Constructing an acidic microenvironment by sulfonated polymers for photocatalytic reduction of hexavalent chromium under neutral conditions

Hexavalent chromium (VI) heavy metal contamination is considered a serious threat to human health and the environment. The photocatalytic reduction of Cr(VI) basically occurs in the acidic environment, severely limiting the application of photocatalysts for the reduction of Cr(VI). Therefore, we designed a microenvironment strategy to achieve efficient reduction of Cr (VI) under neutral conditions by introducing sulfonic acid onto the aromatic conjugated skeleton. A series of characterizations and experiments have shown that the sulfonated aromatic ring conjugated polymer (Arcp-SO 3 H) can efficiently remove Cr(VI) under neutral or even alkaline conditions. In neutral solutions, Arcp-SO 3 H has a rate constant of 0.054 min −1 within 90 min and has an efficiency of nearly 100 %, which is 16 times faster than before sulfonation (k = 0.0316 min −1 ). the Arcp-SO 3 H surpasses all organic polymers and most metal-based photocatalysts in the related field. The capture experiments have proved that •O 2 – is the main role of reducing Cr(VI), and e - is secondary, which is quite different from the mechanism reported in the previous literature. The efficiency of reducing Cr (VI) in the four-cycle experiment is still 96 %, which also proves that Arcp-SO 3 H has strong stability and reproducibility. Thus, Arcp-SO 3 H has great practical application potential in the treatment of wastewater, and microenvironmental strategies also offer new possibilities in the field of environmental remediation.