No abstract

The microbiological extraction of zinc from a high-grade zinc sulfide concentrate has been investigated, using a pure strain of Thwbacillus ferrooziduns. Conditions such as temperature, pH, pulp density, nutrient concentration, and specific surface of solids have been studied in terms of their effects on zinc extraction rate and in some instances on final zinc concentration in solution. Where appropriate, optimum conditions for leaching have been specified.

The effects of carbon dioxide‐enriched air on the rate of zinc extraction during the microbiological leaching of a, high‐grade zinc sulfide concentrate by Thiobacillns ferrooxidans have been studied. Under normal air‐aeration conditions, the leach rate is limited initially by the availability of solid substrate surface area per unit volume of leach liquor, then by availability of carbon dioxide. If carbon dioxide‐enriched air is supplied, along with excess substrate, the zinc extraction rate increases as the carbon dioxide content increases until some other, as yet unknown, factor becomes limiting.

Aspergillus niger, a fungus, was used in the degradation of commercially available thermoplastic polyethylene films. Quantitative calorimetric measurements performed on as-received, abiotic, and biotic treated polyethylene samples, revealed that the amorphocity of the sample decreases during biodegradation. In addition, it was found that the external substrates (sucrose) in the growth medium influenced the biodegradation process of polyethylene. Furthermore, the crystallinity data on different biotreated samples indicated that the adapted microorganisms were able to metabolize a small portion of polyethylene. The significance of the Fourier transform infrared (FTIR) results of polyethylene samples have been discussed.