Synthesis of multi-layer graphene oxide from HCl-treated coke and Brazilian coals by sulfuric acid thermal exfoliation and ozone oxidation.

This study involved the synthesis and characterization of graphene oxide (GO) from mineral coke and bituminous coal. HCl treated and non-HCl treated ultrafine powder obtained from both precursors were treated with H2SO4, followed by thermal treatment, and oxidation with ozone and ultra-sonication for GO production. The synthesized materials were characterized using Fourier transform infrared spectroscopy (FTIR), zeta potential (ZP), particle size distribution (PSD), transmission electron microscopy (TEM), X-ray diffraction (XRD) and Raman spectroscopy. The results confirmed the exfoliation of the material primarily at the edges of its structure and the formation of multilayer graphene oxide (GO) from mineral coke and bituminous coal. Furthermore, it was found that carbonaceous materials with graphitic morphology are easier to exfoliate and oxidize, leading to the production of higher quality graphene oxide. Therefore, the GO synthesized from mineral coke exhibited the best quality in this study. The methodology used proposes an innovative approach, offering a faster, more economical, and environmentally friendly synthesis compared to the traditional Hummers' method, thereby adding value to other raw materials that can be utilized in this process, such as Brazilian coke and coal.

Enhanced degradation and removal of ciprofloxacin and ofloxacin through advanced oxidation and adsorption processes using environmentally friendly modified carbon nanotubes.

This study explores the utilization of adsorption and advanced oxidation processes for the degradation of ofloxacin (OFL) and ciprofloxacin (CIP) using a green functionalized carbon nanotube (MWCNT-OH/COOH-E) as adsorbent and catalyst material. The stability and catalytic activity of the solid material were proved by FT-IR and TG/DTG, which also helped to elucidate the reaction mechanisms. In adsorption kinetic studies, both antibiotics showed similar behavior, with an equilibrium at 30 min and 60% removal. The adsorption kinetic data of both antibiotics were well described by the pseudo-first-order (PFO) model. Different advanced oxidation processes (AOPs) were used, and the photolytic degradation was not satisfactory, whereas heterogeneous photocatalysis showed high degradation (⁓ 70%), both processes with 30 min of reaction. Nevertheless, ozonation and catalytic ozonation have resulted in the highest efficiencies, 90%, and 70%, respectively, after 30-min reaction. For AOP data modeling, the first-order model better described CIP and OFL in photocatalytic and ozonation process. Intermediates were detected by MS-MS analysis, such as P313, P330, and P277 for ciprofloxacin and P391 and P332 for ofloxacin. The toxicity test demonstrated that a lower acute toxicity was observed for the photocatalysis method samples, with only 3.1 and 1.5 TU for CIP and OFL, respectively, thus being a promising method for its degradation, due to its lower risk of inducing the proliferation of bacterial resistance in an aquatic environment. Ultimately, the analysis of MWCNT reusability showed good performance for 2 cycles and regeneration of MWCNT with ozone confirmed its effectiveness up to 3 cycles.

Physiological changes in green and red cherry tomatoes after photocatalytic ethylene degradation using continuous air flux.

In this work photocatalytic ethylene degradation (TiO2-UV) was applied in green cherry tomatoes with the aim to control biochemical and physiological changes during ripening. Photocatalytic process was performed at 18 °C ± 2 °C and 85% HR for 10 days using continuous air flux. Ethylene, O2 and CO2 concentration from cherry tomatoes under TiO2-UV and control (c) fruits, were measured by GC-MS for 10 days. After that, the tomatoes were stored for 20 days. During the photocatalysis process, ethylene was completely degraded and control fruits, the ethylene was 28.73 nL/g. Respiration rate was lower for fruits under TiO2-UV than control. During storage period, cherry tomatoes treated by TiO2-UV, showed lower ethylene concentration, respiration rate, total soluble solid, lycopene, sugar and organic acid content than control showing that the fruits treated with photocatalysis did not reach the full maturity. In addition, all the cherry tomatoes showed different maturity stages. Fungal incidence was higher in control fruits than fruits treated with photocatalysis. This research showed for the first time that photocatalytic technology preserved the physiological quality of cherry tomatoes for 30 days of storage, being a promised technology to preserve cherries tomatoes.

Ecotoxicidade de nanocatalisadores de óxidos de ferro, produzidos a partir da drenagem ácida de mina, quando submetidos à ação de ozônio em meio aquoso / Ecotoxicity of iron oxide nanocatalysts, produced from acid mine drainage, when submitted to the action of ozone in aqueous medium

RESUMO Óxidos de ferro recuperados da drenagem ácida de minas representam uma matéria-prima potencial para a produção de baixo custo de nanogoetita ou nanohematita, com grau de pureza adequado para o seu uso como catalisador em processos de tratamento de efluentes líquidos com ozônio. Assim, a toxicidade das nanopartículas de ferro precisa ser determinada para prever seu impacto no meio ambiente, antes e depois de terem sido utilizadas nesses processos. Nesse contexto, o objetivo deste estudo foi avaliar a toxicidade de nanogoetita e nanohematita produzidas a partir da drenagem ácida de minas bem como comparar os resultados com hematita sintética de alta pureza. A nanogoetita foi obtida da drenagem ácida de minas e, após seu tratamento térmico a 450°C, produziu nanopartículas de hematita. Os materiais foram caracterizados por difração de raios X, microscopia eletrônica de transmissão e determinação da área superficial específica e porosidade com base nas isotermas de adsorção/dessorção de N2. Foram realizados os ensaios de ecotoxicidade usando os protocolos padronizados para bioluminescência com Vibrio fischeri, letalidade da Artemia sp., germinação de sementes de Lactuca sativa L. (alface) e crescimento das raízes de Allium cepa L. (cebola). Os resultados de toxicidade indicaram estabilidade das nanopartículas, que não são alteradas significativamente pela ação do ozônio em meio aquoso. Para todas as amostras, os valores indicaram baixa ou nenhuma toxicidade nas condições dos experimentos, para os bioindicadores utilizados. Esses resultados fornecem indicação de que as nanopartículas de ferro recuperadas da indústria de resíduos podem ser usadas como catalisadores sem efeitos adversos ao meio ambiente.

ABSTRACT Iron oxides recovered from acid mine drainage represent a potential raw material for the low-cost production of nanogoethite or nanohematite, with a degree of purity suitable for its use as a catalyst in processes for treating liquid effluents with ozone. Thus, the toxicity of iron nanoparticles needs to be determined to predict their impact on the environment, before and after they have been used in these processes. In this context, the objective of this study was to evaluate the toxicity of nanogoethite and nanohematite produced from acid mine drainage as well as to compare the results with high-purity synthetic hematite. Nanogoethite was obtained from acid mine drainage and, after its heat treatment at 450°C, produced nanoparticles of hematite. The materials were characterized by X-ray diffraction, transmission electron microscopy, and determination of the specific surface area and porosity based on N2 adsorption/desorption isotherms. Ecotoxicity tests were carried out using standardized protocols for bioluminescence with Vibrio fischeri, lethality of Artemia sp, germination of Lactuca sativa L (lettuce) seeds, and growth of Allium cepa L (onion) roots. The toxicity results indicated stability of the nanoparticles, which are not significantly altered by the action of ozone in aqueous medium. For all samples, the values indicated low or no toxicity under the conditions of the experiments. These results provide an indication that the iron nanoparticles recovered from the waste industry can be used as catalysts without adverse effects on the environment.

A review on TiO2-based photocatalytic systems applied in fruit postharvest: Set-ups and perspectives.

Titanium dioxide (TiO2) is a photocatalytic material used to degrade ethylene, and it has been studied as an alternative postharvest technology. Although several studies have indicated the effective action of TiO2 photocatalysis for delaying the fruit ripening, photocatalytic systems need to be well-designed for this application. Fruit is susceptible to environmental conditions like temperature, relative humidity, atmosphere composition and exposure to UV-light. This fragility associated with its variable ethylene production rate over its maturation stage limits the photocatalysis parameters optimization. Thus, this review aims to detail the reaction mechanisms, set-up, advantages, and limitations of TiO2 photocatalytic systems based on polymers-TiO2 nanocomposites and reactors containing TiO2 immobilized into inorganic supports designed for fruit applications. It is expected that this review can elucidate the fundamental aspects that should be considered for the use of these systems.

Ethylene scavenging properties from hydroxypropyl methylcellulose-TiO2 and gelatin-TiO2 nanocomposites on polyethylene supports for fruit application.

Several technologies have been proposed to preserve fruits and to avoid postharvest losses. The degradation of ethylene produced by the fruits using TiO2 photocatalysis has shown to be a good option to delay the ripening of fruits. This paper proposed a new application of biopolymers-TiO2 nanocomposites developed to extend the shelf-life of fruits. Photocatalytic coatings were applied on the expanded polyethylene foam nets to degrade ethylene. Gelatin and hydroxypropyl methylcellulose (HMPC) were tested as hydrophobic and hydrophilic matrices for the TiO2 incorporation. First, nanocomposite films prepared by casting were evaluated with regards to their photocatalytic properties. Both matrices, which were loaded with 1 wt% TiO2, degraded 40% of the ethylene injected in a batch reactor. By Langmuir-Hinshelwood model, ethylene degradation using gelatin-TiO2 films (kapp = 0.186 ± 0.021 min-1) was faster than the HPMC-TiO2 films (kapp = 0.034 ± 0.003 min-1). Then, gelatin-TiO2 dispersion was applied as a coating on the foam nets by dip coating. The gelatin-TiO2 bilayer exhibited higher concentration of ethylene degraded per photocatalytic area and photocatalyst mass unit (13.297 ± 0.178 ppmv m2 [Formula: see text] ) than its film form (18.212 ± 1.157 ppmv m2 [Formula: see text] ), which makes gelatin-TiO2/foam nets a promising composite design for fruit postharvest application.

Tuning the photoactivity of TiO2 nanoarchitectures doped with cerium or neodymium and application to colour removal from wastewaters.

The impact of cerium (Ce) and neodymium (Nd) rare-earth metal doping of TiO2 prepared by the hydrothermal method was investigated to tailor effective photocatalytic degradation of coloured wastewater under UV or visible illumination. The hydrothermal treatment of TiO2 decreased the pHpzc from 6.3 to 3.1-3.8 favouring the affinity for cationic water contaminants. Doping with Ce and Nd modified the crystallinity and the morphology of the photocatalysts and significantly increased the BET surface area and the adsorption capacity of cationic dyes. The photocatalytic activity under UV light irradiation decreased due to shielding of the catalyst active area by excessive amount of dye adsorbed. Conversely, the photocatalytic activity of the Ce and Nd doped TiO2 increased under visible light irradiation by 1.2 times as a result of the dye photosensitization effect. It was demonstrated that two-steps dark adsorption and photocatalytic reaction or one-step simultaneous adsorption and reaction can produce significantly different results for the photocatalytic degradation of dyes in coloured waters, the rate being controlled by the competitive adsorption of the reacting organics and the H2O/OH- species. The reaction is driven by the radical oxygen species (ROS) formed on the catalyst surface the nature of which, differs under UV or visible light irradiation. The Ce-doped TiO2 and Nd-doped TiO2 photocatalysts with 0.5% rare-earth content were found to be efficient in the degradation of MB in aqueous solution, removing the colour and reducing the toxicity of wastewaters.

Plastic optical fibres applied on the photocatalytic degradation of phenol with Ag2MoO4 and ß-Ag2MoO4/Ag3PO4 under visible light.

In this study, plastic optical fibre (POF) was considered as a light-transmitting medium and substrate for use in a photocatalytic environmental purification system, using Ag2MoO4 and ß-Ag2MoO4/Ag3PO4 as photocatalysts. Pure Ag2MoO4 and a ß-Ag2MoO4/Ag3PO4 composite were synthesized using a facile precipitation method. The composition, structures and optical properties of as-prepared catalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), field-emission scanning electron microscopy (FESEM), UV/Vis diffuse reflectance spectroscopy (UV/Vis DRS), BET surface area and TGA/DTG. The catalysts were immobilized on POF and on the glass reactor surface and their efficiency in the phenol degradation was evaluated in a batch reactor under visible light. The use of POF offers advantages such as ease of handling and good adherence characteristics to support Ag2MoO4. The photoactivity follows the order ß-Ag2MoO4/Ag3PO4 ≅ Ag2MoO4 > TiO2 P25, for photocatalysts immobilized on the glass reactor surface or in aqueous suspension. The immobilization of Ag2MoO4 on POF revealed that thinner Ag2MoO4 coatings achieved faster pollutant removal rates from solution, and the optimal catalyst deposition is 0.64 mg/cm2, causing maximum the light penetration and electron-hole generation close to the solid-liquid interface.

Synthetic dyes biodegradation by fungal ligninolytic enzymes: Process optimization, metabolites evaluation and toxicity assessment.

This work aimed to provide information that contributes to establishing environmental-friendly methods for synthetic dyes' degradation. The potential decolorization capacity of the crude enzymatic extract produced by Phanerochaete chrysosporium CDBB 686 using corncob as a substrate was evaluated on seven different dyes. Critical variables affecting the in-vitro decolorization process were further evaluated and results were compared with an in-vivo decolorization system. Decolorization with enzymatic extracts presented advantages over the in-vivo system (higher or similar decolorization within a shorter period). Under improved in-vitro process conditions, the dyes with higher decolorization were: Congo red (41.84 %), Poly R-478 (56.86 %), Methyl green (69.79 %). Attempts were made to confirm the transformation of the dyes after the in-vitro process as well as to establish a molecular basis for interpreting changes in toxicity along with the degradation process. In-vitro degradation products of Methyl green presented a toxicity reduction compared with the original dye; however, increased toxicity was found for Congo red degradation products when compared with the original dyes. Thus, for future applications, it is crucial to evaluate the mechanisms of biodegradation of each target synthetic dye as well as the toxicity of the products obtained after enzymatic oxidation.

Structural, optical and photocatalytic properties of erbium (Er3+) and yttrium (Y3+) doped TiO2 thin films with remarkable self-cleaning super-hydrophilic properties.

The self-cleaning and super hydrophilic properties of pristine TiO2 and of TiO2 doped with Er3+ or Y3+ transparent thin films deposited onto glass substrates were investigated. The thin films prepared by multiple dipping and drying cycles of the glass substrate into the pristine TiO2 sol and Er3+ or Y3+-doped TiO2 sol were characterized by X-ray diffraction, UV-vis spectrophotometry, and atomic force microscopy (AFM). The self-cleaning photocatalytic activity of the thin films towards the removal of oleic acid deposited on the surface under UVA irradiation was evaluated. A remarkable enhancement was observed in the hydrophilic nature of the TiO2 thin films under irradiation. The optical properties and wettability of TiO2 were not affected by Er3+ or Y3+ doping. However, the photocatalytic degradation of oleic acid under UVA irradiation improved up to 1.83 or 1.95 fold as the Er3+ or Y3+ content increased, respectively, due to the enhanced separation of the photogenerated carriers and reduced crystallite size. AFM analysis showed that the surface roughness increased by increasing the Er3+ or Y3+ content due to the formation of large aggregates. This in turn contributes to the increase of the active surface area enhancing the photodegradation process. This study demonstrates that TiO2 doped with low amounts of Er3+ or Y3+ down to 0.5 mol% can produce transparent, super-hydrophilic, thin film surfaces with remarkable self-cleaning properties.

Photocatalytic effect of addition of TiO2 to acrylic-based paint for passive toluene degradation.

Volatile organic compounds (VOCs) are known to be hazardous and associated with several human health problems. Thus, many technologies have been developed in recent years for their removal, such as thermal catalysis, photocatalysis and ozonization. In this study, the main objective was to evaluate the effects of incorporating titanium dioxide into an acrylic-based paint for gaseous toluene abatement. Paints with photocatalytic properties were prepared by adding TiO2 P25 powder to an acrylic-based paint, using the following proportions: 0, 10, 15, 20 and 50 wt% (dry basis). Toluene and CO2 concentrations at the reactor input and output were determined using GC/MS, and GC/FID, respectively, and the toluene conversion and CO2 formation were assessed. The compounds adsorbed onto photocatalytic paints were extracted and then identified by GC/MS. The results indicated that the addition of 50 wt% of TiO2 P25 results in a paint of reduced quality. The addition of 20 wt% of TiO2 P25 to the paint led to higher values for the photocatalytic conversion of toluene to CO2. The occurrence of two simultaneous processes was observed: the photocatalytic oxidation of toluene to CO2 and the self-degradation of the organic compounds, such as polymeric acrylic, in the paint. The adsorption of different compounds onto the photocatalytic paints was identified by GC/MS analysis. The use of photocatalytic paints is a promising technique for toluene abatement, but it requires further study and improvement particularly with regard to the effects of the self-degradation of the paint.

Hydroxypropyl methylcellulose-TiO2 and gelatin-TiO2 nanocomposite films: Physicochemical and structural properties.

Photocatalytic properties of titanium dioxide (TiO2) have been widely studied. However, its tendency to aggregation in biopolymer-based nanocomposites limits its application for food packaging and has been few studied. The aim of this work was to study the dispersion of TiO2 (0-2 wt%) incorporated in the hydroxypropyl methylcellulose (HPMC-TiO2) and gelatin (gelatin-TiO2) film forming solutions. Particle size and zeta potential of TiO2 nanoparticles were investigated. Nanocomposite films were characterized as to the thickness, moisture content, solubility, color, absorption to the light, relative opacity, morphology, chemical composition, crystallinity, thermal and mechanical properties and water vapor permeability (WVP). TiO2 nanoparticles showed better dispersion in acid medium than water. Moisture content, water solubility and WVP of the gelatin-TiO2 films were influenced by the incorporation of TiO2, while HPMC-TiO2 films were not. The increase of relative opacity of the films as TiO2 was more attenuated for the gelatin-TiO2 films due to lower TiO2 aggregation in gelatin. Morphology, chemical composition, crystallinity and thermal properties of the films evidenced that TiO2 was better dispersed in both matrices at 1 wt%. It was also concluded that TiO2 aggregation generated more biphasic regions in HPMC than generated in gelatin, which caused a microstructural reorganization in the matrices.

Residue-based iron oxide catalyst for the degradation of simulated petrochemical wastewater via heterogeneous photo-Fenton process.

Iron oxide with a high degree of purity was recovered from waste and used as an environmentally friendly, low-cost catalyst in the application of the photo-Fenton process to simulated petrochemical wastewater (SPW). Iron oxide nanoparticles were characterized by X-ray powder diffraction, transmission electron microscopy, N2 adsorption/desorption isotherms, zeta potential, toxicity and atomic absorption spectrometry. The experiments were performed in a batch photochemical reactor, at 20 ± 2.0°C and pH 3.0. The SPW was efficiently mineralized and oxidized using a low catalyst dosage. The results showed that the organic compounds present in the wastewater were not adsorbed onto the solid surface. The solid was found to be stable with negligible leaching and low toxicity. The kTOC/kCOD ratios were calculated and varied according to the process: for a homogeneous reaction, the ratio obtained was 0.31 and for the heterogenous photo-Fenton process, it was closer to 1. The chemical oxygen demand and total organic carbon removal values were very close, indicating that the SPW is immediately mineralized, without producing partially oxidized compounds. The residue-based goethite studied represents a good alternative to commercially available catalysts in terms of sources and availability.

Combustion of pistachio shell: physicochemical characterization and evaluation of kinetic parameters.

The study of different renewable energy sources has been intensifying due to the current climate changes; therefore, the present work had the objective to characterize physicochemically the pistachio shell waste and evaluate kinetic parameters of its combustion. The pistachio shell was characterized through proximate analysis, ultimate analysis, SEM, and FTIR. The thermal and kinetic behaviors were evaluated by a thermogravimetric analyzer under oxidant atmosphere between room temperature and 1000 °C, in which the process was performed in three different heating rates (20, 30, and 40 °C min-1). The combustion of the pistachio shell presented two regions in the derivative thermogravimetric curves, where the first represents the devolatilization of volatile matter compounds and the second one is associated to the biochar oxidation. These zones were considered for the evaluation of the kinetic parameters E a , A, and f(α) by the modified method of Coats-Redfern, compensation effect, and master plot, respectively. The kinetic parameters for zone 1 were E a1 = 84.11 kJ mol-1, A 1 = 6.39 × 106 min-1, and f(α)1 = 3(1 - α)2/3, while for zone 2, the kinetic parameters were E a2 = 37.47 kJ mol-1, A 2 = 57.14 min-1, and f(α)2 = 2(1 - α)1/2.

Photocatalytic degradation of polyvinylpyrrolidone in aqueous solution using TiO2/H2O2/UV system.

The photocatalytic degradation of high molecular weight polyvinylpyrrolidone (PVP), a water-soluble polymer, using a TiO2/H2O2/UV system was studied in an annular photoreactor using a mercury vapor lamp (125 W) as the radiation source. The effect of the initial hydrogen peroxide concentration and the operating conditions, such as initial concentration of PVP, photocatalyst dosage and initial pH, on the reaction rate was also evaluated. It was observed that the efficiency of the TiO2/H2O2/UV system was 33% higher than that of a system without H2O2, reaching total organic carbon removals of above 80% in 6 h of reaction, depending on the experimental conditions. The optimal photocatalyst dosage was found to be 0.50 g L-1. Also, the results demonstrate that the reaction rate increases as the pH and initial concentration of PVP decrease. This treatment can be carried out successfully under optimal conditions and enhance the biodegradability of the organic matter remaining at the end of the application of the TiO2/H2O2/UV system, as assessed by biochemical oxygen demand/chemical oxygen demand measurements.

Bio-syngas production from agro-industrial biomass residues by steam gasification.

This study evaluated the steam gasification potential of three residues from Brazilian agro-industry by assessing their reaction kinetics and syngas production at temperatures from 650 to 850°C and a steam partial pressure range of 0.05 to 0.3bar. The transition temperature between kinetic control and diffusion control regimes was identified. Prior to the gasification tests, the raw biomasses, namely apple pomace, spent coffee grounds and sawdust, were pyrolyzed in a fixed-bed quartz tubular reactor under controlled conditions. Gasification tests were performed isothermally in a magnetic suspension thermobalance and the reaction products were analyzed by a gas chromatograph with TCD/FID detectors. According to the characterization results, the samples presented higher carbon and lower volatile matter contents than the biomasses. Nevertheless, all of the materials had high calorific value. Syngas production was influenced by both temperature and steam partial pressure. Higher concentrations of H2 and CO were found in the conversion range of 50-80% and higher concentrations of CO2 in conversions around 10%, for all the gasified biochars. The H2/CO decreased with increasing temperature, mainly in kinetic control regime, in the lower temperature range. The results indicate the gasification potential of Brazilian biomass residues and are an initial and important step in the development of gasification processes in Brazil.

Recovery of iron oxides from acid mine drainage and their application as adsorbent or catalyst.

Iron oxide particles recovered from acid mine drainage represent a potential low-cost feedstock to replace reagent-grade chemicals in the production of goethite, ferrihydrite or magnetite with relatively high purity. Also, the properties of iron oxides recovered from acid mine drainage mean that they can be exploited as catalysts and/or adsorbents to remove azo dyes from aqueous solutions. The main aim of this study was to recover iron oxides with relatively high purity from acid mine drainage to act as a catalyst in the oxidation of dye through a Fenton-like mechanism or as an adsorbent to remove dyes from an aqueous solution. Iron oxides (goethite) were recovered from acid mine drainage through a sequential precipitation method. Thermal treatment at temperatures higher than 300 °C produces hematite through a decrease in the BET area and an increase in the point of zero charge. In the absence of hydrogen peroxide, the solids adsorbed the textile dye Procion Red H-E7B according to the Langmuir model, and the maximum amount adsorbed decreased as the temperature of the thermal treatment increased. The decomposition kinetics of hydrogen peroxide is dependent on the H(2)O(2) concentration and iron oxides dosage, but the second-order rate constant normalized to the BET surface area is similar to that for different iron oxides tested in this and others studies. These results indicate that acid mine drainage could be used as a source material for the production of iron oxide catalysts/adsorbents, with comparable quality to those produced using analytical-grade reagents.

Aplicação de Fenton, foto-Fenton e UV/H2O2 no tratamento de efluente têxtil sintético contendo o corante Preto Biozol UC / Application of Fenton, photo-Fenton and UV/H2O2 in treating synthetic textile wastewater containing the dye Black Biozol UC

Os efluentes têxteis, geralmente, são carregados de corantes não biodegradáveis, o que dificulta o seu tratamento. Dentre as novas alternativas de tratamento estudadas, estão os Processos Oxidativos Avançados (POA). Os mesmos são processos com potencial de produzir radicais hidroxila (•OH), espécies altamente oxidantes, capazes de mineralizar a matéria orgânica. Assim, o objetivo deste trabalho foi estudar a aplicação dos POA (Fenton, foto-Fenton e UV/H2O2) no tratamento de efluente têxtil sintético contendo o corante Preto Biozol UC. Dentre os processos estudados, o mais eficiente foi o foto-Fenton (H2O2 = 1.500 mg.L-1 e Fe2+ = 75 mg.L-1), em pH = 3, que obteve 95,4 por cento e 73,0 por cento para as remoções de cor e demanda química de oxigênio (DQO), respectivamente.

The textile wastewater is usually loaded with non-biodegradable dyes, which hinder its treatment. Advanced Oxidation Processes (AOP) are among new treatment alternatives. They are processes with potential to produce hydroxyl radicals (•OH), highly oxidizing species, capable of mineralizing the organic matter. Thus, the aim of this work was to study the application of the AOP (Fenton, photo-Fenton and UV/H2O2) in the treatment of synthetic textile wastewater containing the Black Biozol UC dye. Among the studied processes, the most efficient was photo-Fenton (H2O2 = 1,500 mg.L-1 and Fe 2+ = 75 mg.L-1), at pH = 3, for color and chemical oxygen demand (COD) removals of 95.4 percent and 73.0 percent, respectively.

Comparação entre diferentes processos oxidativos avançados para degradação de corante azo / Comparison of various advanced oxidation processes for azo dye degradation

O objetivo deste estudo foi comparar os processos de oxidação avançada (H2O2, UV, UV/H2O2, Fe2+/H2O2, UV/Fe2+/H2O2) para descoloração do corante têxtil Reactive Red 195. Também foi investigada a utilização do pó do desempoeiramento da ala de corrida do alto forno como fonte alternativa de ferro na peroxidação catalítica, com e sem radiação UV, para degradação do corante. O efeito das concentrações de H2O2 e corante na cinética de descoloração foram estudados. Os resultados indicaram que a maior eficiência de descoloração foi obtida através do sistema foto-Fenton com o uso do resíduo; entretanto, a utilização do resíduo no sistema Fenton sem irradiação atingiu a mesma eficiência, com tempo de reação aumentado em apenas 15 minutos. A utilização do resíduo siderúrgico aumentou a velocidade de descoloração, mostrando-se bastante promissora como fonte de ferro.

This study aimed at comparing various advanced oxidation processes (H2O2, UV, UV/H2O2, Fe2+/H2O2, UV/Fe2+/H2O2) for textile dye Reactive Red 195 decolorization. The use of blast furnace dust (BFD) was also investigated as an alternative source of iron in catalytic peroxidation with and without UV radiation. The effects of H2O2 and dye concentrations in kinetics of decolorization were studied. Decolorization reactions follow pseudo-first order kinetics. The results indicated greater efficiency of decolorization in the photo-Fenton system with the use of BFD; however, the use of BFD in the Fenton system without irradiation reached the same efficiency with a reaction time only 15 minutes superior. The use of blast furnace dust increased considerably the rates of reactions and is very promising as a source of iron.

Advanced oxidation processes applied to tannery wastewater containing Direct Black 38--elimination and degradation kinetics.

The application of advanced oxidation processes (H(2)O(2)/UV, TiO(2)/H(2)O(2)/UV and TiO(2)/UV) to treat tannery wastewater was investigated. The experiments were performed in batch and continuous UV reactors, using TiO(2) as a catalyst. The effect of the hydrogen peroxide concentration on the degradation kinetics was evaluated in the concentration range 0-1800 mg L(-1). We observed that the degradation rate increased as the hydrogen peroxide increased, but excessive H(2)O(2) concentration was detrimental because it acted as a hydroxyl radical scavenger since it can compete for the active sites of the TiO(2). In the H(2)O(2)/UV treatment, the COD removal reached around 60% in 4 h of reaction, indicating that the principal pollutants were chemically degraded as demonstrated by the results for BOD, COD, nitrate, ammonium and analysis of the absorbance at 254 nm. Artemia salina toxicity testing performed in parallel showed an increase in toxicity after AOP treatment of the tannery wastewater.