Toward Scaling-Up Photocatalytic Process for Multiphase Environmental Applications

Abstract

Recently, we have witnessed a booming development of composites and multi-dopant metal oxides to be employed as novel photocatalysts. Yet the practical application of photocatalysis for environmental purposes is still elusive. Concerns about the unknown fate and toxicity of nanoparticles, unsatisfactory performance in real conditions, mass transfer limitations and durability issues have so far discouraged investments in full-scale applications of photocatalysis. Herein, we provide a critical overview of the main challenges that are limiting large-scale application of photocatalysis in air and water/wastewater purification. We then discuss the main approaches reported in the literature to tackle these shortcomings, such as the design of photocatalytic reactors that retain the photocatalyst, the study of degradation of micropollutants in different water matrices, and the development of gas-phase reactors with optimized contact time and irradiation. Furthermore, we provide a critical analysis of research–practice gaps such as treatment of real water and air samples, degradation of pollutants with actual environmental concentrations, photocatalyst deactivation, and cost and environmental life-cycle assessment.

Modulation of Z-scheme photocatalysts for pharmaceuticals remediation and pathogen inactivation: Design devotion, concept examination, and developments

“…Different reactor designs have been investigated to address the challenge of expensive filters required to dodge nanomaterials discharges into the environment. This dispersion which results in high quantum efficiency due to good pollutant and catalyst interaction is common despite causing secondary pollution [128] . The widely employed fluidized bed reactor (Fig 9b) contains a system for easy recovery of catalysts after application.…”

Solar photo-oxidation of recalcitrant industrial wastewater: a review

“…The wastewater pH, categories of photocatalyst and structure, pollutant concentration and type, light intensity, photocatalyst dosage, other wastewater constituents, and solvent kind all play a role in photocatalytic degradation of refractory organics (Antonopoulou et al 2021;Samy et al 2021;Yang et al 2021c;Wang et al 2022b). However, low efficiency resulting from poor visible-light capturing catalysts, photo-reactor design, catalyst recovery and reuse, the formation of hazardous intermediates, and concerns about catalyst deactivation are all stated to be important downsides (Assadi et al 2021;Chen et al 2021;Su et al 2021;Yang et al 2021c;Gar Alalm et al 2021).…”

“…Until now, the most ubiquitous applied photocatalyst in water and wastewater treatment research is the P-25 titanium dioxide catalyst. This catalyst is utilized as a benchmark for comparing photocatalytic activity under various treatment circumstances (Gar Alalm et al 2021). P-25 titanium dioxide fine particles have often been administered in the form of slurry.…”

“…The treatment and reuse of industrial wastewaters are critical for the long-term management of water resources because it helps to reduce contamination in water bodies (Ateia et al 2020). The prevalence of pollutants of emerging concern such as pesticides, perfluoroalkyl substances (PFAS), pharmaceuticals, and phenols in industrial effluents has triggered public health worries due to their extreme toxicity and biologically rebellious characteristics (Gar Alalm et al 2021). Various human activities introduce these toxins into the aquatic environment regularly.…”

Catalyst Recovery, Regeneration and Reuse during Large-Scale Disinfection of Water Using Photocatalysis

“…A third proposed solution to the problem of catalyst separation is the use of membrane photocatalytic reactors, a type of hybrid reactor which operates continuously by retaining the catalyst within the reactor while passing the water through a microfiltration/nanofiltration membrane [19]. While these hybrid reactors show some promise in retaining the catalyst while removing certain organic compounds, their implementation on a large scale is hindered due to the vulnerability of the membranes to degradation upon exposure to UV radiation and the high amounts of reactive oxygen species produced by the photocatalyst, as well as membrane fouling owed to catalyst particles blocking the membrane pores [20]. Biofouling of membranes could potentially be a major problem, especially when photocatalysis is implemented for disinfecting water.…”