Degradation of ramipril by residues from the brewing industry: A new carbon-based photocatalyst compound

This study is a pioneer in the use of hydrochar as a support for photocatalytic oxide and its application and evaluation as a catalyst in degradation reactions of ramipril. Novel composites were easily prepared by the support TiO 2 or ZnO nanoparticles on the malt bagasse hydrochar. The preparation of the hydrochar requires low synthesis temperature (250 °C), generating the energy savings of the process. The production of the new composites was well supported by different analytical techniques XRD, FTIR, SSA, SEM, EDS, and reflectance diffuse. The effect of different proportions of TiO 2 or ZnO on the composites was investigated on the degradation efficiency of the pharmaceutical ramipril, without pH adjustment. Composites with a 5:1 hydrochar/TiO 2 or ZnO ratio (MH5T and MH5Z, respectively) showed degradations of 72 and 98% of ramipril at 120 min. This remarkable performance may be associated with the decrease in band gap energy and the electron-hole recombination rate. In addition, the composites were more efficient than metal oxides pristine, and this may be related to the fact that hydrochar have a high concentration of phenolic, hydroxyl, and carboxylic functional groups on their surface. Radical identification tests indicated that h + , O 2 • - , and •OH were the reactive species involved in the degradation. The proposed mechanism was studied via LC-MS/MS indicated that the ramipril molecule degrades into low m/z intermediates in the first 60 min of reaction using the MH5Z. • The malt bagasse biomass (MBB) was used as a precursor in the ramipril degradation. • Hydrochar from MBB was used as carbonaceous support and facilitator for the free radical generation process. • The appropriate amount of hydrochar can promote the photocatalytic activity of TiO 2 or ZnO. • The ZnO-hydrochar composites were more efficient in the degradation of ramipril (98% at 120 min). • The degradation pathways of ramipril by a composite based on residual biomass (HM5Z) are proposed. Capsule: From malt bagasse biomass to photocatalyst composites to ramipril degradation and MH5Z showed higher photocatalytic efficiency.