Recycling of waste has become an important issue considering the depletion of natural sources and discarded valuable particles and metals. Industrial diamond and other valuable particle embedded into metal matrix cutting tools are manufactured by powder metallurgy techniques [1,2]. They have been widely used in cutting, polishing and grinding of hard metallic and nonmetallic materials like stone, marble and other materials. During its lifetime, a saw blade normally processes around 400 m²of stones [3]. This number corresponds to consumption of only about 60 % of composite cutting tools. Therefore, there are plenty of residual hard particles and combined agents in waste cutting tools [4].

Currently, the general processes of recycling cutting tools involve acid dissolution and separation processes that adopt the principle by utilizing the insoluble characteristics of diamond and tungsten carbide, while dissolving metals. After the filtration of valuable particles, the solution that carries dissolved metal ions are discarded [5,6]. This study offers not only recovering diamond and other valuable particles, but also recycling of metals by co-deposition of metal powders. The waste cutting tools used as anode dissolves in relatively weaker acidic electrolytes and metalic parts are collected as powders at the cathode while hard particles sink to the bottom of electrolyte when power is applied. Temperature, current density, acid concentration and CuSO₄concentration of electrolyte are the process parameters to optimize microstructure, density and surface area of metallic powders. It was found that decreasing current density resulted in a more compact and dense powders as it can be seen in Figure below.

References

[1] M. Jeenings, D. Wright, Ind. Dia. Rev. 49 (1989) 70.

[2] M. Meszaros, K. Vadasdi, Process and equipment for electrochemical etching of diamond containing Co–WC tools and recovery of diamond from used steel tools, Int. J. Refrac. Met. Hard Mater. 14 (1996) 229.

[3] A.L.D. Skury, G.S. Bobrovnitchii, S.N. Monteiro, C.C. Gomes, Recovery of synthetic diamonds from scrapped sawblades, Separation and Purification Technology 35 (2004) 185–190

[4] D. Yuan, Method for regenerating diamond with waste material, Chinese Patent Number CN1253116, 2000.

[5] X.D. He, X.Y. Guo, P. Li, K. Huang, and K.H. Xu, Recovery of nickel, cobalt and m anganese from waste acid solution from synthesis of artificial diamond, Hydrometallurgy of China, 2005, 24 (3): 150.

[6] L.H. Guo, and S.T. Cheng, Study on selective leaching and recycling technology of waste diamond tools, Sichuan nonferrous metals, 1996, (1): 19.