Cost-effective conversion into useful

Waste products from many industrial processes contain at times significant concentrations of metals which are objectionable on environmental grounds and yet constitute an appreciable economic asset. The presence of toxic metals in such wastes constitutes an environmental hazard, particularly because the ever-decreasing pH of the rainwater makes their leachability and contamination of the ground water more likely. Careful and costly waste-disposal procedures are thus mandatory so as to prevent this from occurring. A preferred alternative is the cost-effective conversion of such waste into useful products. This provides an optimal solution to the waste-disposal problem because (a) it eliminates the need for a safe and costly disposal of the hazardous waste (b) it maximizes resource utilization and conservation through recycling, and (c) it derives an economic benefit from the sale of the obtained products. 

A further examination of these four requirements shows that items 1 and 3 are relatively fixed in nature, once the approximate characteristics for a petroleum fuel have been established. In contrast, items 2 and 4 are subject to modification, wherein research and engineering can be applied to reduce the cost and increase the convenience of transportation. Obviously the convenience and efficiency of converting the fuel energy into useful work are dependent in major part on the characteristics of the machine which effects the conversion. It is also true, but somewhat less obvious, that the availability and cost of the fuel are equally dependent upon the nature of the engine and vehicle in which the fuel is used. 

The antibacterial effect of penicillin was discovered by Alexander Fleming in 1929. The extensive use of / -lactam antibiotics such as penicillin has saved thousands of lives but also created major resistance problems in hospitals and in the community worldwide, leading to increased morbidity, mortality, and healthcare costs. The conversion of penicillin into penam has been extensively investigated in order to overcome the drug resistance. Two approaches to selenopenams, selenium analogs of the penam, including a selenazole skeleton, have been reported. 

Fabrication of solar cells using ribbon silicon wafers has to be adapted to the material needs to reach satisfactory conversion efficiencies. As for all multicrystalline silicon wafers, material quality should be improved during cell processing to cope with the defect structure present in the as-grown material. The implementation of gettering and hydrogenation steps into the solar cell process is, therefore, crucial, as the efficiency obtainable for solar cells from a given material is important for cost-effectiveness. 

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