Wet peroxide oxidation of dye-containing wastewaters using nanosized Au supported on Al 2 O 3

Adsorption of Azorubine E122 dye via Na-mordenite with tryptophan composite: batch adsorption, Box-Behnken design optimisation and antibacterial activity

In the current investigation, we have reported on the preparation of Na-Mordenite (MOR) modified by tryptophan (MOR-NH2) nanocomposite was synthesized and characterized using FT-IR, XRD, SEM, XPS, and BET that represented that the MOR-NH2 has high surface area 288 m2/g and pore volume 0.38 cm3/g. This composite represented high efficiency in removal of food dye Azorubine (E122) was 1043 mg/g. Study all the factors that affected on the adsorption such as pH, dose, salinity, E122 dye concentration as well as study the adsorption isotherm models that represented that was fitted to Langmuir. Moreover, study the effect of time according to it the adsorption process was fitted to Pseudo-second-order, and the effect of temperature that approved that the reaction was endothermic, spontaneous, and chemisorption process. The MOR-NH2 nanocomposite was tested and proven to effectively inhibit the growth of Escherichia coli ATCC® 25922™ and Staphylococcus aureus ATCC® 25923™ at low concentrations. To the best of our knowledge, this work is the first to report the usage of MOR-NH2 adsorbents for the removal of E122 dye in wastewater samples. The mechanism of interaction between MOR-NH2 and E122 dye was determining as it could be through Hydrogen bonding, pore filling, or through π-π interaction. This research offers a promising solution for purifying water sources that are contaminated with a variety of chemicals, microorganisms, and other contaminants.

Magnetite Nanoparticles as Solar Photo-Fenton Catalysts for the Degradation of the 5-Fluorouracil Cytostatic Drug

Heterogeneous catalysts based on magnetite nanoparticles, Fe₃O₄, were prepared by the chemical coprecipitation method using iron (III) chloride as a salt precursor. The physicochemical properties of the nanoparticles were determined by different techniques and the efficiency was evaluated for the degradation of the cytostatic drug, 5-fluorouracil (5-FU), in aqueous solution by photo-Fenton process under simulated solar radiation. The most influential parameters, namely pH of the solution, catalyst load, H₂O₂ dosage, and use of radiation, were studied and optimized in the degradation process. The optimal conditions to achieve a 100% degradation of 5-FU (10 mg L^-1) and a high mineralization degree (76%) were established at the acidic pH of 3.0, 100 mg L^-1 of catalyst loading, and 58 mM of H₂O₂ under simulated solar radiation. The contribution of iron leaching to the catalyst deactivation, the role of the dissolved iron ions on homogenous reactions, and the stability of the catalyst were assessed during consecutive reaction cycles.

Treatment of Oil Sands’ Mature Fine Tailings Using Advanced Wet Air Oxidation (WAO) and Wet Air Peroxide Oxidation (WAPO)

Mature Fine Tailings (MFT) generated from oil sands processing represent a growing environmental issue, as settling of these tailings’ emulsion can take decades, increasing the risk of the toxic material’s leaching if left untreated. This study uses advanced wet air oxidation (WAO) and wet air peroxide oxidation (WAPO) to break down the MFT emulsions for faster settling. Three oxidation time intervals (5, 15, and 30 min) were investigated using compressed air and hydrogen peroxide in a pressurized vessel of 3.1–3.4 MPa internal pressure and at 200 °C temperature. The results showed that the WAO process was able to break the MFT emulsion, release trapped water, and recover residual bitumen. The WAPO process was much faster in breaking the emulsion; however, the presence of extra oxidants also resulted in the degradation of the residual bitumen. The 5 min oxidation time interval was found to be sufficient in breaking emulsions, separating water from soil particles, and recovering residual bitumen under the tested conditions. The oxidation process proved to be efficient by degrading all inorganic carbon, whereas 70% of the dissolved organic carbon in the recovered water after oxidation comprised only low molecular weight biodegradable hydrocarbons. Therefore, the WAO process was capable of breaking the MFT emulsions and allowing a faster settling of these tailings, with the added benefit of recovering residual bitumen.

A comprehensive review on sustainable greener nanoparticles for efficient dye degradation

The effluents released from textile industries mainly consist of dyes, metals and other pollutants. Dyes often are discharged in wastewater streams causing adverse effect on the environment. To eliminate these harmful dyes, various techniques are emerging out of which nanotechnology is the most reliable and safer. Nanotechnology offers convincing applications in case of environmental and economic concerns. The bio-synthesis of nanoparticles has several advantages over conventional methods and approach towards environment concern as well. Biological method of nanoparticles synthesis is concluded to be the most promising and efficient in action. Bio-synthesised nanoparticles could be used for treatment and decolourisation of dyes in an efficient manner. This review comprises the study of number of bio-synthesised nanoparticles utilised for degradation of various dyes present as pollutants in wastewater. Bio-synthesised nanoparticles such as gold, silver, iron, cobalt, zinc, titanium and molybdenum used for degradation of various dyes have been discussed in this review.

Heterogeneous Gold Nanoparticle-Based Catalysts for the Synthesis of Click-Derived Triazoles via the Azide-Alkyne Cycloaddition Reaction

A supported gold nanoparticle-catalyzed strategy has been utilized to promote a click chemistry reaction for the synthesis of 1,2,3-triazoles via the azide-alkyne cycloaddition (AAC) reaction. While the advent of effective non-copper catalysts (i.e., Ru, Ag, Ir) has demonstrated the catalysis of the AAC reaction, additional robust catalytic systems complementary to the copper catalyzed AAC remain in high demand. Herein, Au nanoparticles supported on Al2O3, Fe2O3, TiO2 and ZnO, along with gold reference catalysts (gold on carbon and gold on titania supplied by the World Gold Council) were used as catalysts for the AAC reaction. The supported Au nanoparticles with metal loadings of 0.7–1.6% (w/w relative to support) were able to selectively obtain 1,4-disubstituted-1,2,3-triazoles in moderate yields up to 79% after 15 min, under microwave irradiation at 150 °C using a 0.5–1.0 mol% catalyst loading through a one-pot three-component (terminal alkyne, organohalide and sodium azide) procedure according to the “click” rules. Among the supported Au catalysts, Au/TiO2 gave the best results.

Gold nanoparticles-modified MnFe2O4 with synergistic catalysis for photo-Fenton degradation of tetracycline under neutral pH

To decrease the adverse environmental and health-related effects of antibiotics, a series of MnFe₂O₄-Au (MFO-Au) composites were prepared by simple co-precipitation and photoreduction methods for efficient photo-Fenton degradation of tetracycline (TC). The synergistic effect of MFO and gold nanoparticles (AuNPs) with high absorption of visible light and strong photogenerated carrier separation efficiency endowed MFO-Au₃ an outstanding photo-Fenton catalytic performance for TC degradation in neutral condition. The surface hydroxyl of MFO profited to generation of •OH, and negative charged or partially polarized AuNPs benefited to adsorption of H₂O₂, which had a synergistic effect on enhancing the photo-Fenton catalytic performance of MFO-Au. 88.3% of TC was efficiently removed and about 51.9% of TOC decreased within 90 min. The electron spin resonance and quenching tests suggested that h⁺ and e^- were responsible for the high catalytic degradation and •OH and •O₂^- participated in the photo-Fenton reaction. The toxicity assessment by seed germination experiments showed efficient toxicity reduction of this system. Besides, MFO-Au exhibited high stability, good cycle, relatively economical and practical application performance, which is expected to provide potential guidance for the design and combination of noble nanoparticles with high stability and spinel bimetallic oxides with high catalytic activity in photo-Fenton reactions.

Supported Gold Nanoparticles as Catalysts for the Oxidation of Alcohols and Alkanes

Supporting gold nanoparticles have shown to be extremely active for many industrially important reactions, including oxidations. Two representative examples are the oxidation of alcohols and alkanes, that are substrates of industrial interest, but whose oxidation is still challenging. This review deals with these reactions, giving an insight of the first studies performed by gold based catalysts in these reactions and the most recent developments in the field.

Wastewater Treatment by Catalytic Wet Peroxidation Using Nano Gold-Based Catalysts: A Review

Nowadays, there is an increasing interest in the development of promising, efficient, and environmentally friendly wastewater treatment technologies. Among them are the advanced oxidation processes (AOPs), in particular, catalytic wet peroxidation (CWPO), assisted or not by radiation. One of the challenges for the industrial application of this process is the development of stable and efficient catalysts, without leaching of the metal to the aqueous phase during the treatment. Gold catalysts, in particular, have attracted much attention from researchers because they show these characteristics. Recently, numerous studies have been reported in the literature regarding the preparation of gold catalysts supported on various supports and testing their catalytic performance in the treatment of real wastewaters or model pollutants by CWPO. This review summarizes this research; the properties of such catalysts and their expected effects on the overall efficiency of the CWPO process, together with a description of the effect of operational variables (such as pH, temperature, oxidant concentration, catalyst, and gold content). In addition, an overview is given of the main technical issues of this process aiming at its industrial application, namely the possibility of using the catalyst in continuous flow reactors. Such considerations will provide useful information for a faster and more effective analysis and optimization of the CWPO process.

Application of Catalytic Wet Peroxide Oxidation for Industrial and Urban Wastewater Treatment: A Review

Catalytic wet peroxide oxidation (CWPO) is emerging as an advanced oxidation process (AOP) of significant promise, which is mainly due to its efficiency for the decomposition of recalcitrant organic compounds in industrial and urban wastewaters and relatively low operating costs. In current study, we have systemised and critically discussed the feasibility of CWPO for industrial and urban wastewater treatment. More specifically, types of catalysts the effect of pH, temperature, and hydrogen peroxide concentrations on the efficiency of CWPO were taken into consideration. The operating and maintenance costs of CWPO applied to wastewater treatment and toxicity assessment were also discussed. Knowledge gaps were identified and summarised. The main conclusions of this work are: (i) catalyst leaching and deactivation is one of the main problematic issues; (ii) majority of studies were performed in semi-batch and batch reactors, while continuous fixed bed reactors were not extensively studied for treatment of real wastewaters; (iii) toxicity of wastewaters treated by CWPO is of key importance for possible application, however it was not studied thoroughly; and, (iv) CWPO can be regarded as economically viable for wastewater treatment, especially when conducted at ambient temperature and natural pH of wastewater.

Degradation of the cytostatic 5-Fluorouracil in water by Fenton and photo-assisted oxidation processes

Cytostatics are part of the forefront research topics due to their high prescription, high toxicity, and the lack of effective solutions to stop their entrance and spread in the environment. Among them, 5-Fluorouracil (5-Fu) has received particular attention because is one of the most prescribed active substances in chemotherapy worldwide. The degradation of 5-Fu by advanced oxidation processes (AOPs) is a poorly addressed topic, and this work brings valuable inputs concerning this matter. Herein, the efficacy of Fenton's process in the degradation of 5-Fu is explored for the first time; the study of the main variables and its successful application to the treatment of real wastewaters is demonstrated. Moreover, hydrogen peroxide-based and photo-assisted techniques (direct photolysis, photodegradation with H₂O₂ and photo-Fenton) are also investigated for purposes of comparison. Under the best operation conditions obtained (T = 30 °C, [Fe²⁺]₀ = 0.5 mM; [H₂O₂]₀ = 240 mM and pH = 3 for [5-Fu]₀ = 0.38 mM), 5-Fu was completely eliminated after 2 h of Fenton's reaction and about 50 % of mineralization was reached after 8 h. The best performance was obtained by the photo-Fenton process, with 5-Fu mineralization level as high as 67 %, using an iron dose within the legal limits required for direct water discharge. Toxicity (towards Vibrio fischeri) of the effluents that resulted from the application of the above-mentioned AOPs was also evaluated; it was found that the degradation products generated from the photo-assisted processes are less toxic than the parent compound, putting into evidence the relevance of such technologies for degradation of cytostatics like 5-Fu.