Photolysis, Photocatalysis, and Sorption of Caffeine in Aqueous Media in the Presence of Chitosan Membrane and Chitosan/TiO2 Composite Membrane

Sorption and advanced oxidative processes (AOPs) are potential strategies for the removal of organic compounds, such as caffeine, from aqueous media. Such strategies tend to be more promising when combined with biopolymeric membranes as sorbents and photocatalyst supports. Therefore, the aim of the present study was to investigate sorption and AOP parameters in the performance of chitosan membranes and chitosan/TiO2 composite membranes in individual and hybrid systems involving the photolysis, photocatalysis, and sorption of caffeine. Caffeine degradation by photolysis was 19.51 &plusmn: 1.14, 28.61 &plusmn: 0.05, and 30.64 &plusmn: 6.32%, whereas caffeine degradation by photocatalysis with catalytic membrane was 18.33 &plusmn: 2.20, 20.83 &plusmn: 1.49, and 31.41 &plusmn: 3.08% at pH 6, 7, and 8, respectively. In contrast, photocatalysis with the dispersed catalyst achieved degradation of 93.56 &plusmn: 2.12, 36.42 &plusmn: 2.59, and 31.41 &plusmn: 1.07% at pH 6, 7, and 8, respectively. These results indicate that ions present in the buffer solutions affect the net electrical charge on the surface of the composite biomaterial with the change in pH variation, occupying active sorption sites in the structure of the biomaterial, which was characterized by Fourier transform infrared spectrometry, thermogravimetric analysis, differential scanning thermogravimetry, and X-ray diffraction. Thus, it is verified that in a combined process of caffeine removal under UV irradiation and use of chitosan/TiO2 composite membranes in phosphate-buffered medium, the photolysis mechanism is predominant, with little or no contribution from sorption, and that the TiO2 catalyst promotes a significant reduction in the percentage of pollutant in the medium only when used dispersed and at low pH.