Study On Removal Of Trace Heavy Metals In Water By Compound Microorganism

The adsorption characteristics of trace heavy metals Cd²⁺, Pb²⁺, As⁵⁺and Cr⁶⁺inmicro-polluted water by effective biosorbents was investigated. And the synergistic effect andbiosafety of compound microorganism which were composed with different biosorbents werestudied.Fragmention, alkalization, salizination, and heating can increase the adsorption capacity ofCd²⁺，Pb²⁺by Aspergillus sojae. The results showed that the optimal pretreatment method was0.15mol/L NaOH-pretreated mycelium with the rate adsorption of Cd²⁺，Pb²⁺increased by74.1%,35.1%separately. The adsorption capacity of Cd²⁺, Pb²⁺reached the maximum sorptioncapacity of0.095mg/g,0.133mg/g accordingly when the biomass dosage was0.8g/L,0.6-0.7g/L separately. The adsorption efficiency of Cd²⁺was relatively stable at pH3.4-8while itarrived highest at pH3.4. The adsorption rate of Pb²⁺was over90%at pH3-6. The adsorptionrate of Cd²⁺was in the range of88.3%-94.4%at15℃-30℃while the adsorption rate of Pb²⁺was93.6%-98.8%at15℃-35℃.Fragmention, alkalization and salizination cannot increase the adsorption capacity of As⁵⁺by Trichoderma viride. The adsorption rate of As⁵⁺reached the highest of46.0%when thebiomass dosage was2.5g/L. The adsorption rate stayed stable at15℃-25℃and themaximumabsorption rate was at20℃. The adsorption rate of As⁵⁺changed little at pH4-9.The adsorption rate of Cr⁶⁺reached the maximum absorption rate of95.8%by the strainwhich was fused by Candida lipolytica and Candida tropicalis when biomass dosage was7g/L.The adsorption rate was in the range of88.6%-98.8%at15℃-35℃. The adsorption rate of Cr⁶⁺changed a lot at pH2-8and the maximum absorption rate reached93.7%at pH2-3.The biosorption kinetics, equilibrium and mechanisms were also discussed. The process ofAspergillus sojae adsorption of trace Cd²⁺and Pb²⁺, Trichoderma viride adsorption of traceAs⁵⁺and Candida （fused strain） adsorption of trace Cr⁶⁺followed the secondary kineticequation. Compared with the model of Langmuir and Freundlich model, the Linear model wasmore suitable for describing the process of adsorption equilibrium.FTIR and SEM observations indicated that Cd²⁺, Pb²⁺were likely to be binded with theactivated groups of hydroxyl, carboxyl, amide, phosphate group and amido on the hyphal cell surfaces, or to form precipitation particles attached to the mycelium.The mixed trace heavy metals could be removed efficiently in the way that addition ofCandida （fused strain） to adsorb Cr⁶⁺fistly, then followed with addition of Aspergillus sojaeand Trichoderma viride mixed to adsorb Cd²⁺, Pb²⁺, As⁶⁺.The results of Vicia Faba Root Tip Cell Micronucleus Test, Alga Growth Inhibition Testand Siphonaptera Activity Inhibition Test showed that the complex microorganism is lowtoxicity.