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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