Citric acid modulated preparation of CdS photocatalyst for efficient removal of Cr(VI) and methyl orange

A coral CdS nanostructure is obtained via a simple one step synthesis with the addition of citric acid. The prepared CdS sample exhibits more superior activity for oxidation and reduction capacities compared with primitive CdS under visible light. Specifically, the CdS-0.5CA sample could reduce 100% of Cr(VI) within 2 min and degrade 94.4% of methyl orange within 180 min. Characterization results show that the dramatically increased photoactivity is attributed to improved specific surface area and meritoriously optimized charge separation after addition of citric acid. Meanwhile, the decrease of conduction band is conducive to photoreduction efficiency of CdS. In addition, the photocatalysis mechanism of CdS modified by citric acid for Cr(VI) and methyl orange removal is also investigated by a series of characterizations and experiments. In summary, this work reported a simple method to meritoriously increase photoactivity and obtained efficient bifunctional CdS modified by citric acid for photooxidation and photoreduction.