No abstract

No abstract

In the present communication, we report a comparative study of Cr (VI) removal using biologically synthesized nano zero valent iron (BS-nZVI) and chemically synthesized nZVI (CS-nZVI), both immobilized in calcium alginate beads. The parameters like initial Cr (VI) concentration, nZVI concentration, and the contact time for Cr (VI) removal were optimized based on Box-Behnken design (BBD) by response surface modeling at a constant pH 7. Under the optimized conditions (concentration of nZVI = 1000 mg L(-1), contact time = ∼ 80 min, and initial concentration of Cr (VI) = 10 mg L(-1)), the Cr (VI) removal by the immobilized BS-nZVI and CS-nZVI alginate beads was 80.04 and 81.08 %, respectively. The adsorption of Cr (VI) onto the surface of alginate beads was confirmed by scanning electron microscopy with energy-dispersive x-ray spectroscopy (SEM-EDX), Fourier transform infrared spectroscopy (FT-IR), and Brunauer-Emmett-Teller (BET) analysis. The applicability of the process using both the sorbents was successfully test medium Cr (VI) spiked environmental water samples. In order to assess the ecotoxic effects of nZVI, the decline in cell viability, generation of intracellular reactive oxygen species (ROS), cell membrane damage, and biouptake was studied at 1000 mg L(-1) concentration, with five indigenous bacterial isolates from chromium-contaminated lake sediments and their consortium.

No abstract

Indigenous isolates from the waters of chromite mining sites at Sukinda Valley, Orissa, India, showed a considerable enhancement in Cr (VI) bioreduction rate through adaptation and consortia development. On the basis of 16S-rRNA sequencing, these isolates were identified as Bacillus subtilis VITSUKMW1, Acinetobacter junii VITSUKMW2, and Escherichia coli VITSUKMW3. The native isolates showed a high tolerance at 500−1000 mg L −1 of Cr (VI). An increase in the reduction rate from 0.199−0.477 mg L −1 h −1 to 0.5−1.16 mg L −1 h −1 at 5−20 mg L −1 of initial Cr (VI) concentration was achieved by the adapted isolates. An increase in the growth rate and Cr (VI) reduction rate [0.86−2.6813 mg L −1 h −1 at 5−100 mg L −1 of initial Cr (VI) concentration] was observed in the ternary consortium of adapted isolates. The FT-IR spectra revealed the active participation of the bacterial surface groups in the reduction. The development of sequential processes (native → adapted → consortia) employing Cr (VI) tolerant isolates, proves to be a potential bioremediation strategy for specific chromite mine sites.