Elsevier

Desalination

Volume 440, 15 August 2018, Pages 18-38
Desalination

A critical review on membrane extraction with improved stability: Potential application for recycling metals from city mine

https://doi.org/10.1016/j.desal.2018.01.007Get rights and content

Highlights

  • Membrane extraction is potentially a highly efficient method for Urban Mining.

  • Historical development in stabilizing the liquid membranes was summarized.

  • Solvent resistant membrane was identified as the key for stable liquid membrane.

  • Membrane contactor demonstrated stable performance in various ion separation tasks.

Abstract

Mining from the city is one of the future directions for sustainable resource management. The separation of highly dispersed, low concentration valuable metals requires highly efficient extraction technology, where membrane extraction has shown significant advantages owing to its potentially high selectivity and low footprint. This review summarizes the recent progress in membrane extraction with respect to the development of membrane materials and the process configurations with special focus on preventing the loss of the organic extractant and/or degradation of the membrane materials. Prior research work was reviewed first on the development of various membrane materials for extending the membrane performance. Further developments on membrane configuration and process are presented on ion exchange membranes and membrane contactors, and composite hollow fiber membranes where the advantages and problems are stressed. Hydrophilic/hydrophobic blend polymers and block co-polymers have shown much more extended lifetime, which is a potential development direction. In summary, this review provides not only the recent development on membrane materials but also the application process/scheme that can help to improve the performance of membrane extraction, which might be beneficial for a broad audience ranging from academic scientists and industrial engineers who are looking for pioneering alternative solutions for city mining.

Introduction

Recycle is a short to medium term sustainable solution for metals. The environmental footprint of humankind is unsustainable due to limited natural resources and aggressive human activity on land, water, energy, and materials. To reduce the environmental footprints, it requires a global transformation of the structure of the economy [1]. Challenges and opportunities coexist. Great business opportunity in a century has been envisioned beyond only social impact [2]. As a pioneer, Apple company's closed-loop supply chain is manufacturing products using only renewable resources or recycled material to reduce the need to mining materials from the earth [3].

Metals are infinitely recyclable, however, progress of recycling is hampered by product design, recycling technologies, and the thermodynamics of separation, and sometimes more importantly social behavior [4].For instance, replacement of copper metal by other metals or alloy will reduce growth in copper demand; as the resources in mines became scarcer, its price will rise till a value which the economic effect of recycling can compete [5].Study showed that multimillion tons of metals, Cu (711.6 m ton), Fe (8.1 m ton), Al (37.0 m ton), and Pb (12.1 m ton) could be sourced out from urban mine by 2040 [6]. In Switzerland, valuable metals (0.4 ± 0.2 mg/kg Au and 5.3 ± 0.7 mg/kg Ag Au, Ag) were found in the incinerated municipal solid waste (MSW) [7].In practice, frequently utilized metals and metalloids are often not reused at the end of the life cycle, as shown in Fig. 1. For the specialty metals or rare earth metals used in very small amounts in high tech products such as consumer electronics, lightening sources, durable automobile parts, sensors, engines etc., this is uniquely true; the short life time of the consumer products imposes recycling barriers. Collection and purification are thermodynamically unfavorable when metals are mixed with other materials in a small quantity [8].

Mining from city is becoming an indispensable choice. Waste materials from mining, infrastructure and products are now becoming valuable ‘above-ground’ mineral resources. Previous studies have indicated that urban mining for metals recycling can decrease energy consumption and pollutants emission compared to the extraction of metals from natural minerals [10].Waste electrical and electronic equipment (WEEE) has become increasingly important over the last years. CSIRO Flagship Collaboration Fund identified that the value of metals in end-of-life products is more than AUD6.0billion per year [11]. For Belgium, 80 and 87% less resource consumption is achieved for desktops and laptops respectively in 2013; the natural resource consumption of the recycling scenario is much smaller than land filling the WEEE [12]. High values of the resource index indicate that the waste is important to the European Union (EU) economy and hence has significant potential for recycling as a resource [13]. Recovery opportunity is widely accessible for metals [14] and phosphorous [15, 16] from sewage sludge, and uranium and rare earth metals from copper mine waste streams [17].

Since city mines covers a large spectrum of metals or metal ions, we will focus on only the widely disperse metals which are suitable for extraction and purification in a liquid form rather than in a bulky solid form. Wastewaters containing precious and heavy metal ions are located at the vicinity of the large cities such as Shanghai, Shenzheng, and many small and medium cities around China. They are the main concerns of the Chinese environment protection plan. Due to the past short-term industry development of Chinese economy, many industries discharging large amount of waste streams are facing stringent environmental regulations. There is a strong incentive for them to adopt a new sustainable development plan to survive. As a retrofit to the existing industry parks, the extraction of the precious and heavy metals ions from their waste streams would be beneficial to both the environment and the economics of the individual industry. Water reuse and mineral recovery could be combined to reduce the cost [18]. Operational cost for an ultrafiltration-nanofiltration membrane processes for gold acid mine drainage was estimated to be 0.263 US$/m3 of effluent [19]. Extraction of the metals from the concentrate is expected to generate extra cash revenue which may cover the operational cost or potentially the capital cost.

Bulk metal materials separated mechanically are responsible for the majority of the common minerals. However, different methods are needed for precious and valuable metals of low content and widely distributed in alloys. To collect, transport and mechanically treat these materials is not the focus of this review. Downstream of this supply chain, separation and purification of the single element from a complicated mixture is difficult and energy intensive. Therefore, an efficient and highly selective separation technique is necessary to extract, separate and purify the metals from a mixture. Table 1 lists the separation and purification approaches currently employed in practice. Obviously, the characteristics of these technologies dictates that no single process is all-purpose to yield products of a high purity. For example, incineration/combustion is suitable for the upstream treatment prior to downstream purification processes; chemical precipitation, nanofiltration, electro dialysis, ion exchange, and adsorption technologies, except for some limited cases, are generally not used for the final purification stage. Chemical precipitation has been used for production of lithium carbonate in salt lake brine in South America, but not suitable for the brine in Northwest China where the salt lake brine is of high magnesium/lithium ratio [20]. The most frequently utilized purification approach is liquid-liquid extraction for obtaining a highly purified form of the metal element, which will be the focus of present review.

The chemistry and the processes to attain the targeted purity of liquid-liquid extraction have been extensively understood. For different mixtures, the extractant and separation processes will be largely different, the variety and complicity is beyond the discussion of this review. Therefore, this review focuses on the core equipment or facilities to realize the extraction processes, particularly, the membrane based liquid-liquid extraction, or membrane extraction. The state-of-the-art of membrane based liquid-liquid extraction will be introduced. The development in this area and the key issues will be analyzed.

Section snippets

Equipment for liquid-liquid extraction

Four types of industrial scale extraction equipment are identified as mix-settler, column, centrifugal machine and membrane. Except for membrane, other systems have been running for different separation purposes (as shown in Fig. 2). Characteristics of these equipment are listed in Table 2. Capital cost, footprint, and energy consumption are the main factors for consideration. Among these parameters, the energy consumption is of utmost importance [37]. Obviously, centrifugal equipment is the

Combination of dispersed phases and supported liquid membranes

Fig. 4 shows a process called emulsion-liquid-membrane extraction in a hollow fiber contactor for the extraction of Cu2+ [47, 48, 52, 53]. Because the hollow fiber membrane is made of hydrophobic material, organic extractant mixed with emulsified stripping droplets (sulfuric acid) wets the pores and the interface at the pore mouth on the fiber outer surface. Aqueous phase is placed in shell side and the pressure is maintained above that of the emulsion phase. There is no direct contact between

Liquid membrane contactor with two protection layers

Fig. 8A shows schematically a composite hollow fiber membrane with two ion exchange coating layers on the inner and outer surfaces. This is theoretically an optimal encapsulated SLM for the stable selective transport of ions. Reduction of the thickness of the porous substrate decreases the mass transfer resistance, leading to improved ion flux [85]. Technical challenges were still a main obstacle for the successful application of such concept. In contrast, Fig. 8B shows a more complicated

Other engineered membranes

Polymer inclusion membranes (PIMs) are an interesting membrane design based on the polymer, extractant and plasticizer. It was a surprise to observe that most of the research activities on PIM was based on two commercially available polymers, polyvinylchloride (PVC) and cellulose acetates. The polymers provide mechanical strength as well as provide physicochemical interaction with the constituents in PIM [100]. Interested readers can find extensive summaries of the applications of PIMs in

Metal ions extracted using membrane extraction

Table 4 lists the various metal ions extracted using various membrane extraction processes, SLM, membrane contactor, renewal liquid membrane etc. The carriers and the membranes tested as well as the ion fluxes were reported. As noticed, the table starts from most common heavy metals, such as copper, nickel and zinc ions [52, 60, 66, 87, 126, 127], then covers the precious metal ions, such as rare earth [[128], [129], [130], [131]], platinum [132, 133], gold [134], etc., and ends with uranium

Summary and outlook

Herein, the state-of-the-art development on the membrane extraction has been reviewed. As a small footprint, low energy process, the liquid membrane/membrane extraction was identified as a potentially attractive technology that can be used for recovery of the highly dispersed and yet limited valuable metals from the city mine. The long-term stability of liquid membrane, particularly in SLMs, has been the key issue in inhibiting the progress of its practical application because of the loss of

Acknowledgments

The authors thank the partial financial support from the National Natural Science Foundation of China (U1507117, 21676290), TMSR from the Chinese Academy of Sciences (XDA02020100) and Newton Advanced Fellowships from the Royal Society (No. NA170113).

References (176)

  • B. Alyuz et al.

    Kinetics and equilibrium studies for the removal of nickel and zinc from aqueous solutions by ion exchange resins

    J. Hazard. Mater.

    (2009)
  • G. Sharma et al.

    Fabrication and characterization of sodium dodecyl sulphate@ironsilicophosphate nanocomposite: ion exchange properties and selectivity for binary metal ions

    Mater. Chem. Phys.

    (2017)
  • S.H. Lin et al.

    Chromic acid recovery from waste acid solution by an ion exchange process: equilibrium and column ion exchange modeling

    Chem. Eng. J.

    (2003)
  • K. Meschke et al.

    Strategic elements from leaching solutions by nanofiltration - influence of pH on separation performance

    Sep. Purif. Technol.

    (2017)
  • C.-V. Gherasim et al.

    Investigation of batch electrodialysis process for removal of lead ions from aqueous solutions

    Chem. Eng. J.

    (2014)
  • T. Mohammadi et al.

    Effect of operating parameters on Pb2+ separation from wastewater using electrodialysis

    Desalination

    (2004)
  • A. Abou-Shady et al.

    Effect of pH on separation of Pb (II) and NO3 from aqueous solutions using electrodialysis

    Desalination

    (2012)
  • A. Jordens et al.

    A review of the beneficiation of rare earth element bearing minerals

    Miner. Eng.

    (2013)
  • D. Zhao et al.

    Facile preparation of amino functionalized graphene oxide decorated with Fe3O4 nanoparticles for the adsorption of Cr(VI)

    Appl. Surf. Sci.

    (2016)
  • C. Ding et al.

    Competitive sorption of Pb(II), Cu(II) and Ni(II) on carbonaceous nanofibers: a spectroscopic and modeling approach

    J. Hazard. Mater.

    (2016)
  • M. Mushtaq et al.

    Eriobotrya japonica seed biocomposite efficiency for copper adsorption: isotherms, kinetics, thermodynamic and desorption studies

    J. Environ. Manag.

    (2016)
  • S.A. Ansari et al.

    A review on solid phase extraction of actinides and lanthanides with amide based extractants

    J. Chromatogr. A

    (2017)
  • A. Kiani et al.

    Solvent extraction with immobilized interfaces in a microporous hydrophobic membrane

    J. Membr. Sci.

    (1984)
  • N.M. Kocherginsky et al.

    Recent advances in supported liquid membrane technology

    Sep. Purif. Technol.

    (2007)
  • A.L. Ahmad et al.

    Emulsion liquid membrane for cadmium removal: studies on emulsion diameter and stability

    Desalination

    (2012)
  • N.N. Li et al.

    Liquid membrane processes for copper extraction

    Hydrometallurgy

    (1983)
  • S.Y.B. Hu et al.

    Feasibility of surfactant-free supported emulsion liquid membrane extraction

    J. Colloid Interface Sci.

    (2003)
  • E.A. Fouad et al.

    Emulsion liquid membrane extraction of zinc by a hollow-fiber contactor

    J. Membr. Sci.

    (2008)
  • M.E. Vilt et al.

    In situ removal of Cephalexin by supported liquid membrane with strip dispersion

    J. Membr. Sci.

    (2011)
  • M.E. Vilt et al.

    Supported liquid membranes with strip dispersion for the recovery of Cephalexin

    J. Membr. Sci.

    (2009)
  • Z. Ren et al.

    New liquid membrane technology for simultaneous extraction and stripping of copper(II) from wastewater

    Chem. Eng. Sci.

    (2007)
  • Z. Hao et al.

    Supported liquid membranes with organic dispersion for recovery of Cephalexin

    J. Membr. Sci.

    (2014)
  • V.S. Kislik et al.

    Hybrid liquid membrane (HLM) system in separation technologies

    J. Membr. Sci.

    (1996)
  • V.S. Kislik et al.

    Hybrid liquid membrane (HLM) and supported liquid membrane (SLM) based transport of titanium(IV)

    J. Membr. Sci.

    (1996)
  • H. Duan et al.

    A novel sandwich supported liquid membrane system for simultaneous separation of copper, nickel and cobalt in ammoniacal solution

    Sep. Purif. Technol.

    (2017)
  • Q. Yang et al.

    The development of chemically modified P84 co-polyimide membranes as supported liquid membrane matrix for Cu(II) removal with prolonged stability

    Chem. Eng. Sci.

    (2007)
  • S. Bey et al.

    Hydrophilic PEEK-WC hollow fibre membrane contactors for chromium (VI) removal

    Desalination

    (2011)
  • A.M. Neplenbroek et al.

    Supported liquid membranes-stabilization bu gelation

    J. Membr. Sci.

    (1992)
  • A.J.B. Kemperman et al.

    Stabilization of supported liquid membranes by interfacial polymerization top layers

    J. Membr. Sci.

    (1998)
  • R. Wang et al.

    Characterization of novel forward osmosis hollow fiber membranes

    J. Membr. Sci.

    (2010)
  • G. Chen et al.

    Open porous hydrophilic supported thin-film composite forward osmosis membrane via co-casting for treatment of high-salinity wastewater

    Desalination

    (2017)
  • G. Chen et al.

    Treatment of shale gas drilling flowback fluids (SGDFs) by forward osmosis: membrane fouling and mitigation

    Desalination

    (2015)
  • Y.C. Wang et al.

    Formation of semi-permeable polyamide skin layers on the surface of supported liquid membranes

    J. Membr. Sci.

    (1998)
  • X.J. Yang et al.

    Stabilization of supported liquid membranes by plasma polymerization surface coating

    J. Membr. Sci.

    (2000)
  • M.C. Wijers et al.

    Supported liquid membranes modification with sulphonated poly(ether ether ketone) - permeability, selectivity and stability

    J. Membr. Sci.

    (1998)
  • O. Kedem et al.

    Ion-exchange membranes in extraction processes

    J. Membr. Sci.

    (1993)
  • T. He et al.

    Composite hollow fiber membranes for organic solvent-based liquid-liquid extraction

    J. Membr. Sci.

    (2004)
  • R. Molinari et al.

    Comparison between stagnant sandwich and supported liquid membranes in copper(II) removal from aqueous solutions: flux, stability and model elaboration

    J. Membr. Sci.

    (2005)
  • T. He et al.

    Preparation of composite hollow fiber membranes: co-extrusion of hydrophilic coatings onto porous hydrophobic support structures

    J. Membr. Sci.

    (2002)
  • Y. Ji et al.

    Morphological control and cross-flow filtration of microfiltration membranes prepared via a sacrificial-layer approach

    J. Membr. Sci.

    (2010)
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