Recovery of metallic values in nickel-titanium rotary file wastes used in endodontics

Nitinol, a nickel titanium alloy which has been very popular throughout various industries, has almost no efficient way of recycling. In this study we tried to recover metallic values as their oxides and hydroxides from endodontical waste nitinol rotary files through a hydrometallurgical method and use the recovered metallic values to produce asymetrical supercapacitors. Supercapacitors has been a popular research subject as an energy storage system because of their fast charge-decharge times, long cycle numbers and high power densities. For these reasons we tried to use the recycled products to produce electrodes to be used in supercapacitors. Metallic values from the rotary files has been recovered as a reflux system was used to perform the leaching experiments. H2SO4 has been used as an leaching agent and leaching efficiencies of %94.75 for titanium and %88.66 for nickel has been achieved in optimum conditions. After successfull leaching of the waste product titanium and nickel has been precipitated seperately. Titanium has been precipitated as TiO2 and nickel has been precipitated as Ni(OH)2. Nickel oxide has been a popular subject for the use of electrode material for supercapacitors. Since NiO was a suitable final product for a supercapacitor electrode in order to convert the precipitated Ni(OH)2 to NiO it was calcinated at the temperatures of 450°C, 650°C and 850°C according to the TG-DTA data that was acquired from the analysis. For the production supercapacitor electrodes, nickel oxide powders obtained after different calcination temperatures and nickel hydroxide was used seperately. The electrochemical behaviour of the asymmetric type coin cell supercapacitors with different electrodes were investigated in a two-electrode system at a scanning rate of 10 mV.s-1. For the electrodes which have been produced from the powders of Ni(OH)2, NiO-450, NiO-650 and NiO-850 the specific capacitance values of 58.01 mF.cm-2, 87.91 mF.cm-2, 73 mF.cm-2 and 61.41 mF.cm-2 were obtained respectively. After calculating the specific capacitance values, long cycle stability tests were performed on the supercapacitors at 1 mA.cm-2 current density and capacitance retention results were %126.24, %103.47, %94.45 and %122 respectively.