Applied Surface Science, Vol.473, 726-737, 2019
Insights into the removal of Bisphenol A by catalytic wet air oxidation upon carbon nanospheres-based catalysts: Key operating parameters, degradation intermediates and reaction pathway
In this study, we evaluate the feasibility of a ruthenium catalyst (CNS-Ru) supported on optimized carbon nanospheres (CNS) for the efficient removal by catalytic we air oxidation of Bisphenol A (BPA), a micro-pollutant exhibiting highly estrogenic properties. The catalyst was fully characterized by several techniques, e.g., N-2 adsorption-desorption isotherms, X-ray photoelectron spectroscopy (XPS), X-ray diffractometry (XRD), X-ray fluorescence (XRF), Fourier transformed infrared spectrometry (FT-IR) and scanning and transmission electronic microscopy (SEM/TEM). The effect of operational conditions such as temperature (110-150 degrees C), total pressure (20-50 bar), catalyst dose (0.5-3.0 g.L-1) BPA concentration (5-30 mg.L-1) and initial pH (3-8) on the BPA degradation by CWAO was evaluated. The synthesized catalyst showed an outstanding catalytic activity over the micro-pollutant degradation, obtaining the complete removal of BPA in only 90 min for a compound concentration of 20 mg.L-1, using 2.0 g.L-1 of catalyst, at mild reaction conditions (130 degrees C, 20 bar). No ruthenium leaching into the reaction medium was observed during the experiments (measured by XRF technique). The stability of the catalyst was confirmed upon two sequential tests, observing that the removal rate and the activity were not affected. Thus, the toxicity of BPA solution could be remarkably reduced after the treatment (from 3.37 to 1.38 TUs). Finally, eight major intermediates were detected in the process, containing most of them both quinonoid derivatives and carboxylic acids. With this information a BPA degradation mechanism by CWAO reaction was proposed.