Preparation And Application Of Heavy Metal Biosorbent Based On Endophytic Bacterial LK9

Due to the arbitrary discharge of wastewater from industries such as mining,metallurgical and chemical manufacturing and battery, heavy metals pollution isbecoming more and more serious. Traditional techniques to treat heavy metalpollution are various such as reduction, chemical precipitation, membrane filtration,ion exchange, electrochemical treatment evaporation, etc. However, these methods areexpensive, not environment-friendly, cannot be reused or ineffective. As we know,heavy metals are high toxic to living organisms and non-biodegradable, it is veryurgent to seek effective methods to treat heavy metals pollution. Biosorption, inrecent years, because of its economical efficiency and safety has raised a worldwideenvironment concern. However, the inefficiency of the natural biosorbents restricts itsfurther application. Against this background, this thesis was based on a strain ofbacterial endophytes, Pseudomonas sp. Lk9, which isolated from aCd-hyperaccumulator, Solanum nigrum L. First, we studied the heavy metalsresistance and adsorption capacity of Lk9; then the Lk9biomass was modifiedthrough the layer-by-layer fattening capacity and a highly efficient biosorbent wasselected; At last, the sorption performance of the biosorbents were investigated indetail. The specific research contents and results are as follows:(1) In this section, we studied the heavy metals resistance and adsorptioncapacity of Lk9and found that Lk9can endure high concentrations of heavy metalions such as lead, zinc, copper, cadmium and chromium. Moreover, some heavy metalions can induce hormesis phenomenon of Lk9, for example, lead, copper. Besides,Lk9has a certain sorption capacity, for the maximum uptake capacities for Pb2+, Cd2+and Cu2+inferred from the Langmuir model were80.49mg/g,23.08mg/g and19.10mg/g respectively. The biosorption process was extremely fast with the equilibriumfast reached in20min.(2) In this section, the layer-by-layer fattening of functional groups on thesurface of Pseudomonas sp. Lk9biomass was achieved by a new layer-by-layerfattening strategy. The presence of PAA layer on the surface of Lk9was confirmed byX-ray photoelectron spectroscopy (XPS), FTIR and elemental analysis. Themodification drastically enhanced the heavy metal adsorption capacity of Lk9, and thePAA bilayer-modified biomass (Lk9-2P) showed the highest sorption capacity. (3) In this section, we investigated the sorption performance of the newbiosorbent Lk9-2P and the biosorption mechanisms. The biosorption can be conductedin a wide pH range of3–6and the optimal pH for Pb2+and Cu2+is5-6, for Cd2+is5-7.The biosorption process was fast with the equilibrium reached in45min. Themaximum uptake capacities of Lk9-2P for Pb2+, Cd2+and Cu2+which inferred from theLangmuir model were480.02mg/g,267.53mg/g, and210.17mg/g, which were4.96,10.60, and10.00times higher than raw Lk9, respectively. The binding of heavymetals on the surface of biosorbent Lk9-2P occurred mainly through coordination.Lk9-2P could be easily regenerated and kept high adsorption capacity after at leastfive successive circles. Moreover, Lk9-2P could effectively treat practical wastewaterfor that all the heavy metals brought down to lower than0.001mg/L after treated.