Efficient degradation of emerging pharmaceuticals in contaminated wastewater using a titanate nanotube coating: Reusability, stability, and mechanisms

Abstract

Hydrogen titanate nanowires were doped with nitrogen at 2 (2TitaN) and 5 (5TitaN) wt% by the hydrothermal method. These powders were deposited on glass substrates as coatings and their physicochemical properties were analyzed by the DRS, FTIR, Raman, XRD and EDS techniques. SEM images displayed a rough morphology with average coating thickness of 2.48 µm. The photocatalytic activity of the 5TitaN powders was evaluated by removing amlodipine besylate (AMLO), reaching up to 95.94 % of degradation percentage and a rate constant (k_app) of 0.0087 min⁻¹ after 240 min. Meanwhile, the 5TitaN coating accomplished 91.69 % of AMLO degradation and k_app= 0.0075 min⁻¹ under the same reaction conditions. Hence, the photocatalytic performance of the coatings was 10.42 % more efficient than that of the powders after 5 reuse cycles. Besides, hydroxyl radicals were found as the main oxidizing species in the AMLO degradation. The reaction pathway was revealed through the UV–vis, TOC, FTIR and HPLC techniques, which confirmed the presence of some by-products as the result of the drug colloidal degradation. The hemolysis test carried out using the 5TitaN material determined non-toxicity in humans, achieving 1.72 and 2.19 %, before and after reaction, respectively. According to this fact, the 5TitaN coating can be considered as a practical and efficient photocatalyst for degrading contaminants of emerging concern (CECs) in wastewater, due to its easy handling and recovery, high photocatalytic performance after reuse and eco-friendly features.