Novel hierarchical carbon quantum dots-decorated BiOCl nanosheet/carbonized eggshell membrane composites for improved removal of organic contaminants from water via synergistic adsorption and photocatalysis

A series of carbon quantum dots (CQDs)-decorated BiOCl/carbonized eggshell membrane (CEM) composites were synthesized with CEMs as bio-templates. The obtained composites, especially BiC-0.05, exhibited superior removal efficiencies of several organic pollutants, i.e. tetracycline hydrochloride (TC), Rhodamine B (RhB), and o-nitrophenol (NP). Approximately, 98% of TC was removed after 30 min dark adsorption and subsequent 30 min visible-light-initiated photocatalytic degradation. BiC-0.05 was also utilized to treat actual industrial wastewater and could reduce 73.1% COD, in comparison to 49.9% with the use of BiOCl. The boosted removal efficiencies were achieved by synergistic effect of adsorption and photocatalysis, where cooperative contribution of oxygen vacancies (OVs), CEMs and CQDs enabled faster charge migration and more effective separation of photogenerated charge carriers. Electron spin resonance (ESR) and trapping experimental results showed that superoxide radical (O2−), along with holes (h+) and hydroxyl radical ( OH) would take part in photocatalytic degradation process. The intermediates of TC and its possible degradation pathway during the photocatalytic reaction were also studied. Our work developed a novel strategy by integrating carbon nanomaterials derived from bio-waste to design efficient photocatalysts for remediation of organic contaminants via adsorption – photocatalysis synergism and OVs – CQDs cooperation.