Engineering & Mining Journal

SEP 2018

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SEPTEMBER 2018 • E&MJ 65 www.e-mj.com PROCESSING SOLUTIONS He said the simple model was an initial attempt to describe a very complex sys- tem: The energy curve project had so far concentrated simply on productivity mea- sures such as kWh/t, but the question had always remained: How would the curves change if energy cost and carbon emis- sions were adequately addressed? "Infl uences on the price a mine pays for electricity include a complex interrelation of factors, many of which are qualitative, time dependent and hard to measure," he said. "Relying solely on mine location to assign an electrical price, therefore, is un- likely to result in an accurate prediction of pricing, but it is suffi cient to capture the likely variability. "For instance, the specifi c timing of con- tract negotiations and the length of the contract are likely to account for a +/- 10% difference in electricity pricing." Enhancements from this project will add capabilities in the following areas: en- ergy cost, ancillary energy, curves across different commodities, embodied ener- gy, comminution circuit type, individual equipment assessment, calibration of fi ne grinding, blasting impact, liberation and recovery, and global hardness approach. Effi cient Approach for Wastewater Precious Metals Analysis Researchers from Japan's Kanazawa Uni- versity recently reported on the applica- tion of a portable and effi cient method for the on-site analysis of wastewaters for quantitative analysis of their gold, plati- num and palladium content. The researchers pointed out that pre- cious metals are mainly sourced through mining, but the possibility of recycling them from metallurgical waste leachates is attracting attention. Compact and por- table instruments performing the analysis of wastewaters in on-fi eld rapid analysis would be useful to improve the effi ciency of the recovery of precious metals. Liquid-electrode plasma-optical emis- sion spectrometry (LEP–OES) has emerged as a tool to implement on-site analysis of elements in aqueous matrices, as it is por- table and much less costly than traditional methods. However, when the concentration of noble metals is very low, as is the case for precious metals in waste spills, the sen- sitivity of the technique becomes insuffi - cient to produce accurate analysis — one of the problems is that in metallurgical waste leachates there are several ions that interfere with the analysis. In this case, an- alyte separation and enrichment steps (that is, steps that remove other substances and increase the concentration of the analyte to make detection easier) have to be included in the analysis of the samples for accurate detection of the precious metals. Suman Barua, Ismail M.M. Rahman, Hiroshi Hasegawa and colleagues from Kanazawa University and Fukushima Uni- versity did this when reporting the fi rst ap- plication of LEP-OES in combination with a solid-phase extraction (SPE) system, which is used as the pre-treatment step to elimi- nate the competing ions and to enrich the noble metals, for the rapid on-site simulta- neous analysis of the precious metals gold, palladium and platinum. The SPE param- eters were optimized to maximize reten- tion and recovery of the precious metals; the LEP-OES parameters to maximize the emission peaks for the individual elements. The method was tested both on cer- tifi ed reference material for wastewater and on real aqueous waste samples, from which more than 95% of the precious metals were recovered. The high-preci- sion on-site measurements could be per- formed in less than 15 minutes, opening the way to practical analysis of the pre- cious metal content of wastewaters. The My Sandvik portal can help users improve operational effi ciency and do preventive maintenance planning. Operating protocol for the on-site analysis of precious metals using LEP-OES coupled with SPE-assisted selective preconcentration. LEP-OES: How it Works In liquid-electrode plasma systems, a liq- uid sample is inserted in a micro chan- nel at the ends of which a high voltage is applied, generating a microplasma that acts as the excitation source for emission spectrometry. Liquid-electrode plasma-optical emis- sion spectrometry is an analytical method that has the advantage of not requiring a nebulizer (unlike most other methods). Moreover, it can operate on batteries and is compact and portable. Howev- er, the sensitivity is not high enough to detect metals in very low-concentration samples. To analyze this type of sample, liquid-electrode plasma-optical emis- sion spectrometry can be combined with solid-phase extraction, a method that is used to increase analyte concentration before the analysis. In solid-phase ex- traction, the analyte is fi rst retained on a supramolecular sorbent that uses host- guest chemistry, then extracted in a more concentrated form.

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