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aluminum oxides, ferric oxides, magnesium oxides, cerium oxides, and graphene
oxides, and zeolites are classified as promising adsorbents for the removal of heavy
metals from aqueous media (Vanbenschoten et al. 1994; Coston et al. 1995; Agrawal
and Sahu 2006). This is partly due to the high surface-to-volume ratio, which significantly reduces the diffusion path and thus leads to high uptakes (Henglein 1989).
However, as the size lowers to nanoscale, the increased surface energy leads to
nanoparticles prone to agglomerate through physical interactions (e.g., van der
Waals forces) (Pradeep and Anshup 2009), and hence high uptake and selectivity of
metal oxide nanoparticles would pronouncedly reduce or even lost. Besides, metal
oxide nanoparticles are not useful in fixed bed or any other dynamic systems due to
the extremely high-pressure drop. In the case of simple batch adsorption processes,
their separations from aqueous phase are another challenge. It is proposed that the
applicability of metal oxide nanoparticles in real wastewater treatments can be
effectively improved by impregnation into porous supports of large size as composite adsorbents (Pan et al. 2009).
Nowadays, membrane technologies have been successfully used in the applications of wastewater. For example, rejection of 98% of initial cadmium cations using
asymmetric polysulfone membrane has been reported (Saljoughi and Mousavi
2012). However, in real wastewater treatment, the concentrated metals cannot be
recovered by these treatments. Further processing is needed to be separated from
other contaminating species (organics and/or inorganics) available in the feed solution. Therefore, a new engineered high-performance membrane architecture is
required for the next-generation reusable and portable water treatments. For this,
polymeric materials combined with inorganic nanoparticles have recently been
designed for specific water treatments (Yin and Deng 2015). Desired outputs by the
so-called membrane adsorbers could be achieved by simply adjusting their hydrophilicity, charge density, pore size, porosity, and mechanical stability. For example,
dispersion of zeolite 4A to the selective layer of the polysulfone membrane helps
both water flux and rejection values were simultaneously improved (Liu et al. 2014).
Moreover, unique properties of nanoparticles such as photocatalytic, antibacterial,
or adsorptive capabilities create a multifunctional membrane (Fathizadeh et al.
2011; Huang et al. 2012; Oh et al. 2009; Arthanareeswaran et al. 2008; Han
et al. 2009).
In this chapter, membrane adsorbers (they represent inorganic nanoparticles
mixed with polymeric membranes), which combine filtration and adsorption processes in one unit, are introduced in terms of their efficiencies on permeability,
antifouling, and heavy metal recovery. Selection of nanoparticle type, size, and
amount on the morphological properties of the membranes is also addressed in this
chapter. Development of a mathematical model that can predict the long-term performances of any flat sheet and hollow fiber-based membrane adsorbers in terms of
their throughput and rejection characteristics is discussed. A model for the prediction of time-derived permeate concentrations through a flat sheet membrane in
dead-end mode is developed to better understand the effect of membrane morphologies and operating conditions on the process effectiveness. Finally, suggestions are
also given for further development of the membrane performances in the removal of
heavy metals.
Y. Yurekli
aluminum oxides, ferric oxides, magnesium oxides, cerium oxides, and graphene
oxides, and zeolites are classified as promising adsorbents for the removal of heavy
metals from aqueous media (Vanbenschoten et al. 1994; Coston et al. 1995; Agrawal
and Sahu 2006). This is partly due to the high surface-to-volume ratio, which significantly reduces the diffusion path and thus leads to high uptakes (Henglein 1989).
However, as the size lowers to nanoscale, the increased surface energy leads to
nanoparticles prone to agglomerate through physical interactions (e.g., van der
Waals forces) (Pradeep and Anshup 2009), and hence high uptake and selectivity of
metal oxide nanoparticles would pronouncedly reduce or even lost. Besides, metal
oxide nanoparticles are not useful in fixed bed or any other dynamic systems due to
the extremely high-pressure drop. In the case of simple batch adsorption processes,
their separations from aqueous phase are another challenge. It is proposed that the
applicability of metal oxide nanoparticles in real wastewater treatments can be
effectively improved by impregnation into porous supports of large size as composite adsorbents (Pan et al. 2009).
Nowadays, membrane technologies have been successfully used in the applications of wastewater. For example, rejection of 98% of initial cadmium cations using
asymmetric polysulfone membrane has been reported (Saljoughi and Mousavi
2012). However, in real wastewater treatment, the concentrated metals cannot be
recovered by these treatments. Further processing is needed to be separated from
other contaminating species (organics and/or inorganics) available in the feed solution. Therefore, a new engineered high-performance membrane architecture is
required for the next-generation reusable and portable water treatments. For this,
polymeric materials combined with inorganic nanoparticles have recently been
designed for specific water treatments (Yin and Deng 2015). Desired outputs by the
so-called membrane adsorbers could be achieved by simply adjusting their hydrophilicity, charge density, pore size, porosity, and mechanical stability. For example,
dispersion of zeolite 4A to the selective layer of the polysulfone membrane helps
both water flux and rejection values were simultaneously improved (Liu et al. 2014).
Moreover, unique properties of nanoparticles such as photocatalytic, antibacterial,
or adsorptive capabilities create a multifunctional membrane (Fathizadeh et al.
2011; Huang et al. 2012; Oh et al. 2009; Arthanareeswaran et al. 2008; Han
et al. 2009).
In this chapter, membrane adsorbers (they represent inorganic nanoparticles
mixed with polymeric membranes), which combine filtration and adsorption processes in one unit, are introduced in terms of their efficiencies on permeability,
antifouling, and heavy metal recovery. Selection of nanoparticle type, size, and
amount on the morphological properties of the membranes is also addressed in this
chapter. Development of a mathematical model that can predict the long-term performances of any flat sheet and hollow fiber-based membrane adsorbers in terms of
their throughput and rejection characteristics is discussed. A model for the prediction of time-derived permeate concentrations through a flat sheet membrane in
dead-end mode is developed to better understand the effect of membrane morphologies and operating conditions on the process effectiveness. Finally, suggestions are
also given for further development of the membrane performances in the removal of
heavy metals.
Y. Yurekli