YAlO(3)/ZnO-TiO(2) amount and solution acidity on the photocatalytic degradation of acid red B dye in aqueous solution were investigated in detail. Simultaneously, the degradation and comparison of other dyes such as methyl orange (MO), rhodamine B (RM-B), azo fuchsine (AF), congo red (CG-R) and methyl blue (MB) were also reviewed. In addition, we attempted to explore both the principle of possible excitation of Er(3+):YAlO(3)/ZnO-TiO(2) under solar light irradiation and the mechanism of photocatalytic degradation.

Study the self cleaning, antibacterial and photocatalytic properties of TiO2 entrapped PVDF membranes.

The modified PVDF membranes were prepared by adding different amounts of TiO(2) particles (0-4 wt.%) into the casting solution. The TiO(2) entrapped PVDF membranes (0-4% PVDF/TiO(2)) were tested for its antibacterial property by using Escherichia Coliform (E. Coli), photoactive property using Reactive Black 5 (RB5) dye and self cleaning (antifouling) properties by fouling using 1% BSA solution. Results showed that TiO(2) addition significantly affects the pore size and hydrophilicity of the PVDF/TiO(2) membrane. This also improves the flux and permeability of modified PVDF/TiO(2) membrane. The results of antibacterial study showed that the composite PVDF/TiO(2) membrane removes E. Coli at a very faster rate than neat PVDF membrane and membrane with 4% TiO(2) possess highest antibacterial property. The RB5 dye removal using PVDF/TiO(2) occurs under UV by photolysis and photocatalysis mechanisms. The rate of RB5 dye color removal was faster as compared to the rate of aromatic ring structure. The resistance study showed 2% TiO(2) membrane having lower fouling resistance as compared to others. The fouling resistance caused by loosely bound protein (R(c)) was lower than the strongly bound protein (R(f)). The performance of fouled membranes flux and TMP can be recovered to its initial value by simple UV treatment.

Effects of TiO2 dosage, pH and temperature on decolorization of C.I. Reactive Red 2 in a UV/US/TiO2 system.

This study elucidates the decolorization of C.I. Reactive Red 2 (RR2) in ultrasound (US), US/TiO(2), ultraviolet (UV)/TiO(2) and UV/US/TiO(2) systems. The effects of TiO(2) dosage, pH and temperature on RR2 decolorization were determined in a UV/US/TiO(2) system. The pseudo-first-order decolorization rate constants of 0.5, 1 and 2g/l TiO(2) in the UV/US/TiO(2) system were 0.45, 0.57 and 0.94 h(-1), respectively. In the UV/US/TiO(2) system, the decolorization rate of RR2 declines as pH increases, and increases as temperature increasing. At pH 7, the decolorization rates followed the order of UV/US/TiO(2) (0.94 h(-1))>UV/TiO(2) (0.85h(-1))>US/TiO(2) (0.25 h(-1))>US. The activation energy of the UV/US/TiO(2) system at pHs of 4, 7 and 10 was 6.58, 11.62 and 21.32kJ/mol, respectively. Experimental results suggest that the RR2 decolorization in the UV/US/TiO(2) system was a diffusion-controlled reaction.

Photodegradation of C.I. Reactive Red 2 in UV/TiO2-based systems: effects of ultrasound irradiation.

This investigation elucidated the decolorization of C.I. Reactive Red 2 (RR2) in US/TiO(2), UV/TiO(2) and UV/US/TiO(2) systems and evaluated the effect of ultrasound (US) irradiation in photocatalysis. The effects of RR2 concentration, temperature and the addition of NaCl, Na(2)S(2)O(8) and radical scavenger were determined. The decolorization reactions obeyed the pseudo-first-order kinetics in all tested systems. In US-related systems, the decolorization rate of RR2 declines as RR2 concentration increases. At pH 7, the decolorization rates followed the order UV/US/TiO(2) (0.94 h(-1))>UV/TiO(2) (0.85 h(-1))>US/TiO(2) (0.25 h(-1)). The promotion efficiencies of adding NaCl in US/TiO(2), UV/TiO(2) and UV/US/TiO(2) systems were 16%, 18% and 29%, respectively. The decolorization rate increased with the temperature; additionally, the decolorization rate in UV/US/TiO(2)/Na(2)S(2)O(8) exceeded that in UV/US/TiO(2). The inhibition of RR2 decolorization by adding 1-butanol reveals that the primary decolorization pathway involves hydroxyl radicals, and that direct oxidation by photogenerated holes is probably important in the UV/TiO(2)-based system. After 120 min of the reaction, the TOC degradation efficiencies of UV/TiO(2) and UV/US/TiO(2) systems were 47% and 63%, respectively.

Photodegration of C.I. Reactive Red 2 by platinized titanium dioxide.

The photodegradation of color index (C.I.) Reactive Red 2 (RR2) using UV/TiO(2), UV/TiO(2)/polyethyleneglycol (PEG) and UV/TiO(2)/PEG/Pt systems was evaluated. The photocatalysts were produced via sol-gel method. The surface morphology of catalysts was observed by scanning electron microscopy. The concentration of RR2, sulfate release and total organic carbon were measured during the photodegradation of RR2. In 254 nm irradiation, the decolorization rate constants of UV/TiO(2), UV/TiO(2)/PEG and UV/TiO(2)/PEG/Pt systems were 1.69, 1.64 and 1.96 h(-1), respectively. Those for 365 nm irradiation were 0.54, 0.64 and 0.74 h(-1), respectively, and those for 410 nm irradiation were 0.34, 0.64 and 0.73 h(-1), respectively.

Ultrasonic dyeing of cationized cotton fabric with natural dye. Part 1: cationization of cotton using Solfix E.

The dyeing of cationized cotton fabric with Solfix E using colouring matter extracted from Cochineal dye has been studied using both conventional and ultrasonic techniques. Factors affecting dye extraction such as ultrasound power, particle size, extraction temperature and time were studied. The results indicated that the extraction by ultrasound at 300 W was more effective at lower temperature and time than conventional extraction. The effect of various factors of dye bath such as pH, salt concentration, ultrasound power, dyeing time and temperature were investigated. The colour strength values obtained were found to be higher with ultrasound than with conventional techniques. The results of fastness properties of the dyed fabrics were fair to good. The scanning electron microscope (SEM) images of the morphological and X-ray analyzes were measured for cationized cotton fabrics dyed with both conventional and ultrasound methods, thus showing the sonicator efficiency.

Rapid decolorization and mineralization of simulated textile wastewater in a heterogeneous Fenton like system with/without external energy.

A novel Fenton like system, employing Zero Valent Iron (ZVI) and air bubbling, was developed to treat a simulated textile wastewater containing azo dye Reactive Black 5 (RB5) and Ethylenediaminetetraacetic acid (EDTA). By dioxygen activation, H(2)O(2) was self-produced continuously in the system through a series of iron-EDTA ligands reactions. After 3h reaction, the removal rates of RB5, EDTA, Total Organic Carbon (TOC), and Chemical Oxygen Demand (COD) were 100%, 96.5%, 68.6% and 92.2%, respectively. The effects of pH, atmosphere as well as the initial concentration of RB5, EDTA and ZVI were also investigated. Two types of external energy-Ultrasound (US) and Ultraviolet (UV) were introduced into the Fenton like system, respectively. The effect of these external energies on the degradation of the wastewater was assessed. It was demonstrated that US presented significant synergistic effect on the degradation and mineralization of both RB5 and EDTA, while UV could not achieve any improvement.

Study on photocatalytic performance and degradation kinetics of X-3B with lanthanide-modified titanium dioxide under solar and UV illumination.

The present work was focused on photocatalytic oxidation of the model molecule reactive brilliant X-3B by lanthanide-modified TiO(2) samples under artificial solar and UV irradiation. Experimental results showed that the TiO(2) samples doping with lanthanide (Ce and Gd) could greatly enhance the activity of pure TiO(2), and could extend the absorption range to visible region. The optimum doping amount was 0.2 and 0.5at.% for Ce- and Gd-doped TiO(2) particles, respectively. The degradation kinetics of X-3B on Ce-doped TiO(2), Gd-doped TiO(2), and pure TiO(2) were studied as well. The results exhibited that the degradation of X-3B on all the samples were in accordance with the first-order model. The trend of apparent reaction rate constants k(app) was as follows, Gd-doped TiO(2)>Ce-doped TiO(2)>pure TiO(2), under solar illumination. Scatchard plot analysis was used to evaluate the adsorption phenomena of as-prepared samples, and it indicated that lanthanide doping can improve the efficiency of interfacial adsorption of TiO(2) samples. The trend was the same as that of photocatalytic activity.

Preparation of Fe-doped mixed crystal TiO2 catalyst and investigation of its sonocatalytic activity during degradation of azo fuchsine under ultrasonic irradiation.

In this work, Fe-doped mixed crystal TiO2 powder as sonocatalyst was prepared by the sol-gel method and heat treatment, and a novel method combined with ultrasonic irradiation was propounded to degrade the organic polluted water. First, the Fe-doped mixed crystal TiO2 powder was characterized by TG-DTA, XRD, and TEM techniques. Ultrasound was used as the irradiation source and the azo fuchsine was chose as the model compound. Then a series of degradation experiments was carried out in the presence of Fe-doped mixed crystal TiO2 powder. Also, the degradation process and some influencing factors, such as irradiation time, doping Fe3+ ion content, added amount of catalyst, and initial concentration of azo fuchsine solution, on the degradation were investigated by UV-vis spectra, ion chromatography, and HPLC. Through the degradation of azo fuchsine, it was found that the combination of ultrasonic irradiation and Fe-doped mixed crystal TiO2 powder can completely degrade the azo fuchsine in aqueous solution. Because of the good degradation efficiency, this method may be an advisable choice for the treatments of non- or low-transparent wastewaters in the future.