Waste biomass from hypersaline potash mining byproducts: Detection and visualization of Cu(II) and Cr(VI) on Croceicoccus sp. FTI14 biosorbent

Abstract

Microorganisms in hypersaline potash mining byproducts and their potential environmental applications have not been extensively reported. This study reports the diverse waste-impacted microbial communities (archaea and bacteria) adapted to extreme salinity (>10–25%). Of these, halotolerant Croceicoccus sp. FTI14 was investigated as a biosorbent for removing dissolved Cu(II) and Cr(VI) from synthetic Cu(II) and Cr(VI)-contaminated DI, groundwater and saline groundwater (0.55 M ionic strength). FTI14 biomass was oven-dried, finely ground, and investigated in batch biosorption experiments. At initial metal concentrations of 40 mg/L, FTI14 removed 40 ± 0.7% (16.3 ± 0.5 mg/g) and 19 ± 0.1% (7.8 ± 0.1 mg/g) of the Cu(II) from deionized water and saline groundwater, respectively, while only 22.9 ± 0.7% (9.6 ± 0.2 mg/g) and 2.1 ± 0.6% (1.0 ± 0.3 mg/g) Cr(VI) removal was achieved. Cu(II) uptake (mg/g) exceeded Cr(VI) uptake by a factor of 1.7–7.8. Langmuir and Freundlich models were applied on FTI14 biosorption isotherm data. The Freundlich model showed a better fit for both Cu(II) and Cr(VI), as indicated by the AIC values compared with evidence ratios. Synchrotron-based scanning transmission X-ray microscopy (STXM) visualizations of the biosorbent showed a mixture of whole cells and indistinct biomass and a spatial association between metals and biomass. Metal exposure alters the amide functional groups peak in Fourier transform Infra-red (FTIR) spectra, suggesting its role in sorption process. Thus, this study indicates culturable halotolerant microorganisms from hypersaline potash mining byproducts and its potential as biosorbent applications for metal removal from impacted groundwater.

Keywords

• Biosorption
• Halophile
• Potash mining byproducts
• Cu(II)
• Cr(VI)