Activated Carbons Prepared from a Broad Range of Residual

Research Article pubs.acs.org/journal/ascecg

Activated Carbons Prepared from a Broad Range of Residual Agricultural Biomasses Tested for Xylene Abatement in the Gas Phase Gerardo Juan Francisco Cruz,† Lenka Kuboňová,‡ Dorian Yasser Aguirre,† Lenka Matějová,‡ Pavlína Peikertová,‡ Ivana Troppová,‡ Erik Cegmed,‡ Anna Wach,§ Piotr Kustrowski,§ Monica Marcela Gomez,∥ and Lucie Obalová*,‡ Downloaded via LA TROBE UNIV on July 4, 2018 at 17:59:35 (UTC). See https://pubs.acs.org/sharingguidelines for options on how to legitimately share published articles.

†

Universidad Nacional de Tumbes, Laboratorio de Análisis Ambiental, Av. Universitaria s/n, Campus Universitario-Pampa Grande, Tumbes, Peru ‡ Institute of Environmental Technology, VŠB-Technical University of Ostrava, 17. listopadu 15/2172, 708 33 Ostrava-Poruba, Czech Republic § Faculty of Chemistry, Jagiellonian University, Ingardena 3, 30-060 Krakow, Poland ∥ Universidad Nacional de Ingeniería, Facultad de Ciencias, Av. Tupac Amaru 210, Lima 25, Peru S Supporting Information *

ABSTRACT: The environmental problems in Peru are rooted in the waste management of the residual agricultural biomass. Via our cooperative international research, nine different agricultural wastes from Peru were used as renewable sources to produce activated carbons that were tested in gas-phase xylene adsorption. The special properties of agro-waste activated carbons are the very large mesopore surface area, the narrow pore size distribution within the microporous−mesoporous region, and the slightly acidic character in the presence of oxygencontaining surface groups. The textural, structural, and surface properties of nine agro-waste activated carbons were correlated with their adsorption capacities in xylene adsorption and compared with those of a commercial activated carbon made of black coal. Adsorption capacities of agro-waste activated carbons were in the range of 371−115 mgxylene/ gAC, whereas the adsorption capacity was 214 mgxylene/gAC for black coalactivated carbon. Higher adsorption capacities of ACs can be assigned to the synergism of their textural properties (larger mesopore surface area and larger micropore volume related to total pore volume) and their surface properties (lower content of surface oxygen functional groups related to their less acidic character and higher π−π* transitions in aromatic rings resulting in fewer defects within the graphitic structure). KEYWORDS: Residual agricultural biomass, Carbonization, Activated carbon, Adsorption, Xylene abatement

■

INTRODUCTION Volatile organic compounds (VOCs) are compounds having vapor tensions at 250 °C of ≥101.3 kPa. VOCs are important pollutants that have harmful effects on human health. A major portion of organic pollutants comes mainly from technological processes and operations using volatile organic solvents such as painting, dyeing, and printing processes. Xylene is an aromatic hydrocarbon that is widely used in industry and medical technology as a solvent. Xylene is also present in gasoline and in waste gas from paint lines. Health and safety authorities in most countries recommend a threshold limit value (TLV) of 100 ppm in a working environment. Recently, the amount of the major metabolite of xylene in urine, methylhippuric acid (MHA), has been recommended as a better indicator of xylene exposure. Xylene vapors are absorbed rapidly from the lungs, and xylene liquid and vapor © 2017 American Chemical Society

are absorbed slowly through the skin. Approximately 95% of the xylene absorbed is metabolized in the liver to MHA, and 70−80% of the metabolites are excreted in the urine within 24 h. At high concentrations, xylene acts as a narcotic, inducing neuropsychological and neurophysiological dysfunction. Respiratory tract symptoms are also frequent. More chronic, occupational exposure has been associated with anemia, thrombocytopenia, and leukopenia.1 Currently, a wide range of methods for reducing VOC emissions are known. Nondestructive methods that allow recovery of the eliminated VOCs include adsorption, absorption, condensation, and membrane separation. On the Received: November 8, 2016 Revised: January 4, 2017 Published: January 20, 2017 2368

DOI: 10.1021/acssuschemeng.6b02703 ACS Sustainable Chem. Eng. 2017, 5, 2368−2374

Research Article

ACS Sustainable Chemistry & Engineering

was performed during the wash step to introduce the surface modifications (Figure S1). Prepared activated carbons were codified as follows: RMS-AC, red mombin seed activated carbon; GS-AC, ice cream bean activated carbon; CPH-AC, cocoa pod husk activated carbon; CH-AC, coffee husk activated carbon; MSEP-AC, mango seed external part activated carbon; MSIP-AC, mango seed internal part activated carbon; and CCAC, corncob activated carbon. Modified activated carbons made of corncob were codified as CC-AC/KOH and CC-AC/HCl for the ACs modified with KOH and HCl, respectively. One commercial AC made from black coal codified as BC-AC (provided by Resorbent, s.r.o., in Ostrava, Czech Republic, with the commercial name MA C6 D40 CZ) was used to compare the properties of the investigated produced adsorbents. Characterization of Activated Carbons. Textural properties of ACs were evaluated from nitrogen physisorption. The nitrogen adsorption−desorption measurements at −196 °C were performed using the 3Flex instrument (Micromeritics). Prior to the nitrogen physisorption measurements, the ACs (3.15−5.6 mm particle size) were degassed at 300 °C for 48 h under a vacuum of 1 (1.068) occurs only in the case of BC-AC, which points to more defects in the sample structure. The second highest ID/IG ratio was calculated for GS-AC (0.812). CC-AC/KOH has the most intense G band, and the ID/IG ratio is the lowest (0.694), which can be due to a more ordered structure with fewer defects. The rest of the ACs have comparable values of ID/IG ratios in the range of 0.7−0.8. The surface composition of all ACs was investigated by XPS. The recorded O 1s spectra can be fitted with three peaks attributed to different oxygen-containing species: (i) carbonyl groups, quinones, and CO in carboxyl acids, esters, and anhydrides (530.8−531.0 eV), (ii) oxygen in hydroxyl, ether, and C−OH in carboxyl acids, esters, and anhydrides (532.6− 533.0 eV), and (iii) oxygen in adsorbed water (536.4−537.7 eV). Furthermore, the C 1s spectra show, besides the component with a binding energy of 284.5−284.7 eV assigned to carbon atoms in graphitic and disordered carbon species (CC sp2 and C−C sp3), three peaks corresponding to carbon atoms: (i) coupled with hydroxyl groups (286.1−286.4 eV), (ii) in a carbonyl group (287.2 eV), and (iii) in a carboxyl group (288.5 eV).27−29 The broad peak at a binding energy of 290.0− 290.3 eV, observed additionally as a shakeup satellite related to π−π* transitions in aromatic rings, confirms the polyaromatic character of the studied activated carbons. The contributions of oxygen- and carbon-containing species determined by XPS are compared in Tables S4 and S5. Generally, the agro-waste ACs, with the exception of the CCAC before and after modification, exhibit surface contents of

q=

Vṫ tx m

tt =

∫0

(1)

∞⎛

x⎞ ⎜1 − ⎟ d t x0 ⎠ ⎝

(2)

where q (milliliters per gram) is the adsorption capacity of AC, V̇ (milliliters per minute) is the total volume flow, tt (minutes) is the time equivalent calculated by numerical integration using the trapezoidal method (eq 2), x is the actual mole fraction of xylene in the gas phase, m (grams) is the mass of AC, and x0 is the initial mole fraction of xylene in the gas phase. Blank experiments for the xylene breakthrough curve through the adsorption unit with a column filled with an inert compound showed a breakdown time of 11.5 s and the area above the breakthrough curves tt = 0.017 mL/g (Figure S10). This value was subtracted from the calculated adsorption capacities of ACs. The evaluated adsorption capacities of ACs are summarized in Table S6. The adsorption capacities of ACs can be divided into three groups according to their similar values within the relative error of measurement: (i) CC-AC > RMS-AC ≈ CC-AC/HCl ≈ CC-AC/KOH with adsorption capacities in the range of 319− 371 mg/g, (ii) MSEP-AC ≈ CH-AC ≈ BC-AC with adsorption 2371


Research Article


of an adsorptive. Therefore, the value of pHZPC is considered to be a crucial parameter in the aqueous adsorption system; however, it is not a leading parameter in gas-phase adsorption.32 More important is the presence of acidic and basic functional groups on the AC surface defined by XPS and FTIR analyses. The basic character of activated carbons primarily comes from a high density of delocalized π-electrons on polyaromatic basal plane sheets.34 Acid oxygen-containing surface groups decrease the level of adsorption of organic compounds as described for aqueous systems.32 The increase in the number of oxygencontaining surface groups increases the surface hydrophilicity and thereby decreases the number of hydrophobic interactions as in the case of xylene adsorption. Another explanation is based on the possible adsorption mechanism of xylene on the surface of AC by a π−π bonding mechanism. Xylene acting as a π-donor interacts with π-acceptor areas of the graphite surface. The species that are bonded to the graphitic edges of AC (i.e., oxygen functional groups) can cause a disturbance in the electron density of the xylene basal plane. Such electronwithdrawing groups will influence the π-electron distribution, resulting in a decrease in the adsorption potential of the carbon surface.35 In our study, the content of surface oxygen functional groups was determined by XPS. In general, the higher the content of surface oxygen functional groups, the lower the adsorption capacity of the AC in the adsorption of xylene.36 CC-AC, which showed the highest adsorption capacity, exhibits the lowest content of surface oxygen functional groups (7.44 atom %), while GS-AC showed the lowest adsorption capacity and the highest content of surface oxygen functional groups (21.08 atom %). The higher content of surface oxygen functional groups is in a good agreement with the lower π−π* transitions in aromatic rings defined by XPS. Xylene is a hydrophobic organic volatile compound; therefore, it is obvious that the presence of water on the adsorbent surface can negatively affect its adsorption as in the case of the GS-AC sample with the lowest adsorption capacity and the highest content of adsorbed water. BC-AC (9.35 atom %) showed a content of surface oxygen groups slightly higher than those of CC-AC and CC-AC/HCl but lower than those of the rest of the ACs. BC-AC with the highest ID/IG ratio (1.068) indicates that more defects in the structure are not beneficial for the sorption of xylene on the AC surface. Together with the smallest mesopore surface area of BC-AC (219 m2/g) compared with those of the rest of the ACs with higher adsorption capacities, these could be the reasons for its lower adsorption capacity. The modification of CC-AC by acidic (CC-AC/HCl) or following basic (CC-AC/KOH) treatment did not lead to a significant increase in the adsorption capacity of CC-AC; however, the adsorption capacities are very similar to that of CC-AC. CC-AC/KOH has the fewest defects according to the ID/IG ratio (0.649) defined by Raman spectroscopy and one of the largest mesopore surface areas (718 m2/g), which should lead to the highest xylene adsorption. On the other hand, nonmodified CC-AC showed the lowest level of acidic groups (O−H, CO, C−O−C, COOH, and COOR), a lower content of surface oxygen groups, and the highest π−π* transitions in aromatic rings, which are the characteristics responsible for the improved performance of CC-AC in xylene sorption. In summary, the main differences between the ACs with the highest and lowest adsorption capacity are as follows. (i) The

capacities in the range of 214−231 mg/g, and (iii) CPH-AC > MSIP-AC > GS-AC with adsorption capacities in the range of 115−178 mg/g. Correlation of Physicochemical Properties of Activated Carbons and Their Adsorption Capacities. The adsorption capacity of ACs depends on different factors as described by Figueiredo et al.32 In the case of gas-phase adsorption, the controlling factors are (i) the properties of ACs such as texture (surface area and pore size distribution) and surface chemistry (functional groups) and (ii) the properties of the adsorptive compounds such as molecular weight, polarity, molecular size, and functional groups. In our previous study,33 the critical molecular dimensions (MIN-1 as the minimal dimension through a molecule and MIN-2 as the second minimal dimension through a molecule perpendicular to MIN-1) of xylene isomers were determined via density functional theory modeling. By considering the molecular size of (i) p-xylene (MIN-1 = 0.451 nm, and MIN-2 = 0.701 nm), (ii) m-xylene (MIN-1 = 0.411 nm, and MIN-2 = 0.734 nm), and (iii) o-xylene (MIN-1 = 0.412 nm, and MIN-2 = 0.780 nm), the access of xylene isomers to micropores of ACs is limited. When the xylene isomers are appropriately oriented, the xylene adsorption may be possible in all tested ACs by considering the dimensions of MIN-1 of xylene isomers. The more interesting parameter is the Vmicro/Vnet ratio as the most active sample, CC-AC, has the largest volume of micropores with respect to the total pore volume (not considering BC-AC) and visa versa for GS-AC with the lowest adsorption capacity. However, there is not a straightforward correlation between Vmicro/Vnet ratios and adsorption capacities for the rest of the ACs. Though the adsorption of xylene isomers can possibly occur in micropores of agro-waste activated carbons, we propose that it is not the prevailing parameter for different adsorption capacities of ACs. As concluded in our previous research,33 the higher adsorption capacity of black coal ACs can be ascribed to the larger mesopore surface area as one of the AC properties. The correlation data of adsorption capacities and mesopore surface areas of ACs can be divided into two group clusters: (i) RMSAC, CC-AC/HCl, and CC-AC/KOH and (ii) CH-AC, BC-AC, CPH-AC, and MSIP-AC. The first group of ACs confirms that their adsorption capacities increased with their larger mesopore surface areas in comparison with those of the second group of ACs. Beyond this distribution is CC-AC, which should have the largest mesopore surface area, and MSEP-AC, which has an adsorption capacity like those of CH-AC and BC-AC; however, its mesopore surface area is more than 2 times larger. Therefore, there must be other reasons for these exceptions. There are two types of interactions between the adsorbate and the activated carbon: electrostatic and dispersive. As for nonionic compounds, such as xylene, the dispersive interactions predominate. There are three mechanisms of dispersive interactions between the adsorptive and the activated carbon: (i) π−π dispersion interaction between the basal plane of the adsorbent and the aromatic ring of the adsorbate, (ii) H-bond formation between the adsorbate and surface functional groups, and (iii) electron donor−acceptor complexes between the AC surface and the aromatic ring of the adsorbate.32,34 The adsorbent with basic surface properties performs generally better for the adsorption of nonionic compounds. In the case of adsorption from the liquid phase, the pH of the solution controls the electrostatic interactions between an adsorbent and an adsorptive as well as dissociation or ionization 2372


Research Article


(5) Lu, C. Y.; Wey, M. Y. Simultaneous removal of VOC and NO by activated carbon impregnated with transition metal catalysts in combustion flue gas. Fuel Process. Technol. 2007, 88 (6), 557−567. (6) Cardoso, B.; Mestre, A. S.; Carvalho, A. P.; Pires, J. Activated carbon derived from cork powder waste by KOH activation: Preparation, characterization, and VOCs adsorption. Ind. Eng. Chem. Res. 2008, 47 (16), 5841−5846. (7) Tham, Y. J.; Latif, P. A.; Abdullah, A. M.; Shamala-Devi, A.; Taufiq-Yap, Y. H. Performances of toluene removal by activated carbon derived from durian shell. Bioresour. Technol. 2011, 102 (2), 724−728. (8) Li, L.; Liu, S.; Liu, J. Surface modification of coconut shell based activated carbon for the improvement of hydrophobic VOC removal. J. Hazard. Mater. 2011, 192 (2), 683−690. (9) Cruz, G.; Pirilä, M.; Huuhtanen, M.; Carrión, L.; Alvarenga, E.; Keiski, R. L. Production of activated carbon from Cocoa (Theobroma cacao) Pod Husk. J. Civ. Environ. Eng. 2012, 2 (2), 1−6. (10) Cruz, G. J. F.; Matejova, L.; Pirila, M.; Ainassaari, K.; Canepa, C. A.; Solis, J.; Cruz, J. F.; Solcova, O.; Keiski, R. L., A Comparative Study on Activated Carbons Derived from a Broad Range of Agro-industrial Wastes in Removal of Large-Molecular-Size Organic Pollutants in Aqueous Phase. Water, Air, Soil Pollut. 2015, 226 (7).10.1007/s11270015-2474-7 (11) Brunauer, S.; Emmett, P. H.; Teller, E. Adsorption of Gases in Multimolecular Layers. J. Am. Chem. Soc. 1938, 60 (2), 309−319. (12) Gregg, S. J.; Sing, K. S. W. Adsorption, surface area, and porosity; Academic Press: London, 1982. (13) Deboer, J. H.; Lippens, B. C.; Linsen, B. G.; Broekhoff, J. C. P.; van den Heuvel, A.; Osinga, T. J. T-Curve of Multimolecular N2Adsorption. J. Colloid Interface Sci. 1966, 21 (4), 405. (14) Micromeritics software within 3Flex Instrument; Micromeritics, 2016. (15) Barrett, E. P.; Joyner, L. G.; Halenda, P. P. The Determination of Pore Volume and Area Distributions in Porous Substances. I. Computations from Nitrogen Isotherms. J. Am. Chem. Soc. 1951, 73 (1), 373−380. (16) Roberts, B. F. A Procedure for Estimating Pore Volume and Area Distributions from Sorption Isotherms. J. Colloid Interface Sci. 1967, 23 (2), 266. (17) Horvath, G.; Kawazoe, K. Method for the Calculation of Effective Pore-Size Distribution in Molecular-Sieve Carbon. J. Chem. Eng. Jpn. 1983, 16 (6), 470−475. (18) Lua, A. C.; Yang, T. Characteristics of activated carbon prepared from pistachio-nut shell by zinc chloride activation under nitrogen and vacuum conditions. J. Colloid Interface Sci. 2005, 290 (2), 505−513. (19) Tsai, W. T.; Chang, C. Y.; Lin, M. C.; Chien, S. F.; Sun, H. F.; Hsieh, M. F. Adsorption of acid dye onto activated carbons prepared from agricultural waste bagasse by ZnCl2 activation. Chemosphere 2001, 45 (1), 51−58. (20) Mohammadi, S. Z.; Karimi, M. A.; Afzali, D.; Mansouri, F. Removal of Pb(II) from aqueous solutions using activated carbon from Sea-buckthorn stones by chemical activation. Desalination 2010, 262 (1−3), 86−93. (21) Angin, D. Production and characterization of activated carbon from sour cherry stones by zinc chloride. Fuel 2014, 115, 804−811. (22) Alabadi, A.; Razzaque, S.; Yang, Y. W.; Chen, S.; Tan, B. Highly porous activated carbon materials from carbonized biomass with high CO2 capturing capacity. Chem. Eng. J. 2015, 281, 606−612. (23) Inal, I. I. G.; Holmes, S. M.; Banford, A.; Aktas, Z. The performance of supercapacitor electrodes developed from chemically activated carbon produced from waste tea. Appl. Surf. Sci. 2015, 357, 696−703. (24) Kumar, A.; Mohan Jena, H. High surface area microporous activated carbons prepared from Fox nut (Euryale ferox) shell by zinc chloride activation. Appl. Surf. Sci. 2015, 356, 753−761. (25) Sun, J.; Lei, Y.; Yang, X.; Du, X. Phase Transformations of Graphite and Carbon Black by Laser with Low Power Density. Trans. Tianjin Univ. 2007, 13, 318−321.

influence of mesopore surface area on adsorption capacity of ACs was the most obvious for the most active ACs such as RMS-AC, CC-AC/HCl, and CC-AC/KOH, but not for CCAC. (ii) The most active CC-AC has the largest volume of micropores with respect to the total pore volume (Vmicro/Vnet) and the lowest content of surface oxygen functional groups and thereby the least acidic character and the highest π−π* transitions in aromatic rings. (iii) The least active GS-AC has the lowest Vmicro/Vnet ratio, the highest content of surface oxygen functional groups with the highest content of surface water, the highest ID/IG ratio (not considering BC-AC), and one of the lowest π−π* transitions in aromatic rings showing more defects in the graphitic structure.

■

ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acssuschemeng.6b02703. Schematic diagram of the preparation of activated carbons (Figure S1), the layout of the adsorption unit (Figure S2), textural properties of activated carbons (Table S1 and Figures S3 and S4), FTIR analysis of activated carbons (Figures S5 and S6 and Table S2), Raman spectroscopy of activated carbons (Figures S7 and S8 and Table S3), XPS of activated carbons (Tables S4 and S5), and xylene adsorption experiments (Figures S9 and S10 and Table S6) (PDF)

■

AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. Phone: +420 596 997 300. ORCID

Lucie Obalová: 0000-0002-7361-2425 Notes

The authors declare no competing financial interest.

■

ACKNOWLEDGMENTS This work was financially supported by EU structural funding Operational Programme Research and Development for Innovation Project CZ.1.05/2.1.00/19.0388. VŠB-Technical University of Ostrava within Institutional development project “Development of International Cooperation of IET” is gratefully acknowledged. The National University of Tumbes provided important financial support for activated carbon production (CANON funding).

■

REFERENCES

(1) Langman, J. M. Xylene: Its toxicity, measurement of exposure levels, absorption, metabolism and clearance. Pathology 1994, 26 (3), 301−309. (2) Sidheswaran, M. A.; Destaillats, H.; Sullivan, D. P.; Cohn, S.; Fisk, W. J. Energy efficient indoor VOC air cleaning with activated carbon fiber (ACF) filters. Build Environ 2012, 47, 357−367. (3) Strots, V. O.; Bunimovich, G. A.; Matros, Y. S. Base metal catalysts for VOC oxidation. Pollut. Eng. 2002, 34 (7), 14−17. (4) Tsai, J.-H.; Chiang, H.-M.; Huang, G.-Y.; Chiang, H.-L. Adsorption characteristics of acetone, chloroform and acetonitrile on sludge-derived adsorbent, commercial granular activated carbon and activated carbon fibers. J. Hazard. Mater. 2008, 154 (1−3), 1183− 1191. 2373


Research Article

ACS Sustainable Chemistry & Engineering (26) Nistor, L. C.; Landuyt, J.; Ralchenko, V. G.; Kononenko, T. V.; Obraztsova, E. D.; Strelnitsky, V. E. Direct Observation of LaserInduced Crystallization of a-C-H Films. Appl. Phys. A: Solids Surf. 1994, 58 (2), 137−144. (27) Sánchez-Sánchez, A.; Suárez-García, F.; Martínez-Alonso, A.; Tascón, J. M. D. Surface modification of nanocast ordered mesoporous carbons through a wet oxidation method. Carbon 2013, 62, 193−203. (28) Jiménez Mateos, J. M.; Fierro, J. L. G. X-ray Photoelectron Spectroscopic Study of Petroleum Fuel Cokes. Surf. Interface Anal. 1996, 24 (4), 223−236. (29) Darmstadt, H.; Roy, C.; Kaliaguine, S.; Choi, S. J.; Ryoo, R. , Surface chemistry of ordered mesoporous carbons. Carbon 2002, 40 (14), 2673−2683. (30) Boehm, H. P. Surface oxides on carbon and their analysis: a critical assessment. Carbon 2002, 40 (2), 145−149. (31) Fuente, E.; Menendez, J. A.; Diez, M. A.; Suarez, D.; MontesMoran, M. A. Infrared spectroscopy of carbon materials: A quantum chemical study of model compounds. J. Phys. Chem. B 2003, 107 (26), 6350−6359. (32) Figueiredo, J. L.; Pereira, M. F. R. Porous Texture Versus Surface Chemistry in Applications of Adsorption by Carbons A2. In Novel Carbon Adsorbents; Tascón, J., Ed.; Elsevier: Oxford, U.K., 2012; Chapter 15, pp 471−498. (33) Troppová, I.; Matějová, L.; Kuboň ová, L.; Strašaḱ , T.; Študentová, S.; Kustrowski, P.; Obalová, L. Molecular dimensions and porous structure of activated carbons for sorption of xylene and isooctane. Chem. Eng. Technol. 2017, 40 (1), 6−17. (34) Knappe, D. R. U. Surface chemistry effects in activated carbon adsorption of industrial pollutants. In Interface Science and Technology; Gayle, N., David, D., Eds.; Elsevier: Amsterdam, 2006; Chapter 9, Vol. 10, pp 155−177. (35) Mcelroy, J. A. Adsorption of substituted aromatic compounds by activated carbon: A mechanistic approach to quantitative structure activity relationships. M.S. Thesis, University of Florida, Gainesville, FL, 2005. (36) Ahnert, F.; Arafat, H. A.; Pinto, N. G. A study of the influence of hydrophobicity of activated carbon on the adsorption equilibrium of aromatics in non-aqueous media. Adsorption 2003, 9 (4), 311−319.

2374


Activated Carbons Prepared from a Broad Range of Residual

Recommend Documents