Dissolution of Iron During Biochemical Leaching of Natural Zeolite

Natural zeolite, including clinoptilolite, often contains iron and manganese which decrease the whiteness of this sharp angular material.The biological treatment of zeolite enables its use as an substitute for tripolyphosphates in wash powders which have to comply with strict requirements as far as whiteness is concerned and rounded off grain content. Insoluble Fe3+ and Mn4+ in the zeolite could be reduced to soluble Fe2+ and Mn2+ by silicate bacteria of Bacillus spp. These metals were efficiently removed from zeolite as documented by Fe2O3 decrease (from 1.37% to 1.08%) and MnO decrease (from 0.022% to 0.005%) after bioleaching. The whiteness of zeolite was increased by 8%. The leaching effect, observed by scanning electron microscopy, caused also a chamfer of the edges of sharp angular grains. Despite the enrichment by fine-grained fraction, the decrease of the surface area of clinoptilolite grains from the value 24.94 m2/g to value 22.53 m2/g was observed. This fact confirms the activity of bacteria of Bacillus genus in the edge corrosion of mineral grains.Removal of iron and manganese as well as of sharp edges together with the whiteness increase would provide a product suitable for industrial applications

The influence of heavy metals on soil microflora

The aim of our contribution was to ascertain an influence of heavy metals on quantitative and qualitative composition of soil microflora. Our experiment was directed to quantitative isolation of culturable bacteria from individual soil samples and to the comparison of the amounts and colony morphology of the isolates from various soil samples. These soil samples were characteristic by a difference in pH, heavy metals and humus contents. Despite the differences between individual soil samples, the most of bacterial isolates were represented by Bacillus genus (especially Bacillus cereus and Bacillus mycoides) which belongs to the heavy metal resistant bacterial kinds