While the copper stills used in the whiskey purifcation process are vital to its avor profile, low levels of copper corrosion lead to low but environmentally relevant copper concentrations in distillery waste. This is particularly the case for spent lees, the by-product of the second distillation, as, unlike the first distillation by-product, its only avenue is treatment and discharge.With diminishing copper reserves, it is increasingly necessary to investigate ways that copper waste, including copper containing solutions, can be recovered for reuse. This work investigates electrochemical copper recovery from spent lees. Initial bench-scale studies investigated the impact of spent lees other waste constituents on copper recovery, finding insignificant or insufficiently large differ-ences between the electrochemical behaviour of simulated waste and pure copper solution.Consequently, copper recovery was tested with weakly acidic copper sulphate in a 4.5 L batch reactor using a porous carbon felt cathode. Application of currents of 105 mA (5 A/m2) could reduce the copper concentration below the reliable detection limit of 2 ppm within 6 hours, albeit at a Coulombic efficiency less than 40 %. Applying less current resulted in lower efficiencies, suspected to be related to corrosion. The efficiency increased to 86.1 + 1.4 % when the current was increased to 1.05 A, and the process duration decreased to under 2 hours.When operating with real spent lees, the process was slower and less efficient. However, the difference was not statistically significant, predominantly due to uncertain copper concentration measurements. Real spent lees are notably more resistive, resulting in nearly double the energy cost compared to pure copper solution. Consequently, despite reasonable rates and efficiencies, the current process requires too much energy due to the high resistivity of the spent lees.
|Date of Award||6 Jun 2019|
- University Of Strathclyde
|Sponsors||University of Strathclyde|
|Supervisor||Sudipta Roy (Supervisor) & Todd Green (Supervisor)|