铬污染的微生物吸附技术研究进展

近年来,铬在工业生产中得到了广泛的应用,随之而来的含铬污染物对周围环境造成严重的污染和破坏,铬污染的修复已成为亟待解决的环境问题。微生物在铬污染的生物修复中发挥着重要的作用。它因铬污染修复过程中环保有效,安全可靠且无二次污染等优点,引起了相关学者们的广泛关注。首先简述了铬污染危害及传统处理技术,重点综述了微生物作为生物吸附剂的吸附机理及影响因素,并分别详述了典型细菌,真菌,酵母和藻类吸附Cr(VI)污染物的机理机制及相关研究进展,然后总结了微生物吸附Cr(VI)过程中铬浓度,赋存状态,微生物营养类型,培养条件及代谢产物等的主要影响因素,最后,分析了以微生物作为生物吸附剂所存在的问题并展望了未来的研究方向,结合基因工程和酶工程选育高效工程菌、开展多种技术联合应用等方法提高微生物对铬污染的去除能力。

Research Progress in Biosorption Technology for Chromium Contamination

The population growth and the intensification of anthropogenic activities have contributed to a worsening of environmental pollution.Such as,industrial waste was stored in an area for a long time without proper management and organization,which was including large amount of the organic and inorganic contaminants,as well as heavy metals(chromium,lead,and crop).More specifically,significant concentration of chromium from leather tanning along with other applications such as metallurgy,alloying,electroplating could be released into the environment by human activities.At present,the chromium contamination had gained substantial consideration worldwide due to its high toxicity,easy solution,strong bioavailability in the water and soil originating from numerous natural and anthropogenic activities.In addition,chromium with high migration and transformation ability could be extracted and accumulated in plant from contaminated soils,and imparted severe health risks in humans via food chain contamination,which with time reached detrimental levels in living systems,resulting in several diseases such as irritation and/or cancer in lungs and digestive tract,low growth rates in plants and death of animals,and other health alterations.For that reason,now the remediation of chromium pollution had become an urgent environmental problem to be solved.Currently,many remediation technologies were used widely,which divide into the physic and chemical methods such as tillage method,reverse osmosis,electrochemical process,ion exchange,adsorption on activated carbon,excavation and solidification/stabilization.Some of the physical and chemical treatment procedures were simple,fast and possibly help metal recovery,but,these methods had significant drawbacks including still had to meet the demand of high operational cost due to its periodical agents addition,high energy consumption,and toxic secondary pollutants generation.Therefore,it was urgently needed to consider for developing a sustainable and economical process for Cr(Ⅵ)removal,and the search for cheaper and more effective technologies had become necessary to develop of more economical,safe,and environmentally friendly methods to remove Cr(Ⅵ)from industrial wastewaters.Microbial remediation methods by biosorption were eco-friendly,efficiency,safety and had no secondary pollution,which was considered as a potential technique in remediation of Cr(Ⅵ)contaminated site.Based on the above background,in this study,the source,toxicity and the remediation technologies of chromium pollution were briefly overviewed firstly.Of these,the application limitations of traditional technologies were analyzed.Moreover,adsorbents and biosorption mechanism were reviewed and explored in detail.Knowing that biosorption was a passive,rapid,and reversible physic-chemical-biological process between heavy metal types and biological material(biosorbent).Several sensitive factors having great influences on biosorption rate,including environmental parameters and microbial culture conditions,were detailed elaborated and carefully analyzed in this study.In addition,the detailed information about research progress of biosorption by different microorganisms(e.g.bacteria,fungi,yeast and algae)were provided in this study.Different microorganisms with the differences of the capacity to remove Cr(Ⅵ)contamination were discussed,and then as well as various binding sites from the functional groups in the process of metabolism were analyzed.Furthermore,the greatest limitations factors by biosorption processes were related to the metabolic parameters and responses,which could be influenced by the Cr(Ⅵ)and by the operational conditions applied.In the process of biosorption,it payed more attention to the effects of some environmental factors of biosorption like initial concentration of chromium,nutrition types(carbon source and nitrogen source),environmental conditions(experimental pH,temperature,inoculation size)and the types,activity,population and metabolites of microorganisms(biomass,extracellular polymeric substance),as well as in processes involving heavy metals(Fe,Cu,Mn).The bio re mediation mechanism of different microorganisms suggested in this review provided an insight into a better understanding of Cr(Ⅵ)removal.This could help in developing the existing technologies of chromium remediation to be more efficient.Finally,the problem of biosorption chromium contamination was analyzed and some future research suggestions were pointed out.Still,a great gap existed between laboratory studies and successful application of biosorption technology for the treatment of chromium contaminated sites.The majority of the laboratory experiments were carried out by using synthetic chromium solutions to analyze the efficiency of the developed system for chromium remediation.Therefore,the potential of biological systems for removal Cr(Ⅵ)in the contaminated soil or industrial effluents needed to be further explored.Currently,it was difficult to carry out the biosorption and make sure the effect of bio re mediation in an open environment of the chromium contaminated sites.In addition,in the process of heavy metal biosorption by microorganisms,the growth conditions,cell activity,functional enzyme synthesis and the competition of indigenous microbes had great impacts on the biosorption rate.In order to solve the above problems,it was very necessary to further study as follows:(1)Based on the combination of genetic engineering and proteomics,the functional microbes with high biosorption capacity of Cr(Ⅵ)are isolated and identified from the chromium contaminated sites,optimized the removal conditions of Cr(Ⅵ),and revealed the biosorption mechanism of Cr(Ⅵ).(2)Through the embedding technology of microorganism,the continuous running bioreactor systems were carried out for removal Cr(Ⅵ)in the industrial effluents.(3)Selecting the combined application of different methods for removal Cr(Ⅵ),for example,the combination of plant-microbial technology.To summary,emerging techniques such as cell immobilization,the application of bioreactors operating in continuous systems,the discovery of new microorganisms and genetic alterations had been potentially indicated for biosorption processes so as to circumvent the restrictions frequently found.