Separation of Cd and Ni from Ni–Cd batteries by an environmentally safe methodology employing aqueous two-phase systems

Abstract

a b s t r a c tThe separation of Cd and Ni from Ni-Cd batteries using an aqueous two-phase system (ATPS) composed of copolymer L35, Li 2 SO 4 and water is investigated. The extraction behavior of these metals from the bottom phase (BP) to the upper phase (UP) of the ATPS is affected by the amount of added extractant (potassium iodide), tie-line length (TLL), mass ratio between the phases of the ATPS, leaching and dilution factor of the battery samples. Maximum extraction of Cd (99.2 ± 3.1)% and Ni (10.6 ± 0.4)% is obtained when the batteries are leached with HCl, under the following conditions: 62.53% (w/w) TLL, concentration of KI equal to 50.00 mmol kg −1 , mass ratio of the phases equal to 0.5 and a dilution factor of battery samples of 35. This novel methodology is efficient to separate the metals in question, with the advantage of being environmentally safe, since water is the main constituent of the ATPS, which is prepared with recyclable and biodegradable compounds.

Recent trends in metals extraction

“…macrocyclic or bifunctional extractants) [75][76][77] , elimination of volatile organic compounds (e.g. the use of aqueous biphasic systems-ABS) [78][79][80] , search for applications for ILs in extraction systems [3 and 81-100] .…”

Monosegmented Flow Analysis Exploiting Aqueous Two-phase Systems for the Determination of Cobalt

“…20 The leachate was filtered into a 1.00-L flask with distilled water. An aliquot of the leachate was dissolved in the ATPS bottom phase, and the solution was injected into the flow system.…”

“…It is important to note that several ATPS methodologies have already been successfully applied to the extraction, separation and determination of different ions in batch experiments, which supports our thesis that ATPS can be used in combination with a flow system. 11,[18][19][20][21][22] Thus, the aim of this work was to develop a novel and green method, exploiting ATPS-MSFA for the first time, using as example the determination of the amount of cobalt in Ni-Cd battery samples. Despite of simplicity of the system used for the application, the major contribution of this work is to show the potentiality of ATPS-MSFA.…”

Metal Recovery from Aqueous Solutions

“…The application of electrochemical techniques in the environmental remediation is increasing because, besides being very versatile, they can be applied in the removal of polluting solids, liquids and gases. The recovery of heavy metals from aqueous solutions is one of the examples of the use of electrochemical methods with environmental purposes [5][6][7][8][9]. In fact, several metal ions in solution can be recovered in the metallic form by reduction at a cathode under specific conditions.…”

“…Examples are silver and copper [5,8,[10][11][12][13][14][15], whose economic value is significant, and cadmium, lead and nickel [6] used in common and car batteries, whose toxicity is high. The recovery of metals from Ni-Cd batteries has also been intensively studied in the last decade [7,[16][17][18]. In the case of lead, besides the reduction at the cathode, its oxidation can also take place at the anode, obtaining lead metallic and lead oxide (IV) [19], respectively, being both useful products.…”