Letter www.acsami.org
Mg-Enriched Engineered Carbon from Lithium-Ion Battery Anode for Phosphate Removal Yan Zhang,†,‡,§ Xingming Guo,†,‡,§ Ying Yao,*,‡,§ Feng Wu,*,‡,§ Cunzhong Zhang,‡,§ Renjie Chen,‡,§ Jun Lu,*,⊥ and Khalil Amine⊥ ‡
School of Materials Science and Engineering, Beijing Key Laboratory of Environmental Science and Engineering, Beijing Institute of Technology, Beijing 100081, China § National Development Center of High Technology Green Materials, Beijing 100081, China ⊥ Chemical Sciences and Engineering Division, Argonne National Laboratory, 9700 South Cass Avenue, Lemont, Illinois 60439, United States S Supporting Information *
ABSTRACT: Three Mg-enriched engineered carbons (mesocarbon microbeads, MCMB) were produced from lithium-ion battery anode using concentrated nitric acid oxidization and magnesium nitrate pretreatment. The obtained 15%MgMCMB, 30%Mg-MCMB, and 40%Mg-MCMB have magnesium level of 10.19, 19.13, and 19.96%, respectively. FTIR spectrum shows the functional groups present on the oxidized MCMB including OH, CO, C−H, and C−O. XRD, SEMEDX, and XPS analyses show that nanoscale Mg(OH)2 and MgO particles were presented on the surface of the Mg-MCMB samples, which could serve as the main adsorption mechanism as to precipitate phosphate from aqueous solutions. The sorption experiments indicate that Mg modification dramatically promotes MCMB’s phosphate removal ability and phosphate removal rates reach as high as 95%. Thus, modification of the spent LIBs anode could provide a novel direction of preparing wastewater adsorbent and develop an innovative way to achieve sustainable development. KEYWORDS: spent battery, phosphate, magnesium, adsorption, mesocarbon microbeads Most of common adsorbents such as activated carbon, fly ash, slag, dolomite, and oxide tailings exhibited very low phosphate adsorption capacity of 100 mg/g). The improved phosphate sorption ability is attributed to the presence of the nanosized MgO particles on the carbon surfaces, which helps to precipitate phosphate from the solution to form Mg3(PO4)2 or MgH2PO4. Thus, it is possible to significantly increase phosphate sorption ability of carbon materials by enriching the carbon matrix with magnesium compound. From the environmental point of view, producing carbon adsorbent from waste materials could be a more eco-friendly approach that will also be beneficial for the economy. With the
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ecause of the large-scale production and application of pesticides, manures, and detergents in the past decades, the discharge of phosphate drastically increased from both point and nonpoint sources into runoff or groundwater that is responsible for accelerating the process of eutrophication.1 With the consequences of the loss of organisms, degradation of aquatic ecosystems, and negative impact on the economy, eutrophication has become a critical environmental problem globally with considerable attention being paid to phosphate pollution in recent years.2,3 In this sense, it is urgent to develop highly efficient and cost-effective technologies for phosphate removal in order to achieve sustainable development. Conventional wastewater treatments including biological, chemical, and physical techniques have been applied to reduce phosphate discharges to natural water bodies. However, both biological and chemical approaches cannot remove phosphate effectively enough because of the strict operation conditions and sludge post-treatment problems,4 whereas most physical methods such as electrodialysis, reverse osmosis, and ion exchange suffer from either high cost or invalidness.5−7 Therefore, simple physical adsorption has been considered as a promising alternative for phosphate removal because of its comparatively easier manipulation, more flexibility, efficiency, and high sensitivity.8 © XXXX American Chemical Society
Received: November 5, 2015 Accepted: January 11, 2016
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DOI: 10.1021/acsami.5b10628 ACS Appl. Mater. Interfaces XXXX, XXX, XXX−XXX
Letter
ACS Applied Materials & Interfaces Table 1. Properties and Elemental Compositions of Three Mg- MCMB Nanocomposites (%) mass based adsorbents
C
H
S
N
Mg
Ca
15%Mg- MCMB 30%Mg- MCMB 40%Mg- MCMB
73.29 49.92 46.03
0.28 0.85 0.78
0.12 0.17 0.37
0.02 0.03 0.04
10.19 19.13 19.96
0.03 0.02 0.03
K
Na
Fe Cu
Zn
Mn
SBET (m2/g)
Pore volume (cm3/g)
Average pore size (nm)
24.99 33.54 28.86
0.06 0.14 0.16
3.21 3.93 3.94
of the carbon matrix.14 The 30%Mg-MCMB sample will be used as an example in the following discussion. To create more active sites for Mg precipitation, we first oxidized raw MCMB by concentrated nitric acid that helps to introduce functional groups on the surface of carbon matrix. The FTIR spectra of MCMB before and after acid treatment were used to examine the vibration frequency changes in its functional groups. After acid treatment, the FTIR spectra display more peaks indicating that the surface of MCMB has been modified (Figure 1). The broad sorption peak at around
recent massive production and consumption of lithium-ion batteries in portable devices and electric vehicles, vast quantities of chemical substances including carbon materials will be produced as waste after the lifetime failure of the LIBs. Such spent batteries will become a serious environmental concern if they are just simply disposed by dumping them in landfill. Recovering the valuable materials contained in the spent LIBs is highly desirable to prevent environmental pollution. Carbon materials from the spent LIBs have advantages in huge quantity, relatively large specific surface area, porous structure, enriched surface functional groups and mineral components, and therefore, are potential candidates for phosphate removal.18,19 In this study, we reported, for the first time, that Mg-enriched carbon adsorbents can be prepared from a LIB anode material for effective phosphate removal. MesoCarbon MicroBeads (MCMB) graphite powder, a common LIBs anode material, is used as feedstock to build nanosized magnesium compound in the carbon matrix through surface modification. The objective of this work is to determine the phosphate removal ability of the-obtained Mg-enriched carbon from LIBs’ anode. Physicochemical properties of this engineered carbon were characterized in detail, because the phosphate sorption ability highly relies on the nature of the carbon materials. A preliminary adsorption experiment was conducted to assess the engineered carbon’s phosphate adsorption ability. To synthesize Mg-enriched MCMB engineered carbon, we prepared three different samples with designed MCMB:Mg mass ratios of 1:0.15, 1:0.3 and 1:0.4, and referred to them as 15%Mg-MCMB, 30%Mg-MCMB, and 40%Mg-MCMB, respectively. The detailed experimental procedure is described in the Supporting Information. Elemental composition analysis indicates that all the samples are carbon-rich with carbon compositions ranging 46.03−73.29% (Table 1). The increase in Mg quantity during sample synthesis results in lower carbon content and higher hydrogen and oxygen content, indicating that Mg species formed on the MCMB likely bonded with H and O. It appears that the maximum amount of Mg formed on MCMB can be reached to about 20 wt % by comparing the elemental composition analysis results of the 30%Mg-MCMB and 40%Mg-MCMB samples. In other words, MCMB carbon powder is unable to host more Mg species when the quantity of Mg in the solution exceeds 30% of that of MCMB. In addition, other heavy metal elements such as Fe, Zn, and Mn were not detected in all the samples, which otherwise will compromise the phosphate removal process. Table 1 also listed the pore structure parameters of the three samples, including specific surface area, pore volume and average pore size, and the results showed that the specific surface areas of the three samples were relatively low. 30%MgMCMB sample has slightly higher surface area with total pore volume of 0.14 m3/g. Because the phosphate removal capacity is highly dependent on the Mg content and the pore structure
Figure 1. FTIR spectra of the MCMB before and after oxidization.
3435 cm−1 is indicative of the existence of bonded hydroxyl group. The band at 2348 cm−1 can be ascribed to stretching vibration of CO2, whereas the band at 1621 cm−1 is characteristic of CO stretching vibration.20 The band at 1439 cm−1 is associated with the C−H bending vibration, whereas the peak appearing at 1119 cm−1 is associated with C− O stretching vibration. In short, the functional groups present on the oxidized MCMB include OH, CO, C−H, and C−O, which are beneficial for hosting more Mg content and providing more adsorption sites. The strong and sharp reflection peaks of XRD spectrum shown in Figure 2 suggest that these carbon materials are well crystallized. Both Mg(OH)2 and MgO are presented in the carbon matrix for all three samples after Mg precipitation, as evident by the characteristic diffraction peaks shown in Figure 2B. The MgO content in 15%Mg-MCMB and 40%Mg-MCMB samples are very low compared to 30%Mg-MCMB, which is in accordance with previous findings.21 The XRD results indicate that Mg species were successfully incorporated into MCMB matrix in this study. The formation of large amount of Mg(OH)2 is mainly attributed to functional groups (hydroxyl groups) on the raw MCMB carbon surface, which concurs with FTIR results. B
DOI: 10.1021/acsami.5b10628 ACS Appl. Mater. Interfaces XXXX, XXX, XXX−XXX
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ACS Applied Materials & Interfaces
Figure 4. EDX mapping elements of carbon, oxygen, and magnesium of the 30%Mg-MCMB. Figure 2. XRD of the (A) raw MCMB and (B) three Mg-MCMB nanocomposites.
The particle size of Mg species within the carbon matrix were calculated using the Scherrer formula.22,23 τ=
Kλ β cos θ
(1)
where K is the shape factor with a typical value of about 0.9, λ is the X-ray wavelength, β is the line broadening at half the maximum intensity (fwhm) in radians, and θ is the Bragg angle; τ is the mean size of the ordered (crystalline) domains. On the basis of the average calculation results of several diffraction peaks, the grain sizes of Mg(OH)2 crystals within 15%MgMCMB, 30%Mg-MCMB, and 40%Mg-MCMB samples are about 18.9, 17.6, and 17.9 nm, respectively, whereas the grain size of MgO crystals within 30%Mg-MCMB sample is 20.8 nm. These results demonstrated that the Mg(OH)2/MgO impregnated in the MBMC carbon matrix has nanoscale particles, which is critical for subsequent phosphate removal. SEM images of the 30%Mg-MCMB sample show a large quantity of nanoscale Mg flakes (nanoplatelet) distributed on the carbon surface, which is a common morphology of Mg hydroxide (Figure 3). Low-magnification SEM image reveals
Figure 5. (A) XPS spectrum of the 30%Mg-MCMB and (B) XPS spectra of Mg 2p region for the 30%Mg-MCMB.
main Mg species on the carbon surface, which play an important role in controlling the surface interactions between P and the Mg-MCMB composites during phosphate removal process. In addition to Mg(OH)2/MgO, XPS measurements also detected the presence of a small amount of Mg(NO3)2 on the surface of MCMB carbon, which is likely due to the residue of solution during the synthesis process of these materials. Adsorption experiments showed that Mg modification dramatically promotes MCMB’s phosphate removal ability (Figure 6), whereas the raw MCMB has very low phosphate
Figure 3. (A, B) SEM images and (C) corresponding EDX spectrum of the 30%Mg-MCMB. Figure 6. Phosphate removal rate from aqueous solutions by raw and Mg enriched MCMB.
that the shapes of the Mg-MCMB were microspheres with relatively rough surface probably due to the intrinsic nature of the MCMB carbon (Figure 3A). High-magnification SEM image (Figure 3B) further shows that the microspheres are mainly composed of large amount of nanoflakes with thickness of merely ∼36 nm growing in different directions. Energydispersive X-ray spectroscopy (EDX) elemental analysis was performed to qualitatively detect the major elements. The EDX spectrum identify extremely high peaks of Mg and oxygen except for the carbon signal with uniform distribution (Figures 3C and 4), which further confirmed the dominance of those Mg(OH)2/MgO nanoparticles on MCMB. XPS survey spectrum of the 30%Mg-MCMB sample shows strong signals of Mg on the carbon surface (Figure 5A), agreeing with the XRD results. The Mg 2p XPS spectrum shown in Figure 5B clearly reveals that Mg(OH)2/MgO are the
removal ability. The 15%Mg-MCMB, 30%Mg-MCMB, and 40%Mg-MCMB samples show phosphate removal rates of 56.1, 95.0, and 95.1%, respectively, which are significantly higher than most of other reported phosphate adsorbents.9,10,12 When increasing adsorbents’ Mg content from zero to 30%, phosphate removal rate increases and reaches its maximum at 95%. These results demonstrate phosphate removal rate is strongly associated with Mg content on MCMB, which is consistent with the previous findings that there is a significant correlation between the Mg content on the adsorbents (in this case is MCMB carbon) and its phosphate removal rate.24 It seems that the Mg compounds (Mg(OH)2 and MgO) on the C
DOI: 10.1021/acsami.5b10628 ACS Appl. Mater. Interfaces XXXX, XXX, XXX−XXX
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ACS Applied Materials & Interfaces
(2) Jung, K. W.; Hwang, M. J.; Ahn, K. H.; Ok, Y. S. Kinetic Study on Phosphate Removal from Aqueous Solution by Biochar Derived from Peanut Shell as Renewable Adsorptive Media. Int. J. Environ. Sci. Technol. 2015, 12, 3363−3372. (3) Smith, V. H. Eutrophication of Freshwater and Coastal Marine Ecosystems - a Global Problem. Environ. Sci. Pollut. Res. 2003, 10 (2), 126−139. (4) Yeoman, S.; Stephenson, T.; Lester, J. N.; Perry, R. The Removal of Phosphorus During Waste-Water Treatment - a Review. Environ. Pollut. 1988, 49, 183−233. (5) Yao, Y.; Gao, B.; Inyang, M.; Zimmerman, A. R.; Cao, X.; Pullammanappallil, P.; Yang, L. Removal of Phosphate from Aqueous Solution by Biochar Derived from Anaerobically Digested Sugar Beet Tailings. J. Hazard. Mater. 2011, 190, 501−7. (6) Momberg, G. A.; Oellermann, R. A. The Removal of Phosphate by Hydroxyapatite and Struvite Crystallization in South-Africa. Water Sci. Technol. 1992, 26, 987−996. (7) Biswas, B. K.; Inoue, K.; Ghimire, K. N.; Harada, H.; Ohto, K.; Kawakita, H. Removal and Recovery of Phosphorus from Water by Means of Adsorption onto Orange Waste Gel Loaded with Zirconium. Bioresour. Technol. 2008, 99, 8685−8690. (8) Yu, Y.; Chen, J. P. Key Factors for Optimum Performance in Phosphate Removal from Contaminated Water by a Fe-Mg-La TriMetal Composite Sorbent. J. Colloid Interface Sci. 2015, 445, 303−311. (9) Kumar, P.; Sudha, S.; Chand, S.; Srivastava, V. C. Phosphate Removal from Aqueous Solution Using Coir-Pith Activated Carbon. Sep. Sci. Technol. 2010, 45, 1463−1470. (10) Namasivayam, C.; Sangeetha, D. Equilibrium and Kinetic Studies of Adsorption of Phosphate onto Zncl2 Activated Coir Pith Carbon. J. Colloid Interface Sci. 2004, 280, 359−365. (11) Bhargava, D. S.; Sheldarkar, S. B. Use of Tnsac in Phosphate Adsorption Studies and Relationships - Literature, Experimental Methodology, Justification and Effects of Process Variables. Water Res. 1993, 27, 303−312. (12) Karaca, S.; Gurses, A.; Ejder, M.; Acikyildiz, M. Adsorptive Removal of Phosphate from Aqueous Solutions Using Raw and Calcinated Dolomite. J. Hazard. Mater. 2006, 128, 273−279. (13) Tan, X.; Liu, Y.; Zeng, G.; Wang, X.; Hu, X.; Gu, Y.; Yang, Z. Application of Biochar for the Removal of Pollutants from Aqueous Solutions. Chemosphere 2015, 125, 70−85. (14) Zhang, M.; Gao, B.; Yao, Y.; Xue, Y.; Inyang, M. Synthesis of Porous Mgo-Biochar Nanocomposites for Removal of Phosphate and Nitrate from Aqueous Solutions. Chem. Eng. J. 2012, 210, 26−32. (15) Karakoyun, N.; Kubilay, S.; Aktas, N.; Turhan, O.; Kasimoglu, M.; Yilmaz, S.; Sahiner, N. Hydrogel-Biochar Composites for Effective Organic Contaminant Removal from Aqueous Media. Desalination 2011, 280, 319−325. (16) Sohi, S. P. Carbon Storage with Benefits. Science 2012, 338, 1034−1035. (17) Yao, Y.; Gao, B.; Chen, J.; Yang, L. Engineered Biochar Reclaiming Phosphate from Aqueous Solutions: Mechanisms and Potential Application as a Slow-Release Fertilizer. Environ. Sci. Technol. 2013, 47, 8700−8708. (18) Bernardes, A. M.; Espinosa, D. C. R.; Tenorio, J. A. S. Recycling of Batteries: A Review of Current Processes and Technologies. J. Power Sources 2004, 130, 291−298. (19) Xu, J.; Thomas, H. R.; Francis, R. W.; Lum, K. R.; Wang, J.; Liang, B. A Review of Processes and Technologies for the Recycling of Lithium-Ion Secondary Batteries. J. Power Sources 2008, 177, 512−527. (20) Zhou, J.; Yang, S.; Yu, J. Facile Fabrication of Mesoporous Mgo Microspheres and Their Enhanced Adsorption Performance for Phosphate from Aqueous Solutions. Colloids Surf., A 2011, 379, 102−108. (21) Yao, Y.; Gao, B.; Chen, J.; Zhang, M.; Inyang, M.; Li, Y.; Alva, A.; Yang, L. Engineered Carbon (Biochar) Prepared by Direct Pyrolysis of Mg-Accumulated Tomato Tissues: Characterization and Phosphate Removal Potential. Bioresour. Technol. 2013, 138, 8−13. (22) Patterson, A. The Scherrer Formula for X-Ray Particle Size Determination. Phys. Rev. 1939, 56, 978.
adsorbent’s surface could help to effectively precipitate phosphate in aqueous solutions. The above result suggests that the MCMB with Mg surface modification can be used as a useful adsorbent to remove phosphate from aqueous solutions. Among all the samples prepared in this work, the 30%Mg-MCMB has the highest phosphate removal rate with a relatively small amount of materials, and therefore, it can be selected for further investigations to determine the detailed mechanisms and characteristics of phosphate adsorption onto the Mg-MCMB. Finally, it should be pointed out that the MCMB from spent Liion batteries may perform significantly different on the phosphate removal compared to the regular MCMB used in this study. A detailed comparison is currently under investigation in our group. However, one could expect that, because of the presence of large amount of functional groups on the carbon surface after the extended cycles during the cell operation, the phosphate removal ability could be further enhanced using MCMB from the spent Li-ion battery. In summary, on the basis of the characterization of physicochemical properties of the obtained engineered carbon samples and the preliminary phosphate sorption evaluation, we demonstrated that the LIB anode material-MCMB could be used as a feedstock for phosphate adsorbent production. Nanosized Mg(OH)2 and MgO were successfully deposited on the surface of MCMB carbon matrix which shows high phosphate removal ability up to 95%. Thus, modification of LIBs anode could provide a novel direction of preparing wastewater adsorbent and develop an innovative way to achieve sustainable development.
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ASSOCIATED CONTENT
S Supporting Information *
The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acsami.5b10628. Experimental details (PDF)
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AUTHOR INFORMATION
Corresponding Authors
*E-mail:
[email protected]. Tel: 86-10-68912657. *E-mail:
[email protected]. Tel: 86-10-68912508. *E-mail:
[email protected]. Tel: 001-630-252-4485. Author Contributions †
Y.Z. and X.G. contributed equally. The manuscript was written through contributions of all authors. All authors have given approval to the final version of the manuscript. Notes
The authors declare no competing financial interest.
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ACKNOWLEDGMENTS This research was supported by the National Natural Science Foundation of China (NSFC) through Grant 51402018 and the National Key Program for Basic Research of China through Grant 2015CB251100. This work was also supported by the U.S. Department of Energy under Contract DEAC0206CH11357 from the Vehicle Technologies Office, Department of Energy, Office of Energy Efficiency and Renewable Energy (EERE).
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REFERENCES
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DOI: 10.1021/acsami.5b10628 ACS Appl. Mater. Interfaces XXXX, XXX, XXX−XXX
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ACS Applied Materials & Interfaces (23) Holzwarth, U.; Gibson, N. The Scherrer Equation Versus The’debye-Scherrer Equation’. Nat. Nanotechnol. 2011, 6, 534−534. (24) Yao, Y.; Gao, B.; Chen, J.; Zhang, M.; Inyang, M.; Li, Y.; Alva, A.; Yang, L. Engineered Carbon (Biochar) Prepared by Direct Pyrolysis of Mg-Accumulated Tomato Tissues: Characterization and Phosphate Removal Potential. Bioresour. Technol. 2013, 138, 8−13.
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DOI: 10.1021/acsami.5b10628 ACS Appl. Mater. Interfaces XXXX, XXX, XXX−XXX
