Efficient magnetic hybrid ZnO-based photocatalysts for visible-light-driven removal of toxic cyanobacteria blooms and cyanotoxins

Abstract

A hybrid magnetic-ZnO-based photocatalyst platform is designed for the efficient and simultaneous sunlight-driven photoremoval of cyanobacteria and mineralization of cyanotoxins (anatoxin-A). The photocatalyst killing ability was evaluated against two types of microalgae with different morpholo-gy and toxicity, Spirulina platensis paracas and Anabaena flos-aquae. The hybrid photocatalyst Ni@ZnO@ZnS-Spirulina was synthetized by means of a multistep process using Spirulina as bio-template. The effects of reactor geometry, magnetic actuation, and concordant architecture on pho-tokilling ability were tested. Moreover, the prepared photocatalysts were demonstrated to be effective for the anatoxin-A degradation under artificial sunlight. In the interest of reducing waste content and optimizing resources, photocatalyst recycling after their useful lifetime has ended is proposed through the fabrication of microalgal biofuel-pellets. This inexpensive circular process involves mul-ti-functional algae-based photocatalysts applied to the simultaneous destruction of algae blooms and cyanotoxins and then recycled to close the circle through cultivating biotemplates.