Advances in powder nano-photocatalysts as pollutant removal and as emerging contaminants in water:Analysis of pros and cons on health and environment

Photocatalysis is an advanced oxidation process where light exposure triggers a semiconducting nanomaterial(nano-photocatalyst)to generate electron-hole(e^(-)/h^(+))pairs and free radicals.This phenomenon is widely used for the photocatalysis-assisted removal of organic and other contaminants using wide range of nanophotocatalysts,offering an efficient approach to environmental remediation.However,the introduction of powdered nano-photocatalysts into water systems often leads to unintended secondary pollution in the form of residual nano-photocatalysts,ion leaching,free radicals,toxic by-products etc.Such practices potentially introduce emerging secondary contaminants into aquatic environments,posing risks to both aquatic life and human health.The resulting chemical by-products and intermediates can effectively induce chronic toxicity,neurological and developmental disorders,cardiovascular defects,and intestinal ailments in humans and aquatic species.Despite having a range of health and environmental consequences,this dark side of nano-photocatalysts has been comparatively less explored and discussed in the literature.In this review,the pros and cons of powder nanophotocatalysts are discussed in view of their advantages as well as disadvantages in wastewater treatment.The discussion encompasses their classification based on composition,dimensions,structure,and activity,as well as recent advancements in improving their photocatalytic efficiency.The article also explores the recent advances on their applications in photocatalytic removal of various water pollutants/contaminants of emerging concern(i.e.,organic pollutants,micro/nano plastics,heavy ions,disinfections,etc.)Furthermore,an emphasis on the role of such nano-photocatalysts as emerging(secondary)contaminants in water system,along with a thorough discussion of latest studies related to the health and environmental issues,has been discussed.Additionally,it addresses critical issues in applying powder nano-photocatalysts for wastewater detoxification and explores potential solutions to these challenges followed by future prospects.

Photocatalytic Degradation of 2,6-Dichlorophenol in Aqueous Phase Using Titania as a Photocatalyst

The paper includes the studies on photocatalytic degradation of 2,6-DCP in aqueous phase using titania (PC-105) as a photocatalyst. The degradation experiments were carried out by irradiating the aqueous suspensions of the model compound in the presence of photocatalysts under UV light. The rate of degradation was estimated from residual concentration spectrophotometrically. Various parameters affecting the degradation process viz. catalyst dose, pH, initial substrate concentration and time were investigated in order to obtain their optimum values. The maximum degradation of 2,6-DCP was achieved with 1.25 g/L catalyst dose at pH-4. The disappearance of 2,6-DCP obeyed pseudo-first order kinetics and the rate constant value was calculated to be 4.78 × 10-4s-1.