Copper recovery in a spouted vessel electrolytic reactor (SBER)

Abstract

An investigation of copper recovery from acidic solutions in a particulate, cylindrical spouted vessel of conductive particles is presented. The effects of current, initial copper ion concentration, supporting electrolyte concentration, particle loading, liquid flow rate, solution pH, and temperature on copper recovery rate, current efficiency and energy efficiency of the electrolytic deposition process were investigated under galvanostatic conditions. Experiments were also conducted to investigate the effects of backdissolution or 'backstripping' of the deposited metal in the acidic solution. It is hypothesized that the latter occurs via both chemical and electrochemical anodic oxidation in the bed of conductive particles. It was found that sparging of the electrolyte solution with selected gases to remove dissolved oxygen increased the current efficiency by as much as 30% under certain conditions. Finally, a numerical kinetic model of electrochemical deposition and backstripping, coupled with mass transfer in the particulate cathode bed, is presented that describes the behaviour of the net copper recovery curves reasonably well. List of symbolsa electrode area per unit volume (m )1 ) C j concentration of species j (mol m )3 ) C js concentration of species j at electrode surface (mol m )3 ) C metal cation concentration in solution, initial (ppm or mol m )3 ) C O initial metal cation concentration in solution, initial (ppm or mol m )3 )backstripping rate constant pre-exponential factor (ppm min )1 )/(mol kg )1 bar )1 ) K B backdissolution rate (mol m )3 s )1 ) K H Henry's law constant for oxygen in water (mol oxygen (kg water) -1 (bar )1 ) n apparent reaction order n j number of electrons in rate j r b backstripping rate (ppm min )1 ) r j rate of reaction or mass transport (mol m )3 s )1 ) R gas constant (J K )1 mol )1 ) Re p particle Reynolds number (= u d p /m) ScSchmidt number (= m/D) Sh particle Sherwood number (= k L d p /D) t time (s) T temperature (K) DH Ã 0 heat of activation at equilibrium potential (kJ mol )1 ) a transfer coefficient (Equation 10) m kinematic viscosity (m 2 s )1 )

Electrochemical copper recovery from galvanic sludge

“…Similar effects have also been observed in other three-dimensional electrode systems [37][38][39] and mainly arise from the highly non-uniform potential distribution [21,28]. These have been analysed [21] for a number of 3D flow-by electrodes with a cylindrical geometry, and these correspond closely to the Porocell configuration shown in Figure 2.…”

“…indicate that the influence of this side reaction can be minimised by operating at low flow rates and high applied currents. As reported by others [36][37][38] the use of inert gas sparging may also improve the current efficiency. Operating at higher temperatures would also reduce the solubility of O2 and therefore its influence on the current efficiency for copper deposition, but with an increased energy cost.…”

“…The phenomenon of low faradiac efficiency in electrowinning when the limiting current for metal ion deposition has not been exceeded has been reported in a number of other studies employing three-dimensional cathodes [33][34][35][36][37][38][39]. For example, Tsapkh and Volkov [33] reported researchers [34][35][36] employing FBEs have also noted current efficiencies less than unity and its tendency to increase at higher currents.…”

“…reactor [37] it was noted that the presence of oxygen reduced the rate of metal ion recovery and the current efficiency. This was attributed to the corrosion of copper by oxygen and the effect could be substantially reduced by sparging the solution with an inert gas.…”

Improvement of cadmium ion electrochemical removal from dilute aqueous solutions by application of multi-stage electrolysis

“…Charge transfer to three-dimensional electrode surfaces has simultaneously been improved by the use of the spouted bed electrodes in which a suitable contact of electrode particles and current feeder has been obtained by providing a packed bed zone (Jiricny et al 2002a, b;Shirvanian and Calo 2005). This process has also been enhanced by Vatistas and Bartolozzi (1990) and Yen and Yao (1991) by the use of three-dimensional current feeders.…”