Pneumatic jigging: Influence of operating parameters on separation efficiency of solid waste materials.
This article aims to provide insights into the factors that contribute to the separation efficiency of solid particles. In this study, a pneumatic jigging technique was used to assess the separation of solid waste materials that consisted of copper, glass and rubber insulator. Several initial experiments were carried out to evaluate the strengths and limitations of the technique. It is found that despite some limitations of the technique, all the samples prepared for the experiments were successfully separated. The follow-up experiments were then carried out to further assess the separation of copper wire and rubber insulator. The effects of air flow and pulse rates on the separation process were examined. The data for these follow-up experiments were analysed using a sink float analysis technique. The analysis shows that the air flow rate was very important in determining the separation efficiency. However, the separation efficiency may be influenced by the type of materials used.
The application of mineral processing techniques for the recovery of metal from post-consumer wastes
Abstract Mineral processing techniques are dominant, and have a very wide field of application, in the secondary metals industries — only the final stages of raw material production involve any chemical operations. There are many basic similarities between primary and secondary feeds — in general the values and gangue materials can be differentiated from each other by several differences in physical properties — however, there are many difficulties encountered in applying techniques developed for separation of minerals to post-consumer waste. Primary feeds to mills are homogeneous when compared to the feed treated by a secondary operation — the heterogeneous nature of scrap feeds causes a lot of problems to the processor. Other characteristics of waste tend to be higher metal content (and metal, rather than mineral, particles), high liberation sizes, and unusual particle shapes. Nearly all methods of concentration utilised in the recycling industries have been developed from mineral beneficiation technology — the major exception is eddy current separation which relies on the presence of large conducting particles (such as the fist sized chunks of aluminium produced in autoshredding). At present applications of eddy current separators are almost exclusively for material reclamation — as eddy current separators suitable for finer feeds are developed it seems likely that they will be applied to primary mineral feeds.
Treatment of manufacturing scrap TV boards by nitric acid leaching
Abstract The leachability tests for manufacturing scrap TV boards (STVB) have indicated the release of metals beyond the limit levels with potential problems for environmental pollution. Treatment of STVB is therefore requisite for its safe disposal in landfills. The nitric acid leaching of STVB for the removal/recovery of valuable metals (Cu and Ag) was studied by adopting the Box–Behnken design. Statistical analysis of data has revealed that the concentration of nitric acid is the most influential parameter affecting the leaching process. Effects of solids ratio and temperature on the rate and extent of the extraction of copper were also proved to be statistically significant. However, the interaction effects of these parameters were found to be insignificant. The leaching kinetics were consistent with the shrinking particle model under chemical control with an activation energy of 38.6 kJ/mol. High concentrations of nitric acid (2–5 M HNO 3 ) were required to achieve high copper extractions (88.5–99.9%) at a pulp density of 6% w/v. The extraction of silver was enhanced from 14% to 68% with increasing the concentration of nitric acid from 1 to 5 M. These findings also demonstrate that copper may well be selectively extracted from STVB by adjusting the concentration of nitric acid.