The Roles of Nanomaterials in Conventional and Emerging Technologies for Heavy Metal Removal: A State-of-the-Art Review

Subramaniam, Mahesan Naidu; Goh, Pei Sean; Lau, Woei Jye; Ismail, Ahmad Fauzi

doi:10.3390/nano9040625

Cited by 63 publications

(22 citation statements)

References 174 publications

(169 reference statements)

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“…The catalytic performance of Co-ACFs with dissimilar Co loading levels (10,20,30,40, and 50 wt. %) in the oxidation of MgSO 3 are investigated.…”

Section: Catalytic Performance Measurementmentioning

confidence: 99%

“…However, a magnesium desulfurization slurry that contains heavy metal impurities cannot be treated using conventional alkaline precipitation because a large amount of magnesium would precipitate prior to the heavy metals. If the porous adsorption properties of cobalt-based catalysts can be used to simultaneously remove heavy metals in the catalytic oxidation process of magnesium sulfite, the purity of the magnesium desulfurization by-products can be significantly improved and the secondary pollution of heavy metals can be reduced, which has significant economic and environmental benefits.Currently, adsorbents used for treating heavy metals in wastewater mainly include porous materials such as activated carbon, carbon nanotubes, metal organic framework (MOF), SBA-15 Silica (SBA, Santa Barbara Amorphous), Calcium Alginate/Graphene and vermiculite-based hydrated zirconia [19][20][21][22][23]. Li et al [24] synthesized a thiol-functionalized activated carbon material from coal-blended sewage sludge, and the material was found to achieve the highest Brunauer-Emmett-Teller (BET) surface area of 1094 m 2 /g when maintained under 500 • C for 30 min.…”

mentioning

confidence: 99%

“…Currently, adsorbents used for treating heavy metals in wastewater mainly include porous materials such as activated carbon, carbon nanotubes, metal organic framework (MOF), SBA-15 Silica (SBA, Santa Barbara Amorphous), Calcium Alginate/Graphene and vermiculite-based hydrated zirconia [19][20][21][22][23]. Li et al [24] synthesized a thiol-functionalized activated carbon material from coal-blended sewage sludge, and the material was found to achieve the highest Brunauer-Emmett-Teller (BET) surface area of 1094 m 2 /g when maintained under 500 • C for 30 min.…”

mentioning

confidence: 99%

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Simultaneous Catalysis of Sulfite Oxidation and Uptake of Heavy Metals by Bifunctional Activated Carbon Fiber in Magnesia Desulfurization

Wang

et al. 2020

Catalysts

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Sulfite and heavy metals are crucial pollutants in the slurry produced by flue gas desulfurization. In this study, a novel cobalt-based activated carbon fiber (Co-ACFs) catalyst-adsorbent was synthesized using an impregnation method; this bifunctional catalyst-adsorbent was used in wet magnesia desulfurization for the simultaneous catalytic oxidation of magnesium sulfite and uptake of heavy metal (Hg 2+ , Cd 2+ , and Ni 2+ ) ions. The morphology and surface chemistry of ACFs before and after cobalt loading were investigated using various characterization methods. The kinetics on catalytic oxidation of magnesium sulfite was investigated, and the effects of operation conditions on the simultaneous adsorption capacity of heavy metals were examined. Relative to a non-catalysis material, the 40% Co-ACFs material increased the oxidation rate of magnesium sulfite by more than five times. The Langmuir model can describe the adsorption behavior of Co-ACFs on Hg 2+ , Cd 2+ , and Ni 2+ , indicating that the simultaneous uptake of heavy metals is a single-layer adsorption process. The maximum adsorption capacities for Hg 2+ , Cd 2+ , and Ni 2+ are 333.3, 500, and 52.6 mg/g, respectively. A pseudo-second-order model confirmed that the removal of heavy metals is controlled by the chemisorption process.Catalysts 2020, 10, 244 2 of 18 oxidation rate of magnesium sulfite, the oxidation is difficult to accomplish in a real desulfurization process. This problem has become the paramount bottleneck of the oxidation enrichment technology. The excessive sulfite might exhaust the dissolved oxygen in the effluent and decomposed into SO 2 , resulting in further environmental risks. Meanwhile, a large number of heavy metal particles are collected in the desulfurization slurry, which can migrate and transform during the desulfurization process. For example, Hg 2+ present in the desulfurized slurry is easily released into the atmospheric environment because the ion is reduced to Hg 0 by sulfite [9][10][11]. Some co-existing Cd 2+ ions may co-crystallize with the saturated magnesium sulfate in the recovered products to cause secondary pollution. Therefore, the simultaneous removal of heavy metals from desulfurized slurries becomes another technical problem for magnesium sulfate recovery.Studies have shown that transition metal ions such as Co 2+ , Mn 2+ , Fe 2+ , and Cu 2+ can be used for improving the oxidation rate of sulfite. Among these ions, Co 2+ exhibits the highest performance in terms of sulfite oxidation [12]. However, separating the homogeneous catalyst from the desulfurization slurry is difficult and the material must be supplemented continuously, thus resulting in a high operation cost and secondary pollution due to the use of magnesium sulfate products. To address this problem, our research group developed a series of cobalt-based heterogeneous catalysts [13-18] by using impregnation, coprecipitation, and hydrothermal synthesis. These catalysts effectively solved the catalyst separation problem. However, a magnesium desulfurizat...

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“…The catalytic performance of Co-ACFs with dissimilar Co loading levels (10,20,30,40, and 50 wt. %) in the oxidation of MgSO 3 are investigated.…”

Section: Catalytic Performance Measurementmentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

See 1 more Smart Citation

Simultaneous Catalysis of Sulfite Oxidation and Uptake of Heavy Metals by Bifunctional Activated Carbon Fiber in Magnesia Desulfurization

Wang

et al. 2020

Catalysts

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“…The two review articles compiled in this Special Issue were contributed by Subramaniam et al [ 8 ] and Tu et al [ 9 ], respectively. The former provided insights into the roles of nanomaterials in established and emerging technologies for hazardous heavy metal removal.…”

mentioning

confidence: 99%

Nanocomposites for Environmental and Energy Applications

Goh

Ismail

2021

Nanomaterials

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“…However, many materials are limited in application due to their low adsorption efficiency, poor chemical stability and difficulty in recycling. Nano materials as adsorbents have unique advantages because their specific surface area increases rapidly with the decrease of particle size [10][11][12]. Several kinds of nano materials such as nano zero valent iron, iron oxide, titanium dioxide have been utilized for OPEN ACCESS RECEIVED…”

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confidence: 99%

Facile fabrication of nanocomposites by modified carbon black loading with magnetite nanoparticles for fast removal of cadmium ions

Xiao

et al. 2020

Nano Ex.

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Magnetic nanomaterials have unique advantages in heavy metal ions absorption because of their large specific surface area and easy magnetic manipulation. Carbon nanotube or graphene loaded with magnetite nanoparticles (MNPs) have been utilized to fabricate absorbents with both high absorption capacity and fast magnetic capture. Herein, cheap commercial carbon black was used as a substitute for expensive carbon nanotube or graphene to fabricate nanocomposites (CB-MNP) by modified carbon black loaded with superparamagnetic MNPs. The fabrication process is accomplished by two steps. Carbon blacks (CB) were modified by nitric acid to produce a large number of carboxyl groups on the surface and make stable aqueous dispersion. Subsequently, CB-MNPs with high water stability and fast magnetic response were facilely prepared by iron precursors (the ratio of ferrous to ferric is 1:2) added into the above CB dispersion and tuned pH=10, finally added polyacrylic acid solution under sonication. Modified CB and CB-MNPs were characterized by transmission electron microscope (TEM), dynamic laser scattering (DLS), thermogravimetric analysis and so on. Water stability and magnetic response can be controlled by changing the proportion of CB and iron precursor. As a proof-of-concept, CB-MNPs were used for absorption removal of cadmium ions. Excellent performance was demonstrated with the removal efficiency of 71.41% and removal capacity of 39.99 mg·g −1 at the initial concentration of Cd 2+ as 5×10 −5 mol·l −1 . The effects of initial concentration of Cd 2+ , pH value and interfering anion ions were also investigated and the results indicate the potential application of CB-MNP in fast removal of heavy metal ions. IntroducationHeavy metal ions have strong toxicity to human beings and other organisms, some of which do harm to human health even in a very small concentration [1]. Effective removal of heave metal ions in waste water has attracted rising attention because these have caused serious environmental problems [2]. Many approaches such as chemical precipitation, adsorption, oxidation-reduction, evaporation, ionic exchange, electrochemical treatment, and membrane separation techniques have been developed for the removal of heavy metals from wastewaters [3][4][5][6].Adsorption technique is considered the most attractive technique because it is easy to operate and recycle [5]. The key to remove heavy metal ions from water by adsorption is the preparation and optimization of adsorption materials. Traditional adsorption materials such as clay, oxide, molecular sieve and activated carbon have been used to remove heavy metal ions [7-9]. However, many materials are limited in application due to their low adsorption efficiency, poor chemical stability and difficulty in recycling. Nano materials as adsorbents have unique advantages because their specific surface area increases rapidly with the decrease of particle size [10][11][12]. Several kinds of nano materials such as nano zero valent iron, iron oxide, titanium dioxide have b...

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The Roles of Nanomaterials in Conventional and Emerging Technologies for Heavy Metal Removal: A State-of-the-Art Review

Cited by 63 publications

References 174 publications

Simultaneous Catalysis of Sulfite Oxidation and Uptake of Heavy Metals by Bifunctional Activated Carbon Fiber in Magnesia Desulfurization

Simultaneous Catalysis of Sulfite Oxidation and Uptake of Heavy Metals by Bifunctional Activated Carbon Fiber in Magnesia Desulfurization

Nanocomposites for Environmental and Energy Applications

Facile fabrication of nanocomposites by modified carbon black loading with magnetite nanoparticles for fast removal of cadmium ions

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