Cr(VI) is a common heavy metal pollutants present in the aquatic environment, which possess toxic and carcinogenic properties. In this study, a solvothermal reaction was used to prepare porphyrin (TCPP)-modified UiO-66-NH2 (UNT). The UNT integrated adsorption and photocatalytics in the application for dealing with Cr(VI). The photocatalytic reduction activities of UNT for Cr(VI) were investigated under visible light illumination. We found that the TCPP doping amount of 15 mg UNT (15-UNT) had a 10 times higher reduction rate of Cr(VI) than pristine UiO-66-NH2. The optimal 15-UNT photocatalyst demonstrated the highest photocatalytic activity, and Cr(VI) was completely removed within 80 min. In addition, the introduction of porphyrin not only enhanced the absorption of light but also enabled the transport of photogenerated electrons from porphyrin to UiO-66-NH2, which promoted the separation of charge carriers. Furthermore, the effects of factors such as porphyrin content, pH and light source on the photocatalytic reduction performances of UNT were also explored. Overall, this work presented a possible relationship between the crystal structures and the performance of UNT.
Photocatalytic degradation is an environmentally friendly way to eliminate environmental pollution. Exploring a photocatalyst with high efficiency is essential. In the present study, we fabricated a Bi2MoO6/Bi2SiO5 heterojunction (BMOS) with intimate interfaces via a facile in situ synthesis method. The BMOS had much better photocatalytic performance than pure Bi2MoO6 and Bi2SiO5. The sample of BMOS-3 (3:1 molar ratio of Mo:Si) had the highest removal efficiency by the degradation of Rhodamine B (RhB) up to 75% and tetracycline (TC) up to 62% within 180 min. The increase in photocatalytic activity can be attributed to constructing high-energy electron orbitals in Bi2MoO6 to form a type II heterojunction, which increases the separation efficiencies of photogenerated carriers and transfer between the interface of Bi2MoO6 and Bi2SiO5. Moreover, electron spin resonance analysis and trapping experiments showed that the main active species were h+ and •O2− during photodegradation. BMOS-3 maintained a stable degradation capacity of 65% (RhB) and 49% (TC) after three stability experiments. This work offers a rational strategy to build Bi-based type II heterojunctions for the efficient photodegradation of persistent pollutants.
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