Degradation of diclofenac sodium using combined processes based on hydrodynamic cavitation and heterogeneous photocatalysis

Abstract

Diclofenac sodium, a widely detected pharmaceutical drug in wastewater samples, has been selected as a model pollutant for degradation using novel combined approach of hydrodynamic cavitation and heterogeneous photocatalysis. A slit venturi has been used as cavitating device in the hydrodynamic cavitation reactor. The effect of various operating parameters such as inlet fluid pressure (2-4 bar) and initial pH of the solution (4-7.5) on the extent of degradation have been studied. The maximum extent of degradation of diclofenac sodium was obtained at inlet fluid pressure of 3 bar and initial pH as 4 using hydrodynamic cavitation alone. The loadings of TiO2 and H2O2 have been optimised to maximise the extent of degradation of diclofenac sodium. Kinetic study revealed that the degradation of diclofenac sodium fitted first order kinetics over the selected range of operating protocols. It has been observed that combination of hydrodynamic cavitation with UV, UV/TiO2 and UV/TiO2/H2O2 results in enhanced extents of degradation as compared to the individual schemes. The maximum extent of degradation as 95% with 76% reduction in TOC has been observed using hydrodynamic cavitation in conjunction with UV/TiO2/H2O2 under the optimised operating conditions. The diclofenac sodium degradation byproducts have been identified using LC/MS analysis.

Optimisation on pretreatment of rubber seed (Hevea brasiliensis) oil via esterification reaction in a hydrodynamic cavitation reactor

“…Several researchers reported that reaction rate increased up to certain upstream pressure. Bagal and Gogate (2014) reported reaction rate was decreased at 4 bar due to degradation reaction and Vichare et al (2000) reported decomposition reaction started at 3.8 bar. Therefore, an optimised inlet pressure of 3 bar was selected for further work.…”

Effect of free radical-induced degradation on water permeation through PFSA ionomer membranes

“…It is also noted that large bubbles and cracks that appear in the degraded membrane which may be due to the heat and gases released from Fenton's reagent reaction [56], and which may also lead to expansion of the water channels. This is illustrated, cartoon-fashion in Fig.…”

Ultrasound assisted enzymatic degradation of diclofenac sodium: Optimization of process parameters and kinetics

“…However, novel advanced treatment processes have also been reported for removal of diclofenac sodium [11,12]. These techniques possess various disadvantages such as slower removal kinetics as well as high operational costs along with hazardous byproducts including 5-hydroxydiclofenac and diclofenac-2,5-iminoquinone in ozonebased methods [10].…”