Pharmaceuticals in wastewater and their photocatalytic degradation using nano-enabled photocatalysts

Pharmaceuticals in the concentration range of hundreds of ng/L to μg/L occur in wastewater and end up in surface water, groundwater and agricultural land where they cause various health risks. These pollutants are classified as emerging and cannot be efficiently removed by conventional wastewater treatment processes. The use of nano-enabled photocatalysts in the removal of pharmaceuticals in aquatic systems has recently received research attention owing to their enhanced properties and effectiveness. The industrial scale application of photocatalytic technology is still limited. A comprehensive review on the removal of pharmaceuticals from real wastewater using the photocatalysts is therefore necessary. This paper reviews literature on the occurrence, fate, and nano-sized photocatalytic removal strategies of pharmaceuticals from wastewater. Modifications of nano-enabled photocatalysts through doping, deposition on various supports, and introducing magnetic character to enhance their photocatalytic efficiency and recyclability were discussed. The synthetic routes of photocatalysts influence the physical and chemical properties which can either enhance or inhibit their effectiveness. The benefits of photocatalytic degradation include easy recycling as they exhibit excellent stability, and can be used for several cycles. Going forward, research should focus on: (1) elucidation of photodegradation mechanisms, (2) real wastewater treatment at industrial scale to remove multiple pharmaceutical compounds, (3) regeneration, and disposal particularly towards large scale application, (4) life cycle assessment of the photocatalysts from synthesis to application, (5) lowering the cost and improving photodegradation efficiency, and (6) investigating the toxicity of intermediates to the photocatalyst and the environment.