A review on nanomaterial-based heterogeneous photocatalysts for removal of contaminants from water

Abstract

The rising concentration of pollutants in the environment due to partially treated or untreated wastewater entering the surface waters has seriously challenged the integrity of the ecosystem and the quality of water for human health. Therefore, it is crucial to establish a productive and economical process to degrade recalcitrant pollutants from various water matrices owing to the ineffectual removal of these contaminants by conventional treatment methods. In this regard, advanced oxidation processes (AOPs), especially photocatalysis, have gained much attention due to their unique properties, such as low-cost, easy synthesis, and ability to produce reactive radicals under light irradiation with complete mineralization of recalcitrant pollutants. In this review, heterogenous photocatalysts, their fundamental properties, and their working mechanism have been described, along with their applications in the degradation of contaminants in water. Recent progress on pristine and modified nanomaterial-based photocatalysts for the degradation of various pollutants in water has been discussed. In particular, the removal of toxic heavy metals, pesticides, dyes, pathogens, pharmaceuticals, and other miscellaneous contaminants from water using a wide variety of nanomaterial-based heterogeneous photocatalysts has been summarized. The effect of temperature, solution pH, and loading of photocatalysts was found to be the most critical factors influencing the photocatalytic degradation of pollutants. Subsequently, the photocatalyst immobilization process using various support materials including carbon-based materials, glass, zeolites, and polymers in designing the efficient photocatalysts and future perspectives have been outlined.

Beyond Conventional: Antibacterial, Antioxidant, and Photocatalytic Properties of Nanofibers Featuring Metal-Oxide-Modified Boron Nitride Nanoparticles

“…were employed to improve the photocatalytic activity of MOs. 21,22 Among them, boron nitride (BN) has attracted considerable attention with a two-dimensional hexagonal network with structural similarity to graphene. 23 It exhibits a high surface area, chemical stability, mechanical strength, thermal conductivity, and optical and catalytic properties.…”

“…Nowadays, organic and inorganic additives such as transition metals (Fe, Cu, Ni, Ce, Ag), nonmetal elements (B, C, N, S, P), oxide (TiO 2 , CuO, ZnO, Bi 2 O 3 , WO 3 , CdO) and nonoxide (BN, TiN, MoN, WC, SiC) ceramics, metal halides (PbX 2 , AgX, CuX), conductive polymers (PANI, PPy, PTh), etc. were employed to improve the photocatalytic activity of MOs. , Among them, boron nitride (BN) has attracted considerable attention with a two-dimensional hexagonal network with structural similarity to graphene . It exhibits a high surface area, chemical stability, mechanical strength, thermal conductivity, and optical and catalytic properties.…”

Recent advances in removal of pharmaceutical pollutants in wastewater using metal oxides and carbonaceous materials as photocatalysts: a review

“…Therefore, heterogeneous photocatalysis has been receiving considerable attention as one of the most attractive, low-cost, efficient and outstanding approaches in the degradation of pharmaceutical pollutants. 19–55 In this regard, a considerable amount of research interest has focused mostly on TiO 2 and to some extent on other semiconducting materials and transition metal oxides as photocatalysts in the degradation of pharmaceutical pollutants in water. 23–39 The choice of semiconducting metal oxides as photocatalysts is motivated by the availability of a renewable energy source (solar energy) and the generation of non-toxic degradation products (chemicals and gases).…”

“…36,39,49 Other approaches involving immobilization and the formation of a heterojunction are reported as imperative alternative strategies for achieving enhanced photocatalytic efficiency for these photocatalysts in water treatment. 51…”

“…According to the available literature, several reviews have been published focusing on metal oxides, 23–30 TiO 2 , 31–33 ZnO-based photocatalysts, 34 semiconductors, 35 doped TiO 2 , 36 hybrids, 37 TiO 2 –carbon dot nanocomposites, 38 plasmonic metal–TiO 2 composites, 39 carbonaceous/carbon-based materials, 40,41 g-C 3 N 4 , 42 MWCNT, 43 carbon dots, 38,44 activated carbon, 45 graphene-based composites, 46–48 graphene–TiO 2 and doped graphene–TiO 2 nanocomposites, 49 graphene-based materials, 50 and nanomaterial-based heterogeneous photocatalysts 51 as photocatalysts for the treatment of wastewater containing pharmaceuticals. Alternatively, several review articles have reported on the photodegradation of antibiotic contaminants in water, such as amoxicillin, 21 ibuprofen, 22 tetracycline, 52,54 ciprofloxacin, 53,54 and norfloxacin 54 antibiotics in wastewater and several others, which are referred to in section 3.…”