Carbon Tube Clusters with Nanometer Walls Thickness, Micrometer

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Carbon Tube Clusters with Nanometer Walls Thickness, Micrometer Diameter from Biomass and Its Adsorption Property as Bioadsorbent Haijie Li, Yanli Li, Yali Chen, Mingyuan Yin, Tingting Jia, Shuya He, Qiliang Deng, and Shuo Wang ACS Sustainable Chem. Eng., Just Accepted Manuscript • DOI: 10.1021/ acssuschemeng.8b04486 • Publication Date (Web): 30 Nov 2018 Downloaded from http://pubs.acs.org on December 3, 2018

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ACS Sustainable Chemistry & Engineering

Carbon Tube Clusters with Nanometer Walls Thickness, Micrometer Diameter from Biomass and Its Adsorption Property as Bioadsorbent Haijie Li†, Yanli Li†, Yali Chen†, Mingyuan Yin†, Tingting Jia†, Shuya He†, Qiliang Deng*†, and Shuo Wang*†‡ † Key Laboratory of Food Nutrition and Safety, Ministry of Education, Tianjin Key Laboratory of Food Nutrition and Safety, College of Chemical Engineering and Materials Science, Tianjin University of Science and Technology, 1038 Dagu South Road, Tianjin, 300457, China. ‡ Tianjin Key Laboratory of Food Science and Health, School of Medicine, Nankai University, 94 Weijin Road, Tianjin, 300071, China. Corresponding Author *Qiliang Deng E-mail: [email protected]; *Shuo Wang E-mail: [email protected].

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ACS Sustainable Chemistry & Engineering 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ABSTRACT: Carbon tube clusters with nanometer wall thickness and micrometer diameter were prepared by carbonizing the pappi of Sonchus oleraceus L. Such tube clusters possessed micro-, meso-pores and large specific surface area (911 m2 g-1). The adsorption properties of the carbon tube clusters were further evaluated by choosing metal ions, dye, lubricating oil and waste oil as the targets, respectively. The maximum adsorption capacities of the materials for lubricating oil and waste oil were 103.76 and 91.70 g g-1, respectively, which benefit from abundant pore structure, large specific surface area and hydrophobic property. Such tube clusters also demonstrated excellent adsorption property for metal ions such as Ag+, which exhibited extremely high selectivity (the highest selectivity coefficient to Cd2+ was 1021.88) and fast adsorption rate (the adsorption amount reached 91% of equilibrium adsorption capacity within 10 min). Owing to low cost, simple preparation and renewable resource, the prepared carbon tube clusters possess great potential as an efficient adsorbent for cleaning marine oil spills and selectively recycling silver ions.

KEYWORDS: Carbon tube clusters; Biomass; Pappi; Adsorption; Selectivity.


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INTRODUCTION Carbon materials have recently drawn broad attention as one of the most important materials for adsorption, catalysis, energy storage and conversion, and water and air purification due to their unique properties including tunable surface properties, controlled surface area, defined size and regular shape 1 2 3 4 5. Over the past ten years, chemical vapor deposition, soft and hard templating, self-assembly and hydrothermal carbonization have been explored to prepare carbon tube, carbon sphere, carbon fiber and carbon sheet 6 7 8 9 10. However, most of these approaches are usually limited to tedious multistep chemical synthesis such as polymerization, carbonization and removal of template, which are costly, lower yield, and environmental unfriendly. Thus, preparation of carbon materials by facile, low-cost and eco-friendly method is of particular importance for their large-scale application. Recently, carbon materials derived from renewable biomass have been widely studied and are still a hot topic because of wide available, low cost, high yield, renewability, environmental friendly and simple synthetic strategy. Renewable biomass including animals, plants, fungi, protozoa, algae and microorganisms has received great attention, especially, the plants are attracting increasing attention due to broad available raw materials. Current carbon materials derived from the plants biomass mainly involved in residual agricultural biomass 11, such as maize residues 12, sugar cane bagasse 13, sweet potato waste 14, grapefruit peel 15 and coconut shells 16. These obtained carbon materials also exhibited a wide range of application, such as adsorption 17, catalysis 18, and energy storage and conversion 19 20. As a novel adsorbents, carbon materials derived from biomass show the potential for removal of metal ions 21 22, adsorption of dyes 23, capture of gasoline vapors 24 and enrichment of gases 25. However, most of previous reported carbon materials derived from biomass have no regular morphology. In fact, carbon 3 Environment ACS Paragon Plus


materials derived from biomass with regular shape will bring them greater promise for many practical applications. Sonchus oleraceus L is an annual herb and usually grows in roadside or wild wetlands field. The pappus of Sonchus oleraceus L owns high cellulose content, drifts in the air and contributes to the wind-dispersal of the seeds. In this research, by carbonizing the pappi of Sonchus oleraceus L from the wild wetlands under low temperature, we obtained novel carbon tube clusters with nanometer wall thickness, micrometer diameter and large specific surface area. Such a structure made them ideal adsorbents because it can significantly improve adsorption capacity and mass transport-relevant processes. The resultant carbon tube clusters were investigated as bioadsorbent for oils, metal ions and methyl violet, respectively. EXPERIMENTAL SECTION Materials The natural plant (the pappi of Sonchus oleraceus L) was collected from the wild wetlands of Tianjin. Standard solution of silver (Ag+), beryllium (Be2+), chromium (Cr3+), cobalt (Co2+), nickel (Ni2+), copper (Cu2+), zinc (Zn2+), cadmium (Cd2+), antimony (Sb2+), and lead (Pb2+) were obtained from National Institute of Metrology (Beijing, China). Methyl violet (MV) was provided by Tianjin Baishi Chemical Co., Ltd. (Tianjin, China). The lubricating oil and waste oil were obtained from Shanghai Zhongjie Industrial Co., Ltd. (Shanghai, China) and the local automobile repair plant (Tianjin, China), respectively. All other reagents were analytical grade and used directly. Preparation of carbon tube clusters


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Carbon tube clusters were prepared by carbonizing of the pappi of Sonchus oleraceus L. More details are shown below. The pappi of Sonchus oleraceus L were washed with deionized water and dried at 80 ºC for 12h. These pre-carbonized tube clusters were then put into a typical ceramic crucible and heated in the tube furnace under N2 atmosphere. Programmed temperature rise was performed using a heating rate of 1 °C min-1 up to 350 °C and kept for 120 min, and then resuming the heating rate up to 600 °C and kept for 240 min. After the system was cooled down to 25 °C at a cooling rate of 5 °C min-1, the dark solid material was finally collected. The pappi of Sonchus oleraceus L were also carbonized at 200 °C, 400 °C and 800 °C, respectively. Characterization and analytical approach SEM pictures were imaged using field emission scanning electron microscope (LEO 1530VP, Germany). The corresponding energy-dispersive X-ray spectroscopy (EDS) using Oxford X-Max 20 (Oxford, UK). TEM images of the pappi of Sonchus oleraceus L were obtained on HT7700 Hitachi (Hitachi, Japan) and a field emission transmission electron microscopy (JEM-2100F, JEOL, Japan), respectively. The carbon tube clusters were characterized by a Fourier transform infrared spectroscopy (Bruker, Germany) in the scanning range of 4000-500 cm-1. X-ray diffraction (XRD) was examined on a diffractometer instrument (D8 Advance, Buker, Germany). The Raman spectra were obtained using an Invia Raman spectrophotometer (Renishaw, Britain).X-ray photoelectron spectroscopy (XPS) was determined using an Escalab 250xi photoelectron spectrometer (Thermo, USA). The elemental contents of the carbon tube clusters were determined using a Vario EL cube (Elementar, Germany) equipped with a TCD detector. The specific surface area of the carbon tube clusters was measured using static volumetric adsorption analyzer (Autosorb IQ, Quantachrome, USA). Pore size and total pore volume were obtained by the Brrett−Joyner−Halenda (BJH) method. The contact angles were measured on a 5 Environment ACS Paragon Plus


DSA30 contact-angle system (KRÜSS, Germany) at room temperature. The concentration of MV and Ag+ in solution were determined by UV−visible spectrophotometer (UV-Vis, TΜ-1901, Puxi, China) and inductively coupled plasma mass spectrometry (ICP-MS 7500CX, Agilent, USA), respectively. Oil adsorption experiment The adsorption experiment of materials toward oil was performed by adding 5.0 mg of the carbon tube clusters to 50.0 mL of oil. After kept for 1h, the carbon tube clusters were taken out from oil to drain for 5 min and the weight was measured (1×105 g accuracy). The maximum adsorption capacity of materials toward oil was calculated by the Equation 1:

q=

mw ― m m

(1)

Where q is the adsorption capacity (g g-1), mw is the weight of the carbon tube clusters after 5 min of drainage (g), and m is the weight of the carbon tube clusters (g) before adsorption. Metal ions and dyes adsorption experiment Adsorption kinetic and isotherm experiments were both performed by adding 2.0 mg of the carbon tube clusters to 5.0 mL of methyl violet (MV) dyes or silver (Ag+) solution of known concentration. In the adsorption isotherm experiments, the concentration of Ag+ was in a range of 5.0 - 200.0 mg L-1, and MV in a range of 10.0 - 400.0 mg L-1. 100.0 mg L-1 of Ag+ and 50.0 mg L-1 of MV were employed in the adsorption kinetic experiments. Batch adsorption experiments were performed on the incubator shaker (IS-RDD3, Crystal, USA) with a shaking speed of 200 rpm at 20 °C for 24 h. The concentrations of MV and Ag+ in solution were checked


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by UV-Vis and ICP-MS, respectively. The adsorption amount of MV or Ag+ was obtained using the Equation 2:

qe =

(C0 ― Ce)V

(2)

m

The amount adsorbed (qt) was calculated by:

qt =

(C 0 ― C t )V

(3)

m

where qe and qt (mg g-1) are the amount of MV or Ag+ adsorbed by the carbon tube clusters at equilibrium and time t, respectively, C0, Ce and Ct (mg L-1) are the initial, equilibrium and time t concentrations of MV or Ag+ , respectively, V (L) and m (g) represent the volume of the solution and the weight of the carbon tube clusters ,respectively. Selective adsorption experiment Selective adsorption experiments were designed with Be2+, Cr2+, Co2+, Ni2+, Cu2+, Zn2+, Cd2+, Sb2+, and Pb2+ as competing ions and Ag+ as the target ion, respectively. Experiment was performed by adding 2.0 mg of the carbon tube clusters to 5.0 mL of mixed metal ions solution containing 10.0 mg L-1 of each ion, and placed on the incubator shaker with a shaking speed of 200 rpm at 20 °C for 24 h. Each metal ion concentration was measured by ICP-MS and the adsorption capacity was calculated by Equation 2. RESULTS AND DISCUSSION Morphology, structure and characterization



The pappi of Sonchus oleraceus L were composed of numerous white fibers by a view of the naked eye (Figure 1a-b), however, one could see each fiber was actual a tube cluster composed of seven tubes with diameter around 6-7 μm and wall thickness around 0.2 μm, where six tubes were arranged around one and each tube shares part of wall with neighbored tube (Figure 1c-f). However, it was worthy to note that the number of tubes was changeable according to the thickness of the tube clusters, such as the tube clusters composed of more than or less than seven tubes was also observed in our research, although the tube diameter and the wall thickness had no significant change. The retaining hollow multiple tubes were beneficial to the mass diffusion/transport. Compared with pre-carbonized materials (Figure 1e), the post-carbonized materials retained well tube structure after 600 ºC carbonization under nitrogen, but the tube diameter size shrank to half original size (Figure 1f). Although, the pappi of Sonchus oleraceus L were also carbonized at 200ºC, 400 ºC and 800 ºC, respectively, the morphologies of the resulted materials had no significant difference (Figure S1). The selected area electron diffraction pattern proved the amorphous nature of the resultant carbon materials at different temperatures (Figure S2). The broadened peak of powder X-ray diffraction spectra further revealed that these materials obtained at different temperatures were amorphous (Figure S3a). These materials were further characterized by Raman spectroscopy (Figure S3b). Although the intensity ratio of the ID/IG value of the materials reduced with the increase of the carbonization temperature, which demonstrated the formation of more sp2 domains from the conversion of sp3 carbons, the materials obtained at 800 ºC still exhibited a broaden ID peak.


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Figure 1. Characteristic images of the pre- and post-carbonized materials: (a, b) Active image; (c, d) SEM; (e, f) TEM. To gain more insight into the structural components of the carbon tube clusters, FT-IR spectra of the pre- and post-carbonized tube clusters were recorded and shown in Figure 2. Compared with the pre-carbonized tube clusters, the two obvious peaks at 1737 and 1247 cm-1, which were attributed to the stretching vibration of C=O and C−O, respectively, were all disappeared for the post-carbonized tube clusters. The characteristic peaks at 3431, 2972 and 2926 cm-1 originated from cellulose molecules 26. The peak at 3431 cm-1 corresponded to the O−H stretching vibration, and the peaks at 2972 and 2926 cm-1 were attributed to the stretching vibration of C-H. Although most of groups containing O-H were decomposed via carbonization process at 600 ºC



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under nitrogen, the peak at 3431 cm-1 had no significant decrease, which might be attributed to the overlap of O-H and N-H stretching vibration .

Figure 2. FT-IR spectra of the pre- and post-carbonized tube clusters. Table 1. Elemental composition of the materials carbonized at different temperatures. C (%)

H (%)

N (%)

S (%)

O (%)

800°C

85.69±0.08

1.11±0.03

1.51±0.01

0.53±0.03

7.40±0.03

600°C

74.79±0.12

2.45±0.01

1.43±0.11

0.55±0.01

12.29±0.08

400°C

72.15±0.01

3.72±0.01

1.17±0.01

0.43±0.01

15.79±0.01

200°C

51.69±0.02

5.83±0.01

0.84±0.05

0.37±0.02

38.28±0.07

Pre-carbonized

45.92±0.01

6.08±0.10

0.74±0.01

Carbon Tube Clusters with Nanometer Walls Thickness, Micrometer

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