Biomass-derived carbon quantum dots modified Bi2MoO6/Bi2S3 heterojunction for efficient photocatalytic removal of organic pollutants and Cr (Ⅵ)

Abstract

A Bi2MoO6/carbon quantum dots/Bi2S3 (BMO/CQDs/BIS) was successfully fabricated as a high-efficient photocatalyst for degradation of some persistent organic pollutants and reduction of Cr (Ⅵ), in which the CQDs was derived from waste sludge biomass. The conversion photoluminescence and electron conductivity of CQDs enhanced the photocatalysis activity of BMO/BIS heterojunction. Compared with BIS (20.8%), BMO (63.3%) and BMO/BIS heterojunction (82.3%), the degradation efficiency of tetracycline hydrochloride (TC) reached to 92.8 % by BMO/CQDs/BIS under visible light. Besides, 88 % reduction rate of hexavalent chromium Cr (Ⅵ) could be obtained. Investigation on influence factors of TC photodegradation revealed that above 90 % of TC degradation rate with a low dosage and initial pH at 4.5 could reach, and under full-spectrum light, the rate could be enhanced up to 96%. Further research indicated that it could be also used for the treatment of TC in different water quality parameters. Based on the assessment of band structure and density functional theory calculation, the effective photogenerated electron transfer could arouse more radical species to attack the chemisorption sites on the TC molecules. The main active species (holes, O2- and OH) were identified by electron spin capture technology and typical active radicals trapping test. The intermediates of TC were detected by LC-MS and the possible mineralization pathway of TC was elaborated. This research might provide a novel approach to support waste sludge treatment and optimize photocatalyst for environmental remediation.