Mechanism and enhancement of Cr(VI) contaminated groundwater remediation by molasses.
Sci Total Environ
; 780: 146580, 2021 Aug 01.
Article
in En
| MEDLINE
| ID: mdl-34030333
The remediation of Cr(VI)-contaminated groundwater with molasses has many advantages compared with traditional in-situ chemical methods, including high cost-effectiveness and negligible secondary contamination. Hence, the reaction conditions and mechanisms of molasses were investigated in this study. The results showed that Cr(VI) was chemically reduced by molasses at acidic pH (3.0), wherein the dominant active components were the hydroxyl and carbonyl groups of molasses. At neutral pH (7.0), molasses mainly acted as an electron donor for direct or indirect reduction of Cr(VI) by microorganisms. The main functional microorganisms were Bacillus and Clostridium Sensu Stricto. Compared with chemical reduction, bio-reduction could completely reduce higher concentrations of Cr(VI) when molasses was added at a concentration of 3 g/L. Ascorbic acid was added to promote the removal rate of bioremediation. Owing to the antioxidant properties of ascorbic acid, the reaction rate increased by 9.3% and 37.5% when 0.05 g/L of ascorbic acid was added to the 50 and 100 mg/L Cr(VI) bioremediation systems, respectively. Due to the decrease in pH during bioremediation, NaHCO3 was added to buffer the pH changes and promote Cr(III) precipitation. Compared with the addition of NaHCO3 and molasses simultaneously, separate additions were more effective for precipitation. Furthermore, X-ray absorption near-edge structure analysis revealed that after chemical reduction and biological reduction, Cr was attached to the solid medium in the form of Cr(III).
Key words
Full text:
1
Collection:
01-internacional
Database:
MEDLINE
Main subject:
Water Pollutants, Chemical
/
Groundwater
Language:
En
Journal:
Sci Total Environ
Year:
2021
Document type:
Article
Country of publication:
Netherlands