Floating Photocatalysts for Passive Solar Degradation of Naphthenic Acids in Oil Sands Process-Affected Water

Abstract

Abstract:Oil sands process-affected water (OSPW), generated from bitumen extraction in the Canadian oil sands, may require treatment to enable safe discharge to receiving watersheds, as dissolved naphthenic acids (NAs) and other acid extractable organics (AEO), identified as the primary toxic components of OSPW, are environmentally persistent and poorly biodegradable. However, conventional advanced oxidation processes (AOPs) are impractically expensive to treat the volumes of OSPW stockpiled in the Athabasca region. Here we prepared floating photocatalysts (FPCs) by immobilizing TiO 2 on glass microbubbles, such that the composite particles float at the air-water interface for passive solar photocatalysis. The FPCs were demonstrated to outperform P25 TiO 2 nanoparticles in degrading AEO in raw OSPW under natural sunlight and gentle mixing conditions. The FPCs were also found to be recyclable for multiple uses through simple flotation and skimming. This paper thus demonstrates the concept of a fully passive AOP that may be scalable to oil sands water treatment challenges, achieving efficient NA reduction solely through the energy provided by sunlight and natural mixing processes (wind and waves).

Reusable floating polymer nanocomposite photocatalyst for the efficient treatment of dye wastewaters under scaled‐up conditions in batch and recirculation modes

“…Among the different substrates used for immobilised photocatalysts, floating photocatalysts have attracted much attention in recent times . Compared to suspended or other forms of immobilised photocatalysts, the floating photocatalysts have distinct advantages such as (i) more efficient utilisation of light, (ii) enhanced utilisation of dissolved oxygen at the air–water interface, (iii) better oxidation efficiency, (iv) effective degradation of most organic contaminants, (v) a high degree of reusability and (vi) a facile post‐treatment separation process . The last point may contribute significantly to a lower cost of wastewater treatment.…”

“…[1][2][3][4] Compared to suspended or other forms of immobilised photocatalysts, the floating photocatalysts have distinct advantages such as (i) more efficient utilisation of light, (ii) enhanced utilisation of dissolved oxygen at the air-water interface, (iii) better oxidation efficiency, (iv) effective degradation of most organic contaminants, (v) a high degree of reusability and (vi) a facile post-treatment separation process. [5][6][7][8][9][10] The last point may contribute significantly to a lower cost of wastewater treatment. Thus, floating photocatalysts can play a vital role in the development of both localised and large-scale wastewater treatment technologies 11 which is the urgently needed owing to the ever-increasing contamination of most freshwater sources.…”

Preparation of supporting photocatalysts for water treatment using natural sunlight as an alternative driving energy

“…On comparing the direct dispersion or other form of suspension of photocatalyst, floating photocatalyst shows an incisive advantage such as maximum potential use of light with enhanced photocatalyst reactivity [12,26] on the bead surface as it receives sufficient amount of dissolved oxygen and H2O present at the air-water contact surface [12,[27][28][29] leads to enhanced oxidation efficiency resulting in efficient degradation of most of the organic contaminants present in water. Post-treatment separation process and recovery of floating beads easily by sieving is proved easy and cost-effective facilitating it for reusing for the next cycle [30][31][32][33][34][35][36]. Due to an exclusive structure of floating beads coated with nanoparticles provides several more advantage such as it reduces the loss and mass of photocatalyst coated on beads, rotation of floating beads on the surface either naturally by wind flow or by providing some kinetics, it provides an enough surface area in order to complete the photodegradation and prevent the interaction between the organic pollutants and photocatalysts for a longer duration which is the reason for decrease in photocatalytic reactivity [1].…”

Comparative Study of Four TiO2-Based Photocatalysts to Degrade 2,4-D in a Semi-Passive System

“…Although photospheres have recently been broadly and successfully studied for degradation of environmental contaminants [20,[78][79][80][81], their usage is still constrained by problems with separation after treatment. Moreover, ensuring the even dispersion of the photospheres for a semi-passive treatment, with no mixing, may be a challenge in practical applications.…”