The research was sponsored by the Combat Capabilities Development Command Army Research Laboratory (Cooperative Agreement Number W911NF-15-2-0020). Any opinions, findings and conclusions, or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the Army Research Lab.
We thank the Center for Advanced Materials Processing (CAMP) at Montana Technological University for the use of some of the specialized equipment required in this study. We also thank Gary Wyss, Nancy Oyer, Rick LaDouceur, John Kirtley, and Katherine Zodrow for the technical assistance and helpful discussions.

1. Preparation of expanded chitin
<ol>
	<li>Prepare a 250 mL solution of 5 wt% LiCl in dimethylacetamide (DMAc) 
	CAUTION: The solvent DMAc is a combustible irritant that may damage fertility and cause birth defects. Handle DMAc in a fume hood using chemical resistant gloves and goggles to avoid contact with skin and eyes.
	<ol>
		<li>Add 15 g of LiCl and 285 g (268 mL) of DMAc into a 500 mL Erlenmeyer flask with, then place a 50 mm Polytetrafluoroethylene (PTFE)-lined magnetic stir bar.</li>
		<li>Cap the flask with a rubber septum and place it on a heating stir plate. Place a temperature probe through the septum into the mixture. Stir the mixture at 400 rpm and 80 &#176;C until all LiCl is dissolved (~ 4 h)</li>
	</ol>
	</li>
	<li>Dissolve 1.0 g of oven-dried chitin flakes in the LiCl/DMAc solution to form a sol-gel
	<ol>
		<li>Dry at least 1.2 g of chitin flakes in an oven at 80&#176;C for 24 h.</li>
		<li>Add 1.0 g of oven-dried chitin flakes and 250 mL of 5 wt% LiCl/DMAc solution into a 500 mL round bottom flask. Place a 50 mm PTFE-lined magnetic stir bar.</li>
		<li>Cap the flask with a rubber septum and place it on a stirring heat block. Pierce the septum with a needle and leave it to allow the flask to vent. Heat the block to 80 &#176;C and stir the mixture at 400 rpm until all the chitin is dissolved (24-48 h).</li>
		<li>Allow the resultant chitin sol-gel to cool down to room temperature slowly while continuing to stir (~ 1 h).</li>
		<li>Once at room temperature, place the flask containing the chitin sol-gel in an ice bath and continue stirring until its temperature stabilizes (~ 20 min).</li>
	</ol>
	</li>
	<li>Prepare a 100 mL slurry of NaH in DMAc. 
	CAUTION: NaH in contact with water releases flammable gases which may ignite spontaneously. To limit contact with moist air, NaH is stored in mineral oil which must be washed off before use. Handle with caution in a fume hood using chemical resistant gloves and goggles.
	<ol>
		<li>Remove approximately 1 g of NaH from its mineral oil storage and wash three times with 10 mL of hexanes.</li>
		<li>Add 100 mL of DMAC into a 250 mL Erlenmeyer flask, then add 0.82 g of the washed NaH and place a PTFE-lined magnetic stir bar.</li>
		<li>Swirl the mixture to produce a NaH/DMAc slurry. 
		NOTE: NaH will not completely dissolve.</li>
	</ol>
	</li>
	<li>Form the chitin gel by adding all the NaH/DMAc slurry to the chitin sol-gel.
	<ol>
		<li>Uncap the cooled sol-gel and add all the NaH slurry while stirring vigorously. Replace the cap and continue to stir the mixture at 400 rpm for 72 h or until a gel forms in the flask.</li>
	</ol>
	</li>
	<li>Form the chitin foam by adding water to the chitin gel.
	<ol>
		<li>After the formation of the gel, uncap the flask and add 100 mL of Deionized (DI) water. 
		NOTE: It is critical to perform this step in a fume hood as the process will evolve H2 gas.</li>
	</ol>
	</li>
	<li>Isolate, and wash the chitin foam in water and methanol to remove DMAc and salts.
	<ol>
		<li>Remove the expanded chitin foam from the flask and place in a crystallization dish or beaker sufficiently large to hold it and 1000 mL of DI water. 
		&#8203;NOTE: The chitin foam will not come out in one piece and may have to be broken up.</li>
		<li>Rinse the isolated gel three times with 500 mL of DI water. Soak the gel in 1000 mL of DI water for 24 h, then in 500 mL of methanol for 24 h, and finally in 1000 mL of DI water for 24 h again.</li>
		<li>Remove the expanded chitin foam from the water wash and allow to air dry for 24-48 h.</li>
	</ol>
	</li>
	<li>Dry the washed chitin gel to form a solid foam and then grind to a powder.
	<ol>
		<li>Dry the gel in the oven at 85 &#176;C for 48 h under ambient air, or in a lyophilizer at -43 &#176;C and 0.024 mbar for 48 h.</li>
		<li>Using a mortar and pestle, grind the dry chitin foam into a fine powder.</li>
	</ol>
	</li>
</ol>
<img alt="Figure 2" class="xfigimg" src="/files/ftp_upload/62301/62301fig02.jpg" /> 
Figure 2. Preparation of expanded chitin foam. (A) The initial chitin in LiCl/DMAc solution. (B) The addition of the NaH/DMAc slurry. (C) The chitin foam after addition of water. (D) The chitin foam as extracted from the reaction flask. (E) The chitin foam during washing with water. <a href="https://www.jove.com/files/ftp_upload/62301/62301fig02large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
2. Development of the adsorption isotherms
<ol>
	<li>Prepare 500 mL stock solutions of aq. Cu2+ (MW 63.5 g/mol) at concentrations 50 mg/L, 100 mg/L, 200 mg/L, 300 mg/L, 400 mg/L, and 450 mg/L. To do this, add 90 mg, 180 mg, 360 mg, 540 mg, 720 mg, and 810 mg of Cu(NO3)2&#903; 2.5 H2O (MW 232.6 g/mol) to six containers, respectively. Add 500 mL of 18 M&#937; water, cap the container, and shake to dissolve the solids.</li>
	<li>Add 50 mg of chitin to 100 mL of each stock solution, adjust the pH to 7, and allow to equilibrate for 48 h.
	<ol>
		<li>Transfer 100 mL of each stock solution to a 100 mL container so the headspace is minimal. Add 50 mg of ground chitin to each container and then cap them.</li>
		<li>Place containers on an orbital shaker and shake at 60 rpm for 30 min. Then take containers off the orbital shaker and adjust the pH to 7 using NH4HCO3 or HNO3.</li>
		<li>Replace containers back on the orbital shaker and shake at 60 rpm and at a constant temperature for 48 h. Maintain the laboratory at 18 &#177; 2 &#176;C throughout.</li>
	</ol>
	</li>
	<li>Measure the Cu concentration of the initial stock solutions and of those to which chitin was added. Use the colorimetric bicinchoninate method, a colorimeter, and pre-measured reagent packets27.
	<ol>
		<li>Remove containers from the orbital shaker, allow the mixtures to settle for a minimum of 30 min, and then take a 1 mL aliquot with a syringe fitted with a 0.3 &#181;m glass microfiber filter.</li>
		<li>Transfer the aliquot to a 250 mL container and dilute to 100 mL with 18 M&#937; water. 
		&#8203;NOTE: This step is necessary due to the low ceiling of detection of Cu (5 mg/L) by the bicinchoninate method using the colorimeter.</li>
		<li>Transfer 10 mL of the diluted sample to a cuvette. Place the cuvette in the colorimeter and zero the instrument.</li>
		<li>Add one packet of premeasured Cu reagent (bicinchoninate method) to the diluted sample in the cuvette and wait 45 s for the chelation reaction to complete. Allow the solution to become purple. The intensity of the color formed is proportional to the Cu concentration.</li>
		<li>Place the cuvette back in the colorimeter and measure the Cu concentration of the diluted sample. Multiply the concentration of the diluted sample by 100 to obtain that of the original sample.</li>
	</ol>
	</li>
	<li>Extract the maximum Cu uptake from the adsorption isotherm data.
	<ol>
		<li>Calculate the uptake of each sample for each equilibrium Cu concentration using the equation28: 
		<img alt="Equation 1" src="/files/ftp_upload/62301/62301eq01.jpg" /></li>
		<li>Plot the adsorption uptake versus equilibrium concentration of the samples to produce a standard Cu adsorption isotherm.</li>
		<li>Plot the ratio of equilibrium concentration to uptake versus the equilibrium concentration to produce the linearized Cu adsorption isotherm. 
		NOTE: The plot should be linear, and the inverse of the slope represents the maximum Cu uptake.</li>
	</ol>
	</li>
</ol>

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The authors have nothing to disclose.

The proposed method for chitin foam fabrication allows for the production of such foams without the need for specialized equipment or techniques. Production of the chitin foam relies on the suspension of sodium hydride within a chitin sol-gel. Contact with water from the atmosphere induces gelling of the chitin matrix and evolution of hydrogen gas by decomposition of the sodium hydride. Therefore, the critical steps of the preparation are (1) formation of the sol-gel, (2) introduction of the sodium hydride in anhydrous c...

Chitin is a mechanically robust and chemically inert biopolymer, second only to cellulose in natural abundance1. It is the major component in the exoskeleton of arthropods and in the cell walls of fungi and yeast2. Chitin is similar to cellulose, but with one hydroxyl group of each monomer replaced with an acetyl amine group (Figure 1A,B). This difference increases the strength of hydrogen bonding between adjacent polymer chains and gives chitin its characteristic structural resilience and chemical inertness2,3. Due to its properties and abundance, chitin has attracted significant industrial and academic interest. It has been studied as a scaffold for tissue growth4,5,6, as a component in composite materials7,8,9,10,11, and as a support for adsorbents and catalysts11,12,13,14. Its chemical stability, in particular, makes chitin attractive for adsorption applications that involve conditions inhospitable to common adsorbents14. In addition, the abundance of amine groups make chitin an effective adsorbent for metal ions15. However, the protonation of the amine groups under acidic conditions reduces the metal adsorption capacity of chitin16. A successful strategy is to introduce adsorption sites more resistant to protonation17,18. Instead, herein is described a simple method to increase the specific surface area and, therefore, the number of adsorption sites in chitin.
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/62301/62301fig01.jpg" /> 
Figure 1. Chemical structure. (A) cellulose, (B) chitin, (C) chitosan. <a href="https://www.jove.com/files/ftp_upload/62301/62301fig01large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
In spite of its many potential uses, chitin is underutilized. Chitin processing is challenging due to its low solubility in most solvents. A key limitation to its use in catalysis and adsorption is its low specific surface area. While typical carbon and metal oxide supports have specific surface areas in the order 102-103 m2/g, commercial chitin flakes have surface areas in the order of 10 m2/g19,20,21. Methods to expand chitin into foams exist, but they invariably rely on high temperature and pressure, strong acids and bases, or specialized equipment that represent a significant entry barrier5,21,22,23,24,25. In addition, these methods tend to deacetylate chitin to form chitosan (Figure 1C)-a more soluble and reactive biopolymer5,25,26.
Herein, a method is described to expand chitin into solid foams, increase its specific surface area and adsorption capacity, and maintain its chemical integrity. The method relies on the rapid evolution of gas from within a chitin gel and requires no specialized equipment. The increased adsorption capacity of the expanded chitin is demonstrated with aqueous Cu2+-a common contaminant in the local groundwater26.
<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td></td>
			<td>Unit</td>
			<td>Neat Flake</td>
			<td>Baked Foam</td>
			<td>Lyophilised Foam</td>
		</tr>
		<tr>
			<td>Crystallinity</td>
			<td>%</td>
			<td>88</td>
			<td>74</td>
			<td>58</td>
		</tr>
		<tr>
			<td>Crystal size</td>
			<td>nm</td>
			<td>6.5</td>
			<td>4.4</td>
			<td>4.4</td>
		</tr>
		<tr>
			<td>Surface Area</td>
			<td>m2/g</td>
			<td>12.6 &#177; 2.1</td>
			<td>43.1 &#177; 0.2</td>
			<td>73.9 &#177; 0.2</td>
		</tr>
		<tr>
			<td>Cu Uptake</td>
			<td>mg/g</td>
			<td>13.8 &#177; 2.9</td>
			<td>48.6 &#177; 1.9</td>
			<td>73.1 &#177; 2.0</td>
		</tr>
		<tr>
			<td>Cu Uptake</td>
			<td>atom/nm2</td>
			<td>10.5 &#177; 2.8</td>
			<td>10.7 &#177; 0.4</td>
			<td>9.4 &#177; 0.3</td>
		</tr>
	</tbody>
</table>
Table 1. Summary of material properties. Chitin foams have lower crystallinity and crystal size relative to neat chitin flakes. However, the specific surface area and Cu uptake of the chitin foams are proportionally higher than that of the neat chitin flakes.

<table><tbody><tr><td>Ammonium bicarbonate</td><td>Sigma-Aldrich</td><td>9830</td><td>NH4HCO3, &amp;ge;99.5 %</td></tr><tr><td>Chitin</td><td>Sigma-Aldrich</td><td>C7170</td><td>Pandalus borealis, practical grade</td></tr><tr><td>Colorimeter</td><td>Hanna Instruments</td><td>HI83399-01</td><td>Photometer for wastewater analysis</td></tr><tr><td>Copper High Range Checker</td><td>Hanna Instruments</td><td>HI702</td><td>Bicinchoninate colorimetric titration</td></tr><tr><td>Copper nitrate hydrate&amp;nbsp;</td><td>Sigma-Aldrich</td><td>223395</td><td>Cu(NO3)2 &amp;middot; 2.5 H2O, 98 %</td></tr><tr><td>Dimethylacetamide (DMAc)</td><td>Sigma-Aldrich</td><td>271012</td><td>Anhydrous, 99.8 %</td></tr><tr><td>IR Spectrophotometer</td><td>Thermo Nicolet</td><td>Nexus 670</td><td>Fitted with an ATR cell</td></tr><tr><td>Lithium chloride</td><td>Sigma-Aldrich</td><td>310468</td><td>LiCl, &amp;ge;99 %</td></tr><tr><td>N2 Physisorption Apparatus</td><td>Micromeritics</td><td>Tristar II</td><td></td></tr><tr><td>Nitric acid</td><td>BDH</td><td>BDH7208-1</td><td>HNO3, 0.1 N</td></tr><tr><td>Scanning electron microscope</td><td>Zeiss LEO</td><td>1430 VP</td><td>15 kV, secondary electron detector, 29-31 mm working distance</td></tr><tr><td>Sodium hydride</td><td>Sigma-Aldrich</td><td>223441</td><td>NaH, packed in mineral oil, 90 %</td></tr><tr><td>Thermogravimetric analyzer</td><td>TA Instruments</td><td>Q500</td><td>100 ml/min N2, 10 &amp;deg;C/min to 800 &amp;deg;C</td></tr><tr><td>Water Purification System</td><td>Millipore</td><td>Milli-Q</td><td>Type A water (18 M&amp;Omega;)</td></tr><tr><td>X-Ray Diffractometer</td><td>Rigaku</td><td>Ultima IV</td><td>Cu K-&amp;alpha; radiation, 8.04 keV</td></tr></tbody></table>

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.

Expanded chitin shows the same morphology regardless of the drying method. Figure 3 shows images of neat chitin flakes (Figure 3A1), oven-dried expanded chitin (Figure 3B1), and lyophilized expanded chitin (Figure&#160;3C3). While the neat flakes have the appearance of coarse sand, the expanded chitin foam has the appearance of a kernel of popped corn. Scanning electron micrographs show a similar ch...

Watch this Scientific Journal Video about Preparation of Expanded Chitin Foams and their Use in the Removal of Aqueous Copper at JoVE.com

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

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, ...

preparation-expanded-chitin-foams-their-use-removal-aqueous

Research

JoVE Journal

Chemistry

3.6K Views.  Montana Technological University. Dit protocol maakt de nieuwe fysieke transformatie van chitine mogelijk, een afvalmateriaal met een hoog volume, dat notoir moeilijk is om mee te werken. Het belangrijkste voordeel van deze techniek is de eenvoud van de verwerkingsmethodologie. Omdat het geen gespecialiseerde materialen vereist.Alleen de basisuitrusting die vaak wordt aangetroffen in chemische laboratoria. We hebben deze methode gedemonstreerd met chitine, maar deze techniek kan worden aangepast om uitgebreide versies ...

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

Preparation of Hydrophobic Metal-Organic Frameworks via Plasma Enhanced Chemical Vapor Deposition of Perfluoroalkanes for the Removal of Ammonia

Plasma enhanced chemical vapor deposition (PECVD) of perfluoroalkanes has long been studied for tuning the wetting properties of surfaces. For high surface area microporous materials, such as metal-organic frameworks (MOFs), unique challenges present themselves for PECVD treatments. Herein the protocol for development of a MOF that was previously unstable to humid conditions is presented. The protocol describes the synthesis of Cu-BTC (also known as HKUST-1), the treatment of Cu-BTC with PECVD of perfluoroalkanes, the aging of materials under humid conditions, and the subsequent ammonia microbreakthrough experiments on milligram quantities of microporous materials. Cu-BTC has an extremely high surface area (~1,800 m2/g) when compared to most materials or surfaces that have been previously treated by PECVD methods. Parameters such as chamber pressure and treatment time are extremely important to ensure the perfluoroalkane plasma penetrates to and reacts with the inner MOF surfaces. Furthermore, the protocol for ammonia microbreakthrough experiments set forth here can be utilized for a variety of test gases and microporous materials.

Herein the procedures for plasma enhanced chemical vapor deposition of perfluoroalkanes on microporous materials such as metal-organic frameworks to enhance their stability and hydrophobicity are described. Furthermore, breakthrough testing of milligram quantities of samples is described in detail.

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

Casting Protocols for the Production of Open Cell Aluminum Foams by the Replication Technique and the Effect on Porosity

Metal foams are interesting materials from both a fundamental understanding and practical applications point of view. Uses have been proposed, and in many cases validated experimentally, for light weight or impact energy absorbing structures, as high surface area heat exchangers or electrodes, as implants to the body, and many more. Although great progress has been made in understanding their structure-properties relationships, the large number of different processing techniques, each producing material with different characteristics and structure, means that understanding of the individual effects of all aspects of structure is not complete. The replication process, where molten metal is infiltrated between grains of a removable preform material, allows a markedly high degree of control and has been used to good effect to elucidate some of these relationships. Nevertheless, the process has many steps that are dependent on individual &#8220;know-how&#8221;, and this paper aims to provide a detailed description of all stages of one embodiment of this processing method, using materials and equipment that would be relatively easy to set up in a research environment. The goal of this protocol and its variants is to produce metal foams in an effective and simple way, giving the possibility to tailor the outcome of the samples by modifying certain steps within the process. By following this, open cell aluminum foams with pore sizes of 1&#8211;2.36 mm diameter and 61% to 77% porosity can be obtained.

Replication is one of the processing techniques used for the production of porous metal sponges. In this paper one implementation of the method for the production of open celled porous aluminum is shown in detail.

Metal foams are interesting materials from both a fundamental understanding and practical applications point of view. Uses have been proposed, and in many ...

Engineering

Layer-by-layer Synthesis and Transfer of Freestanding Conjugated Microporous Polymer Nanomembranes

CMP as large surface area materials have attracted growing interest recently, due to their high variability in the incorporation of functional groups in combination with their outstanding thermal and chemical stability, and low densities. However, their insoluble nature causes problems in their processing since usually applied techniques such as spin coating are not available. Especially for membrane applications, where the processing of CMP as thin films is desirable, the processing problems have hindered their commercial application.
Here we describe the interfacial synthesis of CMP thin films on functionalized substrates via molecular layer-by-layer (l-b-l) synthesis. This process allows the preparation of films with desired thickness and composition and even desired composition gradients.
The use of sacrificial supports allows the preparation of freestanding membranes by dissolution of the support after the synthesis. To handle such ultra-thin freestanding membranes the protection with sacrificial coatings showed great promise, to avoid rupture of the nanomembranes. To transfer the nanomembranes to the desired substrate, the coated membranes are upfloated at the air-liquid interface and then transferred via dip coating.

In this paper we describe the interfacial synthesis of conjugated microporous polymers (CMP) on sacrificial substrates, and the dissolution of the substrate for the preparation of freestanding CMP nanomembranes. In addition, we will describe how the fragile nanomembranes can be transferred to other substrates.

CMP as large surface area materials have attracted growing interest recently, due to their high variability in the incorporation of functional groups in ...

Capillary Electrophoresis to Monitor Peptide Grafting onto Chitosan Films in Real Time

Free-solution capillary electrophoresis (CE) separates analytes, generally charged compounds in solution through the application of an electric field. Compared to other analytical separation techniques, such as chromatography, CE is cheap, robust and effectively requires no sample preparation (for a number of complex natural matrices or polymeric samples). CE is fast and can be used to follow the evolution of mixtures in real time (e.g., chemical reaction kinetics), as the signals observed for the separated compounds are directly proportional to their quantity in solution.
Here, the efficiency of CE is demonstrated for monitoring the covalent grafting of peptides onto chitosan films for subsequent biomedical applications. Chitosan&#39;s antimicrobial and biocompatible properties make it an attractive material for biomedical applications such as cell growth substrates. Covalently grafting the peptide RGDS (arginine - glycine - aspartic acid - serine) onto the surface of chitosan films aims at improving cell attachment. Historically, chromatography and amino acid analysis have been used to provide a direct measurement of the amount of grafted peptide. However, the fast separation and absence of sample preparation provided by CE enables equally accurate yet real-time monitoring of the peptide grafting process. CE is able to separate and quantify the different components of the reaction mixture: the (non-grafted) peptide and the chemical coupling agents. In this way the use of CE results in improved films for downstream applications.
The chitosan films were characterized through solid-state NMR (nuclear magnetic resonance) spectroscopy. This technique is more time-consuming and cannot be applied in real time, but yields a direct measurement of the peptide and thus validates the CE technique.

Free solution capillary electrophoresis is a fast, cheap and robust analytical method that enables the quantitative monitoring of chemical reactions in real time. Its utility for rapid, convenient and precise analysis is demonstrated here through analysis of covalent peptide grafting onto chitosan films for improved cell adhesion.

Free-solution capillary electrophoresis (CE) separates analytes, generally charged compounds in solution through the application of an electric field. ...

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.

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.

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

Environment

Fabrication and Testing of Catalytic Aerogels Prepared Via Rapid Supercritical Extraction

Protocols for preparing and testing catalytic aerogels by incorporating metal species into silica and alumina aerogel platforms are presented. Three preparation methods are described: (a) the incorporation of metal salts into silica or alumina wet gels using an impregnation method; (b) the incorporation of metal salts into alumina wet gels using a co-precursor method; and (c) the addition of metal nanoparticles directly into a silica aerogel precursor mixture. The methods utilize a hydraulic hot press, which allows for rapid (&#60;6 h) supercritical extraction and results in aerogels of low density (0.10 g/mL) and high surface area (200-800 m2/g). While the work presented here focuses on the use of copper salts and copper nanoparticles, the approach can be implemented using other metal salts and nanoparticles. A protocol for testing the three-way catalytic ability of these aerogels for automotive pollution mitigation is also presented. This technique uses custom-built equipment, the Union Catalytic Testbed (UCAT), in which a simulated exhaust mixture is passed over an aerogel sample at a controlled temperature and flow rate. The system is capable of measuring the ability of the catalytic aerogels, under both oxidizing and reducing conditions, to convert CO, NO and unburned hydrocarbons (HCs) to less harmful species (CO2, H2O and N2). Example catalytic results are presented for the aerogels described.

Here we present protocols for preparing and testing catalytic aerogels by incorporating metal species into silica and alumina aerogel platforms. Methods for preparing materials using copper salts and copper-containing nanoparticles are featured. Catalytic testing protocols demonstrate the effectiveness of these aerogels for three-way catalysis applications.

Protocols for preparing and testing catalytic aerogels by incorporating metal species into silica and alumina aerogel platforms are presented. Three ...

Electrophoretic Crystallization of Ultrathin High-performance Metal-organic Framework Membranes

We report the synthesis of thin, highly intergrown, polycrystalline metal-organic framework (MOF) membranes on a wide range of unmodified porous and non-porous supports (polymer, ceramic, metal, carbon, and graphene). We developed a novel crystallization technique, which is termed the ENACT approach: the electrophoretic nuclei assembly for the crystallization of highly intergrown thin films (ENACT). This approach allows for a high density of heterogeneous nucleation of MOFs on a chosen substrate via the electrophoretic deposition (EPD) directly from the precursor sol. The growth of well-packed MOF nuclei leads to a highly intergrown polycrystalline MOF film. We show that this simple approach can be used for the synthesis of thin, intergrown zeolite imidazole framework (ZIF)-7 and ZIF-8 films. The resulting 500 nm-thick ZIF-8 membranes show a considerably high H2 permeance (8.3 x 10-6 mol m-2 s-1 Pa-1) and ideal gas selectivities (7.3 for H2/CO2, 15.5 for H2/N2, 16.2 for H2/CH4, and 2655 for H2/C3H8). An attractive performance for C3H6/C3H8 separation is also achieved (a C3H6 permeance of 9.9 x 10-8 mol m-2 s-1 Pa-1 and a C3H6/C3H8 ideal selectivity of 31.6 at 25 &#176;C). Overall, the ENACT process, owing to its simplicity, can be extended to synthesize intergrown thin films of a wide range of nanoporous crystalline materials.

A simple, reproducible, and versatile approach for the synthesis of intergrown, polycrystalline metal-organic framework membranes on a wide range of unmodified porous and non-porous supports is presented.

We report the synthesis of thin, highly intergrown, polycrystalline metal-organic framework (MOF) membranes on a wide range of unmodified porous and ...

Accumulation and Analysis of Cuprous Ions in a Copper Sulfate Plating Solution

Knowledge of the behavior of cuprous ions (monovalent copper ion: Cu(I)) in a copper sulfate plating bath is important for improving the plating process. We successfully developed a method to quantitatively and easily measure Cu(I) in a plating solution and used it for evaluation of the solution. In this paper, a quantitative absorption spectrum measurement and a time-resolved injection measurement of Cu(I) concentrations by a color reaction are described. This procedure is effective as a method to reproduce and elucidate the phenomenon occurring in the plating bath in the laboratory. First, the formation and accumulation process of Cu(I) in solution by electrolysis of a plating solution is shown. The amount of Cu(I) in the solution is increased by electrolysis at higher current values &#8203;&#8203;than the usual plating process. For the determination of Cu(I), BCS (bathocuproinedisulfonic acid, disodium salt), a reagent that selectively reacts with Cu(I), is used. The concentration of Cu(I) can be calculated from the absorbance of the Cu(I)-BCS complex. Next, the time measurement of the color reaction is described. The color reaction curve of Cu(I) and BCS measured by the injection method can be decomposed into an instantaneous component and a delay component. By analysis of these components, the holding structure of Cu(I) can be clarified, and this information is important when predicting the quality of the plating film to be produced. This method is used to facilitate the evaluation of the plating bath in the production line.

Here, accumulation of cuprous ions in a copper sulfate plating solution in a model experiment and an analysis based on quantitative measurements are described. This experiment reproduces the accumulation process of cuprous ions in the plating bath.

Knowledge of the behavior of cuprous ions (monovalent copper ion: Cu(I)) in a copper sulfate plating bath is important for improving the plating process. ...

Synthesis of Biocompatible Liquid Crystal Elastomer Foams as Cell Scaffolds for 3D Spatial Cell Cultures

Here, we present a step-by-step preparation of a 3D, biodegradable, foam-like cell scaffold. These scaffolds were prepared by cross-linking star block co-polymers featuring cholesterol units as side-chain pendant groups, resulting in smectic-A (SmA) liquid crystal elastomers (LCEs). Foam-like scaffolds, prepared using metal templates, feature interconnected microchannels, making them suitable as 3D cell culture scaffolds. The combined properties of the regular structure of the metal foam and of the elastomer result in a 3D cell scaffold that promotes not only higher cell proliferation compared to conventional porous templated films, but also better management of mass transport (i.e., nutrients, gases, waste, etc.). The nature of the metal template allows for the easy manipulation of foam shapes (i.e., rolls or films) and for the preparation of scaffolds of different pore sizes for different cell studies while preserving the interconnected porous nature of the template. The etching process does not affect the chemistry of the elastomers, preserving their biocompatible and biodegradable nature. We show that these smectic LCEs, when grown for extensive time periods, enable the study of clinically relevant and complex tissue constructs while promoting the growth and proliferation of cells.

This study presents a methodology to prepare 3D, biodegradable, foam-like cell scaffolds based on biocompatible side-chain liquid crystal elastomers (LCEs). Confocal microscopy experiments show that foam-like LCEs allow for cell attachment, proliferation, and the spontaneous alignment of C2C12s myoblasts.

Here, we present a step-by-step preparation of a 3D, biodegradable, foam-like cell scaffold. These scaffolds were prepared by cross-linking star block ...

Bioengineering

A Freeze-Thawing Method to Prepare Chitosan-Poly(vinyl alcohol) Hydrogels Without Crosslinking Agents and Diflunisal Release Studies

Chitosan-poly(vinyl alcohol) hydrogels can be produced by the freeze-thawing method without using toxic crosslinking agents. The applications of these systems are limited by their characteristics (e.g., porosity, flexibility, swelling capacity, drug loading and drug release capacity), which depend on the freezing conditions and the kind and ratio of polymers. This protocol describes how to prepare hydrogels from chitosan and poly(vinyl alcohol) at 50/50 w/w % of polymer composition and varying the freezing temperature (-4 &#176;C, -20 &#176;C, -80 &#176;C) and freeze-thawing cycles (4, 5, 6 freezing cycles). FT-IR spectra, SEM micrograph and porosimetry data of hydrogels were obtained. Also, the swelling capacity and drug loading and release of diflunisal were assessed. Results from SEM micrographs and porosimetry show that the pore size decreases, while the porosity increases at lower temperatures. The swelling percentage was higher at the minor freezing temperature. The release of diflunisal from the hydrogels has been studied. All the networks maintain the drug release for 30 h and it has been observed that a simple diffusion mechanism regulates the diflunisal release according to Korsmeyer-Peppas and Higuchi models.

A Freeze-Thawing Method to Prepare Chitosan-Polyvinyl alcohol Hydrogels Without Crosslinking Agents and Diflunisal Release Studies

The freezing-thawing method is used to produce chitosan-poly(vinyl alcohol) hydrogels without crosslinking agents. For this method, it is important to consider the freezing conditions (temperature, number of cycles) and polymer ratio, which can affect the properties and applications of the obtained hydrogels.

Chitosan-poly(vinyl alcohol) hydrogels can be produced by the freeze-thawing method without using toxic crosslinking agents. The applications of these ...

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

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