Highly porous lignin composites for dye removal in batch and continuous-flow systems

Materials Letters 263 (2020) 127289

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Highly porous lignin composites for dye removal in batch and continuous-flow systems Martín Esteban González-López a, Jorge Ramón Robledo-Ortíz b, Denis Rodrigue c, Aida Alejandra Pérez-Fonseca a,⇑ a b c

Departamento de Ingeniería Química, CUCEI, Universidad de Guadalajara, Blvd. Gral. Marcelino García Barragán # 1451, Guadalajara, Jalisco 44430, Mexico Departamento de Madera, Celulosa y Papel, CUCEI, Universidad de Guadalajara, Carretera Guadalajara-Nogales km 15.5, Las Agujas, Zapopan, Jalisco 45510, Mexico Department of Chemical Engineering and CERMA, Université Laval, Quebec City, Quebec G1V 0A6, Canada

a r t i c l e

i n f o

Article history: Received 21 November 2019 Received in revised form 20 December 2019 Accepted 30 December 2019 Available online 31 December 2019 Keywords: Composite materials Polymeric composites Porous materials Lignin Adsorption Methylene blue

a b s t r a c t This work aimed at developing a highly porous polymeric lignin composite and to evaluate its adsorptive properties in batch and continuous experiments. Lignin has a strong dye-binding capacity due to its abundant phenolic and carboxyl groups, presenting a removal efficiency of 77% and an adsorption capacity of 8.1 mg/g. The novelty of this work was to develop a suitable lignin composite, with a dye removal efficiency of 80% achieved in batch using a 40% lignin composite (C0 = 40 mg/L and sorbent loading of 50 g/L). The continuous-flow operation was successfully carried out in a fixed-bed column operating at 3.0 mL/min and C0 = 40 mg/L with removal of 0.55 mg/g of lignin, which is promising in terms of generating added-value applications for lignin. Ó 2019 Published by Elsevier B.V.

1. Introduction Methylene blue is a cationic dye highly soluble and extensively used for cotton and silk. Exposures to this pollutant can result in eye burns, breathing complications, nausea, vomiting, etc. It also decreases the water reoxygenation capacity and light transmission, representing an acute threat to human health and aquatic ecosystems even at low concentrations [1–3]. Lignin represents an extensively available resource with high potential to develop added-value products. Due to its low cost and extensive industrial availability, it has been used as a precursor in the synthesis of carbon nanocages [4]. Another recent lignin application is as an adsorbent to remove pollutants (such as dyes) from water [5]. For adsorption applications, fixed-bed columns for continuous-flow removal of these pollutants are more efficient [6]. Lignin is usually recovered as a powder after the pulping process of wood and acid precipitation of black liquor [7]. Thus, its use in continuous-flow systems requires the development of dimensionally stable and porous structures or composites [8,9]. The objective of this work was to develop a highly porous polymeric lignin composite and to evaluate its adsorption properties in ⇑ Corresponding author. E-mail address: [email protected] (A.A. Pérez-Fonseca). https://doi.org/10.1016/j.matlet.2019.127289 0167-577X/Ó 2019 Published by Elsevier B.V.

batch experiments and to determine its potential in a continuousflow system as a fixed-bed adsorption column.

2. Materials and methods 2.1. Materials The materials used were low-density polyethylene (LDPE, PX20020X, Pemex, Mexico) with a density of 0.92 g/cm3, polystyrene (PS, Pemex, Mexico) with a density of 1.04 g/cm3, azodicarbonamide (Sigma-Aldrich, USA) as a chemical blowing agent (CBA) and zinc oxide (J.T. Baker, Mexico) as activator. Hardwood Kraft lignin was obtained from PFInnovations (Quebec, Canada) and used as received. Methylene blue (Sigma-Aldrich, USA) was the dye used in the adsorption experiments. 2.2. Sorbent preparation and characterization The composites were based on LDPE:lignin with different ratios of 80:10, 70:20, 60:30 and 50:40. The compounds were prepared with 10% of PS in a twin-screw extruder Thermo Scientific Process 11 with temperatures between 160 and 180 °C and a screw speed of 100 rpm. The PS was included to have a low surface tension

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interphase to promote cell formation using 1% of azodicarbonamide and 0.1% of zinc oxide.

3. Results and discussion 3.1. Lignin

2.3. Fourier transform infrared spectroscopy (FTIR) Functional groups of lignin were characterized via FTIR using a Spectrum 100 FTIR spectrometer (Perkin-Elmer, USA) with ATR accessories. A total of 32 scans were acquired at a resolution of 4 cm
1 within a frequency range of 4000–700 cm
1. 2.4. Morphology SEM micrographs were obtained after cryogenic fracture on a scanning electron microscope (SEM) TESCAN MIRA 3 LMU to observe the cellular structure. 2.5. Density and porosity The porosity of the composites (/) was calculated via the relationship between the skeletal density (qs) and bulk density (qb) as:

  q /ð%Þ ¼ 1
b  100

qs

ð1Þ

The skeletal density was determined by a gas pycnometer ULTRAPYC 1200e (Quantachrome Instruments, USA) using nitrogen. The bulk density was determined according to ASTM D2395. 2.6. Batch adsorption Batch adsorption was carried out by placing 0.5 g of adsorbent and 10 mL of a dye solution in 15 mL glass vials. The system was placed in an orbital shaker incubator (NB-T205, N-BIOTEK) at 150 rpm and 30 °C. The dye concentration was directly quantified by a UV/Vis Cary 50 BIO spectrometer at 665 nm. The amount of adsorbed dye per unit weight of adsorbent (q) was calculated as:

q¼

ðC 0
C t ÞV m

ð2Þ

where C0 is the initial concentration (mg/L), Ct is the concentration at time t (mg/L), V is the volume of the solution (L), and m represents the mass of sorbent (g). The pseudo-second order model was used to describe the adsorption kinetics [9]:

1 1 ¼ þ k2 t ðqe
qt Þ qe

Independently of its extraction process and source, lignin has a large number of functional groups that are suitable for cations removal (Fig. 1). Typically, the band at 3400 cm
1 corresponds to hydroxyls in both aromatics and aliphatic chains, while the peaks at 2900 and 2850 cm
1 correspond to C–H stretching vibrations. Carbonyl frequencies are observed at 1700 cm
1, while carboxylates appear at lower frequencies around 1650 cm
1. Finally, signals at 1100 and 1200 cm
1 are attributed to C–O groups of sinapyl alcohols [11,12]. Kraft lignins usually present a large amount of carboxyl and phenolic groups becoming negatively charged and resulting in favorable cations binding [7,10]. Through batch experiments, a maximum adsorption capacity of 8.1 mg/g was determined and the kinetics were found to be favorable towards adsorption as the equilibrium was reached in less than 60 min, which indicates that mass transfer resistance from the solution’s bulk to the sorbent’s surface, as well as the chemisorption step, were both very low. Nevertheless, centrifugation was necessary after the adsorption experiments to separate the lignin from the solution. 3.2. Lignin composite Given the need to provide structure to lignin, a highly porous polymeric lignin composite was extruded at different lignin concentrations (10, 20, 30 and 40 wt%). Porosity values are reported in Table 1 along with the adsorptive properties of these composites compared to other reports in the literature. Porosity increases with the incorporation of lignin as a result of the weak surface adhesion in the polymer blend; i.e. once the blowing agent decomposes, these are not restricted to expand into the formation of cells [13]. This indicates that a highly porous lignin composite (up to 60% of porosity at 40% lignin) was effectively developed as an adsorbent. Its removal efficiency and kinetics were tested in the batch process for a 40 mg/L dye solution with a sorbent loading of 50 g/L. Increasing the amount of lignin increased removal efficiency. It is expected that lignin adsorption capacity can be hindered inside the composite because its adsorption capacity was smaller than raw lignin, indicating that not all the lignin particles are available at the surface but rather trapped within the matrix where the

ð3Þ

where k2 is the rate constant (g/mg min), while qe represents the equilibrium uptake (mg/g). 2.7. Fixed-bed adsorption A glass column of 2.54 cm internal diameter and 30 cm in length was packed with the cylinder-like sorbent particles of 3.83 mm average diameter and 2.74 average length. The contaminated solution was pumped in the upward-direction using a peristaltic pump. At the column exit, samples were collected every 20 min. The model of Thomas was used for the bed adsorption capacity (qTh) [1]:

Ct 1    ¼ C 0 1 þ exp kTh ðq m
C 0 QtÞ Th Q

ð3Þ

where Q is the volumetric flow rate (mL/min) and kTh is the Thomas constant (mL/min g).

Fig. 1. FTIR spectrum of the hardwood Kraft lignin used.

M.E. González-López et al. / Materials Letters 263 (2020) 127289

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Table 1 Properties of the lignin composites compared to other sorbents. Sorbent

U (%)

Removal efficiency (%)

10% 20% 30% 40%

38.7 49.0 54.6 61.0

56.1 67.6 70.8 80.0

Kinetic model parameters k2 (g/mg min)

qe (mg/g)

0.0033 0.0042 0.0049 0.0050

0.228 0.256 0.355 0.415

Sorbent

Removal efficiency (%)

Pollutant

Reference

Fe3O4 nanoparticles Bottom ash De-oiled soya Mesoporous carbon

96.9 70.0 64.0 99.9

Methylene blue

[14]

Chrysoidine Y

[15]

Methyl orange

[16]

solution could not penetrate. However, lignin becomes less hindered by increasing the sorbent’s porosity and the removal efficiency becomes higher with faster kinetics (enhanced diffusion) (Fig. 2). SEM micrographs confirmed that porosity increases with the amount of lignin while the pore size became smaller. These effects can promote the use of lignin in a continuous-flow system.

3.3. Breakthrough curve The main objective of this work was to develop a lignin-based material to be used in a fixed-bed column. The breakthrough curve in Fig. 3 indicates that it was possible to treat a solution of methylene blue dye with an inlet concentration of 40 mg/L by operating at 3.0 mL/min with 25 g of the 40% lignin sorbent fixed in the bed which became saturated after 5 h (while it became saturated after 2 h with the 20% lignin composite). The capacity of the fixed-bed (qTh) was 0.55 mg/g of lignin, while kTh was 0.822 mL/min g. To put in perspective this result, Han et al. [1] adsorbed methylene blue dye using natural zeolite with removal capacities ranging between 1.83 and 4.36 mg/g within 200 and 1000 min depending on the conditions: between 2.2 and 7.2 mL/min for flow rate and between 30 and 72 mg/L for inlet concentration. Despite the amount of dye removed in this study being lower, lignin is a low-cost residue which makes this result promising in terms of generating added-value applications for lignin, especially after more optimization.

Fig. 3. Breakthrough curve of 20% and 40% lignin composites.

4. Conclusions In this study, a polymeric lignin composite was prepared with the objective of using lignin as an adsorbent for the removal of methylene blue dye in a continuous-flow system. Lignin has a strong dye-binding capacity of 8.1 mg/g with a maximum removal efficiency of 77%. Although lignin was hindered inside the composites, it became less hindered by increasing the sorbent’s porosity improving the removal efficiency and increasing the kinetics. The breakthrough curve indicated that it was possible to treat an effluent containing an inlet concentration of 40 mg/L of methylene blue dye with a removal amount of 0.55 mg/g of lignin within 5 h. CRediT authorship contribution statement Martín Esteban González-López: Methodology, Validation, Investigation, Writing - original draft. Jorge Ramón RobledoOrtíz: Conceptualization, Formal analysis, Resources, Writing review & editing. Denis Rodrigue: Formal analysis, Resources, Writing - review & editing. Aida Alejandra Pérez-Fonseca: Conceptualization, Investigation, Resources, Writing - review & editing, Supervision.

Fig. 2. Adsorption kinetics of the lignin composites in a batch process and their morphology.

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Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. Acknowledgment One of the authors (M.E. González-López) acknowledges a scholarship from the Mexican National Council for Science and Technology (CONACyT #481448). References [1] R. Han, Y. Wang, W. Zou, Y. Wang, J. Shi, Comparison of linear and nonlinear analysis in estimating the Thomas model parameters for methylene blue adsorption onto natural zeolite in fixed-bed column, J. Hazard Mat. 145 (2007) 331–335, https://doi.org/10.1016/j.jhazmat.2006.12.027. [2] N. Mohammed, N. Grishkewich, H.A. Waeijen, R.M. Berry, K.C. Tam, Continuous flow adsorption of methylene blue by cellulose nanocrystal-alginate hydrogel beads in fixed bed columns, Carbohyd. Polym. 136 (2016) 1194–1202, https:// doi.org/10.1016/j.biortech.2009.06.093. [3] Y. Fu, L. Qin, D. Huang, G. Zeng, C. Lai, B. Li, J. He, H. Yi, M. Zhang, M. Cheng, X. Wen, Chitosan functionalized activated coke for Au nanoparticles anchoring: Green synthesis and catalytic activities in hydrogenation of nitrophenols and azo dyes, Appl. Catal. B-Environ. 255 (2019), https://doi.org/10.1016/j. apcatb.2019.05.042 117740. [4] L. Klapiszewski, P. Bartczak, M. Wysokowski, M. Jankowska, K. Kabat, T. Jesionowski, Silica conjugated with kraft lignin and its use as a novel ‘green’ sorbent for hazardous metal ions removal, Chem. Eng. J. 260 (2015) 684–693, https://doi.org/10.1016/j.cej.2014.09.054. [5] H. Qin, S. Kang, Y. Huang, S. Liu, Y. Fang, X. Li, Y. Wang, Lignin based synthesis of carbon nanocages assembled from graphitic layers with hierarchical pore structure, Mater. Lett. 159 (2015) 463–465, https://doi.org/10.1016/ j.matlet.2015.06.002.

[6] V.K. Gupta, I. Tyagi, S. Agarwal, R. Singh, M. Chaudhary, A. Harit, S. Kushwaha, Column operation studies for the removal of dyes and phenols using a low cost adsorbent, Global J. Environ. Sci. Manage. 2 (2016) 1–10. [7] Y. Wu, S. Zhang, X. Guo, H. Huang, Adsorption of chromium (III) on lignin, Bioresour. Tech. 99 (2008) 7709–7715, https://doi.org/10.1016/j. biortech.2008.01.069. [8] Y. Yang, Z. Wei, C. Wang, Z. Tong, Lignin-based Pickering HIPEs for macroporous foams and their enhanced adsorption of copper (II) ions, Chem. Comm. 49 (2013) 7144–7146, https://doi.org/10.1039/c3cc42270d. [9] V. Nair, A. Panigrahy, R, Vinu, Development of novel chitosan–lignin composites for adsorption of dyes and metal ions from wastewater, Chem. Eng. J. 254 (2014) 491–502, https://doi.org/10.1016/j.cej.2014.05.045. [10] H. Harmita, K.G. Karthikeyan, X. Pan, Copper and cadmium sorption onto kraft and organosolv lignins, Bioresour. Tech. 100 (2009) 6183–6191, https://doi. org/10.1016/j.biortech.2009.06.093. [11] D. Zhu, C. Qin, S. Ao, M. Wang, M. Wu, Y. Lü, P. Ye, Hypercrosslinked functionalized lignosulfonates prepared via Friedel-Crafts alkylation reaction for enhancing Pb (II) removal from aqueous, Sep. Sci. Tech. 54 (2019) 2830– 2839, https://doi.org/10.1080/01496395.2018.1554686. [12] Y. Fu, P. Xu, D. Huang, G. Zeng, C. Lai, L. Qin, B. Li, J. He, H. Yi, M. Cheng, C. Zhang, Au nanoparticles decorated on activated coke via a facile preparation for efficient catalytic reduction of nitrophenols and azo dyes, Appl. Surf. Sci. 473 (2019) 578–588. [13] Z. Xing, M. Wang, G. Du, T. Xiao, W. Liu, D. Qiang, G. Wu, Preparation of microcellular polystyrene/polyethylene alloy foams by supercritical CO2 foaming and analysis by X-ray microtomography, J. Supercrit. Fluids. 82 (2013) 50–55, https://doi.org/10.1016/j.supflu.2013.06.003. [14] M. Ghaedi, S. Hajjati, Z. Mahmudi, I. Tyagi, S. Agarwal, A. Maity, V.K. Gupta, Modeling of competitive ultrasonic assisted removal of the dyes–Methylene blue and Safranin-O using Fe3O4 nanoparticles, Chem. Eng. J. 268 (2015) 28– 37. [15] A. Mittal, J. Mittal, A. Malviya, V.K. Gupta, Removal and recovery of Chrysoidine Y from aqueous solutions by waste materials, J. Colloid Interface Sci. 344 (2010) 497–507. [16] N. Mohammadi, H. Khani, V.K. Gupta, E. Amereh, S. Agarwal, Adsorption process of methyl orange dye onto mesoporous carbon material–kinetic and thermodynamic studies, J. Colloid Interface Sci. 362 (2011) 457–462.