Combining photocatalytic and electrocatalytic oxidation for dibutyl phthalate degradation: the influence of carbon-coated titanium anode and metal oxide catalysts.

Plasticisers, such as dibutyl phthalate (DBP), are contaminants of emerging concern (CEC) that are toxic to living things and the environment. Unlike hydrophilic pollutants, DBP shows the characteristics of hydrophilic and hydrophobic nature which makes its degradation or removal difficult using conventional treatment technologies. The current study explored the potential of photocatalysis followed by electrocatalytic oxidation (PC + EC) using vanadium pentoxide (V2O5) and carbon-coated titanium (C/Ti) anode for the removal of 75 mg L-1 DBP from water. The structural stability and changes in the functional groups after treatment of the catalyst were determined using powder XRD and FTIR studies that found the catalyst structure to be stable. Optimization studies showed that UV-A (315-400 nm) irradiation source, 112 mA cm-2 current density, 50 mg L-1 catalyst dosage, 360 min PC, 210 min EC at pH 3 and 20 mM sodium sulphate managed to degrade 99.5% of DBP with 97% COD and 87.7% TOC removal. Compared to electrocatalytic oxidation (EC), PC + EC showed 40% higher TOC removal. Reusability studies found the reduction of 45% for COD removal after four treatment cycles with V2O5, while the anode material showed no considerable decrease in its degradation efficiency. High-resolution mass spectrometry (HRMS) studies established that complete degradation was preceded by the oxidation of DBP to phthalic anhydride and phthalic acid responsible for the increase in TOC during the initial treatment period. Overall, this study lays out insights for the application of photo-electrocatlytic oxidation for the removal of ubiquitous poorly soluble water pollutants such as phthalates.

Sustainable application of electrocatalytic and photo-electrocatalytic oxidation systems for water and wastewater treatment: a review.

Wastewater treatment and reuse have risen as a solution to the water crisis plaguing the world. Global warming-induced climate change, population explosion and fast depletion of groundwater resources are going to exacerbate the present global water problems for the forthcoming future. In this scenario, advanced electrochemical oxidation process (EAOP) utilising electrocatalytic (EC) and photoelectrocatalytic (PEC) technologies have caught hold of the interest of the scientific community. The interest stems from the global water management plans to scale down centralised water and wastewater treatment systems to decentralised and semicentralised treatment systems for better usage efficiency and less resource wastage. In an age of rising water pollution caused by contaminants of emerging concern (CECs), EC and PEC systems were found to be capable of optimal mineralisation of these pollutants rendering them environmentally benign. The present review treads into the conventional electrochemical treatment systems to identify their drawbacks and analyses the scope of the EC and PEC to mitigate them. Probable electrode materials, potential catalysts and optimal operational conditions for such applications were also examined. The review also discusses the possible retrospective application of EC and PEC as point-of-use and point-of-entry treatment systems during the transition from conventional centralised systems to decentralised and semi-centralised water and wastewater treatment systems.

Electrooxidation of amoxicillin in aqueous solution with graphite electrodes: Optimization of degradation and deciphering of byproducts using HRMS.

Contaminants of emerging concern (CECs) such as antibiotics have become a matter of worry in aquatic environments worldwide. Their presence in the environment has been increasing due to the inability of conventional wastewater and water treatments to annihilate them. Hence, attempts have been made to remove CECs using electrochemical oxidation (EO). Present study employed the low cost, active carbon based graphite sheet electrodes as anode and cathode to oxidize and degrade Amoxicillin (AMOX)- a ß-lactum thiazolidine antibiotic. Optimization studies found pH 9, 45 mA cm-2, 81 cm2 electrode surface area, 6 mM electrolyte concentration and 60 min treatment time to be optimal for AMOX removal. Studies with varying concentrations of AMOX (20 mg L-1, 30 mg L-1 and 40 mg L-1) found that increase in concentrations of AMOX require higher current densities and treatment time for better TOC removal. High performance liquid chromatography photo diode array (HPLC-PDA) studies found 94% removal for 40 mg L-1 of AMOX at optimal conditions with 90% COD and 46% TOC removal. High resolution mass spectrometry (HRMS) studies using Ultra performance liquid chromatography-quadrupole time of flight-mass spectrometry (UPLC-Q-ToF-MS) identified major degradation mechanisms to be hydroxylation, ß-lactum ring cleavage, breakage of thiazolidine ring chain from the aromatic ring and piperazinyl ring formation. The final byproducts of AMOX oxidation were carboxylic acids.