Metal-free activation of Oxone using one-step prepared sulfur-doped carbon nitride under visible light irradiation.

While Oxone can be activated by catalysts for efficient generation of sulfate radicals, most of catalysts are transition metals, which could lead to secondary pollution and relatively high costs. Thus, non-metal catalysts consisting of earth-abundant elements are promising metal-free alternatives for activating Oxone. As graphitic carbon nitride (CN) has been demonstrated to activate Oxone under visible light irradiation, sulfur-doping CN (SCN) is expected to exhibit a relatively high catalytic activity for activating Oxone. However, few studies have been conducted to investigate SCN for activating Oxone. Additionally, SCN should be prepared conveniently to reduce usage of associated reagents during the doping. To this end, a one-step preparation method is adopted in this study to convert trithiocyanuric acid to SCN. The as-prepared SCN shows the morphology of crumpled micro-bags with porous surfaces, enabling it to exhibit a much higher surface area (86.8 m 2 g −1 ) than typical CN (ca. 10 m 2 g −1 ). As Rhodamine B (RB) decolorization was employed as a model test to evaluate sulfate radicals generated from activation of Oxone, SCN also exhibited a much higher catalytic activity (rate constant ( k 1 ) = 0.107 min −1 ) to activate Oxone than CN ( k 1 = 0.037 min −1 ). SCN-activated Oxone for RB decolorization was relatively favorable at elevated temperatures as well as neutral conditions; it also remained quite effective even in the presence of NaCl. Through examining effects of radical scavengers, the RB mechanism can be primarily attributed to sulfate radicals. SCN was also reusable to activate Oxone for RB decolorization over 6 cycles. These features indicate that SCN is an easy-to-prepare and promisingly effective non-metal catalyst to activate Oxone. [ABSTRACT FROM AUTHOR]