PEUF process with electrochemical regeneration for the recovery of copper
Advancing the chemical engineering fundamentals
Membranes and Membrane Science (T2-8P)
Keywords: Polymer Enhanced Ultrafiltration, Electrochemical Regeneration, Copper recovery, Ethoxylated Polyethylenimine
Copper is a valuable and toxic metal present in effluents such as metal surface treatment or electronic industries. The removal of this heavy metal ion has been widely studied using the polymer enhanced ultrafiltration (PEUF) technique. In the vast majority of the works previously published, polymer regeneration step has been carried out by a chemical technique that involves a decrease in pH followed by an ultrafiltration step in which permeate contains the target ion. Some attempts have been done with electrochemical regeneration and with other metal ions [1]. In electrochemical regeneration, metal is electrodeposited in the cathode of an electrochemical cell meanwhile polymer remains in solution and can be recycled. This regeneration technique offers the clear advantage of lacking of a discharge effluent with metallic content.
In this investigation, the removal of Cu2+ from a synthetic effluent has been confronted using partially ethoxylated polyethylenimine (PEPEI) as water-soluble polymer. Firstly, the value of temperature (T) , transmembrane pressure (DP) and pH have been studied and optimised with polymer solutions (0.06 % w/w) in total recirculation mode, in order to maximize the value of the design parameters (permeate flux and rejection coefficients) [2]. Secondly, the loading capacity of PEPEI at pH 6 in respect of Cu2+ ions was determined. This study resulted in a loading capacity of PEPEI of 208 mg Cu2+/g PEPEI, which represent a value in the same order than that obtained for the non-ethoxylated polyethylenimine [3]. Thirdly, the influence of pH on copper retention has been studied, what allows the determination of the optimal working pH for retention and regeneration steps, if the latter were carried out chemically. To finish with ultrafiltration experiments, both concentration polarization and fouling phenomena were studied and modelled for PEPEI and PEPEI-Cu solutions in discontinuous mode.
In respect of the polymer electrochemical regeneration study, it comprised two stages. Firstly, voltamperometric analyses of increasing complexity solutions were carried out. From these experiments, one can determine the optimal operation voltage in order to avoid competitive reactions and verify that the polymer does not suffer any oxidation or reduction process. Secondly, the influence of pH and run time in the electrodeposition process in solutions with Cu2+, PEPEI and Na2SO4 as electrolyte at constant voltage was studied. An optimal pH value less extreme (pH = 3.3) was obtained for electrochemical regeneration than that necessary if the regeneration were carried out chemically (pH = 2).
References
[1] Barron-Zambrano, J.; Laborie, S.; Viers, Ph.; Rakib, M.; Durand, G. Mercury removal and recovery from aqueous solutions by coupled complexation–ultrafiltration and electrolysis. J. Membrane Sci. 229 (2004) 179-186.
[2] Cañizares, P.; De Lucas, A.; Pérez, Á.; Camarillo, R. Effect of polymer nature and hydrodynamic conditions on a process of polymer enhanced ultrafiltration. J. Membrane Sci. 253 (2005) 149-163.
[3] Kislenko, V. N.: Oliynyk, L. P. Complex formation of polyethylenimine with copper(II), nickel(II) and cobalt(II) ions. J. Polym. Sci. Pol. Chem. 40 (2002) 914-922.
Presented Tuesday 18, 13:30 to 15:00, in session Membranes and Membrane Science (T2-8P).
