A Review on Diclofenac Removal from Aqueous Solution, Emphasizing on Adsorption Method

Diclofenac is a drug with an analgesic effect that accumulates and results in adverse consequences if it enters the human body more than needed. Low concentrations of diclofenac have been detected in different water resources through leachates of landfills and agricultural areas, human and animal excreta, expired drug discharge, and hospital effluents. To eliminate diclofenac from the aquatic environment, different removal methods such as membrane filtration, ozonation, advanced oxidation, Fenton oxidation, electrochemical oxidation, photocatalysis, soil aquifer treatment, ion exchange, and adsorption are studied. Adsorption is considered to be more effective and economical than other methods in case of wastewater treatment. In this review paper, studies on diclofenac removal applying different methods, especially adsorption, are inquired and the adsorbents are divided into two main categories; carbonaceous and other adsorbents. The effect of different parameters such as contact time, pH, adsorbent dosage, initial concentration, and temperature on the adsorption process in the related studies is also mentioned. Furthermore, the equilibrium isotherms and the adsorption kinetics of the studies were also noted. By studying the literature, it was clear that the pH value was a key parameter among all, because it has a main effect on the removal efficiency and it is dependent on the pK(a) of diclofenac and the pH(ZPC) of the adsorbent.