159
unique graphitized planar structure, and easy surface functionalization (Sangil et al.
2007). These unique properties of graphene oxide were introduced with the polysulfone for the development of highly permeable and adsorptive ultrafiltration membranes (Mukherjee et al. 2016). Different amounts of graphene oxide nanoparticles
(dp190 nm.) were mixed with polysulfone, and the ultrafiltration membranes were
prepared based on the nonsolvent-induced phase separation process. According to
the simple batch adsorption results, the prepared membrane configuration was
reported that it had a high sorption capacity as 79, 75, 68, and 154 mg/g for the Pb,
Cu, Cd, and Cr cations, respectively, at natural pH. The increase in permeability and
adsorptivity by the addition of graphene oxide was attributed to the alteration of
properties of the polysulfone membranes such as hydrophilicity, negative charge
density, roughness, and pore size. Dynamic studies revealed that 90 and 96% of
rejection values with breakthrough times around 10 h were observed for different
operating conditions and metal ions. An acidic solution at pH 5.5 was found to be
sufficient to regenerate the membrane in situ.
In spite of inorganic nanomaterials alone meeting the desired requirements for
adsorption processes, it is believed the use of two or more metal oxides in a composite form exhibits a synergistic effect using the benefits of the distinguished properties of the individuals. For example, adsorption and oxidation properties originated
from the individuals in the metal oxide composite would signify synergistic effect
during recovery of heavy metals. This approach is especially valuable for the metallic pollutants which are neutral in the wide range of pH. As an example, arsenite
(As(III)) available in wastewater in the neutral form in the pH range of 1.0 and 9.22
has higher toxicity and is more dangerous compared to arsenate (As(V)). Nasir et al.
(2019a, b) prepared new hydrous iron–nickel–manganese trimetal oxide-embedded
PSF hollow fiber membranes for the recovery of As(III). In fact, iron-based composite metal oxides for arsenic removal have already been used because of their
superior properties such as environmentally friendly, regenerability, and strong
affinity to arsenic. In the case of composite metal oxide architecture, manganese
dioxide has a function of oxidation (oxidation agent for arsenite), and positively
charged Ni on the surface of hydrous iron–nickel–manganese trimetal oxides could
form electrostatic interaction with the negatively charged of the oxidized arsenite.
The as-synthesized particle size of the nanocomposite metal oxide was determined
by scanning tunneling electron microscopy image and reported in between 34 and
68 nm. The elemental compositions determined as 45.4%, 39.4%, and 15.2% for
lead, nickel, and manganese, respectively, from energy dispersive X-ray analysis
were similar to the compositions in the synthesis conditions of hydrous iron–nickel–
manganese trimetal oxides (3:2:1). Based on 12 h. of batch adsorption studies, the
highest arsenite adsorption was achieved (62 mg/g) when the loading of hydrous
iron–nickel–manganese trimetal oxides was 1.5 wt% in the PSF. The highest adsorption was explained by the uniform distribution of hydrous iron–nickel–manganese
trimetal oxides throughout the cross-section, which was evidenced from energy dispersive X-ray mapping. The uniformity of nanoparticles ensured more active sites
which enhanced the rate of adsorption of arsenite. However, the addition of 2.0 wt%
hydrous iron–nickel–manganese trimetal oxides caused agglomeration that might
block the sorption sites for arsenite. Leaching of the nanoparticles is another
6 Recovery of Heavy Metals by Membrane Adsorbers
unique graphitized planar structure, and easy surface functionalization (Sangil et al.
2007). These unique properties of graphene oxide were introduced with the polysulfone for the development of highly permeable and adsorptive ultrafiltration membranes (Mukherjee et al. 2016). Different amounts of graphene oxide nanoparticles
(dp190 nm.) were mixed with polysulfone, and the ultrafiltration membranes were
prepared based on the nonsolvent-induced phase separation process. According to
the simple batch adsorption results, the prepared membrane configuration was
reported that it had a high sorption capacity as 79, 75, 68, and 154 mg/g for the Pb,
Cu, Cd, and Cr cations, respectively, at natural pH. The increase in permeability and
adsorptivity by the addition of graphene oxide was attributed to the alteration of
properties of the polysulfone membranes such as hydrophilicity, negative charge
density, roughness, and pore size. Dynamic studies revealed that 90 and 96% of
rejection values with breakthrough times around 10 h were observed for different
operating conditions and metal ions. An acidic solution at pH 5.5 was found to be
sufficient to regenerate the membrane in situ.
In spite of inorganic nanomaterials alone meeting the desired requirements for
adsorption processes, it is believed the use of two or more metal oxides in a composite form exhibits a synergistic effect using the benefits of the distinguished properties of the individuals. For example, adsorption and oxidation properties originated
from the individuals in the metal oxide composite would signify synergistic effect
during recovery of heavy metals. This approach is especially valuable for the metallic pollutants which are neutral in the wide range of pH. As an example, arsenite
(As(III)) available in wastewater in the neutral form in the pH range of 1.0 and 9.22
has higher toxicity and is more dangerous compared to arsenate (As(V)). Nasir et al.
(2019a, b) prepared new hydrous iron–nickel–manganese trimetal oxide-embedded
PSF hollow fiber membranes for the recovery of As(III). In fact, iron-based composite metal oxides for arsenic removal have already been used because of their
superior properties such as environmentally friendly, regenerability, and strong
affinity to arsenic. In the case of composite metal oxide architecture, manganese
dioxide has a function of oxidation (oxidation agent for arsenite), and positively
charged Ni on the surface of hydrous iron–nickel–manganese trimetal oxides could
form electrostatic interaction with the negatively charged of the oxidized arsenite.
The as-synthesized particle size of the nanocomposite metal oxide was determined
by scanning tunneling electron microscopy image and reported in between 34 and
68 nm. The elemental compositions determined as 45.4%, 39.4%, and 15.2% for
lead, nickel, and manganese, respectively, from energy dispersive X-ray analysis
were similar to the compositions in the synthesis conditions of hydrous iron–nickel–
manganese trimetal oxides (3:2:1). Based on 12 h. of batch adsorption studies, the
highest arsenite adsorption was achieved (62 mg/g) when the loading of hydrous
iron–nickel–manganese trimetal oxides was 1.5 wt% in the PSF. The highest adsorption was explained by the uniform distribution of hydrous iron–nickel–manganese
trimetal oxides throughout the cross-section, which was evidenced from energy dispersive X-ray mapping. The uniformity of nanoparticles ensured more active sites
which enhanced the rate of adsorption of arsenite. However, the addition of 2.0 wt%
hydrous iron–nickel–manganese trimetal oxides caused agglomeration that might
block the sorption sites for arsenite. Leaching of the nanoparticles is another
6 Recovery of Heavy Metals by Membrane Adsorbers