In situ immobilization of δ-MnO2 nanosheets on a porous support for rapid and continuous cleaning of bisphenol A-spiked water

Abstract

Bisphenol A (BPA), a building block of various plastics, is invading biosystems through drinking water and raising concerns about their adverse impacts on human health. Filtration, biological, and oxidation methods have been developed to decontaminate BPA, but high energy demand or lengthy biodegradation process acts as limiting factors. Recently, δ-MnO2 with layered structure has emerged as a promising tool for BPA degradation. However, the reaction rate of BPA degradation suffers from the nature of aggregation in free-standing δ-MnO2 nanosheets with limited accessible active sites towards BPA. To overcome this critical challenge, this study demonstrates that the immobilization of δ-MnO2 nanosheets on a porous support can enhance BPA degradation rate due to the increased exposure of active sites of δ-MnO2. As a result, the δ-MnO2 nanosheets immobilized on porous diatom particles via polydopamine (PDA) binder degrades BPA (k’ ∼0.774 L g−1 min−1) 14 times faster than free-standing δ-MnO2 (k’ ∼0.056 L g−1 min−1). Furthermore, the resulting δ-MnO2-PDA-diatom degrades ∼ 99 % of BPA within 20 min and can be recycled without any performance loss up to 7 times, providing the reusability towards BPA removal in a sustainable and eco-friendly manner. More importantly, the degraded products of BPA resulting from radical transfers, coupling, and fragmentation reactions do not cause any estrogenic response or toxicity to ecological systems, as examined with human and fish cells. Finally, a column packed with δ-MnO2-PDA-diatom demonstrates 99 % BPA removal with continuous flows of BPA-spiked wastewater. We propose that this advanced system will be readily extended to remove a broad array of water contaminants that will disrupt the physiological function of organs and their roles in the endocrine cross-talk between the reproductive hormones.