Fixed-bed column study for As(III) and As(V) removal and recovery by bacterial cells immobilized on Sawdust/MnFe2O4 composite

• Bacillus arsenicus MTCC 4380 was immobilized on SD/MnFe2O4 composite.
• Effect of bed height, flow rate and initial concentration on removal of arsenic was determined.
• The effect of co-existing ions present in copper smelting wastewater on removal was investigated.
• 0.05 M NaOH was used for regeneration of biosorbent bed.
• BDST model was applied to determine critical bed height.

The current study describes the research on treatment of arsenic (As(III) or As(V)) containing industrial wastewater in a bio-column reactor. Bacillus arsenicus MTCC 4380 has been immobilized on Sawdust/MnFe2O4 composite bed in the bio-column reactor. The significant influence of bed height (20–100 cm), flow rate (251.2–837.33 mL/h), empty bed contact time (8–20 h), and initial arsenic (either As(III) or As(V)) concentration (2000–5000 mg/L) on the arsenic (either As(III) or As(V)) removal was investigated. The breakthrough curve for the bed height specified that a longer bed column extended the life span of the column with a maximum capacity of 87.573 and 88.990 mg/g for the As(III) and As(V) column, respectively. The impact of co-existing ions on biosorption/bioaccumulation of arsenic was investigated in column mode. The column was regenerated by eluting As(III) or As(V) using 0.05 M NaOH after biosorption/bioaccumulation studies. The desorption of As(III) or As(V) in each three cycles was about 51–64% and 53–65%, respectively. The critical bed depth, graphically determined using BDST model for As(III) and As(V) removal were 17.778 and 18.095 cm at 1% breakthrough, respectively. The working lifetime of MTZ (Tc), HMTZ, RMTZ were estimated to be 66 h, 80.291 cm, 1.409 cm/h and 9 h, 80.516 cm 1.413 cm/h at 100 cm bed depth for the removal of As(III) and As(V) by immobilized bacterial cells, respectively.

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