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The soil in the Sangan iron-mining region in the east of Iran is contaminated with a high concentration of heavy metals, especially iron. The release of these pollutants into environment results in the transfer and accumulation of iron through the food chains, hence a reasonable solution is required to restore it. Bioaugmentation is an environmental friendly option to reduce the hazard effects of heavy metal in the contaminated soil. In this study, the consortia of two indigenous cyanobacteria isolated from soil of Sangan iron mining and used to bioremediate soil contaminated with iron, chromium, copper, lead, and nickel. The experiments were carried out by three treatment methods, including control soil, surface soil sprayed with cyanobacteria, and soil mixed with cyanobacteria for six months under laboratory condition. The scanning electron microscope showed the development of a network of filaments of the inoculated cyanobacteria (Oscillatoria sp. and Leptolyngbya sp.) with soil particles in both treatments. Bio-augmentation of the soil increased initial nitrogen content from 406 mg/kg in control to 664 mg/kg in soil mixed with cyanobacteria and 710 mg/kg in soil sprayed with cyanobacteria. Cyanobacteria inoculation decreased the available concentration of lead and nickel. The nonavailable heavy metal of soil in sample sprayed with cyanobacteria was in decreasing order: Cr > Fe > Ni > As > Pb > Cu. The maximum metal removal efficiency was 32%. In soil mixed with cyanobacteria increased in the root and hypocotyl lengths of radish and lettuce was observed compared to that in the control soil, indicated in the improvement of soil quality after bioremediation.

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Nature is full of various nanomaterials and nanostructures that have inspired and helped human life and civilization in the advancement of science and technology. Among these materials are clays, which are abundantly found in rocks and earth structures. The mineral montmorillonite, known as a clay nanoparticle, is the major phase in bentonite. This nanoclay, with a thickness of about 10 angstroms, includes unique properties such as expansion, high specific surface area, electrical properties, cation exchange capacity, and has found applications in industry and research. Amongst its uses are the basis for catalytic filler reactions and its application in the removal of potentially toxic elements (PTEs) from the environment. This study includes many reports related to purified montmorillonite as a nano-adsorbent, particularly for the removal of a range of PTEs from the environment. In addition, the review considers sources, special structural features, as well 2 as the different forms of montmorillonite, whether modified or unmodified, as ecofriendly components for environmental treatment.

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