جستجوی مقالات مرتبط با کلیدواژه « Electronic Waste » در نشریات گروه « مهندسی شیمی، نفت و پلیمر »

Electronic wastes are known as the most important solid wastes in 21th century. They are producing two or three time faster than other solid waste streams. Many researchers studied bioleaching of e-wastes using Acidithiobacillus ferrooxidans. The presence of alkaline metals cause e-wastes show an alkalinity nature. By adding e-wastes to the environment the pH of solution increases sensibly. Many researchers supposed the optimal pH range of A. ferrooxidans which is 1.5-2.5 as the optimal pH range to reach maximum recovery. So in the bioleaching process by daily pH adjusting in the range and using sensible amount of sulfuric acid, control the pH of solution about 2. In this research two same experiments, just the pH of one of them was adjusted daily, were done. In both experiments the environmental situation including pulp density of 15 g/l, inoculum 10% (v/v), the temperature of 30ºC, and shaking rate of 130 rpm was the same. For 25 days Cu recovery, bacterial count, pH, and Eh were examined. The results showed the maximum Cu recovery at the sample without pH adjusting was about 100% but at the sample with pH adjusting recovery was reduced to 90%. The bacterial count diagram showed the bacterium is well active in both experiments. To maximize recovery, reducing acid consumption, and increasing process economy there is no need to adjust the pH of solution.

In recent years the market demand for electronic instruments with attention to their low life time is increasing rapidly which create a new environmental challenge. E-waste contains a vast range of hazardous metals which an improper management can threat human society seriously. On the other hand on average e-waste can supply about 40 million ton of materials. But the complex and non heterogeneous nature of this waste was the main barrier for recycling. Traditional methods are highly cost and produce hazardous intermediate material. Bioleaching is environmental-friendly and economical for recovery of metals from e-waste by using microorganisms such as bacteria and fungi. In this article, previous articles about bioleaching of e-waste are studied. The result showed bioleaching is an effective method for metal extraction from e-waste. Some base metals as like as Cu, Ni, and Zn were extracted totally and Au, a stable metal, can recovered about 50%.