Arsenic (III) and (V) remediation in water using a particulate photocatalytic carbon nitride (CNx) system

• Modified carbon nitride (CNx) for arsenic water remediation. • Dual function of photooxidation of As(III) and adsorption of As species. • Up to 97 % remediation of As(III) under photooxidation conditions. • Use of colorimetric and electrochemical techniques for As speciation. Carbon nitride (CN x ) has recently gained widespread attention as a greener material for water remediation. The inherent biocompatibility of CN x coupled with its adsorption and photocatalytic abilities underscore its potential utilization to overcome the major challenge of arsenic (As) contamination in water. Nonetheless, CN x typically exhibits poor dispersibility in aqueous media, suppressing its effectiveness as both adsorbent and photocatalyst. Herein, we present the use of CN x and its modified counterpart as effective agents for remediating As(III) and As(V) in water. Our results reveal that both benchmark CN x (CN x0 ) and the modified CN x (CN x50 ) exhibit promising As remediation effectiveness driven by photooxidation and adsorption. CN x0 exhibits strong affinity for As(III) with an adsorption effectiveness of 89 %, whereas CN x50 demonstrates an adsorption effectiveness of 76 % for As(V). Notably, CN x50 outperforms CN x0 in the photoconversion of As(III) into As(V) under simulated solar irradiation and quasi-monochromatic irradiation due to its lower amount of trapped charges and improved water dispersibility. In fact, the more toxic As(III) species is remediated by CN x50 with an efficiency of ≥ 95 %, through the combination of photooxidation and adsorption. Overall, this study emphasizes, for the first time, the potential of CN x to integrate both photocatalysis and adsorption processes for As remediation, providing a simplistic approach to addressing As contamination in water.