Study On Bacterial Adsorption Of Heavy Metal Ions

In recent years, the problem of heavy metal pollution which is brought by the development of industry has been more and more serious. Microbial adsorption is a kind of new method in the treatment of heavy metal wastewater. It has the advantages of low cost, easy to control the adsorption conditions, high adsorption rate and selective adsorption conditions, no secondary pollution, and the treatment effect of low concentrations of heavy metals in wastewater is very well, It has broad application prospects in the treatment of heavy metal pollution.The microbial adsorbent can be used to remove heavy metal ions in the solution. This subject first deter mines the optimal conditions for microbial adsorption of metal ions:the adsorption time is60min, pH is6.5, the initial concentration of heavy metal ions is15mg/L, the concentration of microbial bacteria is1g/L.Using atomic force microscopy, we can observe and compare the bacterial morphological changes before and after the adsorption of metal ions, it shows that the adsorption is on the surface of the bacterial cells. The Langmuir equation further validate the bacterial adsorption of metal ions is mainly surface adsorption.The bacterial adsorption property of heavy metal ions has an important relationship with extracellular polymeric substance. The main components of the measured extracellular polymeric substance are polysaccharides and proteins. Infrared spectral analysis indicates that the amide, hydroxyl and carbonyl functional groups of polysaccharides and proteins on cell surface play a key role in the adsorption process.The experiments show that the impact of the alkali metal ions (Na+, K+) and NH4+on biosorption of heavy metal ions is very small, while the H+and transition metal ions have great influences on the biosorption of target heavy metal ion.Further experimental results show that pretreatment of0.1mol/L ammonia on cell can significantly increase the bacterial adsorption capacity;0.02mol/L HC1solution can make more than96%of the heavy metal ions to be desorbed from the microbial cell, and after desorption, the bacteria can be reused. With regard to the biofilm which is cultured by the do minant bacteria, the effect of the adsorption and desorption of heavy metal ions is very ideal, it shows that the microbial adsorption process has great practical value in the removal of heavy metal pollution.