Removal of 4-Chlorophenol by Bacillus flexus as free and immobilized system: Effect of process variables and kinetic study

Abstract In this work, Bacillus flexus GS1 IIT (BHU) as free and immobilized cells on low-density polyethylene (LDPE) were used to remove 4-Chlorophenol (4-CP) from the synthetic wastewater. The effect of the process variables, namely process time, pH, temperature, and 4-CP concentration, were optimized and obtained as 7.0 days, 7.0, 30 °C, and 50 mg/L, respectively. At optimum conditions, the maximum removal efficiencies (REs) were obtained to be 90.34 and 78.12% for the immobilized and free cells, respectively, at 50 mg/L concentration of 4-CP. Furthermore, a packed bed bioreactor (PBBR) was continuously operated for 60 days with the immobilized LDPE. The maximum RE of 82.4% and elimination capacity (EC) of 29.6 mg/L/d were obtained at 50 mg/L of the initial concentration of 4-CP. The growth kinetic parameters for Bacillus sp. were obtained to be: μ m a x : 0.205 h−1, K s : 3.3 mg/L, K i : 220 mg/L for Aiba model; μ m a x : 0.197 h−1, K s : 1.4 mg/L, K i : 220 mg/L for Edward model; and m u m a x : 0.185 h−1, K s : 1.6 mg/L, K i : 200 mg/L for Andrew-Haldane model, respectively.