Advanced oxidation processes: photo-electro-Fenton remediation process for wastewater contaminated by organic azo dyes

Abstract The threat of dye contamination has achieved an unsurpassed abnormal state lately due to their massive consumption in several enterprises including textile, leather, cosmetic, plastic, and paper industries. This review focuses on the integrations of various advanced oxidation processes (AOPs), such as Fenton, photocatalysis, and ozonation, with biodegradation for the treatment of textile azo dyes. Such integrations have been explored lately by researchers to bring down the processing cost and improve the degree of mineralization of the treated dyeing wastewater. The review refers to the basic mechanisms, the influence of various process parameters, outcomes of recent works, and future research directions. All the three AOPs, independently, demonstrated substantial color reduction of 54–100%. The ozonation process, stand-alone, showed the most efficient decolorization (of 88–100%) consistently in all reviewed research works. In contrast, all three AOPs independently offered varied and inadequate COD reduction in the range of 16–80%. The AOPs, after getting integrated with biodegradation, yielded an additional reduction (of 11–70%) in the COD-levels and (of 16–80%) in the TOC-levels. Further, the integration of AOPs with biodegradation has potential to significantly reduce the treatment costs. The review suggests further research efforts in the direction of sequencing chemical and biological routes such that their synergistic utilization yield complete detoxification of the textile azo dyes economically at large-scale.

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Emerging Aspects of Photo-catalysts (TiO2 & ZnO) Doped Zeolites and Advanced Oxidation Processes for Degradation of Azo Dyes: A Review

Current Analytical Chemistry ◽

10.2174/1573411016999200711143225 ◽

2020 ◽

Vol 17 (1) ◽

pp. 82-97

Author(s):

Syed M. Hussain ◽

Tabassum Hussain ◽

Moeen Faryad ◽

Qasim Ali ◽

Shafaqat Ali ◽

...

Keyword(s):

Water Treatment ◽

Photocatalytic Degradation ◽

Azo Dyes ◽

Advanced Oxidation Processes ◽

Treatment Strategies ◽

Advanced Oxidation ◽

Industrial Effluents ◽

Dye Molecules ◽

Oxidation Processes ◽

By Products

Background: Azo dyes are recognized as non-decomposable and recalcitrant compounds and can be depleted into more dangerous secondary products in anaerobic environments. In the current scenario, different water treatment strategies, including adsorption, photocatalysis, and advanced oxidation processes based practices, are facing different limitations. Method: A literature survey was accomplished by searching the scientific data from different search engines, including Scopus, PubMed, Science Direct, Springer, Taylor and Francis, Google Scholar, Blackwell-Synergy, Wiley-Interscience and Research-Gate, etc. This article has been compiled after intensively reviewing about 231 research papers, reviews, and book chapters in the fields of industrial effluents, hazardous materials, and water treatment strategies with their advantages and limitations. Results: Molecular oxygen and other active species, such as O2•−, HO2•, H2O2, and •OH, play a significant role in the degradation of dyes in AOPs and photocatalyst utilizes sunlight energy and accelerates some chemical reactions depending upon the activation energies. Different reaction parameters, including calcination temperature, pH, initial dye concentration, and catalyst dosage, have a significant impact on photocatalytic degradation performance. Characterization of degradation processes of dye-stuffs could be carried out by the state-of-the-art analytical techniques i.e. UV-Visible spectroscopy, powdered XRD, FTIR (ATR), EDX-SEM, BET, and differential pulse voltammetry. GC-MS and LC-MS investigation of photodegradation by-products and intermediates could provide identification and possible degradation pathway for target dye molecules. This review covers research related to photocatalytic degradation of azo dyes by TiO2 and ZnO, widely used photocatalysts, and various combinations of zeolites. Conclusion: It can be concluded that the combination of nano-sorbents (Fly Ash Zeolites) and photocatalysts not only enhances the degradation but also effectively removes toxic dye molecules and their by-products. The review explains the suitability of synergic applications of catalysts (TiO2, ZnO) and catalytic bed (zeolites) for different industrial effluents and waste water treatment at a significant pace towards green technology.

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Nonlinear Modeling for the Degradation of Aqueous Azo Dyes by Combined Advanced Oxidation Processes Using Artificial Neural Networks

Chemical Product and Process Modeling ◽

10.2202/1934-2659.1562 ◽

2011 ◽

Vol 6 (1) ◽

Author(s):

Masroor Mohajerani ◽

Mehrab Mehrvar ◽

Farhad Ein-Mozaffari

Keyword(s):

Neural Networks ◽

Artificial Neural Networks ◽

Azo Dyes ◽

Advanced Oxidation Processes ◽

Removal Rate ◽

Advanced Oxidation ◽

Ultrasonic Power ◽

Oxidation Processes ◽

Degradation Rates ◽

Artificial Neural

One-hidden-layer artificial neural networks (ANNs) using a back-propagation structure have been trained on different sets of experimental data to identify and evaluate the degradation of different azo dyes (Reactive Yellow 84, Reactive Blue 19, Direct Red 23, Direct Red 28, and Acid Blue 193) by photo-Fenton process and combined ozonation and ultrasonolysis processes. Different input variables such as pH, initial concentrations of dyes and ozone, reaction time, ultrasonic power density, and initial concentrations of hydrogen peroxide and ferrous in aqueous solution were employed to model the degradation rates of azo dyes based on the decolorization efficiency and the removal rate using chemical oxygen demand (COD) and total organic carbon (TOC). A new model expression is developed to find the effect of individual parameters and their interactions on the efficiency of organic degradation by advanced oxidation processes.

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Solar-driven advanced oxidation processes for full mineralisation of azo dyes in wastewater

Environmental Chemistry ◽

10.1071/en16202 ◽

2017 ◽

Vol 14 (3) ◽

pp. 188 ◽

Cited By ~ 6

Author(s):

Chunhong Nie ◽

Pingping Sun ◽

Lingyue Zhu ◽

Simeng Gao ◽

Hongjun Wu ◽

...

Keyword(s):

Methyl Orange ◽

Solar Energy ◽

Small Molecules ◽

Azo Dyes ◽

Industrial Wastewater ◽

Advanced Oxidation Processes ◽

Advanced Oxidation ◽

Azo Compounds ◽

Oxidation Processes ◽

Toc Removal

Environmental contextFull mineralisation of synthetic azo dyes in industrial wastewater is a tough job for traditional wastewater treatment technologies. There is an urgent need for the development of both sustainable and environmentally friendly technology capable of fully mineralising these azo compounds. We show that solar-driven advanced oxidation processes are capable of completely mineralising azo compounds with high utilisation of solar energy. AbstractMineralisation of synthetic azo dyes in industrial wastewater is an energy-intensive process in treatment technology. The Solar Thermal Electrochemical Process for advanced oxidation processes (STEP-AOPs) utilises solar energy and electricity for the activation and electrooxidation of organic pollutants to harmless, small and non-toxic molecules with no other energy consumption. Based on molecular structure and chemistry, the STEP-AOPs for the treatment of azo dyes in wastewater, as exemplified with a typical azo dye, methyl orange, is reported for the first time. Thermodynamic calculations of the temperature-dependent potentials of methyl orange demonstrate that Gibbs free energy decreased by 161kJmol–1 and the potential decreased by 0.019V with an increase of temperature from 20 to 80°C, which indicates that the drop in both energy and potential specifically fits the STEP-AOPs technique. Experimental results showed that the STEP-AOPs achieved a total organic carbon (TOC) removal of 95.6% for methyl orange. The TOC removal rate improved by 39.8% and the unit TOC electricity consumption decreased by 53.8% at 80°C compared with conventional methods (20°C). The mineralisation mechanism for methyl orange was a gradual shortening of the molecular chain through cleavage of the azo bond, breakdown of the benzene ring and formation of inorganic small molecules susceptible to be oxidised to non-toxic small molecules, and carbon dioxide via STEP-AOPs. The evidence shows that the STEP-AOPs is capable of mineralising azo compounds completely.

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