Citric acid-assisted hydrothermal synthesis of a self-modified Bi2SiO5/Bi12SiO20 heterojunction for efficient photocatalytic degradation of aqueous pollutants

• Published in: Catalysis science & technology 2018, Vol.8 (4), p.151-161
• Main Authors: Li, W. Q, Wen, Z. H, Tian, S. H, Shan, L. J, Xiong, Y
• Format: Article
• Language: English
• Subjects: Acids; Bismuth silicon oxide; Chlorophenol; Citric acid; Dyes; Heterojunctions; Hydrothermal crystal growth; Oxalic acid; Photocatalysis; Photodegradation; Pollutants; Rhodamine; Specific surface; Sulfonic acid; Surface area; Titanium oxides
• ISSN: 2044-4753; 2044-4761
• DOI: 10.1039/c7cy02272g

A self-modified Bi 2 SiO 5 /Bi 12 SiO 20 heterojunction was synthesized for the first time via a citric acid-assisted hydrothermal method. It was found that citric acid (CA) played two roles in the formation of the Bi 2 SiO 5 /Bi 12 SiO 20 heterojunction: enhancement of the specific surface area due to the release of many volatiles from the decomposition of CA and tuning the weight ratio of Bi 2 SiO 5 and Bi 12 SiO 20 in the heterojunction by forming different complexes with Bi 3+ . Thus, a self-modified Bi 2 SiO 5 /Bi 12 SiO 20 heterojunction prepared at a CA dosage of 11.25 mmol presented an I 27.9  :  I 29.2 value of 1.52 and a BET specific surface area of 32.6 m 2 g −1 , 5.7 times that without addition of CA . It showed the highest first-order apparent reaction constant of 0.1694 min −1 in the photocatalytic degradation of acid orange 7 (AO7), which is 1.8, 53.0, and 2.2 times that of Bi 2 SiO 5 , Bi 12 SiO 20 , and TiO 2 (P25), respectively. The capture experiments show that the main active species that degraded AO7 are not O 2 &z.rad; − and &z.rad;OH but h + vb . During the AO7 degradation, four intermediates, sulfonic acid, oxalic acid, benzenesulfonic acid, and 4-aminobenzenesulfonic acid, were identified by capillary electrophoresis/capacitively coupled contactless conductivity detection. Finally, other pollutants, rhodamine B, p -chlorophenol, and tetracycline, were also found to be efficiently removed by the Bi 2 SiO 5 /Bi 12 SiO 20 -mediated photocatalysis system. The phase composition and weight ratio of Bi 12 SiO 20 and Bi 2 SiO 5 in the heterojunction can be tuned by simply adjusting the CA dosage.