Recovery of synthetic diamond and copper from diamond tool scraps that used in marble cutting industry

Diamond, an allotropic form of carbon, is the hardest mineral known to man. The perfect, or virtually perfect, pieces of diamond, when cut and polished, have always been valued as the most valuable gems. Except rarity of gemstones and their decorative merits, there are also many other properties that makes diamond a unique material. It has the highest thermal conductivity at room temperature, the highest bulk modulus and the highest critical tensile stress for rupture, an extremely high thermal conductivity, low coefficients of friction and thermal expansion, and it is relatively inert to chemical attack by common acids and bases. Till now, just a few of these properties were fully exploited in advanced industrial applications because of the limited size and high price of diamond. The last progress in diamond synthesis, however, is starting to remove the existing barriers, opening new facilities for diamond as an advanced engineering material. The first diamond sawblades that used in cutting stone were developed by Fromholt in France in 1885. Thirteen years later, a large diameter blade was first used in practice in the Euville stone quarries. The early blades were used Brazilian carbonado diamonds set around their periphery. Carbonado was a valuable material at that time because, being a cryptocrystalline mass of small crystals locked in random directions, it was strong and resistant to rupture. Such carbonado blades were utilised to cut limestone and marble during the construction of large buildings in Paris in the 1900s. In the new millennium the market for diamond tools continues to grow swiftly. The recent figures indicate that the demand for diamond abrasives reached an impressive volume of 1 billion carats in 2000, as compared with approximately 380 million carats in 1990 and 100 million carats in 1980. The current bent is to diversify into applications still dominated by traditional abrasives with particular interest in developing linear blades for sawing granite as well as in applying diamond grits on a broader scale in the surface finishing operations. In these days the rapid diamond price decrease makes industrial diamond a commoditised product capable of competing, in terms of its price/performance ratio, with conventional abrasives such as silicon carbide and aluminium oxide. Diamond tools are widely used for cutting, grinding, drilling, and polishing of hard materials. Abrasive diamond circular sawblades for use in cutting concrete, brick, block, stone, and many other materials are well-known in the prior art. In general, such saw blades comprise a metal disk or core having abrasive segments, also called teeth, mounted along the entire periphery of the core. Generally, the abrasive segments are welded to the periphery of the metal disk, and composed of diamond particles and other abrasive material together with a bonding agent. A typical segment contains cobalt, tungsten carbide, various alloys, and up to 20% of diamond particles (approximately 35 ct) or grit. This quantity is depends on strongly on geometry and dimensions of the tool. During that tool's lifetime, a sawblade normally processes around 400 m of stones. For a large industry, this represents a significant number of these cutting tools, which is scrapped every year. In these days the sawblades at the end of their useful lifetime are turned into scrap without practically any commercial value. Also, there are estimates in the literature that approximately 10% of the existing diamonds could still remain in the teeth of a scrapped sawblade. Although this preliminary evidence attesting the possibility of diamond recovery no further information exists on the situation of the left over crystals. Since this is important information for recycling the diamonds, the present work investigates not only the amount but also the integrity of recovered diamonds from scrapped sawblades obtained from one industry at the above-mentioned region. In Europe and North America, there many environmental legislation. More stringent environmental legislation is one reason why companies need to look carefully at their waste management and deal with waste in a responsible way. Punishments for failing to deal with waste can be punitive but apart from the potential there are other significant losses such a loss of honor and tarnishing of brand image to be considered. Corporate Social Responsibility is a philosophy now firmly embedded in corporate culture and programmes such as waste minimisation, recycling and recovery demonstrates to the world at large what a company's attitude is towards its workers, customers and society at large. That can have an impact on brand images which refl ects on customer perceptions and buying patterns. Neediness landfill sites for waste disposal and the increasing cost to companies to use this diminishing resource also supports the economics of recycling to minimise annihilation costs. It is a plus that there is the potential residual material value in the used tooling to be considered as part of the recycling mix. Generally, environmental legislation is moving towards managing products 'from cradle to grave' i.e. from raw materials, production, use and disposal, manufacturers have to consider the environmental impact of its products and processes. Products suitable for diamond recovery are dressers, turning tools, mining bits, oil well bits, rotary dressers, metal bond wheels, saw segments, bit segments, vitrified wheels, plating tanks, saw blades. Modern diamond recovery processes have become more productive but consist essentially of the same processes that are used in high temperature, high pressure diamond synthesis. Actually the diamond is recovered by dissolving metals and other materials to seperate the diamond. The recovery and grading removes all the particles that may be of marginal quality. In the USA Norton offers a programme for customers to annihilate of used conventional grinding wheels and are one of a few manufacturing companies that offer this service in USA. Keith Reckling explains that recovered material, properly processed and graded, can be used in new tools and deliver high performance and both of them (diamond and cubic boron nitride) can be recycled in this way. By the way synthetic diamond based cutting tools which are used in processing of natural stones also used extensively in Turkey, are not recovered after their service life. Scrap cutting tools contains relatively large amount of diamond together metallic materials in matrix such as iron, copper, cobalt, nickel, silver etc. The aim of the thesis is, primarily, the recovery of diamond from scrap cutting tools. For this reason, scrap cutting tools was leached by using suitable acids leading the recovery of diamond particles by the dissolution of metals in matrix. The optimal conditions of leaching was determined by investigating parameters such as the amount of acids, solid/liquid ratio, duration and temperature. While there are studies related with the acidic leaching of scrap cutting tools in the literature, no any investigations have been noticed about the recovery of metals from the solution obtained after the dissolution of metal matrix. For this purpose recovery of metals from the solution obtained after the leaching in the thesis. Copper was separated from the solution by solvent extraction technique. The next stage of the proposal consist of investigations about the pregnant solutions obtained after solvent extraction technique will be experimentally processed to produce saleable products. Experimental studies was carried out to produce copper by cementation with iron from the pregnant copper solution obtained by solvent extraction.