Recovery of zinc and cadmium from spent batteries using Cyphos IL 102 via solvent extraction route and synthesis of Zn and Cd oxide nanoparticles

Highlights

• First time Cyphos IL102 explored for recovery of Zn/Cd from spent batteries.

• Recovery of metals with high purity was achieved at room temperature.

• Quantitative extraction was achieved in two stages for Zn and Cd.

• Loaded organic phases were used to synthesize ZnO and CdO nanoparticles.

• Simple strippants for stripping isotherm was used.

Abstract

The overall aim of this study is to separate and recover zinc and cadmium from spent batteries. For this purpose Cyphos IL 102 diluted in toluene was employed for the extraction and recovery of Zn and Cd from Zn-C and Ni-Cd batteries leach liquor. The influence of extractant concentration for the leach liquors of Zn-C (0.01–0.05 mol/L) and Ni-Cd (0.04–0.20 mol/L) batteries has been investigated. Composition of the leach liquor obtained from Zn-C/Ni-Cd spent batteries is Zn - 2.18 g/L, Mn - 4.59 g/L, Fe - 4.0 × 10⁻³ g/L, Ni - 0.2 × 10⁻³ g/L/Cd - 4.28 g/L, Ni - 0.896 × 10⁻¹ g/L, Fe - 0.148 g/L, Co - 3.77 × 10⁻³ g/L, respectively. Two stage counter current extraction at A/O 1:1 and 3:2 with 0.04 mol/L and 0.2 mol/L Cyphos IL 102 for Zn and Cd, respectively provide more than 99.0% extraction of both the metal ions with almost negligible extraction of associated metal ions. A stripping efficiency of around 99.0% for Zn and Cd was obtained at O/A 1:1 using 1.0 mol/L HNO₃ in two and three counter current stages, respectively. ZnO and CdO were also synthesized using the loaded organic phase and characterized using XRD, FE-SEM and EDX techniques. XRD peaks of ZnO and CdO correspond to zincite and monteponite, respectively. The average particle size was ∼27.0 nm and ∼37.0 nm for ZnO and CdO, respectively. The EDX analysis of ZnO and CdO shows almost 1:1 atomic percentage.

Introduction

Use of zinc-carbon (Zn-C) and nickel-cadmium (Ni-Cd) batteries in various electronic portable devices such as cell phones, cameras, laptops and recorders has increased in the last 35 years because of their versatility, low maintenance, long life and low cost (De Souza et al., 2001). The spent batteries, when improperly disposed, lead to environmental pollution due to their metallic contents. In this scenario, recycling of spent batteries for the recovery of precious metal values will be significant from both economic and environmental point of view.

A number of extractants such as Tri-n-butylphosphate (TBP) (Fernandes et al., 2012), Cyanex 301 (Biswas et al., 2016, Reddy et al., 2006), D2EPHA (Babakhani et al., 2014, Falco et al., 2014), Cyanex 302 (Babakhani et al., 2014), Cyanex 272 (Biswas et al., 2016, Falco et al., 2014), TOPS 99 and Cyanex 471 X (Reddy et al., 2008) have been investigated either singly or as a mixture for the separation and recovery of Zn(II) and Cd(II) from spent batteries.

Attempts have also been made to synthesize metal oxides from battery waste. Ebin et al. (2016) prepared ZnO and MnO₂ particles from alkaline and Zn-C battery waste by pyrolysis method. Pyrolysis involves large amount of energy accompanied by evolution of harmful gases. Synthesis of ZnO and MnO₂ particles from Zn-C cell powder by classical precipitation method was reported by Biswas et al. (2016). Deep et al., recovered ZnO nanoparticles from spent alkaline Zn-MnO₂ batteries following extraction-combustion (Deep et al., 2011) and leaching-combustion (Deep et al., 2016) methods. Combustion leads to loss of extractant. Khayati and co-workers, for the first time, reported the synthesis of CdO nanoparticles from spent Ni-Cd batteries (Khayati et al., 2014). They precipitated CdO from the leach liquor of anodic material, this may lead to incorporation of impurities in synthesized nanoparticles.

Lately phosphonium based ionic liquids have attracted the attention of separation chemists, because of their very low vapour pressure, high thermal stability, good extraction power for metal ions and good recycling capacity (Regel-Rosocka, 2009, Makanyire et al., 2016, Rout and Binnemans, 2014). These ionic liquids are different from conventional acidic extractants as they may not release H⁺ into the raffinate and thus neutralization of released acid and saponification of the extractant is not required (Kumari et al., 2016).

Till date no literature is available on the use of Cyphos ionic liquids for the recovery of Zn and Cd from spent batteries. Preliminary studies carried out in our laboratory established Cyphos IL 102 as an efficient extractant for Zn(II) and Cd(II). Keeping this in mind Cyphos IL 102 was explored for the recovery of Zn(II) and Cd(II) from spent batteries.

Present work demonstrates extraction and recovery of Zn and Cd from powder of spent Zn-C and Ni-Cd batteries using chloride medium. Conditions were optimized for the selective extraction of Zn and Cd from the leach liquor. Process parameters such as phase ratio, extraction and stripping isotherm, counter current extraction and stripping simulation have been worked out on leach liquors of spent batteries. Loaded organic phases obtained after the extraction of pure Zn and Cd were used to synthesize high purity ZnO and CdO nanoparticles by precipitation method followed by thermal decomposition. Characterization of synthesized nanoparticles has been ascertained by X-ray diffraction spectroscopy (XRD), field emission scanning electron microscopy (FESEM) and energy dispersive X-ray spectroscopy (EDX). ZnO and CdO nanoparticles find many applications in optical waveguides, varistors, piezoelectric transducers, photonic crystals, light-emitting devices, phototransistors, photodiodes, gas sensors, transparent conductive films, and solar cells (Askarinejad and Morsali, 2008, Wang and Muhammed, 1999).

Fast growing urbanization and market expansion has resulted into increased production and consumption of portable batteries. As a consequence, spent batteries containing various metals such as Zn, Mn, Cd, Ni, Co, Fe are being discharged as waste. This indicates that waste batteries can serve as secondary source to overcome the scarcity of metals. In Europe alone, more than 50,000 tons of Zn-C waste batteries were discarded in 2003 (EPBA, 2006) and 2.044 tons of Ni-Cd batteries were disposed in 2002 (EU, 2003). In India approximately 8,00,000 tons e-waste was generated by the end of 2012 (Basu, 2010). Top 10 cities generating major portion of e-waste in India are Mumbai, Delhi, Chennai, Bengaluru, Kolkata, Ahmedabad, Hyderabad, Pune, Surat and Nagpur. Tons of battery waste being generated every year all over the globe requires appropriate management.

Waste management strategies of spent batteries involve collection, landfilling, incineration and recycling. Some countries have established collection system for waste batteries with the objective of improving environment. However a separate collection system for each type of battery is inconvenient to implement because consumers find it difficult to identify various type of batteries (Xará et al., 2015). In the absence of an established method of collection, transport and recycling of batteries, landfilling or incineration is employed for the disposal of spent batteries.

Landfill can be categorised into three types, open dumps, controlled dumps or secure landfilling (Chandrappa and Das, 2012). Among these secure landfilling is the long term confinement process for disposal of waste batteries. Pre-treatment processes such as minimization or elimination of hazardous properties, reduction of volume and waste stabilization are carried out before disposal. In case of landfilling, constituents are leached by rainy water and infiltration occurs. Leaching and infiltration increase the toxicity of metal constituents in surface and ground water streams (Karnchanawong and Limpiteeprakan, 2009). Due to limited landfill deposition sites and high amount of battery waste being generated, safe disposal of spent batteries is becoming increasingly expensive.

Incineration process includes collection of spent batteries followed by mass burn of spent waste. This process is popular in countries facing scarcity of land. Incineration process converts the waste into ash, flue and heat. Moreover, spent batteries on incineration cause environmental hazard due to the release of toxic metals such as Cd, Hg and dioxins to the atmosphere. Landfilling of fly and bottom ash leachate causes marine eutrophication (Sadeghi et al., 2017, Provazi et al., 2011). In recent years landfilling and incineration are restricted by environmental legislations.

In view of above, most effective and important way to manage the problem of waste batteries is recycling and reuse, as it preserves primary raw materials, recovers precious metals and reduces adverse effects on the environment (Bahaloo-Horeh and Mousavi, 2017).

In 2012 European Battery Recycling Association (EBRA) has recycled 38,591 tons spent batteries out of which 26,660 tons were Zn batteries and 6632 tons were Ni-Cd batteries (EBRA, 2012). Recycling based management of waste batteries has mainly two operations pyro metallurgical and hydrometallurgical processes. Major limitations of pyro metallurgical route are consumption of high energy, evolution of gases and emission of dust into the environment (Duan et al., 2016, Sadeghi et al., 2017. Hydrometallurgical processes are usually more economical and efficient. The advantages are less air pollution, less energy consumption, easy scale up and high selectivity (Fernandes et al., 2013, Sadeghi et al., 2017). A number of hydrometallurgical processes have been reported for the recovery of valuable metals from spent batteries such as Zn-C (Baba et al., 2009), Ni-Cd (Fernandes et al., 2012), Ni-metal hydride (Rodrigues and Mansur, 2010) and lithium ion (Chen et al., 2011).

In the present study hydrometallurgical route has been applied for the recovery of Zn and Cd from spent batteries.