Isolation And Identification Of A Heavy Metal Resistance Strain And Its Characterization And Mechanism Of Zinc Biosorption

With the rapid development of industries,a large number of heavy metals were discharged into our surroundings,and these toxic metals are becoming the main pollution sources to water resources,which has posed a serious threat on the health of human beings,our living environments,and the ecological systems.There are few disadvantages about the traditional treatment methods such of high operating costs,inefficient and secondary pollution.As a new waste-water treatment technology,biological means has become the hotspot of environmental in recent years.A highly zinc-resistant bacterial strain,which was named as XMHC-1,was isolated from sewage of an electroplating factory in Xiamen,Fujian Province.After the enrichment culture,the resistance capability to zinc?II?of the strain increased to 5000 mg/L.The 16 S r DNA sequence,physiological and biochemical characteristics of the strain were analysed.As the result,XMHC-1 was identified as Arthrobacter sp.The result of plasmid detection shows that the gene relating to heavy metal resistance might lie on chromosome rather than on plasmids.The optimal growth conditions of XMHC-1 was investigated as p H 8.0,30 ?,rotation speed 120 r / min,and 0.5% Na Cl solution.The strain showed high resistance to 8 heavy metals including Ni2+,Zn²⁺,Cu2+,Cd2+,Cr6+,and it is most resistant to Zn²⁺.The adsorption process would be affected by various factors such as adsorption time,p H,initial zinc?II?concentration,bacteria dosage,temperature and co-existing ions.The adsorption rate against zinc?II?could 90% in 90 min under the condition of 1.7 g/L of dry bacteria concentration,10 mg/L of Zn²⁺,p H 7.0 and 25?.The isothermal adsorption model analysis and the kinetic studies showed that the zinc adsorption process of XMHC-1 followed pseudo-second-order?R2>0.99?.In the analysis of the adsorption isotherm model,Langmuir model can be used to describe the adsorption of Zn²⁺strainsSome modern analytical techniques were used in preliminary study of the absorption mechanism of XMHC-1.The fourier transform infrared spectroscopy?FTIR?analysis before and after absorption showed that hydroxyl,amide,carboxyl and other active groups on XMHC-1 cell surface were involved in zinc?II?reactions;Under the SEM,shiny metallic droplets and sediments were observed at some places;results of EDX spectroscopy suggested that the cellsurface occurred ion exchange reaction in the adsorption process;X-ray diffraction showed that bacterial cells formed the diffraction peak was still only the crystalline state of aggregation after zinc?II?absorption.Besides,X-ray photoelectron spectroscopy results suggested that the cell surface exists ion redox reactions in the adsorption process,the zinc?II?adsorbent is mostly composed of Zn O.Results of the whole study showed that XMHC-1 can resist and adsorb zinc?II?in wastewater,which has great potential to be used as an bio-adsorbent and apply in the remediation of zinc contaminated environments.