The Biosorption Study Of Pb～(2+) On Candida Untilis By Negative Pressure Cavitation From Polluted Water

This study was based on the foundation of The National Basic Research Program (973) of China (No. 2004CB418505),which named "The ecological rehabilitation and formative mechanism study of the environmental pollution of northeast industrial area in China". We have applied the technology of negative pressure cavitation to adsorb and remove the heavy metal of the polluted water for the first time, for research and search a whole new technology and high efficiency method to adsorb the heavy metal from polluted water.Through the contrast value of the adsorption rate,unit adsorption rate,adsorption speed between the traditional shaking adsorption mode and negative pressure cavitation adsorption mode. And by the advanced technique of micro-observe, we have researched and analyzed the process and reaction which on adsorption of Pb²⁺ adsorbed by Candida Utilis in-depth and carefully, also the yeast physiological variety, moreover, we have analyzed the two adsorption models by kinetics, in order to account for the advantage of the negative pressure cavitation adsorption mode. We have concluded the following results:(1)acquire the optimal adsorption technology conditions: the range of pH is between 3.8 and 4.72; the range of Pb²⁺ concentration which is fit negative pressure cavitation adsorption mode is between 20 and 80 mg·L^-1; when the Pb²⁺ concentration at 50mg·L^-1, the fittest yeast concentration on study is 2.5g·L^-1; the optimal reaction time is 60 minutes.(2)dye the yeast cell with BCECF reagent, then use laser scanning confocal microscope (LSCM) to detect the inner pH of yeast cell, we can acquire such results that the pH value is increasingly rise within time, from acid to weak alkaline, we infer that this phenomenon maybe related with environmental stress.(3)dye the yeast cell with Phen Green SK (dipotassium salt) which after biosorption reaction, then use laser scanning confocal microscope (LSCM) to detect the distributing of Pb²⁺ in inner and exterior yeast cell. We conclude the reason why the adsorption rate of negative pressure cavitation adsorption mode higher then conventional shaking adsorption mode is that there has special kinetics characteristic in the former one, and it can compel Pb²⁺ into the yeast cell inner, so the adsorption rate is higher then the former.(4)sampling the yeast after 60min's negative pressure cavitation adsorb reaction, use atomic force microscope(AFM) to observe the surface of yeast cell, we can see that after the shaking adsorb reaction, the surface of yeast appear litter pleat; and on the other hand, after the negative pressure cavitation adsorb reaction, the pleat on the yeast surface are more badly then the former, we infer that this phenomenon is related to the ultrasonic which can generate the power of cut. (5)fitting the Pb²⁺ biosorption process by Langmuir isotherm, we achieved the maximal adsorption capacity is q_max32.68mg/g and 35.09mg/g respectively, namely the adsorption capacity of negative pressure cavitation adsorption mode is more then shaking adsorption mode. The K_d is 0.553 and 0.559 respectively, namely under the same conditions, the adsorb speed of negative pressure cavitation adsorption is more then shaking adsorption.(6) fitting the Pb²⁺ biosorption process by Freundlich isotherm, we achieved the constant K_f is 13.56mg/g and 13.05mg/g respectively, nearly consistent. But the corresponding number n is 5.75 and 6.11 respectively, so it can proved that negative pressure cavitation adsorption can easier react then shaking adsorption under the same conditions.This study can explain the mechanism and parameter of the negative pressure cavitation adsorption technology. And we explained that why it can intensity the biosorption process of Pb²⁺ on Candida Utilis, we have elementary proved that this technology is a effective new way to dispose the heavy metal polluted water. This study has concluded a series technology datas through the abundant experiments, and all we done will establish a well foundation on biosorption of heavy metal polluted water by negative pressure cavitation technology in future.