18/09/2025
The water pollution caused by heavy metal is a serious environmental issue that humans are facing. As a typical heavy metal, hexavalent chromium has been confirmed to have various adverse effects on health, such as skin allergy, tissue cell damage and cancer. Thus, it is of great importance to develop effective techniques for removing Cr(VI) from wastewater. Owing to the advantages of high efficiency, low energy consumption and easy operation, photocatalysis is regarded as one of the most promising methods in the removal of Cr(VI).
In general, the reason why photocatalysis can achieve the removal of Cr(VI) is that reaction system will produce some active species with reduction ability under visible light irradiation, which can realize the reduction transformation of Cr(VI) to Cr(III). So far, it is widely accepted that photogenerated electrons play a chief part in Cr(VI) reduction. Meanwhile, many studies also reported that O2•− can also reduce Cr(VI) to Cr(III). To clarify the role of O2•− in Cr(VI) reduction, the radicals scavenging experiments were often performed by using p-benzoquinone (PBQ) as scavenger. In theory, the introduction of PBQ can capture O2•−, thereby inhibiting the Cr(VI). However, current work found that the addition of PBQ has an obvious promotion effect on Cr(VI) reduction, and similar phenomena was also observed in other studies. Thus, it is controversial to identify the role of O2•− by using PBQ as trapping agent during the process of Cr(VI) reduction, and the positive effect of PBQ on Cr(VI) reduction should be also explored and clarified.
Graphitic carbon nitride (g-C3N4), a promising visible-light photocatalyst, has received great attention in the field of catalysis, due to its low cost, high chemical stability and special optical features. Nevertheless, the application of g-C3N4 still exists many problems to be deal with necessarily, and one of the main challenges is the fast recombination of photo-excited charge carrier, which severely limiting its photocatalytic performance. In order to overcome this problem, modification means are proposed. Because of the features of being simple and effective, doping metal ion in g-C3N4 has attracted intensive research interest.
Based on above background, herein, Fe-doped g-C3N4 (denoted as Fe-g-C3N4) was fabricated by a simple method. After that, Fe-g-C3N4 was employed as photocatalyst to perform the tests of Cr(VI) reduction. Meanwhile, the roles of PBQ in the Cr(VI) reduction process were also investigated in detailed. All in all, current work will share some novel insights into the effects of PBQ on photocatalytic Cr(VI) reduction.
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