دانلود رایگان مقاله انگلیسی رویکردهای بیولوژیکی برای مقابله با آلودگی فلزات سنگین - الزویر 2018

abstract

Pollution by heavy metals has been identified as a global threat since the inception of industrial revolution. Heavy metal contamination induces serious health and environmental hazards due to its toxic nature. Remediation of heavy metals by conventional methods is uneconomical and generates a large quantity of secondary wastes. On the other hand, biological agents such as plants, microorganisms etc. offer easy and eco-friendly ways for metal removal; hence, considered as efficient and alternative tools for metal removal. Bioremediation involves adsorption, reduction or removal of contaminants from the environment through biological resources (both microorganisms and plants). The heavy metal remediation properties of microorganisms stem from their self defense mechanisms such as enzyme secretion, cellular morphological changes etc. These defence mechanisms comprise the active involvement of microbial enzymes such as oxidoreductases, oxygenases etc, which influence the rates of bioremediation. Further, immobilization techniques are improving the practice at industrial scales. This article summarizes the various strategies inherent in the biological sorption and remediation of heavy metals.

Conclusion

Anthropogenic activities such as mining, smelting operations, industrial and domestic, agricultural use of metals and metal containing compounds are the major contributors of heavy metals that result in environmental contamination and subsequent human exposure. Numerous physical, chemical and biological methods have been extensively used for their effectiveness in the removal of metals from different environmental media. Among these methods, biosorption is considered as an innovative technology and remedial strategy to remove the contaminants in view of its cost effectiveness and ecofriendly nature. Microbial systems, characterized by high surface to volume ratios are considered as superior bioremediation agents. Moreover, the microbial membranes harbor abundant potentially active chemosorption sites and hosts multiple functionally and structurally different proteins that aid redox reactions in the bioremediation process. The effectiveness of microbial bioremediation also depends on various biotic and abiotic factors. The microbial enzymes like reductases, oxygenases etc., also influence the process of bioremediation. Phytoremediation,a process involving bioremediation by plants has also emerged as an alternative technology for the management of toxic chemicals. Cell immobilization is a well known technique, which increases the performance of metal uptake from the contaminated environment. An accelerated research interest in this field has resulted in the exploration of nanoparticles for augmenting the properties of biomaterials to tackle heavy metal stress. The extensive review of the literature available in bioremediation indicates that genetic engineering of the biosorbents to improve their heavy metal sorbing properties, the utilization of biomaterials left out after commercially important production processes for biosorption and the fate of the biosorbed materials as growth enhancing factors are still largely unexplored and offer scope for future research.