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Ni, Ce, and Ta modified Ti/SnO2–Sb2O5–RuO2 anodes were first prepared by thermal decomposition strategy and applied for Orange G degradation to explore the effect of Ni, Ce, and Ta modification on electrocatalytic property. The Ta modified anode showed the highest ·OH generation capability and the lowest charge transfer resistance among all samples, conducive to electrocatalytic degradation of Orange G. Besides, the Ta modified anode shows more cracks than Ni and Ce modified anodes, which is expected to create more specific surface areas and more exposed active sites for Orange G degradation. The degradation efficiency and the total organic carbon (TOC) removal rate increased in the order Ru

The defiance of this study was to explore the potential of alginate/MIL-101 beads containing Fe3O4 nanoparticles as a catalyst for the reduction of dyes. The Fe3O4@MIL-101 magnetic composite was obtained by the mechanical method and then encapsulated using calcium alginate (CA) as a crosslinked matrix. The Fe3O4(X)@MIL-101/CA composites beads at different content (X) of Fe3O4 nanoparticles were evaluated for the catalytic reduction of methylene blue (MB) and orange G (OG). The aerogel beads have completed the MB dye reduction after 7 min with a rate constant of 0.962 min–1. This strong activity is assigned to the synergistic effect between Cr containing MIL-101 the Fe3O4 particles and the hydrides formed on the catalyst surface. The obtained optimal conditions of MB dye reduction were used for the reduction of OG dye in simple and binary system.The best catalyst M(1)@MIL-101/CA showed a high affinity via MB dye in a binary system. Then was easily recovered by an external magnetic field and reused for 4 cycles. On the other hand, the time of the catalytic activity clearly increased in its 4th reuse in the reduction of MB dye but did not affect the efficiency of catalytic reduction.

In this study, tungsten trioxide/titanium dioxide (WO3–TiO2) nanohybrid structures were prepared using a facile hydrothermal method. The nanosheets-like morphology was achieved for the prepared WO3–TiO2 nanohybrid that were confirmed by scanning electron microscopy. Provided X-ray photoelectron spectroscopy results also confirm the element existence and surface composition of the nanohybrid structure. The optical properties of the WO3–TiO2 nanohybrid were verified using UV–Visible diffuse reflectance spectroscopy (UV–Vis DRS) and photoluminescence spectroscopy. The UV–Vis DRS results indicated that the absorption edge for the WO3–TiO2 nanohybrid found a red shift towards the visible region due to the reduced bandgap (2.83 eV). The photocatalytic activity of the as-prepared WO3–TiO2 nanohybrid was evaluated by the photocatalytic degradation of Orange G dye in wastewaters under visible light. 94% Orange G dye was degraded in 210 min at neutral pH in the presence of WO3–TiO2 nanohybrid, which indicates the enhanced photocatalytic activity. The photo-luminescence technique has also confirmed the formation of –OH radicals during photodegradation by utilizing terephthalic acid as a probe molecule. These results indicate that the prepared nanohybrid material is a simple, low-cost, and efficient photocatalyst for the degradation of pollutants in wastewater treatment applications.

In this work, MgO nanoparticles were synthesized via the combustion method using glutamine and L-arginine as fuels for the first time. Also, the synthesized MgO products were identified utilizing FT-IR, XRD, HR-TEM, FE-SEM, UV–Vis, and PL techniques. Besides, the synthesized MgO samples were used for the photochemical degradation of orange G dye as well as biological activity against some bacterial (Staphylococcus aureus and Escherichia coli) and fungal (Candida albicans and Aspergillus flavus) strains. The XRD confirmed that the average crystallite size of MgO products, which were produced using glutamine and L-arginine fuels, is 35.19 and 26.45 nm, respectively. Also, The FE-SEM images confirmed that the MgO products, which were produced using glutamine and L-arginine fuels, is comprised of irregular and flaky shapes with an average size of 13.16 and 9.02 µm, respectively. Additionally, the greatest percent of degradation of orange G dye was 92.30 and 96.60% after 120 min using the MgO samples which were synthesized using glutamine and L-arginine fuels, respectively. Furthermore, the MgO samples show moderate biological activity against bacterial strains whereas they show no biological activity against fungal strains.

This study investigated the removal of Orange-G dye (OG) using a hybrid adsorbent developed from Opuntia Ficus Indica (OFI) activated with NaOH (OFI-A) were reinforced by polyaniline (PANI) by a fast chemical method. PANI@OFI-A and OFI-A adsorbents having different physicochemical characteristics as FTIR, XRD, TGA, SEM and nitrogen adsorption isotherms are used to analyze the structure of the resulting materials. Besides, the effect of several parameters including contact time (0–24 h), pH (1–12) and initial OG concentration (300–1000 mg L−1) were evaluated on the adsorption efficiency. The modified OFI-A by PANI was employed as an excellent adsorbent for the removing of OG from aqueous solutions. The results indicated that OG adsorption basically relies on adsorbing time, solution pH and initial OG concentration. Furthermore, the PANI@OFI-A also shows a high adsorption capacity of 303.94 mg g−1 for OG, quite higher than that of OFI-A (8.04 mg g−1). The kinetic results were adapted well to the pseudo second order kinetic model resemble chemisorption by two samples prepared. Based on the obtained results, the PANI@OFI-A has potential to be used in sensitive environment that need to completely remove OG.

Mesoporous magnesium oxide–graphene oxide composite (MGC) has been synthesized using a facile post-immobilization method by mixing pre-synthesized magnesium oxide (MgO) with graphene oxide (GO). MgO used for fabrication of the composite has been synthesized using an environment-friendly method involving gelatin as a template. XRD, Raman and EDX analyses have confirmed the presence of MgO and GO in the composite. FTIR and SEM analyses of synthesized MGC have further elucidated the surface functionalities and morphology, respectively. Using N2 adsorption–desorption isotherm, BET surface area of MGC has been calculated to be 55.9 m2 g−1 and BJH analysis confirmed the mesoporous nature of MGC. The application of synthesized MGC as a selective adsorbent for various toxic anionic dyes has been explored. Batch adsorption studies have been carried out to investigate the influence of different adsorption parameters on the adsorption of two anionic dyes: indigo carmine (IC) and orange G (OG). The maximum adsorption capacities exhibited by MGC for IC and OG are 252.4 and 24.5 mg g−1, respectively. Plausible mechanism of dye adsorption has been explained in detail using FTIR analysis. In a mixture of cationic and anionic dyes, MGC selectively adsorbs anionic dyes with high separation factors, while in binary mixtures of anionic dyes, both dyes are adsorbed efficiently. Thus, MGC has been shown to be a potential adsorbent for the selective removal of anionic dyes from wastewater.

The main objective of this research was to study the catalytic activation of two different oxidants (potassium persulfate, PS and peroxymonosulfate, PMS) employing sulfate-based Advanced Oxidation Processes (AOPs). For this purpose, heterogeneous copper and cobalt catalysts were synthesized supported on MCM-41 mesoporous material. These catalysts were characterized by means of Atomic Absorption Spectroscopy (AA), X-ray diffraction (XRD), and Transmission Electron Microscopy (TEM). The metal charge of the catalysts ranged from 5% to 18%. The mesoporous arrangement was held after the metal loading and calcination, as shown by XRD patterns and TEM micrographs. The catalytic degradation of Orange G azo dye (Orange G: OG, disodium 7-hydroxy-8-[(E)-phenyldiazenyl]-1,3-naphthalenedisulfonate) was analysed, and the catalyst activities were determined in a batch reactor. The combination of PMS and higher metal-content Co-supported catalyst attained the best efficiency. In these conditions, the complete decolourization (100%) of the dye was achieved in the first minutes of reaction, while its mineralization reached after 4 h was 49%. Additionally, the catalytic activity of the Co/PMS system (a measure of the catalyst’s reusability) remained constant after three cycles of usage. Fil: Schlichter, Sofia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Química del Sur. Universidad Nacional del Sur. Departamento de Química. Instituto de Química del Sur; Argentina Fil: Dennehy, Mariana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Química del Sur. Universidad Nacional del Sur. Departamento de Química. Instituto de Química del Sur; Argentina Fil: Alvarez, Mariana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Química del Sur. Universidad Nacional del Sur. Departamento de Química. Instituto de Química del Sur; Argentina

A BiPO4/g-C3N4 photoactive system has been prepared by means of a practical ultrasound-assisted procedure in aqueous medium. The obtained hybrid composites were widely characterized by X-ray powder diffraction, Fourier-transform infrared spectroscopy, UV–vis diffuse reflectance spectroscopy, scanning electron microscopy and N2 adsorption–desorption measurements. The photocatalytic features of the samples were examined through the degradation of orange G dye and ciprofloxacin antibiotic, where the higher photocatalytic performance for the degradation of both pollutants was achieved for the g-C3N4 with 1 wt% loading of BiPO4 (1-BiPO4 sample). To explain this outstanding performance, a possible mechanism involving the delocalization of the photogenerated charge carriers in the BiPO4/g-C3N4 system is discussed. Also, total organic carbon analysis and photocatalytic tests with radical scavengers were performed to elucidate the importance of the reactive oxidizing species during the photocatalytic process.

In this work, bismuth phosphate photocatalysts have been obtained via co-precipitation and solid-state methods. The synthesized samples were calcinated at uniform temperature and were analyzed by scanning electron microscopy, X-ray diffraction, energy dispersive X-ray analysis and Raman spectroscopy. The photocatalytic activity of the synthesized samples was evaluated by the degradation of anionic and cationic organic dyes [Rhodamine B and Orange G] in aqueous medium under UV light irradiation (λ > 254 nm). The results showed that the synthesis technique considerably affects the morphology, structure, photoluminescent and photocatalytic process properties. Indeed, samples obtained through solid-state reaction approach exhibited higher catalytic activity in comparison with those prepared via co-precipitation method. Photoluminescence experiments revealed unexpected emissions in the green-orange range, with the presence of two bands characteristic of the two monoclinic phases of BiPO4.

A multitude of industrial processes are catalyzed by two or more enzymes working together in a cascade way. However, designing efficient enzymatic cascade reactions is still a challenge. In this work, a TiO2 thin film with mesoporous pores was prepared and used as carrier for co-immobilization of chloroperoxidase (CPO) and glucose peroxidase (GOx). By adjusting the dosage of hexadecyltrimethylammonium bromide (CTAB) and the ratio of the two enzymes, CPO and GOx were well distributed and positional orientated to their own appropriate pores to form an ordered “occupation” based on a “feet in right shoes” effect. Moreover, when the pore size was controlled around 12 nm, the enzymes aggregation was inhibited so as to avoid the decrease of activity of enzyme; The catalytic performance of TiO2–GOx and CPO composites was evaluated by the application of decolorization of Orange G dye in a cascaded manner. The oxidant H2O2 needed by CPO is generated in situ through glucose oxidation by GOx. Upon co-immobilization of CPO and GOx on the same carrier, a large increase in the initial catalytic efficiency was detected when compared to an equimolar mixture of the free enzymes, which was four times greater. Moreover, the affinity of the enzyme toward substrate binding was improved according to the kinetic assay. The thermal stability of TiO2–GOx and CPO composites were greatly improved than free enzymes. The TiO2–GOx and CPO composites can be easily separated from the reaction media which facilitate its recycle use.

In this work, the capacity of Trametes polyzona in degrading three textile dyes (amaranth, denim blue, and orange G) to three different concentrations (100, 150, and 200 mg/L) was evaluated. Two growth conditions were tested; in the first condition, the fungus was grown in a defined minimal medium with an initial glucose concentration of 10 g/L and adding the different concentrations of each of the dyes, and in the second condition, the same minimum medium was used but with a concentration of 3 g/L of glucose, after 7 days of fungus growth, at which time the glucose in the medium was completely consumed; each of the dyes was added at the three different concentrations. T. polyzona was able to decolorize the three dyes at the concentrations tested and a 200% increase in the decolorization rate was observed when the medium lacks glucose. Enzymatic activities of laccase, lignin peroxidase, and manganese peroxidase were detected; the enzyme laccase was the one that presented the greatest enzymatic activities in all the media tested. A simultaneous process of adsorption by the mycelium and degradation of extracellular enzymes was observed. A decrease of more than 90% COD was observed and the effluent generated showed no algal growth toxicity.

Carbon nitride is a commonly used photocatalyst for the degradation of organic dyes. However, the high rate of charge carrier recombination limit the photocatalytic activity. Here, a series of porous carbon nitride with AgBr nanoparticles (CN/AgBr) heterojunction are fabricated by thermal condensation of urea with the water and an in situ ion exchange approach. The porous structure of CN is beneficial to improve the photocatalytic performance and enhance the absorption of light energy, which is due to the multiple reflections of light within the macropores layered structure. And the incorporation of AgBr inhibit the charge carriers recombination due to the formation of heterojunction with CN. Furthermore, the photocatalytic activity of all samples are evaluated and display excellent activity in the degradation of orange G under visible light illumination. Among them, the CN/AgBr30 perform the most degradation efficiency, with a removal ratio of up to 92% within 10 min, which is attributed to efficient charge separation and transfer. At last, a photocatalytic mechanism is put forward and explained based on the ESR experiments, free radical and hole scavenging experiments and transient response photocurrent results.

Advanced oxidation processes offer effective solutions in treating wastewater from various industries. The process of alkali-activated hydrogen peroxide (H2O2) was superior for the treatment of alkaline dye wastewater because no additional reagents were required except H2O2. However, an important and interesting phenomenon had been observed that the primary reactive species were found different for degrading organic pollutants with the process of alkali-activated H2O2. Azo dye of Orange G (OG) and triphenylmethane dye of Rhodamine B (RhB) were chosen as the target organic pollutants. The influences of various parameters on OG and RhB degradation by alkali-activated H2O2 were evaluated. Furthermore, different scavengers, including ascorbic acid, methanol, t-butanol, isopropyl alcohol, furfuryl alcohol, and nitro blue tetrazolium, have been tested to identify the active species involved in dye degradation, and it was found that O2·- was mainly responsible for degrading OG, while HO2- anion was the primary oxidant for degrading RhB.

Textile effluents containing synthetic dyes are one of the most important sources of water pollution. Several dyes are toxic to the aquatic life and indirectly to humans, and therefore should be treated before rejection to natural water streams. As conventional wastewater treatment systems remain inefficient for treatment of these recalcitrant pollutants, the use of advanced oxidation processed is required. The degradation of the Orange G dye was studied using the photo-Fenton process. Results showed that the use of experimental kinetics rate constants to optimize the ratio R = [H2O2]/[Fe3+] constitutes a suitable way to minimize the occurrence of side reactions. An optimal molar ratio R of 13.8 was found allowing complete degradation of Orange G in 4 min and 93.41% total organic carbon (TOC) removal in 180 min. Based on detected intermediates and end-products, a plausible degradation mechanism of Orange G dye is proposed. Therefore, we demonstrated that the photo-Fenton process can be applied efficiently to the removal of toxic/persistent organic pollutants such as synthetic dyes from water.

Titanium dioxide (TiO2) is one among the best photocatalysts used in commercial applications. However, its large intrinsic bandgap (~ 3.23 eV) limits its photocatalytic application only to the ultraviolet (UV) region that is only 4% of the solar spectrum. The recombination of photogenerated electron–hole pairs reduces the quantum efficiency and photocatalytic activity. The visible region allows us to use 43% of the solar spectrum. Therefore, to extend the photocatalytic activity of TiO2 to visible light spectrum, its bandgap must be decreased that suppresses the recombination reactions. This can be achieved by coupling of semiconductor metal oxides having different bandgap values with TiO2 for the efficient use in the visible light region. In this work, magnetite (Fe3O4) nanoparticles were synthesized by a modified co-precipitation method, and it was used to prepare a TiO2/Fe3O4 nanocomposite with three different ratios (0.2/0.8, 0.5/0.5, and 0.8/0.2). The obtained nanocomposite was characterized using X-ray diffraction, Raman and ultraviolet–visible spectroscopies, and scanning electron microscopy fitted with scanning transmission electron microscopy to understand the various properties such as crystallinity, optical properties, and morphology of the nanocomposites. We noticed that the crystallite size of TiO2 in the nanocomposite, as well as the bandgap energy of the nanocomposite, decreases with the increasing Fe3O4 content. The degradation of Orange G with Fe3O4, TiO2, and nanocomposites with three different ratios was studied in a solar simulator under different exposure times. Our studies show that (TiO2)0.2(Fe3O4)0.8 nanocomposite having small crystallite size and bandgap gives the best photocatalytic activity under visible light among other ratios.

Acacia gum–Fe0Np–silica nanocomposite (GFS1) has been crafted through sol–gel technique using a two-step process that involved the reduction of iron salt to zerovalent iron nanoparticles (Fe0Nps) followed by their impregnation within Acacia gum–silica matrix. GFS1 was characterized using Fourier transform infrared spectroscopy (FTIR), high-resolution transmission electron microscopy (HR-TEM), energy dispersive X-ray analysis (EDX), field emission scanning electron microscopy (FE-SEM), vibrating sample magnetometry (VSM), and X-ray photoelectron spectroscopy (XPS) techniques. GFS1 is decorated with Fe0Nps of ~ 5 nm average size. The VSM study revealed that GFS1 has ferromagnetic nature. GFS1 was used as a heterogeneous Fenton-like catalyst for the degradation of azo dyes using Remazol Brilliant Violet (RBV) dye as a model dye. In first 5 min of operation, > 86% dye degradation was achieved and 94% dye (from 100 mg L−1 dye solution) was successfully degraded in 50 min. The dye degradation followed pseudo-first-order kinetics. The GFS1 performed efficiently well over the wide range of dye concentrations (25–200 mg L−1). The catalyst was reused for eight repeated cycles where 12.5% dye degradation was possible even in the eighth cycle. The catalyst behaved fairly well for the degradation of Metanil Yellow (MY) and Orange G (OG) dyes also. Under the optimum conditions of RBV dye degradation, Metanil Yellow (MY) and Orange G (OG) dyes were degraded to the extent of 97 and 26.3%, respectively.

A layer nanostructure of g–C3N4 catalyst doped with transition metals like Ni, Co, and Fe were synthesized. The structure morphology of the metal doped g–C3N4 were studied using XRD, SEM-EDAX, UV-DRS and FT-IR spectroscopy techniques. The presence of transition metals enhanced the visible light absorbance and reduced the electron hole recombination. The efficiency of the catalyst was also enhanced using PMS activation and minimization of charge carrier recombination. The photocatalytic effect of the transition metal doped g–C3N4 nanosheet activated by PMS on the degradation of organic pollutants like Reactive Red 120, Orange G and 2-Amino-4-chlorophenol was investigated. Degradation efficiency in the case of RR120 was nearly 100% with Co–C3N4-PMS-Light system in a time duration of 120 min. Whereas it was 60% in 2-amino-4-chlorophenol and 100% in orange-G, in the same catalyst system and time duration. The findings reveal that the catalyst could play a key role in the treatment of organic pollutants.

Activated carbon fiber (ACF) has become an emerging activator for peroxydisulfate (PDS) to generate sulfate radical (SO4•−). However, the relative low activation efficiency and poor contaminant mineralization limited its widespread application. Herein, ultrasound (US) was introduced to the ACF activated PDS system, and the synergistic effect of US and ACF in PDS activation and the enhancement of contaminant mineralization were investigated. The synergistic effect of US and ACF was observed in the PDS activation to decolorize orange G (OG). The decolorization efficiency increased with increasing ACF loading and US power, and PDS/OG ratio from 1 to 40. The activation energy was determined to be 24.065 kJ/mol. The radical-induced decolorization of OG took place on the surface of ACF, and both SO4•− and hydroxyl radical (•OH) contributed to OG decolorization. The azo bond and naphthalene ring on OG were destructed to other aromatic intermediates and finally mineralized to CO2 and H2O. The introduction of US in the ACF/PDS system significantly enhanced the mineralization of OG. The combination of US and PDS was highly efficient to activate PDS to decolorize azo dyes. Moreover, the introduction of US remarkably improved the contaminant mineralization.

This work deals with the effect of chromium (Cr) dopant on structural, optical and photocatalytic properties of TiO2 nanoparticles by a novel microwave irradiation method. The concentration of Cr is varied from 0 to 5 wt%. X-ray diffraction results suggest that both pure and Cr doped TiO2 had tetragonal anatase type structure with single crystalline nature. Transmission electron microscope measurement showed that well crystalline spherical morphology and the average particles size was found to be about 25–45 nm. The absorption edges of TiO2 shift towards longer wavelengths (i.e. red shifted) from 366 to about 459 nm with increasing Cr concentration, which greatly improve the UV absorption of TiO2 nano-materials. The photocatalytic activity of the catalyst powders evaluated by using three types of dyes such as azo-Methyl Red, Congo Red, Orange G under UV light irradiation. The result showed that the photocatalytic property was significantly improved by Cr doping. The superior photocatalytic mechanism by Cr doping was also discussed in detail. The samples were further characterized by photoluminescence and energy dispersive spectra analysis.

In the present study, batch experiments were used to determine adsorption characteristics of Watermelon Shell Biosorbent (WSB) for the uptake of anionic and cationic dyes from aqueous solution. Various factors such as initial dye concentration, adsorbent dosage, pH, contact time and temperature were systematically investigated and discussed. WSB was characterized by Scanning Electron Microscopy, Energy Dispersive X-ray Spectroscopy and Fourier Transform Infrared Spectroscopy. The adsorption kinetics was best described by Elovich and Diffusion-Chemosorption models for Basic red 2 (BR2) (cationic dye) and Orange G (OG) (anionic dye) respectively. However, the fractional time index “α” and non-integer “n” order by Fractal-like pseudo-first order kinetic affirmed that the mechanism of interaction of both dyes with WSB was by chemical reaction. The applicability of four adsorption isotherm models for the present system was tested. The equilibrium data were found to be well represented by the Extended Langmuir isotherm equation. The monolayer adsorption capacity of WSB for BR2 and OG adsorption was found to be 125 and 27 mg/g, respectively. The effect of temperature on the adsorption process was also investigated and the values of thermodynamic parameters ΔG°, ΔH° and ΔS° revealed that the adsorption system was spontaneous.

We herein report the preparation of Co3O4, α-Fe2O3, and CoFe2O4 nanostructures through a hydrothermal method followed by a subsequent heat treatment. The as-prepared nanostructures exhibited good adsorption properties for the removal of Orange G (OG) textile dye. Various parameters influencing the adsorption process have been investigated such as contact time, initial dye concentration, ionic strength, adsorbent dose, and temperature. The maximum adsorption capacity values were found to be 33.3, 53.2, and 62.0 mg/g, for Co3O4, CoFe2O4, and α-Fe2O3 nano-adsorbents, respectively. The adsorption data fit the pseudo-second-order kinetic and Langmuir isotherm models well. Based on the calculated thermodynamic constants: ΔH° (3.660, 14.82, and 0.4710 kJ/mol), ΔG° (from −0.8090 to −1.109, from −0.6444 to −1.682, and from −3.665 to −3.943 kJ/mol), and Ea (9.277, 5.060, and 12.10 kJ/mol), the adsorption of OG dye on the aforementioned nano-adsorbents, respectively, was found to be endothermic, spontaneous, and physisorption process. In addition, because of the relatively high adsorption capacity and chemical stability, the as-synthesized α-Fe2O3 adsorbent is suggested as a promising candidate for the removal of OG textile dye from aqueous solutions.

A novel CaBiVMoO8 photocatalyst has been prepared by a simple coprecipitation technique at several pH values. The obtained samples were thoroughly characterized by X-ray powder diffraction analysis, ultraviolet–visible (UV–Vis) diffuse reflectance spectroscopy, scanning electron microscopy, and nitrogen adsorption–desorption measurements, and their degradation of orange G and rhodamine B dyes evaluated under UV–Vis irradiation conditions. The sample prepared at pH ~6 showed the best photocatalytic performance for both dyes. Also, photodegradation was favored under acidic conditions (pH ~4) of the aqueous solution, with degradation rate increased by about 4 and 18 times for rhodamine B and orange G, respectively. A tentative explanation is provided by taking into account the point of zero charge of the photocatalyst. In addition, several radical scavenger agents were used to elucidate the importance of different reactive oxygen species during the photocatalytic process.

Persulfate (PS) can be activated by transition metal to generate a sulfate radical and oxidize persistent organic pollutants. However, activation with excessive Fe(II) causes unnecessary self-degradation of PS. In this study, Fe(II) was slowly and continuously injected electrochemically using an iron anode to minimize the self-degradation of PS. Additionally, reaction rate was controlled by adjusting the current intensity applied to the system. Total organic carbon (TOC) was analyzed as an indicator of complete mineralization because the model pollutant, orange G (OG), produced secondary pollutants after disruption of the azo bonds. The removal rate of TOC was 1/10-th of that for OG. In addition, the effect of molar ratio of OG and PS was also studied to confirm the complete mineralization of OG.

It would be of great significance to introduce a new biocompatible Layered Double Hydroxide (LDH) for the efficient remediation of wastewater. Herein, we designed a facile, biocompatible and environmental friendly layered double hydroxide (LDH) of NiFeTi for the very first time by the hydrothermal route. The materialization of NiFeTi LDH was confirmed by FTIR, XRD and Raman studies. BET results revealed the high surface area (106 m2/g) and the morphological studies (FESEM and TEM) portrayed the sheets-like structure of NiFeTi nanoparticles. The material so obtained was employed as an efficient adsorbent for the removal of organic dyes from synthetic waste water. The dye removal study showed >96% efficiency for the removal of methyl orange, congo red, methyl blue and orange G, which revealed the superiority of material for decontamination of waste water. The maximum removal (90%) of dyes was attained within 2 min of initiation of the adsorption process which supported the ultrafast removal efficiency. This ultrafast removal efficiency was attributed to high surface area and large concentration of -OH and CO32− groups present in NiFeTi LDH. In addition, the reusability was also performed up to three cycles with 96, 90 and 88% efficiency for methyl orange. Furthermore, the biocompatibility test on MHS cell lines were also carried which revealed the non-toxic nature of NiFeTi LDH at lower concentration (100% cell viability at 15.6 μg/ml). Overall, we offer a facile surfactant free method for the synthesis of NiFeTi LDH which is efficient for decontamination of anionic dyes from water and also non-toxic.

EDTA functionalized CoFe2O4 nanoparticles (EDTA-CoFe2O4) synthesized using a facile one-pot solvothermal method were employed as catalysts to activate peroxymonosulfate (PMS) with Orange G (OG) as the target pollutant. Effects of operating parameters including initial solution pH, catalyst dosage, PMS dosage, and water matrix components such as Cl-, NO3-, CO32-, and humic acid were evaluated. A degradation efficiency of 93% was achieved in 15 min with 1 mM PMS and 0.2 g/L EDTA-CoFe2O4 catalyst, while only 57% of OG was degraded within 15 min in CoFe2O4/PMS system. The degradation of OG followed pseudo-first-order kinetics, and the apparent first-order date constant (k obs) for OG in EDTA-CoFe2O4/PMS and CoFe2O4/PMS system was determined to be 0.152 and 0.077 min-1, respectively. OG degradation by EDTA-CoFe2O4/PMS was enhanced with the increase of catalyst and PMS doses at respective range of 0.1-2.0 g/L and 0.5-10.0 mM. Higher efficiency of OG oxidation was observed within a wide pH range (3.0-9.0), implying the possibility of applying EDTA-CoFe2O4/PMS process under environmental realistic conditions. Humic acid (HA) at low concentration accelerated the removal of OG; however, a less apparent inhibitive effect was observed at HA addition of 10 mg/L. The k obs value was found to decrease slightly from 0.1601 to 0.1274, 0.1248, and 0.1152 min-1 with the addition of NO3-, CO32-, and Cl-, respectively, but near-complete removal of OG could still be obtained after 15 min. Both of the sulfate radicals and hydroxyl radicals were produced in the reaction, and sulfate radicals were the dominant according to the scavenging tests and electron paramagnetic resonance (EPR) tests. Finally, a degradation mechanism was proposed, and the stability and reusability of the EDTA-CoFe2O4 were evaluated.

In this paper, nanostructured CuWO4 prepared by precipitation method was characterized using X-ray diffraction analysis, scanning electron microscope, and UV–Vis diffuse reflectance spectroscopy. We evaluated the photocatalytic activity of nanostructured CuWO4 by the degradation of methylene blue (MB), amido black (AB) and orange G (OG) dyes in aqueous solutions under sunlight irradiation. The degradation efficiency of the three dyes within 120 min followed the order: MB > AB > OG. The results demonstrated that the dyes degradation process follows Langmuir–Hinshelwood first order kinetics. The effect of pH has been studied to the MB decolorization. High photocatalytic efficiency 96 % was observed for the degradation of MB at pH 10 after 120 min under natural sunlight irradiation. The stability of the nanostructured CuWO4 for the degradation of MB has also been investigated and highly stable performance in recycling photocatalytic reaction was obtained after 5 cycles of use.

Iron anode was employed to enhance the degradation of Orange G (OG) by permanganate (EC/KMnO4). Continuously generated Fe2+ from iron anode facilitated the formation of fresh MnO2, which plays a role in catalyzing permanganate oxidation. The EC/KMnO4 system also showed a better performance to remove OG than Fe2+/KMnO4, indicating the importance of in situ formed fresh MnO2. Besides, the effects of applied current, KMnO4 dosage, solution pH, and natural organics were evaluated and results demonstrated that high current and oxidant dosage are favorable for OG removal. And the application of iron anode has a promoting effect on the KMnO4 oxidation over a wide pH range (5.0–9.0), while the Fe2+/KMnO4 process does not. For natural organics, its presence could inhibit OG removal due to its competitive role. And the promoting effect of OG removal by the EC/KMnO4 process in natural water was confirmed. At last, the EC/KMnO4 process showed a satisfying performance on the decolorization and mineralization of OG. This study provides a potential technology to enhance permanganate oxidation and broadens the knowledge of azo dye removal.

Activated carbon fiber (ACF) was used as a green catalyst to activate persulfate (PS) for oxidative decolorization of azo dye. ACF demonstrated a higher activity than activated carbon (AC) to activate PS to decolorize Orange G (OG). The decolorization efficiency of OG increased as ACF loading, PS dosage, and temperature increased. OG decolorization followed a pseudo first-order kinetics, and the activation energy was 40.902 kJ/mol. pH had no apparent effect on OG decolorization. Radical quenching experiments with various radical scavengers (e.g., alcohols, phenol) showed that radical-induced decolorization of OG took place on the surface of ACF, and both SO4 ·− and HO· were responsible for OG decolorization. The impact of inorganic salts was also evaluated because they are important compositions of dye wastewater. Cl− and SO4 2− exhibited a promoting effect on OG decolorization, and the accelerating rate increased with elevating dosage of ions. Addition of Cl− and SO4 2− could increase the adsorption of OG on ACF surface, thus favorable for OG decolorization caused by the surface-bound SO4 ·− and HO·. Conversely, HCO3 − and humic acid (HA) slightly inhibited OG decolorization. The azo band and naphthalene ring on OG were remarkably destructed to other intermediates and finally mineralized to CO2 and H2O.

In the present study, superabsorbents (SAPs) of cationic monomer [2-(methacryloyloxy) ethyl] trimethylammonium chloride have been prepared by free radical solution polymerization with different crosslinkers. They were subjected to repeated cycles of swelling and de-swelling in deionized water and NaCl solution. The conductivity of the swelling medium was measured and related to the swelling/de-swelling characteristics of the SAPs. The swelling capacity was also determined in saline solution. The swelling and de-swelling processes were described by first-order kinetics. The SAPs exhibited varied swelling capacity for crosslinkers of the same functionality as well as different functionality. The SAPs were used to adsorb the dye Orange G at different initial concentrations of the dye. The equilibrium adsorption data followed the Langmuir adsorption isotherms. The SAPs were also used to adsorb three other dyes, namely, Congo red, Amido black and Alizarin cyanine green. They exhibited different adsorption capacities for different dyes. The adsorption phenomenon was found to follow first-order kinetics.

We synthesized a series of poly(N-isopropylacrylamide)-based ionic hydrogels with dicationic ionic liquid crosslinking structures. The obtained ionic hydrogels showed typical feature of poly(ionic liquid) in aqueous solutions, of which the quaternized imidazolium moieties could interfacially interact with anionic dyes, such as methyl orange (MO), methyl blue (MB), congo red (CR), orange G (OG), thymol blue (TB) and bromothymol blue (BTB), which were strongly dependent on the chemical structures of the dyes.

In this study, undoped ZnO and Mn-doped ZnO nanostructured with different doping concentrations were prepared through a facile chemical method. Then, X-ray diffraction (XRD), scanning electron microscopy (SEM), and UV–Vis diffuse reflectance spectra (DRS) techniques were used to characterize the samples. The XRD patterns demonstrated that the synthesized powders had hexagonal wurtzite structure and partial Mn loads on the surface of ZnO. The photocatalytic activities of the samples were investigated by the degradation of orange G solution under sunlight irradiation. The results demonstrated that doping Mn greatly improved the photocatalytic efficiency of ZnO and 6 % Mn-doped ZnO nanostructured exhibited the highest photocatalytic activity under an irradiation time of 1 h. The effect of operating parameters such as amount of catalyst, initial pH, and the initial dye concentration on the rate of dye degradation using 6 % Mn-doped ZnO nanostructured was studied. Under the optimum operation conditions, approximately 94 % dye removal was achieved after 1 h of irradiation.

The degradation of Orange G (OG) by persulfate (PS, S2O8 2−) activated with dual catalysts that combined zero-valent iron (ZVI) and copper oxide (CuO) was investigated through batch experiments. Effects of pH, initial OG concentration, persulfate dosages, and dosages of dual catalysts on OG degradation were also examined. Higher persulfate concentration and catalysts dosages resulted in higher OG degrading rates. The OG degradation was higher under acidic conditions (pH 3.0 and 5.0) when compared to alkaline conditions. The constituents and the morphology of the catalysts coating before and after reaction were also investigated with X-ray diffraction and scanning electron microscopy. Radical mechanism was studied and three radical scavengers [methanol (MA), tert-butanol (TBA), phenol] were used to determine the type of major active species taking part in the degradation of OG. It was assumed that the $${\text{SO}}_{4}^{ \cdot - }$$ or $${\text{HO}} \cdot$$ played a major role in the OG degradation. In conclusion, the ZVI/CuO/PS system is a good candidate for use in detoxifying water contaminants.

In this study, FeVO4 was prepared and used as Fenton-like catalyst to degrade orange G (OG) dye. The removal of OG in an aqueous solution containing 0.5 g·L–1 FeVO4 and 15 mmol·L–1 hydrogen peroxide at pH 7.0 reached 93.2%. Similar rates were achieved at pH 5.7 (k = 0.0471 min–1), pH 7.0 (k = 0.0438 min–1), and pH 7.7 (k = 0.0434 min–1). The FeVO4 catalyst successfully overcomes the problem faced in the heterogeneous Fenton process, i.e., the narrow working pH range. The data for the removal of OG in FeVO4 systems containing H2O2 conform to the Langmuir–Hinshelwood model (R2 = 0.9988), indicating that adsorption and surface reaction are the two basic mechanisms for OG removal in the FeVO4–H2O2 system. Furthermore, the irradiation of FeVO4 by visible light significantly increases the degradation rate of OG, which is attributed to the enhanced rates of the iron cycles and vanadium cycles.

Increasing textile industries in the last few decade has resulted in the discharge of very large quantities of complex chemical dye to the water system. This has affected the ecological and biological balance causing immense destruction to the nature. In this work, azo dye (Orange G 16) degradation studies by Pseudoalteramonas sp. were investigated. From the experiments, Pseudoalteromonas species degraded the Orange G 16 azo dye at a short time span within 3 h. The assay time for azoreductase activity was standardized, and maximum activity was observed at 24th. The protein concentration was estimated at three different stages of dye degradation. First stage is before addition of dye, second stage is 3 h after addition of the dye during which the dye had completely decolourized, and the third stage is 18 h after the addition of dye. From the study, it was observed that protein concentration was higher in the 24-h sample which has been induced with Orange G 16 azo dye having a concentration of 0.92 mg/ml. While comparing the total activity and specific activity of the enzyme for three samples, it was observed that the activity was higher at the 24th s and then subsided gradually. Thus, Pseudoalteromonas sp. is found to be efficient in degrading azo dyes because of its potential to degrade the dyes rapidly which also has a higher azoreductase activity.

Functionalised electrospun polyamide-6 (PA-6) nanofibres incorporating gadolinium oxide nanoparticles conjugated to zinc tetracarboxyphenoxy phthalocyanine (ZnTCPPc) as the sensitizer were prepared for the photocatalytic degradation of Orange G. Fibres incorporating the phthalocyanine alone or a mixture of the nanoparticles and phthalocyanine were also generated. The singlet oxygen-generating ability of the sensitizer was shown to be maintained within the fibre mat, with the singlet oxygen quantum yields increasing upon incorporation of the magnetic nanoparticles. Consequently, the rate of the photodegradation of Orange G was observed to increase with an increase in singlet oxygen quantum yield. A reduction in the half-lives for the functionalised nanofibres was recorded in the presence of the magnetic nanoparticles, indicating an improvement in the efficiency of the degradation process.

By introducing 1,2,3-triazole-ester groups on thiacalix[4]arene based on click chemistry and then ammonolysis with ethylenediamine, diethylenetriamine or triethylenetetramine, three novel 1,2,3-triazole-modified thiacalix[4]arene polymers were conveniently prepared in “4+2” condensation mode in ideal yields. The structures of polymers 4a–4c were confirmed by elemental analysis, FTIR and 1H NMR spectra. The surface morphologies of polymers 4a–4c were investigated by SEM micrographs. The M n of novel polymers 4a–4c indicated approximately 18–20 calixarene units in each polymer molecule. The dye adsorption abilities of polymers 4a–4c for series of organic dyes (alizarin green, orange I, neutral red (NR), Congo red (CR), orange G (OG), crystal violet, Victoria blue B and methylene blue) were studied by solid–liquid adsorption experiments. The adsorption experimental results implied that they had excellent adsorption abilities for tested organic dyes. The highest adsorption percentage reached 97 % for OG. The best saturation adsorption capacities for NR and CR were as high as 1.282 and 1.407 mmol/g, respectively. These novel polymers possessed stable adsorption abilities in the scopes of pH 5–9 and had good reused properties after desorption. The adsorption mechanism proposed that not only dipole interaction, electrostatic interaction and hydrogen bonding interaction, but also the π–π stacking interaction plays important role in binding dyes.

The production of ligninolytic enzymes by the fungus Schizophyllum sp. F17 using a cost-effective medium comprised of agro-industrial residues in solid-state fermentation (SSF) was optimized. The maximum activities of the enzymes manganese peroxidase (MnP), laccase (Lac), and lignin peroxidases (LiP) were 1,200, 586, and 109 U/L, respectively, on day 5 of SSF. In vitro decolorization of three structurally different azo dyes by the extracellular enzymes was monitored to determine its decolorization capability. The results indicated that crude MnP, but not LiP and Lac, played a crucial role in the decolorization of azo dyes. After optimization of the dye decolorization system with crude MnP, the decolorization rates of Orange IV and Orange G, at an initial dye concentration of 50 mg/L, were enhanced to 76 and 57%, respectively, after 20 min of reaction at pH 4 and 35°C. However, only 8% decolorization of Congo red was observed. This enzymatic reaction system revealed a rapid decolorization of azo dyes with a low MnP activity of 24 U/L. Thus, this study could be the basis for the production and application of MnP on a larger scale using a low-cost substrate.

The first example of triphenylene-modified chitosan 4 was prepared by reacting chitosan with triphenylene aldehyde derivative 3. Its structure and morphology was characterized by elemental analysis, 1H NMR, FTIR, XRD, SEM and AFM image. The triphenylene units in Tp-chitosan 4 appended on the skeleton of chitosan and possessed orderly layered structure. Adsorption experiments of Tp-chitosan 4 indicated that it possessed excellent adsorption capacities for both cationic and anionic dyes [Orange G sodium salt, Brilliant ponceau 5R, Victoria blue B (VB), Crystal violet (CV), Neutral red (NR) and Methylene blue]. The highest adsorption capacities for CV, VB and NR were 5.612, 5.353 and 5.375 mmol/g, respectively. Adsorption kinetics and isotherms analysis showed that the adsorption processes obeyed pseudo second-order model and the Langmuir isotherm equation. The adsorption processes were exothermic and spontaneous. The best pH values for adsorption were pH = 6–8.

PbMoO4 oxide with scheelite structure was obtained by hydrothermal synthesis in the absence of additives. The material was characterized by X-ray powder diffraction, scanning electron microscopy, diffuse reflectance spectroscopy, and adsorption–desorption N2 isotherms. The organic dyes rhodamine B (rhB), indigo carmine (IC), orange G (OG), and methyl orange (MO) were selected as molecules model to study its photocatalytic degradation over PbMoO4 oxide under UV irradiation. Total organic carbon analysis of samples irradiated revealed that mineralization of organic dyes by the action of PbMoO4 was feasible in 80 % (rhB), 69 % (IC), 71 % (MO), and 65 % (OG) after 96 h of UV irradiation.

PbMoO4 molybdate with scheelite structure was synthesized by a simple co-precipitation method. The material was characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), diffuse reflectance spectroscopy (DRS), and adsorption–desorption N2 isotherms (BET). The photocatalytic activity of PbMoO4 molybdate was evaluated with the degradation reactions of rhodamine B (rhB), indigo carmine (IC), orange G (OG), and methyl orange (MO) under UV irradiation. In order to elucidate aspects of the degradation mechanism of the organic dyes, some experimental variables were modified such as pH and O2 level in solution. The total organic carbon (TOC) analysis of samples irradiated revealed that mineralization of organic dyes by the action of PbMoO4 was feasible in rhB (60%), IC (80%), and OG (65%) after 96 h of irradiation. For the same time of irradiation, a recalcitrant behavior to the mineralization was observed in MO reaching only a 10% of mineralization degree.

The efficiency of hematite for the removal of Orange G from aqueous solution has been studied at various concentrations as a function of time, temperatures and pH. It was found that the low initial concentration, low temperature and low pH favor the removal process. The maximum adsorption of the dye on hematite has been recorded at 25 mg/l concentration, 303 K temperature and pH 3. The negative values of change in free energy and enthalpy indicate the spontaneous and exothermic nature of the process, respectively. Fixation and immobilization of the dye molecules at the surface of hematite as a result of adsorption are responsible for the negative entropy effect. The effect of pH was described by considering coulombic attraction and aqua complex formation approaches. The applicability of various adsorption isotherms—Langmuir, Freundlich and Jossens—was tested in order to find the most suitable isotherm. The Freundlich isotherm was fitted with the data of the present study.

Biosorption is an eco-friendly and cost-effective method for treating the dye house effluents. Aspergillus niger and Trichoderma sp. were cultivated in bulk and biomasses used as biosorbents for the biosorption of an azo dye Orange G. Batch biosorption studies were performed for the removal of Orange G from aqueous solutions by varying the parameters like initial aqueous phase pH, biomass dosage, and initial dye concentration. It was found that the maximum biosorption was occurred at pH 2. Experimental data were analyzed by model equations such as Langmuir and Freundlich isotherms, and it was found that both the isotherm models best fitted the adsorption data. The monolayer saturation capacity was 0.48 mg/g for Aspergillus niger and 0.45 mg/g for Trichoderma sp. biomasses. The biosorption kinetic data were tested with pseudo first-order and pseudo second-order rate equations, and it was found that the pseudo second-order model fitted the data well for both the biomasses. The rate constant for the pseudo second-order model was found to be 10–0.8 (g/mg min−1) for Aspergillus niger and 8–0.4 (g/mg min−1) for Trichoderma sp. by varying the initial dye concentrations from 5 to 25 mg/l. It was found that the biomass obtained from Aspergillus niger was a better biosorbent for the biosorption of Orange G dye when compared to Trichoderma sp.

Zn2Al-layered double hydroxides (LDH) were intercalated with anions of the dyes Orange G, Orange II, and Methyl Orange by alkaline co-precipitation of aqueous solutions of zinc chloride and aluminum nitrate simultaneously in the presence of dye sodium salts. Transparent, homogeneous, and colored nanocomposite films were obtained by casting after dispersing the dye-intercalated LDHs (pigments) into commercial poly(vinyl alcohol) (PVA). The films were characterized by X-ray diffraction, ultraviolet–visible spectroscopy, thermal analysis (thermogravimetric analysis (TGA)) and differential thermal analysis (DTA)), and mechanical testing. Mechanical reinforcement of the PVA compounded with the dye-intercalated LDHs was achieved, and reasonable increases in Young’s modulus and ultimate tensile strength were observed with as little as 0.5% added filler, while larger amounts tended to decrease the reinforcement effect. These results demonstrate the onset of a new range of potential applications for layered double hydroxide intercalated with dyes in the preparation of polymer composite multifunctional materials.

Polyorganosiloxane spherical particles were synthesized by a sol-gel method from methyltrimethoxysilane (MTMS) using a reaction field of W/O emulsion consisting of sorbitantrioleate (SPAN85), n-octane, and aqueous solutions of basic, acid, and oil-soluble organic dyes. The investigation focused on the types of dyes suitable for incorporation into the spherical particles by using this method. The morphology of the particles was observed with scanning electron microscopy (SEM). Fluorescence and ultraviolet-visible (UV-vis) reflectance spectra of dye-doped spherical particles were measured. Basic dyes [Rhodamine B (RB), Rhodamine 6G (R6G), Crystal Violet (CV), Malachite Green (MG), and Thioflavin T (TT)] were doped into the spherical particles. Spherical particles obtained from aqueous solutions of RB, R6G, and CV were colored deeply. However, the MG- and TT-doped particles were scarcely colored. The reason for this color difference was discussed based on the comparison of UV-vis reflectance spectra of dye-doped spherical particles with absorption spectra of starting solutions of the dyes. It is found that the dye that tends to form dimers in aqueous solution was doped more easily than the dyes that tend to form monomers only. On the other hand, spherical particles obtained from acid dyes [Fluorescein Sodium Salt (FSS), Orange G (OG), Naphthol Green B (NGB), and Erythrosin B (EB)] and oil-soluble dye [Fluorescein (FLU)] were all white, confirming that these dyes were not doped in the particles. The reason was discussed in terms of the nature of the dyes and the formation mechanism of the spherical particles.

By reacting cyclodextrin-grafted thiacalix [4]arene derivative 9 containing three alkynyl groups with bis-azido compound 6, the first example of cyclodextrin-grafted thiacalix [4]arene netty polymer 10 was designed and prepared by the click chemistry in yield of 76 %. Its structure was confirmed by elemental analysis, 1H NMR spectrum, FTIR spectrum and XRD curve. The M n of polymer 10 was 48,677, indicating average approximately 22 units of compound 9 in each polymer molecule. Its SEM image showed porous and loose morphology. Adsorption experiments of polymer 10 indicated that it possessed excellent adsorption capacities for both cationic and anionic dyes [Orange G sodium salt (OG), Brilliant ponceau 5R (BP), Victoria blue B (VB), Crystal violet (CV), Neutral red (NR) and Methylene blue (MB)]. The highest adsorption capacities for VB, CV, NR and MB were 5.821, 6.825, 6.135 and 5.381 mmol/g, respectively. Adsorption kinetics and isotherms analysis suggested that all the adsorption processes were exothermic and spontaneous. The adsorption processes obeyed pseudo second-order model and the Langmuir isotherm equation. The adsorption abilities of polymer 10 at pH values 3–11 were keep stable between 1.5–4 mmol/g. The adsorption abilities for anionic dyes decreased with the increase of pH values but opposite phenomena for cationic dyes. Polymer 10 showed good reused adsorption property after desorption in five times’ cycles.

Geotrichum sp. strain, which is able to decolorize azo dyes enzymatically, was used in this study for decolorization of synthetics solutions contaminated by toxic azo dyes orange G, trypan blue, azorubine, and methyl red. The biomass of Geotrichum sp. was immobilized in calcium alginate and polyacrylamide gels and used for the decolorization of tested azo dyes in fluidized bed bioreactor. The highest specific decolorization rate was obtained when the fungal biomass was entrapped in calcium alginate beads. Immobilized biomass in calcium alginate continuously decolorized azo dyes after eight repeated batch decolorization experiments without significant loss of activity whereas polyacrylamide immobilized biomass retained only 10% of its activity after 4 days of incubation. The effects of some physicochemical parameters such as temperature, pH, and dyes concentration on decolorization performance of isolated fungal strain were also investigated.

New photocatalytically active isostructural two-dimensional mixed metal-pyridine dicarboxylates, $[M(H_2O)_3Co\{C_5N_1H_3 (COO)_2 \}_3])\infty]$, M = Gd (1), Dy (2) and Y (3) have been prepared under hydrothermal conditions. The structure consists of a network of $MO_6(H_2O)_3$, $CoO_3N_3$ polyhedral units connected by the pyridine dicarboxylates forming two-dimensional layers, which are arranged in an AAAA... fashion. The photocatalytic studies on 1 – 3 indicate that they are active catalysts for the degradation of simple organic dyes, such as Remazol brilliant blue R (RBBR) and Orange G (OG) in the presence of UV light. The compounds have also been characterized by powder XRD, IR, TGA, UV-Vis and magnetic studies.

Even though dye degradation is a successful application of semiconductor photocatalysis, the roles of reactive species in dye degradation have not received adequate attention. In this study, we systematically investigated the degradation of two cationic dyes (rhodamine B and methylene blue) and two anionic dyes (methyl orange and orange G) over negatively surface-charged In2S3 nanoflowers synthesized at 80 °C under indoor daylight lamp irradiation. It is notable to find In2S3 nanoflowers were more stable in anionic dyes degradation compared to that in cationic dyes removal. The active species trapping experiments indicated photogenerated electrons were mainly responsible for cationic dyes degradation, but holes were more important in anionic dyes degradation. A surface-charge-dependent role of reactive species in ionic dye degradation was proposed for revealing such interesting phenomenon. This study would provide a new insight for preparing highly efficient daylight-driven photocatalyst for ionic dyes degradation.

The effect of enhanced laccase (Lac) activity (obtained after copper addition to cultivation media) on decolorization of azo dye Orange G in two basidiospore-derived monokaryotic isolates of Pleurotus ostreatus was determined. The high Lac-producing isolate efficiently decolorized Orange G. The low-producing isolate showed only poor decolorization ability during cultivation in liquid medium and no decolorization on agar plates containing Orange G after a 25-d growth. A substantial enhancement of Lac activity caused by copper addition into cultivation media was detected in both isolates but, at the same time, the biomass production decreased and decolorization rate was reduced.

A sequential anaerobic aerobic treatment process based on mixed culture of bacteria isolated from textile dye effluent-contaminated soil was used to degrade sulfonated azo dyes Orange G (OG), Amido black 10B (AB), Direct red 4BS (DR) and Congo red (CR). Under anaerobic conditions in a fixed-bed column using glucose as co-substrate, the azo dyes were reduced and amines were released by the bacterial biomass. The amines were completely mineralized in a subsequent aerobic treatment using the same isolates. The maximum degradation rate observed in the treatment system for OG was 60.9 mg/l per day (16.99 mg/g glucose utilized), for AB 571.3 mg/l per day (14.46 mg/g glucose utilized), for DR 112.5 mg/l per day (32.02 mg/g glucose utilized) and for CR 134.9 mg/l per day (38.9 mg/g glucose utilized).