Recent advances in photocatalytic remediation of emerging organic pollutants using semiconducting metal oxides: an overview

Abstract

Many untreated and partly treated wastewater from the home and commercial resources is being discharged into the aquatic environment these days, which contains numerous unknown and complex natural and inorganic compounds. These compounds tend to persist, initiating severe environmental problems, which affect human health. Conventionally, physicochemical treatment methods were adopted to remove such complex organic chemicals, but they suffer from critical limitations. Over time, photocatalysis, an advanced oxidation process, has gained its position for its efficient and fair performance against emerging organic pollutant decontamination. Typically, photocatalysis is a green technology to decompose organics under UV/visible light at ambient conditions. Semiconducting nanometal oxides have emerged as pioneering photocatalysts because of large active surface sites, flexible oxidation states, various morphologies, and easy preparation. The current review presents an overview of emerging organic pollutants and their effects, advanced oxidation processes, photocatalytic mechanism, types of photocatalysts, photocatalyst support materials, and methods for improving photodegradation efficiency on the degradation of complex emerging organic pollutants. In addition, the recent reports of metal-oxide-driven photocatalytic remediation of emerging organic pollutants are presented in brief. This review is anticipated to reach a broader scientific community to understand the first principles of photocatalysis and review the recent advancements in this field.

Removal of Emerging Organic Pollutants by Zeolite Mineral (Clinoptilolite) Composite Photocatalysts in Drinking Water and Watershed Water

“…However, emerging organic pollutants (EOPs), including pharmaceuticals and personal care products (PPCPs) [10], persistent organic pollutants (POPs) [11], disinfectant by-products (DBPs) [12], endocrine disruptors compounds (EDCs) [13,14], antibiotics [15], and microplastics (MPs) [16,17], cannot be decomposed after adsorption, which would lead to the long-term pollution of the environment. Particularly, agricultural runoff, domestic waste, sewage overflow, and the partly metabolized pharmaceuticals excreted by humans and animals bring high EOP emissions to an urban environment [18]. Although the wastewater might meet the discharge standard through wastewater treatment plants (WWTPs), persistent pollutant residues are still detected at the ng/L or mg/L level in surface water and groundwater.…”

Titanium Dioxide Nanoparticles Doped with Iron for Water Treatment via Photocatalysis: A Review

“…It is worthwhile to investigate how efficacy varies with operating conditions, aiming to identify the optimal catalyst, whose properties can be modulated based on the iron amount (or different dopants) used, depending on the effluent, conditions, and the target molecule, resulting in selective degradation. Additionally, it is essential to define accurate criteria for the selection of a photocatalytic reactor [134] with the optimal geometry necessary to provide effective irradiation [11]. For future commercial and research applications, especially in the water treatment field, it will be necessary not only to synthesize a high-performance photocatalyst in a simple and environmentally friendly manner able to operate under visible light but also to develop an effective strategy to iin my opinion they do not need an explanation in the text, they serve to indicate the order of the stepsmmobilize the photocatalytic nanoparticles onto the surface of the supporting material [130,131] (to avoid costly phases of catalyst separation from the treated water [132,133]).…”

“…It is worthwhile to investigate how efficacy varies with operating conditions, aiming to identify the optimal catalyst, whose properties can be modulated based on the iron amount (or different dopants) used, depending on the effluent, conditions, and the target molecule, resulting in selective degradation. Additionally, it is essential to define accurate criteria for the selection of a photocatalytic reactor [134] with the optimal geometry necessary to provide effective irradiation [11].…”

Photocatalytic Removal of Water Emerging Pollutants in an Optimized Packed Bed Photoreactor Using Solar Light

“…However, it is mandatory to develop an accessible and valuable packed bed reactor system that allows scaling and studying the possible industrial applications of photocatalytic materials. In photocatalysis, metal-transition oxides such as TiO2, ZnO, Fe2O3, SnO, and V2O5 have been pointed as the most photo-active materials due to their physicochemical properties, together with high chemical stability and non-toxicity [26][27][28][29][30]. TiO2, with a bandgap of 3.2 eV, is one of the most studied photocatalysts in the last years, with a broad range of organic compounds such as hydrocarbons, and aromatic compounds, among others.…”