The authors acknowledge the Fundamental Research Funds for the Central Universities of China (No.KYZ201562), China Postdoctoral Science Fund (No. 2014M560429) and the Key research and development plan of Jiangsu Province (No. BE2018708).

1. Preparation of Bagasse-based Activated Carbon
<ol>
	<li>Preparation of the precursor for bagasse-based activated carbon
	<ol>
		<li>Rinse the bagasse (obtained from a farm in Jiangsu, China) with deionized water and put the samples in a drying oven at 100 &#176;C for 10&#160;h.</li>
		<li>Crush the dried bagasse with a grinder and sieve the powder through a 50-mesh sieve.</li>
		<li>Place 30 g of fine bagasse powder into a 15 wt% phosphoric acid (H3PO4) solution in a 1:1 weight ratio for 24 h. Dry the mixture in an oven at 105 &#176;C for 6 h. Collect the resulting product as the precursor for bagasse-based activated carbon (BAC).</li>
	</ol>
	</li>
	<li>Conventional electric-heating pyrolysis of the precursor
	<ol>
		<li>Put 15 g of the precursor into a quartz boat and then insert the quartz boat into a quartz glass tube of an electric furnace.</li>
		<li>Set the heating rate of the furnace at 5 &#176;C min-1 to carbonize the sample. When the temperature reaches 500 &#176;C, keep the temperature for 90 min and then allow the resulting activated-carbon sample to cool to room temperature in nitrogen. Ensure a nitrogen flow of 80 mL min-1 with a rotor flowmeter during the overall process.</li>
		<li>Triturate and collect the electrical-furnace-pyrolyzed bagasse-based activated carbon (EBAC) in a beaker and then heat it in a vacuum drying oven at 105 &#176;C for 24 h.</li>
	</ol>
	</li>
	<li>Microwave pyrolysis of the precursor
	<ol>
		<li>Put 15 g of the precursor in a microwave oven (with a 2.45 GHz frequency).</li>
		<li>Set the power of the microwave oven at 900 W to pyrolyze the sample for 22 min, and ensure the nitrogen flow rate at 20 mL min-1 with a rotor flowmeter. The air inlet of the rotor flowmeter is connected to a nitrogen cylinder using a hose, while the outlet is connected to the air inlet of the microwave oven.</li>
		<li>Allow the resultant carbon to cool to room temperature in nitrogen. Triturate and collect the carbon sample in a beaker and then add 300 mL of hydrochloric acid (0.1 M). Stir the mixture using a magnetic stirrer (at 200 rpm) for more than 12 h at room temperature.</li>
		<li>Filter the carbon by filter paper with vacuum filtration and rinse the sample with deionized water until the pH value of the wash water is &#62; 6. Dry the microwave-pyrolyzed bagasse-based activated carbon (MBAC) in a vacuum drying oven at 105 &#176;C for 24 h.</li>
	</ol>
	</li>
</ol>
2. Modification of Electrical-furnace-pyrolyzed Bagasse-based Activated Carbon and Microwave-pyrolyzed Bagasse-based Activated Carbon
Note: The modification of the two samples was conducted according to the literature29.
<ol>
	<li>Nitrification
	<ol>
		<li>Mix 50 mL of concentrated sulfuric and 50 mL of concentrated nitric acids in a beaker at 0 &#176;C (in an ice bath). 
		CAUTION: When the mixture of concentrated sulfuric acid and concentrated nitric acid is mixed, the concentrated sulfuric acid should be slowly added to the concentrated nitric acid and stirred with a glass rod and cooled in time.</li>
		<li>Add 10 g of EBAC/MBAC to the mixed solution. Use a magnetic stirrer to stir the mixture for 120 min (at 200 rpm).</li>
		<li>Filter the nitrified EBAC/MBAC by filter paper with vacuum filtration. Wash the carbon with deionized water until the wash water reaches pH 6, and then dry it in a drying oven at 90 &#176;C for 24 h.</li>
	</ol>
	</li>
	<li>Reductive modification
	<ol>
		<li>In a three-necked flask, add the 5.05 g of resulting product, 50 mL of deionized water, and 20 mL of ammonia solution (15 M). Stir this mixture for 15 min with a magnetic stirrer (at 200 rpm), then add 28 g of Na2S2O4, and leave the mixture stirring at room temperature for 20 h.</li>
		<li>Fit a reflux condenser to the flask and warm the mixture up to 100 &#176;C using an oil bath. Add 120 mL of CH3COOH (2.9 M) to the flask and allow the mixture to stir for 5 h with a magnetic stirrer (at 200 rpm) under reflux.</li>
		<li>Remove the oil bath to allow the solution to cool down to room temperature. Filter the carbon sample and wash it with deionized water until the solution pH &#62; 6. Dry the modified EBAC/MBAC at 90 &#176;C and denote it as &#8220;EBAC-N/MBAC-N&#8221;.</li>
	</ol>
	</li>
</ol>
3. Adsorbent Characterization
<ol>
	<li>Structural characterization&#8212;Nitrogen adsorption/desorption isotherms 
	<ol>
		<li>Weigh an empty sample tube. Add a carbon sample (~0.15 g) to the sample tube.</li>
		<li>Degas the sample at 110 &#176;C for 5 h in a vacuum. Weigh the sample tube containing carbon. Calculate the weight of the carbon sample.</li>
		<li>Install the sample tube into the test area of the surface-area and porosimetry analyzer using liquid nitrogen to measure it at -196 &#176;C30.</li>
	</ol>
	</li>
	<li>Chemical characterization&#8212;Fourier transform infrared spectroscopy
	<ol>
		<li>Check the temperature and hygrometer and observe whether the environment meets the requirements: the temperature should be 16 - 25 &#176;C and the relative humidity 20% - 50%.</li>
		<li>Remove the desiccant and dust cover in the sample storehouse.</li>
		<li>Dry the carbon sample and potassium bromide at 110 &#176;C for 4 h to avoid the effect of water on the spectrum. Mix the carbon sample with potassium bromide and then use a press mechanism to prepare the test sample.</li>
		<li>Put the sample in the test area and set the parameters of the software.</li>
		<li>Save the spectra and take out the sample. Perform a required data processing for the spectra31.</li>
	</ol>
	</li>
</ol>
4. Cu(II)-adsorption Experiments
<ol>
	<li>Adsorption isotherm
	<ol>
		<li>Place 0.05 g of adsorbent in each of the conical flasks, which contain 25 mL of a CuSO4 solution (pH 5) with a selected initial concentration (10, 20, 30, 40, 50, 60, 80, and 100 mg L-1). Use a 0.1 M HNO3 and 0.1 M NaOH solution to adjust the pH of each copper solution. 
		Note: A solution with the selected initial concentration is diluted by a 1 g L-1 CuSO4 solution, which is made up of a dissolved 3.90625 g of blue vitriol solid using the vase with a 1,000 mL volume.</li>
		<li>Fit lids on the conical flasks and put them in a thermostatic orbital shaker (with a stirring rate of 150 rpm) at 5 &#176;C/25 &#176;C/45 &#176;C for 240&#160;min.</li>
		<li>Use 0.22 &#956;m membrane filters to separate the adsorbents from the solution.</li>
		<li>Use a flame atomic absorption spectrophotometry to determine the copper concentration of the filtrate. 
		Note: All experiments were carried out in triplicate and the data were averaged. The adsorption capacity for Cu(II), qe, was calculated as follows: 
		<img alt="Equation" src="/files/ftp_upload/58161/58161eq1v2.jpg" />&#160;(1) 
		Here, 
		C0 = the initial copper concentration (mg L-1), 
		Ce = the final concentration (mg L-1), 
		V = the solution volume, and 
		m = the weight of each adsorbent (g).</li>
	</ol>
	</li>
	<li>Influence of pH
	<ol>
		<li>Place 0.05 g of adsorbent in each of conical flasks, which contain 25 mL of a CuSO4 solution (40 mg L-1) with a selected initial pH (2, 3, 4, 5, 6, and 7).</li>
		<li>Fit lids on the conical flasks and put them in a thermostatic orbital shaker (with a stirring rate of 150 rpm) at 25 &#176;C for 24 h to reach adsorption equilibrium conditions.</li>
		<li>Repeat step 4.1.3-4.1.4.</li>
	</ol>
	</li>
	<li>Adsorption kinetics
	<ol>
		<li>Place 0.25 g of adsorbent in a beaker which contains 125 mL of a CuSO4 solution (30 mg L-1 or 100 mg L-1, pH 5) in a 25 &#176;C water bath with magnetic stirring (at 200 rpm).</li>
		<li>Use pipettes to draw 5 mL of the solution when the contact time reaches 0.5, 1, 2.5, 5, 10, 30, 60, 120, and 180 min.</li>
		<li>Repeat step 4.1.3-4.1.4.</li>
	</ol>
	</li>
</ol>

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</ol>

The authors have nothing to disclose.

In this protocol, one of the critical steps is the successful preparation of mesoporous carbon with better physicochemical properties by the one-step approach, where optimal experimental conditions need to be determined. So, in a previous study28, we have carried out orthogonal array microwave pyrolysis experiments, considering the effect of the impregnation ratio of bagasse and phosphoric acid, pyrolysis time, microwave oven power, and drying time. Besides, great care must be taken in tedious Cu(II)-adsorption experiments, especially when the pH value of the solution is adjusted, because the pH value has a great influence on Cu(II) removal by activated carbon (Figure 3). It is imperative to test the actual copper concentration of the CuSO4 solution with a defined initial concentration and use this value as C0 in Equation (1).
A larger specific surface area and higher pore volume of biomass-based activated carbon can be obtained by chemical activation. However, the specific surface area and total pore volume both decrease during the subsequent pyrolysis and modification process, which is likely due to the collapse and blockage of the pores27, resulting in a reduction of the adsorption capacity. Therefore, further work is required to prepare biomass-based mesoporous carbon with both a high surface area and abundant functional groups.
Microwave pyrolysis is verified to more adequately synthesize biomass-based mesoporous carbon with a higher nitrogen/oxygen-chelating adsorption for Cu(II), which has many advantages over widely used conventional heating methods. However, it is not possible to control the instantaneous temperature accurately during the microwave pyrolysis process. Biomass is a good microwave absorption material, whose temperature can rapidly increase under the effect of a microwave. Clearly, future work needs to examine how the pyrolysis temperature affects the physicochemical properties of the biomass-based carbon.
A detailed description of the modification mechanism is beyond the scope of this article, but it can be found in earlier published literature27. The potential importance of nitrification and reduction modification which can effectively introduce more N/O functional groups concurrently on the surface of carbon samples is worth appreciating. However, the modification process contains numerous experimental steps and the utilization of dangerous concentrated strong acid. A simpler and more effective nitrogen/oxygen modification method may be tested and adopted in further studies.
We have demonstrated an environment-friendly energy-efficient method for preparing biomass-based mesoporous carbon by microwave pyrolysis and dope N/O groups simultaneously on the carbon using a nitrification and reduction route. Such N/O dual-doped activated carbon owns a higher adsorption capacity of heavy-metal ions in an aqueous solution, which is applicable for wastewater remediation. We expect that this protocol will provide ideas for the rapid preparation of high-adsorptive carbon from biomass by time-saving, effective microwave pyrolysis and will be optimized in the future.

Activated carbon has unique adsorption properties, such as a developed porous structure, a high specific surface area, and various surface functional groups; therefore, it is employed as an adsorbent in water treatment or purification1,2,3,4. Besides its physical advantages, activated carbon is cost-effective and harmless to the environment, and its raw material (e.g., biomass) is abundant and easily obtained5,6. The physicochemical properties of activated carbon depend on the precursors that are used in its preparation and on the experimental conditions of the activation process7.
Two methods are typically used to prepare activated carbon: a one-step and a two-step approach8. The term one-step approach refers to precursors being carbonized and activated simultaneously while the two-step approach refers to that sequentially. In view of energy conservation and environmental protection, the one-step approach is more preferred for its lower temperature and pressure demanding.
Besides, chemical and physical activation are utilized to improve the textural properties of activated carbon. Chemical activation possesses apparent advantages over physical activation because of its lower activation temperature, shorter activation time, higher carbon yield, and more developed and controllable pore structure in a certain degree9. It has been tested that chemical activation can be performed by impregnating biomass used as feedstock with H3PO4, ZnCl2, or other specific chemicals, followed by pyrolysis to increase the porosity of the activated carbon, because lignocellulosic components of biomass can be easily removed by a subsequent heating treatment, owing to the dehydrogenation capability of these chemicals10,11. Hence, chemical activation greatly enhances the formation of activated carbon&#39;s pores or improves the adsorptive performance to contaminants12. An acidic activator is preferred to H3PO4, due to its relatively lower energy demand, higher yield, and less impact on the environment13.
Microwave pyrolysis has the superiority in time savings, uniform interior heating, energy-efficiency, and selective heating, making it an alternative heating method to synthesis-activated carbon14,15. Compared with conventional electric heating, microwave pyrolysis can enhance thermo-chemical processes and promote certain chemical reactions16. Recently, extensive studies have focused on preparing activated carbon by chemical activation from biomass using one-step microwave pyrolysis9,17,18,19. So, it is considerably informative and environment-friendly to synthesis biomass-based activated carbon by microwave-assisted H3PO4 activation.
In addition, to improve the adsorption affinities of activated carbon toward specific heavy-metal ions, modification by heteroatom [N, O, sulfur (S), etc.] doping into carbon structures has been proposed, and this has proven to be a desirable method20,21,22,23,24,25,26. Defective sites in or at the edges of a graphite layer can be replaced by heteroatoms to generate functional groups27. Hence, nitrification and reduction modification are used to modify resultant carbon samples to dope N/O functional groups which play a crucial role in efficiently coordinating with heavy metal to form complexing and ion-exchange28.
Based on the findings above, we present a protocol to synthesize N/O dual-doped mesoporous carbon from biomass by chemical activation and two different pyrolysis methods followed up by modification. This protocol also determines which heating method favors the ensuing modification for doping of the N/O functional groups and, thus, enhancing the adsorption performance.

<table><tbody><tr><td>All chemicals and reagents (phosphoric acid, etc.)</td><td>Nanjing Chemical Reagent Co., Ltd</td><td></td><td>Analytical grade</td></tr><tr><td>Electric furnace</td><td>Luoyang Bolaimaite Experiment Electric Furnace Co., Ltd</td><td></td><td></td></tr><tr><td>Microwave oven</td><td>Nanjing Yudian Automation Technology Co., Ltd</td><td></td><td>2.45 GHz frequency</td></tr><tr><td>Surface-area and porosimetry analyzer</td><td>Beijing Gold APP Instrument Co., Ltd</td><td></td><td>Vc-Sorb 2800TP</td></tr><tr><td>Fourier transform infrared (FTIR) spectrometer</td><td>Nicolet</td><td></td><td>6700</td></tr><tr><td>Flame atomic absorption spectrophotometry</td><td>Beijing Purkinje General Instrument Corporation</td><td></td><td>A3</td></tr><tr><td>Element Analyzer</td><td>Germany Heraeus Co.</td><td></td><td>CHN-O-RAPID&amp;nbsp;</td></tr></tbody></table>

preparation of biomass-based mesoporous carbon with higher nitrogen-/oxygen-chelating adsorption for cu(ii) through microwave pre-pyrolysis

An environment-friendly technique for synthesizing biomass-based mesoporous activated carbon with high nitrogen-/oxygen-chelating adsorption for Cu(II) is proposed. Bagasse impregnated with phosphoric acid is utilized as the precursor. To pyrolyze the precursor, two separate heating modes are used: microwave pyrolysis and conventional electric-heating pyrolysis. The resulting bagasse-derived carbon samples are modified with nitrification and reduction modification. Nitrogen (N)/oxygen (O) functional groups are simultaneously introduced to the surface of activated carbon, enhancing its adsorption of Cu(II) by complexing and ion-exchange. Characterization and copper adsorption experiments are performed to investigate the physicochemical properties of four prepared carbon samples and determine which heating method favors the subsequent modification for doping of N/O functional groups. In this technique, based on analyzing data of nitrogen adsorption, Fourier transform infrared spectroscopy, and batch adsorption experiments, it is proven that microwave-pyrolyzed carbon has more defect sites and, therefore, time-saving effective microwave pyrolysis contributes more N/O species to the carbon, although it leads to a lower specific surface area. This technique offers a promising route to synthesis adsorbents with higher nitrogen and oxygen content and a higher adsorption capacity of heavy-metal ions in wastewater remediation applications.

Nitrogen adsorption/desorption isotherms of four samples are presented in Figure 1. All adsorption isotherms show a rapid increase in low P/P0 region and these isotherms belong to type IV (IUPAC classification) demonstrating their pore structure that consists of micropores and dominant mesopores32.
The surface physical parameters for all samples obtained from the nitrogen adsorption isotherms are shown in Table 1. Microwave pyrolysis and modification both contribute to a smaller Brunauer-Emmett-Teller (BET) surface area and total pore volume, changing the physical morphology of the samples.
Fourier transform infrared (FTIR) spectra of the four samples are given in Figure 2. Bands of MBAC at 1167 cm-1 [carbon (C) - O stretching vibration], 1620 cm-1 (C = O stretching vibration), 2852 cm-1 [N - hydrogen (H) stretching vibration], 2922 cm-1 (C - H stretching vibration), and 3442 cm-1 (O - H stretching vibration) are more intense than EBAC. These may be attributed to the microwave pyrolysis contributing more oxygen functional groups to the BAC surface. For EBAC-N and MBAC-N, bands around 1573 cm-1 and 1400 cm-1 likely represent C = N and N - H groups, respectively. It can be found that the modified carbon materials have obtained distinct nitrogen/oxygen functional groups, and the microwave-pyrolyzed carbon gets more, which is in accordance with the elemental analysis as shown in Table 1. It can be speculated that microwave pyrolysis is more adequate to activate the precursor and lay root for further modifications than conventional electric-heating pyrolysis. MBAC-N possesses mainly hydroxyl, carboxyl, amino, and imine functional groups.
Figure 3 shows the adsorption capacity of the four samples under different pH conditions. The four adsorbents reach the optimal adsorption capacity at pH 5, so the following adsorption experiments are all carried out at pH 5. The samples prepared by microwave pyrolysis exhibited better Cu(II) adsorption capacity before and after the modification, although they had a lower specific surface area and pore volume. In general, the adsorbability of adsorbents depends on the pore structure and surface functional groups. Therefore, the high adsorption capacity of MBAC-N is attributed to more abundant N/O surface groups. The results confirm that the microwave pyrolysis benefits the follow-up introduction of surface functional groups to improve the adsorption capacity more than electric-heating pyrolysis.
The adsorption isotherms of MBAC-N on Cu(II) at 5 &#176;C, 25 &#176;C, and 45 &#176;C are shown in Figure 4a. The adsorption properties of samples for Cu(II) become better when the temperature increases. By comparing the isotherm parameters in Table 2, it is clear that the Langmuir isotherm model indicates a higher linear correlation coefficient (R2) which is over 0.99 (the fitting line in Figure 4b), and the measured adsorption capacity (q0mea) is identical with the calculated one (q0cal). Therefore, the model is more suitable than the Freundlich and Temkin isotherm models, which indicates that the absorption of Cu(II) is a chemical adsorption process33.
As shown in Figure 4c, MBAC-N can reach about 75% of Cu(II) equilibrium adsorption capacity within 15 min, and it can almost reach the adsorption equilibrium of Cu(II) in about 50 min at different initial concentrations. These prove that MBAC-N has excellent adsorption properties. As can be seen from Table 3, the pseudo-second-order model is better than the Lagergren and Elovich models with R2 = 0.999 (the fitting line in Figure 4d). The above results confirm that the adsorption of Cu(II) on MBAC-N is chemisorption. Hence, the chemical interaction mechanism of Cu(II) by the modified carbon is proposed in Figure 5. Table 4 compares the adsorption capacity of Cu(II) by biomass-based activated carbon reported in recent references34,35,36,37,38. It is found that MBAC-N has a higher adsorption capacity than other adsorbents reported in the literature, demonstrating it as a promising adsorbent for removing Cu(II).
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/58161/58161fig1.jpg" /> 
Figure 1: Nitrogen adsorption/desorption isotherms of carbons. The inset graph in Figure 1 shows the nitrogen adsorption/desorption isotherm of MBAC-N in a smaller ordinate range. The data were obtained from the supporting software of the surface-area and porosimetry analyzer. This figure has been modified from Wan and Li27. <a href="https://www.jove.com/files/ftp_upload/58161/58161fig1large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 2" class="xfigimg" src="/files/ftp_upload/58161/58161fig2.jpg" /> 
Figure 2: FTIR spectra of EBAC, EBAC-N, MBAC, and MBAC-N. The spectra can confirm the chemical compositions and surface functional groups of the samples. This figure has been modified from Wan and Li27. <a href="https://www.jove.com/files/ftp_upload/58161/58161fig2large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 3" class="xfigimg" src="/files/ftp_upload/58161/58161fig3.jpg" /> 
Figure 3: Effect of solution pH on Cu(II) adsorption. The concentration of copper in the solutions is 40 mg L-1. The test is conducted at 25 &#176;C and at 150 rpm for 24 h, to reach adsorption equilibrium. This figure has been modified from Wan and Li27. <a href="https://www.jove.com/files/ftp_upload/58161/58161fig3large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 4" class="xfigimg" src="/files/ftp_upload/58161/58161fig4.jpg" /> 
Figure 4: Representative adsorption property analysis of MBAC-N. (a) This panel shows the adsorption isotherms of Cu(II) on MBAC-N at 5 &#176;C, 25 &#176;C, and 45 &#176;C. (b) This panel shows the fitting result for copper adsorption by using the Langmuir isotherm. (c) This panel shows the kinetics of Cu(II) on MBAC-N at the initial concentrations of 30 mg L-1 and 100 mg L-1. (d) This panel shows the fitting result for copper adsorption at 25 &#176;C by using the Pseudo-second-order model. This figure has been modified from Wan and Li27. <a href="https://www.jove.com/files/ftp_upload/58161/58161fig4large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 5" class="xfigimg" src="/files/ftp_upload/58161/58161fig5.jpg" /> 
Figure 5: Proposed mechanism for Cu(II) adsorption by modified carbon. In this reaction process, the chemical adsorption mainly involves ion exchange and complexing. <a href="https://www.jove.com/files/ftp_upload/58161/58161fig5large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<table fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Adsorbents</td>
			<td>EBAC</td>
			<td>EBAC-N</td>
			<td>MBAC</td>
			<td>MBAC-N</td>
		</tr>
		<tr>
			<td>Pore structure parameters</td>
			<td></td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>BET surface area (m2 g&#8722;1)</td>
			<td>978</td>
			<td>609</td>
			<td>543</td>
			<td>61</td>
		</tr>
		<tr>
			<td>Total pore volume (cm3 g&#8722;1)</td>
			<td>1.22</td>
			<td>0.59</td>
			<td>0.68</td>
			<td>0.13</td>
		</tr>
		<tr>
			<td>Mesoporous volume (cm3 g&#8722;1)</td>
			<td>1.09</td>
			<td>0.47</td>
			<td>0.58</td>
			<td>0.11</td>
		</tr>
		<tr>
			<td>Mean pore size DP (nm)</td>
			<td>4.97</td>
			<td>3.84</td>
			<td>5.01</td>
			<td>8.89</td>
		</tr>
		<tr>
			<td>Mesoporous rate (%)</td>
			<td>89.52</td>
			<td>80.24</td>
			<td>85.32</td>
			<td>84.61</td>
		</tr>
		<tr>
			<td>Elemental content (wt%)</td>
			<td></td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>C</td>
			<td>92.23</td>
			<td>79.31</td>
			<td>87.28</td>
			<td>72.44</td>
		</tr>
		<tr>
			<td>H</td>
			<td>1.76</td>
			<td>1.26</td>
			<td>1.65</td>
			<td>1.12</td>
		</tr>
		<tr>
			<td>N</td>
			<td>0.08</td>
			<td>4.01</td>
			<td>0.58</td>
			<td>5.52</td>
		</tr>
		<tr>
			<td>O</td>
			<td>5.82</td>
			<td>15.15</td>
			<td>10.33</td>
			<td>20.54</td>
		</tr>
		<tr>
			<td>S</td>
			<td>0.11</td>
			<td>0.27</td>
			<td>0.16</td>
			<td>0.38</td>
		</tr>
		<tr>
			<td>Yield (%)</td>
			<td>53.35</td>
			<td>/</td>
			<td>57.23</td>
			<td>/</td>
		</tr>
	</tbody>
</table>
Table 1: Structural characteristics and elemental compositions of EBAC, EBAC-N, MBAC, and MBAC-N. The textural data are analyzed using the BET method. The relative weight percentage of the elements is calculated based on the dry ash-free basis. This table has been modified from Wan and Li27.
<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td></td>
			<td></td>
			<td colspan="3">MBAC-N</td>
		</tr>
		<tr>
			<td>Isotherm models</td>
			<td>Parameters</td>
			<td>5 &#176;C</td>
			<td>25 &#176;C</td>
			<td>45 &#176;C</td>
		</tr>
		<tr>
			<td rowspan="4">Langmuir&#160;</td>
			<td>q0cal (mg g&#8722;1)</td>
			<td>20.82</td>
			<td>24.09</td>
			<td>25.97</td>
		</tr>
		<tr>
			<td>q0mea (mg g&#8722;1)</td>
			<td>20.23</td>
			<td>23.47</td>
			<td>25.12</td>
		</tr>
		<tr>
			<td>b (L mg&#8722;1)</td>
			<td>0.73</td>
			<td>0.51</td>
			<td>0.49</td>
		</tr>
		<tr>
			<td>R2</td>
			<td>0.999</td>
			<td>0.996</td>
			<td>0.995</td>
		</tr>
		<tr>
			<td rowspan="3">Freundlich&#160;</td>
			<td>KF (L mg&#8722;1)</td>
			<td>8.802</td>
			<td>9.65</td>
			<td>10.56</td>
		</tr>
		<tr>
			<td>n</td>
			<td>3.937</td>
			<td>3.902</td>
			<td>4.032</td>
		</tr>
		<tr>
			<td>R2</td>
			<td>0.907</td>
			<td>0.967</td>
			<td>0.987</td>
		</tr>
		<tr>
			<td rowspan="3">Temkin&#160;</td>
			<td>AT (L mg&#8722;1)</td>
			<td>29.57</td>
			<td>32.3</td>
			<td>49.8</td>
		</tr>
		<tr>
			<td>B (L mg&#8722;1)</td>
			<td>2.94</td>
			<td>3.19</td>
			<td>3.16</td>
		</tr>
		<tr>
			<td>R2</td>
			<td>0.969</td>
			<td>0.985</td>
			<td>0.955</td>
		</tr>
	</tbody>
</table>
Table 2: Isotherm parameters of Cu(II) on MBAC-N at different temperatures. The fitted parameters are from linearized Langmuir, Freundlich, and Temkin adsorption models. This table has been modified from Wan and Li27.
<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td></td>
			<td></td>
			<td colspan="2">MBAC-N</td>
		</tr>
		<tr>
			<td>Kinetic models</td>
			<td>Parameters</td>
			<td>30 mg L&#8722;1</td>
			<td>100 mg L&#8722;1</td>
		</tr>
		<tr>
			<td rowspan="2">Lagergren&#160;</td>
			<td>k1 (min&#8722;1)</td>
			<td>0.037</td>
			<td>0.045</td>
		</tr>
		<tr>
			<td>R2</td>
			<td>0.714</td>
			<td>0.934</td>
		</tr>
		<tr>
			<td></td>
			<td>qe,mea (mg g&#8722;1)</td>
			<td>13.39</td>
			<td>22.69</td>
		</tr>
		<tr>
			<td>Pseudo-second-order</td>
			<td>qe,cal (mg g&#8722;1)</td>
			<td>13.44</td>
			<td>23.25</td>
		</tr>
		<tr>
			<td></td>
			<td>k2 (g (mg min)&#8722;1)</td>
			<td>0.08676</td>
			<td>0.03031</td>
		</tr>
		<tr>
			<td></td>
			<td>R2</td>
			<td>0.999</td>
			<td>0.999</td>
		</tr>
		<tr>
			<td></td>
			<td>qe,mea (mg g&#8722;1)</td>
			<td>13.39</td>
			<td>22.69</td>
		</tr>
		<tr>
			<td>Elovich&#160;</td>
			<td>&#945;E (g (mg min)&#8722;1)</td>
			<td>379.73</td>
			<td>312.25</td>
		</tr>
		<tr>
			<td></td>
			<td>&#946;E (mg g&#8722;1)</td>
			<td>0.738</td>
			<td>0.411</td>
		</tr>
		<tr>
			<td></td>
			<td>R2</td>
			<td>0.799</td>
			<td>0.901</td>
		</tr>
	</tbody>
</table>
Table 3: Kinetic parameters of Cu(II) on MBAC-N at different initial concentrations. The fitted parameters are from linearized Lagergren, Pseudo-second-order, and Elovich models. This table has been modified from Wan and Li27.
<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Adsorbents</td>
			<td>pH</td>
			<td>qe (mg g&#8722;1)</td>
			<td>References</td>
		</tr>
		<tr>
			<td>Wood-based granular activated carbon</td>
			<td>5.5</td>
			<td>6.016</td>
			<td>34</td>
		</tr>
		<tr>
			<td>Baobab fruit shell-derived activated carbon</td>
			<td>6</td>
			<td>3.0833</td>
			<td>35</td>
		</tr>
		<tr>
			<td>Olive stone AC (COSAC)</td>
			<td>5</td>
			<td>17.08</td>
			<td>36</td>
		</tr>
		<tr>
			<td>Activated carbonfrom date stones</td>
			<td>5.5</td>
			<td>18.68</td>
			<td>37</td>
		</tr>
		<tr>
			<td>Walnut shell based activated carbon</td>
			<td rowspan="2">5</td>
			<td>9.3</td>
			<td rowspan="2">38</td>
		</tr>
		<tr>
			<td>Plasma modified activated carbon</td>
			<td>21.4</td>
		</tr>
		<tr>
			<td>MBAC-N</td>
			<td>5</td>
			<td>25.12</td>
			<td>This study</td>
		</tr>
	</tbody>
</table>
Table 4: Comparison of the adsorption capacity of Cu(II) on different adsorbents. The ability of activated carbon to remove Cu(II) is significantly affected by the pH of the solution, so the adsorption capacity of the contrast biomass-based carbon materials should be obtained close to pH 5.

Watch this Scientific Journal Video about Preparation of Biomass-based Mesoporous Carbon with Higher Nitrogen-/Oxygen-chelating Adsorption for CuII Through Microwave Pre-Pyrolysis at JoVE.com

Preparation of Biomass-based Mesoporous Carbon with Higher Nitrogen-/Oxygen-chelating Adsorption for CuII Through Microwave Pre-Pyrolysis

Here, we present a protocol to synthesize nitrogen/oxygen dual-doped mesoporous carbon from biomass by chemical activation in different pyrolysis modes followed by modification. We demonstrate that the microwave pyrolysis benefits the subsequent modification process to simultaneously introduce more nitrogen and oxygen functional groups on the carbon.

Preparation of Biomass-based Mesoporous Carbon with Higher Nitrogen-/Oxygen-chelating Adsorption for Cu(II) Through Microwave Pre-Pyrolysis

An environment-friendly technique for synthesizing biomass-based mesoporous activated carbon with high nitrogen-/oxygen-chelating adsorption for Cu(II) is ...

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9.9K Views.  Nanjing Agricultural University. Here, we present a protocol to synthesize nitrogen/oxygen dual-doped mesoporous carbon from biomass by chemical activation in different pyrolysis modes followed by modification. We demonstrate that the microwave pyrolysis benefits the subsequent modification process to simultaneously introduce more nitrogen and oxygen functional groups on the carbon.

Video: Preparation of Biomass-based Mesoporous Carbon with Higher Nitrogen-/Oxygen-chelating Adsorption for CuII Through Microwave Pre-Pyrolysis

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Silica nanoparticles were prepared using acid-catalysis of a siloxane precursor and microwave-assisted synthetic techniques resulting in the controlled growth of nanomaterials ranging from 30-250 nm in diameter. The growth dynamics can be controlled by varying the initial silicic acid concentration, time of the reaction, and temperature of reaction.

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Plasma enhanced chemical vapor deposition (PECVD) of perfluoroalkanes has long been studied for tuning the wetting properties of surfaces. For high ...

Reverse Microemulsion-mediated Synthesis of Monometallic and Bimetallic Early Transition Metal Carbide and Nitride Nanoparticles

A reverse microemulsion is used to encapsulate monometallic or bimetallic early transition metal oxide nanoparticles in microporous silica shells. The silica-encapsulated metal oxide nanoparticles are then carburized in a methane/hydrogen atmosphere at temperatures over 800 &#176;C to form silica-encapsulated early transition metal carbide nanoparticles. During the carburization process, the silica shells prevent the sintering of adjacent carbide nanoparticles while also preventing the deposition of excess surface carbon. Alternatively, the silica-encapsulated metal oxide nanoparticles can be nitridized in an ammonia atmosphere at temperatures over 800 &#176;C to form silica-encapsulated early transition metal nitride nanoparticles. By adjusting the reverse microemulsion parameters, the thickness of the silica shells, and the carburization/nitridation conditions, the transition metal carbide or nitride nanoparticles can be tuned to various sizes, compositions, and crystal phases. After carburization or nitridation, the silica shells are then removed using either a room-temperature aqueous ammonium bifluoride solution or a 0.1 to 0.5 M NaOH solution at 40-60 &#176;C. While the silica shells are dissolving, a high surface area support, such as carbon black, can be added to these solutions to obtain supported early transition metal carbide or nitride nanoparticles. If no high surface area support is added, then the nanoparticles can be stored as a nanodispersion or centrifuged to obtain a nanopowder.

A &#8220;removable ceramic coating method&#8221; is presented in visual format for the synthesis of non-sintered and metal-terminated monometallic and bimetallic early transition metal carbide and nitride nanoparticles with tunable sizes and crystal structures.

A reverse microemulsion is used to encapsulate monometallic or bimetallic early transition metal oxide nanoparticles in microporous silica shells. The ...

Detection and Recovery of Palladium, Gold and Cobalt Metals from the Urban Mine Using Novel Sensors/Adsorbents Designated with Nanoscale Wagon-wheel-shaped Pores

Developing low-cost, efficient processes for recovering and recycling palladium, gold and cobalt metals from urban mine remains a significant challenge in industrialized countries. Here, the development of optical mesosensors/adsorbents (MSAs) for efficient recognition and selective recovery of Pd(II), Au(III), and Co(II) from urban mine was achieved. A simple, general method for preparing MSAs based on using high-order mesoporous monolithic scaffolds was described. Hierarchical cubic Ia3d wagon-wheel-shaped MSAs were fabricated by anchoring chelating agents (colorants) into three-dimensional pores and micrometric particle surfaces of the mesoporous monolithic scaffolds. Findings show, for the first time, evidence of controlled optical recognition of Pd(II), Au(III), and Co(II) ions and a highly selective system for recovery of Pd(II) ions (up to ~95%) in ores and industrial wastes. Furthermore, the controlled assessment processes described herein involve evaluation of intrinsic properties (e.g., visual signal change, long-term stability, adsorption efficiency, extraordinary sensitivity, selectivity, and reusability); thus, expensive, sophisticated instruments are not required. Results show evidence that MSAs will attract worldwide attention as a promising technological means of recovering and recycling palladium, gold and cobalt metals.

Because of the importance and extensive use of palladium, gold and cobalt metals in high-technology equipment, their recovery and recycling constitute an important industrial challenge. The metal recovery system described herein is a simple, low-cost means for the effective detection, removal, and recovery of these metals from the urban mine.

Developing low-cost, efficient processes for recovering and recycling palladium, gold and cobalt metals from urban mine remains a significant challenge in ...

Engineering

Synthesis and Testing of Supported Pt-Cu Solid Solution Nanoparticle Catalysts for Propane Dehydrogenation

A convenient method for the synthesis of bimetallic Pt-Cu catalysts and performance tests for propane dehydrogenation and characterization are demonstrated here. The catalyst forms a substitutional solid solution structure, with a small and uniform particle size around 2 nm. This is realized by careful control over the impregnation, calcination, and reduction steps during catalyst preparation and is identified by advanced in situ synchrotron techniques. The catalyst propane dehydrogenation performance continuously improves with increasing Cu:Pt atomic ratio.

A convenient method for the synthesis of 2 nm supported bimetallic nanoparticle Pt-Cu catalysts for propane dehydrogenation is reported here. In situ synchrotron X-ray techniques allow for the determination of the catalyst structure, which is typically unobtainable using laboratory instruments.

A convenient method for the synthesis of bimetallic Pt-Cu catalysts and performance tests for propane dehydrogenation and characterization are ...

Surface Properties of Synthesized Nanoporous Carbon and Silica Matrices

In this work, we report the synthesis and characterization of ordered nanoporous carbon material (also called ordered mesoporous carbon material [OMC]) with a 4.6 nm pore size, and ordered silica porous matrix, SBA-15, with a 5.3 nm pore size. This work describes the surface properties of nanoporous molecular sieves, their wettability, and the melting behavior of D2O confined in the differently ordered porous materials with similar pore sizes. For this purpose, OMC and SBA-15 with highly ordered nanoporous structures are synthesized via impregnation of the silica matrix by applying a carbon precursor and by the sol-gel method, respectively. The porous structure of investigated systems is characterized by an N2 adsorption-desorption analysis at 77 K. To determine the electrochemical character of the surface of synthesized materials, potentiometric titration measurements are conducted; the obtained results for OMC shows a significant pHpzc shift toward the higher values of pH, relative to SBA-15. This suggests that investigated OMC has surface properties related to oxygen-based functional groups. To describe the surface properties of the materials, the contact angles of liquids penetrating the studied porous beds are also determined. The capillary rise method has confirmed the increased wettability of the silica walls relative to the carbon walls and an influence of the pore roughness on the fluid/wall interactions, which is much more pronounced for silica than for carbon mesopores. We have also studied the melting behavior of D2O confined in OMC and SBA-15 by applying the dielectric method. The results show that the depression of the melting temperature of D2O in the pores of OMC is about 15 K higher relative to the depression of the melting temperature in SBA-15 pores with a comparable 5 nm size. This is caused by the influence of adsorbate/adsorbent interactions of the studied matrices.

Here we report the synthesis and characterization of ordered nanoporous carbon (with a 4.6 nm pore size) and SBA-15 (with a 5.3 nm pore size). The work describes the surface and textural properties of nanoporous molecular sieves, their wettability, and the melting behavior of D2O confined in the materials.

In this work, we report the synthesis and characterization of ordered nanoporous carbon material (also called ordered mesoporous carbon material [OMC]) ...

Reducing Willow Wood Fuel Emission by Low Temperature Microwave Assisted Hydrothermal Carbonization

Biomass is a sustainable fuel, as its CO2 emissions are reintegrated in biomass growth. However, the inorganic precursors in the biomass cause a negative environmental impact and slag formation. The selected short rotation coppice (SRC) willow wood has a high ash content (<img alt="Equation 1" src="/files/ftp_upload/58970/58970eq1.jpg" /> = 1.96%) and, therefore, a high content of emission and slag precursors. Therefore, the reduction of minerals from SRC willow wood by low temperature microwave assisted hydrothermal carbonization (MAHC) at 150 &#176;C, 170 &#176;C, and 185 &#176;C is investigated. An advantage of MAHC over conventional reactors is an even temperature conductance in the reaction medium, as microwaves penetrate the whole reactor volume. This allows a better temperature control and a faster cooldown. Therefore, a succession of depolymerization, transformation and repolymerization reactions can be analyzed effectively. In this study, the analysis of the mass loss, ash content and composition, heating values and molar O/C and H/C ratios of the treated and untreated SCR willow wood showed that the mineral content of the MAHC coal was reduced and the heating value increased. The process water showed a decreasing pH and contained furfural and 5-methylfurfural. A process temperature of 170 &#176;C showed the best combination of energy input and ash component reduction. The MAHC allows a better understanding of the hydrothermal carbonization process, while a large-scale industrial application is unlikely because of the high investment costs.

A protocol for the emission precursor depletion from low quality biomass by low temperature microwave assisted hydrothermal carbonization treatment is presented. This protocol includes the microwave parameters and the analysis of the biocoal product and process water.

Biomass is a sustainable fuel, as its CO2 emissions are reintegrated in biomass growth. However, the inorganic precursors in the biomass cause a negative ...

Tuning the Acidity of Pt/ CNTs Catalysts for Hydrodeoxygenation of Diphenyl Ether

We herein present a method for the synthesis of HNbWO6, HNbMoO6, HTaWO6 solid acid nanosheet modified Pt/CNTs. By varying the weight of various solid acid nanosheets, a series of Pt/xHMNO6/CNTs with different solid acid compositions (x = 5, 20 wt%; M = Nb, Ta; N = Mo, W) have been prepared by carbon nanotube pretreatment, protonic exchange, solid acid exfoliation, aggregation and finally Pt particles impregnation. The Pt/xHMNO6/CNTs are characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy and NH3-temperature programmed desorption. The study revealed that HNbWO6 nanosheets were attached on CNTs, with some edges of the nanosheets being bent in shape. The acid strength of the supported Pt catalysts increases in the following order: Pt/CNTs &#60; Pt/5HNbWO6/CNTs &#60; Pt/20HNbMoO6/CNTs &#60; Pt/20HNbWO6/CNTs &#60; Pt/20HTaWO6/CNTs. In addition, the catalytic hydroconversion of lignin-derived model compound: diphenyl ether using the synthesized Pt/20HNbWO6 catalyst has been investigated.

A protocol for the synthesis of HNbWO6, HNbMoO6, HTaWO6 solid acid nanosheet modified Pt/CNTs is presented.

We herein present a method for the synthesis of HNbWO6, HNbMoO6, HTaWO6 solid acid nanosheet modified Pt/CNTs. By varying the weight of various solid acid ...

Preparation of Expanded Chitin Foams and their Use in the Removal of Aqueous Copper

Chitin is an underexploited, naturally abundant, mechanically robust, and chemically resistant biopolymer. These qualities are desirable in an adsorbent, but chitin lacks the necessary specific surface area, and its modification involves specialized techniques and equipment. Herein is described a novel chemical procedure for expanding chitin flakes, derived from shrimp shell waste, into foams with higher surface area. The process relies on the evolution of H2 gas from the reaction of water with NaH trapped in a chitin gel. The preparation method requires no specialized equipment. Powder X-ray diffraction and N2-physisorption indicate that the crystallite size decreases from 6.6 nm to 4.4 nm and the specific surface area increases from 12.6 &#177; 2.1 m2/g to 73.9 &#177; 0.2 m2/g. However, infrared spectroscopy and thermogravimetric analysis indicate that the process does not change the chemical identity of the chitin. The specific Cu adsorption capacity of the expanded chitin increases in proportion to specific surface area from 13.8 &#177; 2.9 mg/g to 73.1 &#177; 2.0 mg/g. However, the Cu adsorption capacity as a surface density remains relatively constant at an average of 10.1 &#177; 0.8 atom/nm2, which again suggests no change in the chemical identity of the chitin. This method offers the means to transform chitin into a higher surface area material without sacrificing its desirable properties. Although the chitin foam is described here as an adsorbent, it can be envisioned as a catalyst support, thermal insulator, and structural material.

This study describes a method to expand chitin into a foam by chemical techniques that require no specialized equipment.

Chitin is an underexploited, naturally abundant, mechanically robust, and chemically resistant biopolymer. These qualities are desirable in an adsorbent, ...

Synthesis of Metal Nanoparticles Supported on Carbon Nanotube with Doped Co and N Atoms and its Catalytic Applications in Hydrogen Production

A method for facile synthesis of nanostructured catalysts supported on carbon nanotubes with atomically dispersed cobalt and nitrogen dopant is presented herein. The novel strategy is based on a facile one-pot pyrolysis treatment of cobalt (II) acetylacetonate and nitrogen-rich organic precursors under Ar atmosphere at 800 &#176;C, resulting in the formation of Co- and N- co-doped carbon nanotube with earthworm-like morphology. The obtained catalyst was found to have a high density of defect sites, as confirmed by Raman spectroscopy. Here, cobalt (II) nanoparticles were stabilized on the atomically dispersed cobalt- and nitrogen-doped carbon nanotubes. The catalyst was confirmed to be effective in the catalytic hydrolysis of ammonia borane, in which the turnover frequency was 5.87 mol H2&#183;molCo-1&#183;min-1, and the specific hydrogen generation rate was determined to be 2447 mL H2&#183;gCo-1&#183;min-1. A synergistic function between the Co nanoparticle and the doped carbon nanotubes was proposed for the first time in the catalytic hydrolysis of ammonia borane reaction under a mild condition. The resulting hydrogen production with its high energy density and minimal refueling time could be suitable for future development as energy sources for mobile and stationary applications such as road trucks and forklifts in transport and logistics.

Here, we present a protocol to synthesize Co nanoparticles supported on carbon nanotubes with Co- and N- dopants for hydrogen productions.

A method for facile synthesis of nanostructured catalysts supported on carbon nanotubes with atomically dispersed cobalt and nitrogen dopant is presented ...