Insight into Cr(VI) biosorption onto algal-bacterial granular sludge: Cr(VI) bioreduction and its intracellular accumulation in addition to the effects of environmental factors

• Published in: Journal of hazardous materials Vol. 414; p. 125479
• Main Authors: Yang, Xiaojing, Zhao, Ziwen, Zhang, Guanghao, Hirayama, Shota, Nguyen, Bach Van, Lei, Zhongfang, Shimizu, Kazuya, Zhang, Zhenya
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 15.07.2021
• Subjects: Algal-bacterial aerobic granular sludge; Bioreduction; Cr(VI) removal; Environmental factors; Intracellular accumulation; Algal-bacterial aerobic granular sludge; Cr(VI) removal; Bioreduction; Environmental factors; Intracellular accumulation
• ISSN: 0304-3894; 1873-3336
• DOI: 10.1016/j.jhazmat.2021.125479

Hexavalent chromium (Cr(VI)) is one of the typical heavy metals that pose a great threat to the environment. As a novel biotechnology, algal-bacterial aerobic granular sludge (AGS) possesses the merits of both bacterial AGS and algae. This study firstly evaluated Cr(VI) removal via biosorption by algal-bacterial AGS under different operation conditions and then some environmental factors. Results show that the highest Cr(VI) reduction (99.3%) and total Cr removal (89.1%) were achieved within 6 h at pH 2 and 6, respectively. The coexisting oxyanions exhibited slight effects, while both tested natural organic matters (humic acid and tannic acid) and carbon sources promoted Cr(VI) reduction at some appropriate concentrations. The coexistence of metal cations favored Cr(VI) reduction, achieving the highest enhancement of 8.1% by Cu2+ at 5 mg/L, while the total Cr removal was suppressed to some extent. Salinity > 5 g/L severely inhibited both Cr(VI) reduction and total Cr removal. Moreover, the loaded Cr in algal-bacterial AGS was found to be almost in the form of Cr(III), with 66.8% being contributed by intracellular accumulation. This work suggests that Cr(VI) reduction and intracellular accumulation are the main mechanisms involved in Cr(IV) biosorption onto algal-bacterial AGS. [Display omitted] •Microbial activity and granular stability were maintained after Cr(VI) biosorption.•Optimal pH for Cr(VI) reduction was pH 2 while that for total Cr removal was pH 6.•Metal cations may enhance Cr(VI) reduction while suppress total Cr removal.•Organics may promote Cr(VI) removal, especially for Cr(VI) reduction.•The adsorbed Cr in granules was in form of Cr(III) with 66.8% being intracellular.