Layer-by-layer strategy for adsorption capacity fattening of endophytic bacterial biomass for highly effective removal of heavy metals

Abstract

In this study, the layer-by-layer fattening of functional groups on the surface of endophytic bacterial biomass of Pseudomonas sp. Lk9 was achieved by stepwise grafting polyallylamine (PAA). The presence of the PAA layer on the biomass surface was confirmed by FTIR, X-ray photoelectron spectroscopy (XPS), and elemental analysis. The PAA modification drastically enhanced the adsorption capacity of biomass LK9 toward heavy metals. In contrast, the PAA bilayer-modified Lk9 (Lk9-2P) showed the highest uptake capacity and presented high uptake capacities for Cd2+ and Cu2+. The adsorption could be conducted in a wide pH range of 3–6 and the equilibrium fast reached in 45min. The results of XPS and FTIR analysis reflected that the binding of heavy metals on the biosorbents occurred mainly through coordination. Recyclability test revealed that Lk9-2P remained stable and high sorption capacity after five successive cycles. More importantly, the application of Lk9-2P to practical industrial effluent demonstrated that the new biosorbent could effectively treat practical wastewater with all the heavy metals brought down to lower than 0.001mg/L. This study shows that the layer-by-layer fattening strategy is very effective for the development of high performance adsorbents for the removal of heavy metal ions from wastewater.