Cr(VI) Reduction and Cr(III) Immobilization by Acinetobacter sp. HK-1 with the Assistance of a Novel Quinone/Graphene Oxide Composite

Abstract

Cr(VI) biotreatment has attracted a substantial amount of interest due to its cost effectiveness and environmental friendliness. However, the slow Cr(VI) bioreduction rate and the formed organo-Cr(III) in solution are bottlenecks for biotechnology application. In this study, a novel strain, Acinetobacter sp. HK-1, capable of reducing Cr(VI) and immobilizing Cr(III) was isolated. Under optimal conditions, the Cr(VI) reduction rate could reach 3.82 mg h(-1) g cell(-1). To improve the Cr(VI) reduction rate, two quinone/graphene oxide composites (Q-GOs) were first prepared via a one-step covalent chemical reaction. The results showed that 2-amino-3-chloro-1,4-naphthoquinone-GO (NQ-GO) exhibited a better catalytic performance in Cr(VI) reduction compared to 2-aminoanthraquinone-GO. Specifically, in the presence of 50 mg L(-1) NQ-GO, a Cr(VI) removal rate of 190 mg h(-1) g cell(-1), which was the highest rate obtained, was achieved. The increased Cr(VI) reduction rate is mainly the result of NQ-GO significantly increasing the Cr(VI) reduction activity of cell membrane proteins containing dominant Cr(VI) reductases. X-ray photoelectron spectroscopy analysis found that Cr(VI) was reduced to insoluble Cr(III), which was immobilized by glycolipids secreted by strain HK-1. These findings indicate that the application of strain HK-1 and NQ-GO is a promising strategy for enhancing the treatment of Cr(VI)-containing wastewater.

Fast start-up of the anammox process with addition of reduced graphene oxides

“…Furthermore, the contrast of R1 and R2 in cell quantities proved that RGO addition accelerated the growth of anammox biomass. properties of redox mediates because of epoxide, carboxyl, and hydroxyl groups on 15 their basal planes and edges, which can lead to a good electron transfer ability and microbial affinity as redox mediates [10,20]. Compared with coenzyme Q (CoQ), RGO as an essential component participated in the electron transfer from HDH to cytochrome bc1 complex due to the faster electron transfer ability [12,21].…”

“…This phase lasted for 17 days (day 20-36) and 10 days (day[16][17][18][19][20][21][22][23][24][25], respectively, for R1 (control) and R2 (RGO addition), On day 35, the average ammonium removal rates for two reactors in this phase were calculated as 14.7 and 82.8g-N/(m 3 .d). The effluent nitrate of R1 and R2 reached 5.99 and 9.38 mg/L, showing a juvenile anammox activity in both reactors (Fig.2C).…”

Addition of graphene sheets enhances reductive dissolution of arsenic and iron from arsenic contaminated soil

“…Additionally, another new peak of C–N (287.5 eV) emerged during biotic incubation. This might be attributed to the accumulation of biofilm in GO sheets during the biotic culture (Zhang, Lu, Wang, Zhou, & Sui, ). Overall, the reduction performance for GO was stronger than that of rGO under the interaction with microbial activity.…”

Application of 2‐hydroxy‐1,4‐naphthoquinone‐ graphene oxide (HNQ‐GO) composite as recyclable catalyst to enhance Cr(VI) reduction by Shewanella xiamenensis

“…The peak locations [574.9 and 584.4 eV for Cr 3+ 2p3/2 and Cr 3+ 2p1/2 in Fig. (b)] showed a downward shift in Cr 2p spectra, demonstrating transformation of the initial Cr(VI) to Cr(III). Hence, the appearance of the HNO‐GO composite greatly facilitated the biotransformation of the more soluble and toxic Cr(VI) species to a less water‐soluble and less toxic Cr(III) species.…”