The photocatalytic degradation of azo dyes containing different functionalities has been reviewed using TiO2 as photocatalyst in aqueous solution under solar and UV irradiation. The mechanism of the photodegradation depends on the radiation used. Charge injection mechanism takes place under visible radiation whereas charge separation occurred under UV light radiation. The process is monitored by following either the decolorization rate and the formation of its end-products. Kinetic analyses indicate that the photodegradation rates of azo dyes can usually be approximated as pseudo-first-order kinetics for both degradation mechanisms, according to the Langmuir–Hinshelwood model. The degradation of dyes depend on several parameters such as pH, catalyst concentration, substrate concentration and the presence of electron acceptors such as hydrogen peroxide and ammonium persulphate besides molecular oxygen. The presence of other substances such as inorganic ions, humic acids and solvents commonly found in textile effluents is also discussed. The photocatalyzed degradation of pesticides does not occur instantaneously to form carbon dioxide, but through the formation of long-lived intermediate species. Thus, the study focuses also on the determination of the nature of the principal organic intermediates and the evolution of the mineralization as well as on the degradation pathways followed during the process. Major identified intermediates are hydroxylated derivatives, aromatic amines, naphthoquinone, phenolic compounds and several organic acids. By-products evaluation and toxicity measurements are the key-actions in order to assess the overall process.

TiO2-assisted photocatalytic degradation of azo dyes in aqueous solution: kinetic and mechanistic investigations A review

https://opus.lib.uts.edu.au/bitstream/10453/33344/4/A%20review%20on%20the%20occurrence%20of%20micropollutants%20in%20the%20aquatic%20environment%20and%20their%20fate%20and%20removal%20during%20wastewater%20treatment.pdf

A review on the occurrence of micropollutants in the aquatic environment and their fate and removal during wastewater treatment

Ecotoxicology of human pharmaceuticals.

The science of the total environment

Advanced oxidation processes (AOP) for water purification and recovery

https://web.iitd.ac.in/~arunku/files/CEL411_Y12/Elimination%20of%20pharmaceuticals%20in%20sewage%20treatment%20plants%20in%20Finland_Vieno.pdf

Elimination of pharmaceuticals in sewage treatment plants in Finland.

Occurrence of acidic pharmaceuticals in raw and treated sewages and in receiving waters.

The occurrence of four beta blockers, one antiepileptic drug, one lipid regulator, four anti-inflammatories, and three fluoroquinolones was studied in a river receiving sewage effluents. All compounds but two of the fluoroquinolones were observed in the water above their limit of quantification concentrations. The highest concentrations (up to 107 ng L-1) of the compounds were measured during the winter months. The river water was passed to a pilot-scale drinking water treatment plant, and the elimination of the pharmaceuticals was followed during the treatment. The processes applied by the plant consisted of ferric salt coagulation, rapid sand filtration, ozonation, two-stage granular activated carbon filtration (GAC), and UV disinfection. Following the coagulation, sedimentation, and rapid sand filtration, the studied pharmaceuticals were found to be eliminated only by an average of 13%. An efficient elimination was found to take place during ozonation at an ozone dose of about 1 mg L-1 (i.e., 0.2−0.4 m...

Occurrence of pharmaceuticals in river water and their elimination in a pilot-scale drinking water treatment plant.

The occurrence of five pharmaceuticals (ibuprofen, naproxen, ketoprofen, diclofenac, and bezafibrate) in the influent and effluent water of a sewage treatment plant (STP) in the recipient river water and in a drinking water treatment plant (DWTP) located downstream from the STP was followed during three seasons:  winter, spring, and summer. In the STP, the elimination of the pharmaceuticals decreased significantly (an average of 25% compared to spring and summer) in wintertime leading to increased concentrations of pharmaceuticals in the effluent water. The total concentration of all the studied pharmaceuticals in the effluent water was 3−5 times higher in wintertime (about 2500 ng L-1) than during the other seasons (about 500−900 ng L-1). Accordingly, the highest concentrations (up to 129 ng L-1) in the recipient river were measured in the wintertime. Pharmaceuticals were carried longer distances downstream from the STP when the river was covered by ice and snow. During a drastic increase in water flow r...

Seasonal variation in the occurrence of pharmaceuticals in effluents from a sewage treatment plant and in the recipient water

Analysis of neutral and basic pharmaceuticals in sewage treatment plants and in recipient rivers using solid phase extraction and liquid chromatography-tandem mass spectrometry detection.

Tuula Tuhkanen

Papers

Elimination of pharmaceuticals in sewage treatment plants in Finland.

Occurrence of acidic pharmaceuticals in raw and treated sewages and in receiving waters.

Occurrence of pharmaceuticals in river water and their elimination in a pilot-scale drinking water treatment plant.

Seasonal variation in the occurrence of pharmaceuticals in effluents from a sewage treatment plant and in the recipient water

Analysis of neutral and basic pharmaceuticals in sewage treatment plants and in recipient rivers using solid phase extraction and liquid chromatography-tandem mass spectrometry detection.