Canada holds very rich mineral resources. Many world-class mining companies, such as Vale, Xstrata, Barrick, Teck, Rio Tinto etc. are involved in producing different commodities including base and precious metals from their mines located all over Canada. While virgin materials will remain the primary source of metals for the growing world, considering its sustainability and economic benefit, the policy-makers, environmentalists, and engineers in Canada are now considering metals recovery and recycling from its secondary sources to make the modern society environmentally friendly. Canada’s metals recycling sector is mature and extensive and consists of more than 2,800 firms including brokers, peddlers, collectors, processors and consumers. In 2006, Teck Cominco first started recycling metals from electronic scraps in their integrated metallurgical facilities at Trail which is located in British Columbia. Although most recycling firms are practising conventional methods to recover metals from the waste materials, some Canadian researchers have considered the needs of future generations and, as such, are now active in developing sustainable technologies. This paper gives an overview on metallurgical industries and metal recycling in Canada, focusing on recent developments on scrap mining and its technological advancement.
In recent years, the demand for the lithium-ion battery is increasing due to the increasing demand for laptop computer, cellular phone and automobiles. The positive electrode of the lithium-ion secondary battery is made of lithium oxide with mainly cobalt, nickel and manganese etc.. An effective recycling method not only would collect cobalt and lithium, but also separate other materials from the used batteries. In this research, the optimum processing flow sheet is investigated and their efficiency is evaluated. The battery is safely decomposed by underwater explosion and then cutter mill. After the over 1mm in size particles are separated by the magnetic separation, eddy current separation and gravity separation by air table, the plastic, Al, Fe, and Cu products are obtained. On the other hand, the particles less than 1mm in size are effectively separated by flotation and carbon and positive electrode powders are recovered. The lithium cobalt powders are leached, neutralized and heated as Co3O4 and lithium is recovered by the adsorption method.
Application of flotation for upgrading and recovery of copper (Cu) and molybdenum (Mo) contained in flotation tailings from a copper/molybdenum mine was investigated in this study. The sample contained mainly pyrite (FeS2) and quartz (SiO2) as dominant phases with Cu and Mo contents at 0.38% and 0.23% respectively. A flotation system employing use of collector/frother mixture [kerosene + sodium dodecyl sulphate (SDS) + polyethylene alkyl ethyl] with tannic acid and sodium silicate as FeS2 and SiO2 depressants, compared against potassium amyl xanthate (PAX) and methyl isobutyl carbinol (MIBC) additions were investigated to evaluate Cu and Mo recovery. According to the results, the grades of Cu and Mo in the concentrate did not increase to above 1% when PAX and MIBC were used as collector and frother, even at increased PAX addition. Also grades for tests performed at varying pH rangig from pH 3 to 11 showed no significant improvement. However, with the use of the collector/frother mixture and tannic acid, Cu and Mo grades increased to 1.4 and 2.4% respectively. The grade of Mo was further increased to 8.0% at 52% recovery when sodium silicate was used with the collector/frother mixture. These results indicate that Cu and Mo lost in such tailings can be upgraded and offered as additional resource for possible recovery.
In anticipation of a new selective grinding technique for printed circuit board (PCB) scraps, this study explored the kinetics of the impact grinding of copper and phenol resin used in PCBs as the base material. The selective and breakage functions of these materials were measured and grinding matrices were determined. Then the variation of the particle size distribution as a function of the impact velocity and grinding time was investigated by model calculation. As a result, it was indicated that the grinding rate of the phenol resin was much higher than that for the copper and that the optimum conditions for increasing the difference in size between copper and phenol resin particles are an impact velocity of 50–60 m/s and grinding time of approximately 6.0 s. These values are also applicable to the grinding of a printed circuit board scrap; Newton’s efficiency as a parameter of the selective grinding effect reached 57%, which is approximately 1.4 times as large as that for the conventional impact grinding method.