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Biodegradation is an environmentally friendly and cost-effective alternative that proved to be efficient for the removal of toxic phenol compounds from aqueous solutions. However, it has been reported that phenol is inhibitory to bacterial growth at concentrations above 0.05 g/L. This study was undertaken to study the degradation of phenol at initial concentrations of 20 mg/L by Bacillus cells individually immobilized in two different matrices including polyvinyl alcohol-sodium alginate (PVA-SA) and polyvinyl alcohol-guar gum (PVA-GG). Results of batch experiments demonstrated that complete removal of phenol was obtained using immobilized cells in the first cycle after 270 and 300 min using cells immobilized in PVA-SA and PVA-GG. Additional cycles were conducted to evaluate the validity of recycling the beads of immobilized cells for phenol biodegradation. Results revealed that the phenol percentage removals were 96, 90, 83, and 75% for the second, third, fourth, and fifth cycles, respectively after 270 min. However, complete removal of phenol was obtained at extended time durations up to 300, 360, and 390 for the second, third, and fourth cycles, respectively. Also, the potential of immobilized cells versus free cells for the degradation of higher phenol concentration up to 50 mg/L was investigated.
