Comparative screening study on the adsorption of Aqueous Pb(II) using different metabolically inhibited bacterial cultures from industry

Abstract

The current study aimed at investigating the bioremediation removal effectiveness of Pb(II) by metabolically inhibited microbial cultures: a) Waste activated sewage sludge obtained from a local wastewater treatment plant (SS), commercially sourced industrial bioremediation microbes b) bran-based filler with bacteria (BB), and c) salt-and-starch based filler with bacteria (S&S), d) an industrially obtained Pb(II) remediating consortium (Cons), and purified strains of e) Paraclostridium bifermentans (PB), and f) Klebsiella pneumoniae (KP) isolated from the consortium. The study’s focus was specifically targeted towards operational analysis. This study demonstrated that the metabolically inactive SS, BB, S&S, Cons, PB, and KP bacteria adsorbed 55.4 mg/g, 54.6 mg/g, 50.6 mg/g, 54.4 mg/g, 27.4 mg/g, and 23.1 mg/g of Pb(II) within 3 h, respectively. In addition, maximum adsorption capacities of 141.2 mg/g, 208.5 mg/g, 193.8 mg/g, 220.4 mg/g, 153.2 mg/g, and 217.7 mg/g were measured respectively. FTIR spectroscopy supported the chemisorption of Pb(II) onto functional groups as being responsible for this removal. Two-phase pseudo-first-order kinetics fits best described the adsorption kinetics of the adsorbents which might be as a result of the separation of fast and slow adsorption rates into separate compartments, thereby allowing for better representation of a heterogeneous surface. The Crank mass transfer model shows that external mass transfer is the main mechanism of Pb(II) removal due to the high molecular diffusivity of Pb(II) as compared to the effective diffusion coefficients of the metabolically inhibited adsorbents. The equilibrium isotherm was well described by two-surface Langmuir equilibrium isotherm model likely due to different adsorption sites with different adsorption energies which allows a comparably better description of the adsorption. The morphology of the adsorbents showed that the surface of the metabolically inhibited adsorbents was rough, coarse, with observable pores, and irregular iii crevices. The results from the EDS analyses indicated the presence of Pb on the surface of the metabolically inhibited adsorbents confirming the adsorbents were able to remove Pb(II) from the aqueous systems. Recovery of Pb(II) from the biosorbents were further tested and showed 72.4 %, 68.6 %, 69.7 %, 69.6 %, 61.0 %, and 72.4 % for the SS, BB, S&S, Cons, PB, and KP bacteria, respectively. The results demonstrate the remarkable potential of these low cost, self- generating biosorbents for the treatment of Pb(II) contaminated aqueous streams.