TiO 2 mediated semiconductor photocatalysis is an established advanced oxidation process for the treatment of contaminated aqueous and gaseous streams. However, TiO 2 exhibits low adsorption ability, especially for non-polar substances due to its polar structure. Low adsorption ability of non-porous TiO 2 particles can be improved by surface augmentation using inert supports. In this work, TiO 2 was impregnated on three different kinds of adsorbents, mesoporous (MCM-41), microporous (β-zeolite) and pillared structure (montmorillonite) where different loadings (10-80%) of TiO 2 were obtained using sol-gel method. The catalysts were characterized by several analytical techniques including XRD, SEM-EDX, XPS, and BET analyzer. Subsequent to the dark adsorption studies, photocatalytic efficiency of the supported catalysts was evaluated using an azo-dye, orange II in water as model compound under different operating conditions. All supported catalysts exhibit good photodegradation efficiency of orange II, and their overall removal efficiency was always better than that of bare TiO 2 produced by the sol-gel method and commercial catalyst, Degussa-P25.

Photocatalytic degradation of orange II by TiO2 catalysts supported on adsorbents

Utilization of solar energy for wastewater treatment: Challenges and progressive research trends.

Hazardous organic pollutants have been attracting heightened interest in recent years due to their persisting properties, low biodegradability, and negative influence on aquatic life, wildlife, and humans even at low concentrations. Considering their dangerous effect on the environment, several treatments using different techniques were adopted to remove them from water and wastewater. Herein, electrochemical advanced oxidation processes (EAOPs), especially anodic oxidation (AO), electro-Fenton (EF), heterogeneous electro-Fenton (HEF), and photoelectro-Fenton (PEF), have been thoroughly reviewed and found to be promising compared to conventional methods. The state of the art of the previous treatment processes has been discussed in detail, where each technique has its own merits and challenges. These processes depend on their operating conditions mainly pH, current density, nature of electrodes used, and conductivity of the solution, etc. The efficiencies of EAOPs follows the order as PEF > EF > AO and can mineralize the recalcitrant organic pollutants completely.

An overview on the elimination of organic contaminants from aqueous systems using electrochemical advanced oxidation processes

Agricultural development, extensive industrialization, and rapid growth of the global population have inadvertently been accompanied by environmental pollution. Water pollution is exacerbated by the decreasing ability of traditional treatment methods to comply with tightening environmental standards. This review provides a comprehensive description of the principles and applications of electrochemical methods for water purification, ion separations, and energy conversion. Electrochemical methods have attractive features such as compact size, chemical selectivity, broad applicability, and reduced generation of secondary waste. Perhaps the greatest advantage of electrochemical methods, however, is that they remove contaminants directly from the water, while other technologies extract the water from the contaminants, which enables efficient removal of trace pollutants. The review begins with an overview of conventional electrochemical methods, which drive chemical or physical transformations via Faradaic reactions at electrodes, and proceeds to a detailed examination of the two primary mechanisms by which contaminants are separated in nondestructive electrochemical processes, namely electrokinetics and electrosorption. In these sections, special attention is given to emerging methods, such as shock electrodialysis and Faradaic electrosorption. Given the importance of generating clean, renewable energy, which may sometimes be combined with water purification, the review also discusses inverse methods of electrochemical energy conversion based on reverse electrosorption, electrowetting, and electrokinetic phenomena. The review concludes with a discussion of technology comparisons, remaining challenges, and potential innovations for the field such as process intensification and technoeconomic optimization.

Electrochemical Methods for Water Purification, Ion Separations, and Energy Conversion

Organics removal from shale gas wastewater by pre-oxidation combined with biologically active filtration.

Advanced oxidation processes in the removal of organic substances from produced water: Potential, configurations, and research needs

Evaluation of Fenton and modified Fenton oxidation coupled with membrane distillation for produced water treatment: Benefits, challenges, and effluent toxicity.

Peracetic acid has quickly gained ground in water treatment over the last decade. Specifically, its disinfection efficacy toward a wide spectrum of microorganisms in wastewater is accompanied by the simplicity of its handling and use. Moreover, peracetic acid represents a promising option to achieve disinfection while reducing the concentration of typical chlorination byproducts in the final effluent. However, its chemical behavior is still amply debated. In this study, the reactivity of peracetic acid in the presence of halides, namely, chloride and bromide, was investigated in both synthetic waters and in a real contaminated water. While previous studies focused on the ability of this disinfectant to form halogenated byproducts in the presence of dissolved organic matter and halides, this work indicates that peracetic acid also contributes itself as a primary source in the formation of these potentially carcinogenic compounds. Specifically, this study suggests that 1.5 mM peracetic acid may form around 1–10 μg/L of bromoform when bromide is present. Bromoform formation reaches a maximum at near neutral pH, which is highly relevant for wastewater management.

https://pubs.acs.org/doi/pdf/10.1021/acs.est.1c06118

Marco Coha

Papers

Advanced oxidation processes in the removal of organic substances from produced water: Potential, configurations, and research needs

Evaluation of Fenton and modified Fenton oxidation coupled with membrane distillation for produced water treatment: Benefits, challenges, and effluent toxicity.

Formation of Halogenated Byproducts upon Water Treatment with Peracetic Acid