Construction of novel metal-free photocatalyst: Perylene adsorbed on g-C3N4 for Cr(VI) photoreduction under visible light irradiation

Photoreduction of hexavalent chromium (Cr(VI)) using perylene loaded on g-C3N4 (Pe/g-C3N4) as a novel metal-free photocatalyst has been studied. The Xe lamp (>420 nm) irradiation to a Cr(VI) solution (0.10 mM, pH 2) with Pe/g-C3N4 powder resulted in a 64.2 % Cr(VI) reduction for 60 min. The rate constant of Pe/g-C3N4 was 12.2 times higher than that of g-C3N4. The improvement of the photocatalytic activity would be due to the Z-scheme electron transfer between g-C3N4 and perylene. Pe/g-C3N4 exhibits a significant photocatalytic activity for Cr(VI) reduction under sunlight irradiation and reduced 99.4 % of the Cr(VI) within 30 min. Additionally, we tried to make the separation and reuse of Pe/g-C3N4 easier by immobilization on an alginate sponge. The sponge also showed photocatalytic activity for Cr(VI) reduction during the irradiation by a Xe lamp or sunlight. No obvious decrease in the photocatalytic activity of the sponge was observed for 5 cycles, and the sponges could be immediately reused after washing with water and squeezing. Furthermore, the sponge adsorbed the formed Cr(III) and the total Cr removal from the solution was achieved. This study provides a new strategy to develop a g-C3N4 based metal-free photocatalyst for Cr(VI) photoreduction using sunlight. [Display omitted] •Pe/g-C3N4 as a novel metal-free photocatalyst was developed.•Loding of perylene on g-C3N4 improved photocatalytic activity for Cr(VI) reduction.•Pe/g-C3N4 could efficiently reduce Cr(VI) under sunlight irradiation.•Immobilization of Pe/g-C3N4 on the alginate sponge was prepared.•The catalyst sponge has good reusability and catalytic activity.