Name: functionalization and dispersion of carbon nanomaterials using an environmentally friendly ultrasonicated ozonolysis process
Uploaded: 2017-05-30T12:30:00
Description: Watch this Scientific Journal Video about Functionalization and Dispersion of Carbon Nanomaterials Using an Environmentally Friendly Ultrasonicated Ozonolysis Process at JoVE.com

The non-salary component of the work was funded by the Commonwealth of Australia. The author from the University of Delaware gratefully acknowledges the support of the US National Science Foundation (Grant #1254540, Dr. Mary Toney, Program Director). The authors thank Mr. Mark Fitzgerald for his assistance with the electrophoretic deposition measurements.

1. Functionalization of CNTs and GNPs by Ultrasonic Ozonolysis
<ol>
	<li>Weigh the nanomaterials in a glove box inside a HEPA filter-equipped fume cupboard. Weigh the desired quantity of nanomaterials into a beaker. Transfer to a bottle and add ultrapure water to make a concentration of 1 g/L.</li>
	<li>Seal the bottle with a lid. Ultrasonicate in a standard ultrasonic bath (see Materials List; frequency: ~43 &#177;2 kHz; power: 60 W) to disperse the CNTs or GNPs. 
	NOTE: CAUTION. See the Work Health and Safety No...

<ol>
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T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electrophoretic+deposition+of+carbon+nanotubes+onto+carbon-fiber+fabric+for+production+of+carbon/epoxy+composites+with+improved+mechanical+properties.">Electrophoretic deposition of carbon nanotubes onto carbon-fiber fabric for production of carbon/epoxy composites with improved mechanical properties.</a> Carbon. 50 (11), 4130-4143 (2012).</li><li>An, Q., Rider, A. N., Thostenson, E. T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Heirarchical+composite+structures+prepared+by+electrophoretic+deposition+of+carbon+nanotubes+onto+glass+fibers.">Heirarchical composite structures prepared by electrophoretic deposition of carbon nanotubes onto glass fibers.</a> ACS Appl. Mater. Interfac. 5 (6), 2022-2032 (2013).</li><li>Rider, A. N., An, Q., Thostenson, E. 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C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Formation+of+a+Deposit+by+Electrophoresis.">Formation of a Deposit by Electrophoresis.</a> T. Faraday Soc. 35, 279-287 (1940).</li><li>Rider, A. N., An, Q., Brack, N., Thostenson, E. T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Polymer+nanocomposite+-+fiber+model+interphases:+Influence+of+processing+and+interface+chemistry+on+mechanical+performance.">Polymer nanocomposite - fiber model interphases: Influence of processing and interface chemistry on mechanical performance.</a> Chem. Eng. J. 269, 121-134 (2015).</li></ol>

When working with nanoparticles of high hardness, such as CNTs, the potential erosion effect on containers and tubing should not be overlooked. Step 1.14 in the protocol was inserted after the tubing became worn at a bend due to CNTs impinging on the tube side wall, causing a system leak.
Also, note that the CNTs are in suspension, not solution, and that they must be stirred before each use if a homogeneous suspension is desired. For example, this would be necessary to maintain the desired con...

The use of carbon nanomaterials to modify polymeric and composite systems has seen intensive research interest over the past 20 years. Recent reviews on both the use of carbon nanotubes1 (CNTs) and graphene nanoplatelets2 (GNPs) provide an indication of the breadth of research. The high specific stiffness and strength of CNTs and GNPs, as well as their high intrinsic electrical conductivity, make the materials ideally suited for incorporation into polymeric systems to enhance both the mechanical and electrical performance of the nanocomposite materials. CNTs and GNPs have also been used for the development of hierarchical composite structures by using the carbon nanomaterials to modify both fiber interfacial adhesion and matrix stiffness3,4.
The homogeneous dispersion of carbon nanomaterials into polymeric systems often requires processing steps, which chemically alter the nanomaterials to improve the chemical compatibility with the polymer matrix, remove impurities, and reduce or remove agglomerates from the as-received materials. A variety of methods to chemically modify carbon nanomaterials are available and may include wet chemical oxidation using strong acids5,6, modification with surfactants7, electrochemical intercalation and exfoliation8, or dry chemical processing using plasma-based processes9.
The use of strong acids in the oxidation step of CNTs introduces oxygen functional groups and removes impurities. However, it has the disadvantage of significantly reducing the CNT length, introducing damage to the CNT outer walls and using dangerous chemicals, which need to be isolated from the treated material for further processing10. The use of surfactants combined with ultrasonication offers a less aggressive method to prepare stable dispersions, but the surfactant is often difficult to remove from the treated material and may not be compatible with the polymer being used to prepare the nanocomposite materials1,11. The strength of the chemical interaction between the surfactant molecule and CNT or GNP may also be insufficient for mechanical applications. Dry plasma treatment processes conducted under atmospheric conditions may be suitable for functionalizing arrays of CNTs, present on fiber or planar surfaces, used to prepare hierarchical composites9. However, the atmospheric plasma is more difficult to apply to dry powders and does not address the problems with agglomerates present in as-manufactured raw carbon nanomaterials.
In the present work, we introduce a detailed description of the ultrasonicated-ozonolysis (USO) method that we have previously applied to carbon nanomaterials12,13,14. The USO process is used to prepare stable, aqueous dispersions that are suitable for electrophoretically depositing (EPD) both CNTs and GNPs onto carbon and glass fibers. Examples of EPD using USO-functionalized CNTs to deposit thin, uniform films onto stainless steel and carbon fabric substrates will be provided. Methods and typical results used to chemically characterize the functionalized CNTs and GNPs will also be provided, using both X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. A brief discussion of the characterization results in comparison with other functionalization techniques will be provided.
Work Health and Safety Notice
The effects of exposure to nanoparticles such as CNTs, on human health are not well understood. It is recommended that special measures be taken to minimize exposure to and avoid environmental contamination with CNT powders. Suggested hazard isolation measures include working within a HEPA filter-equipped fume cupboard and/or glove box. Occupational hygiene measures include wearing protective clothing and two layers of gloves and performing regular cleaning of surfaces using damp paper towels or a vacuum cleaner with a HEPA filter to remove stray CNT powders. Contaminated articles should be bagged for hazardous waste disposal.
Exposure to ozone can irritate the eyes, lungs, and respiratory system, and at higher concentrations may cause lung damage. It is recommended that measures be taken to minimize personal and environmental exposure to generated ozone gas. Isolation measures include working within a fume cupboard. As the return air stream will contain unused ozone, it should be passed through an ozone destruct unit before being releasing into the atmosphere. Dispersions that have had ozone bubbled through them will contain some dissolved ozone. After ozonolysis operations, allow the dispersions to sit for 1 h before undertaking further processing so that the ozone can undergo natural decomposition.

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	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Ultrasonic bath</td>
			<td style="width:87px;">Soniclean</td>
			<td style="width:119px;">80TD</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Ultrasonic horn</td>
			<td style="width:87px;">Misonix</td>
			<td style="width:119px;">S-4000-010 with CL5 converter</td>
			<td>Daintree Scientific</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Flocell stainless steel water jacketed</td>
			<td style="width:87px;">Misonix</td>
			<td style="width:119px;">800BWJ</td>
			<td>Daintree Scientific</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Peristaltic pump</td>
			<td style="width:87px;">Masterflex easy-load</td>
			<td style="width:119px;">7518-00</td>
			<td></td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;width:216px;">Controller for peristaltic pump</td>
			<td style="width:87px;">Masterflex modular controller</td>
			<td style="width:119px;">7553-78</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Ozone generator</td>
			<td style="width:87px;">Ozone Solutions</td>
			<td style="width:119px;">TG-20</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Ozone destruct unit</td>
			<td style="width:87px;">Ozone Solutions</td>
			<td style="width:119px;">ODS-1</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Recirculating liquid cooler</td>
			<td style="width:87px;">Thermoline</td>
			<td style="width:119px;">TRC2-571-T</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Multi-mode power supply unit</td>
			<td style="width:87px;">TTi&#160;</td>
			<td style="width:119px;">EX752M</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">High resolution computing multimeter</td>
			<td style="width:87px;">TTi&#160;</td>
			<td style="width:119px;">1906</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">X-ray photoelectron spectroscopy</td>
			<td style="width:87px;">Kratos Analytical</td>
			<td style="width:119px;">Axis Nova</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">XPS analysis software</td>
			<td style="width:87px;">Casa Software</td>
			<td style="width:119px;">Casa XPS</td>
			<td>www.casaxps.com</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Kratos elemental library for use with Casa XPS</td>
			<td style="width:87px;">Casa Software</td>
			<td style="width:119px;">Download Kratos Related Files</td>
			<td>http://www.casaxps.com/kratos/</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Raman dispersive confocal microscope</td>
			<td style="width:87px;">Thermo</td>
			<td style="width:119px;">DXR</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Field emission scanning electron microscope</td>
			<td style="width:87px;">Leo</td>
			<td style="width:119px;">1530 VP</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Sputter coater with iridium target</td>
			<td style="width:87px;">Cressington</td>
			<td style="width:119px;">208 HR</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Thickness measurement unit</td>
			<td style="width:87px;">Cressington</td>
			<td style="width:119px;">mtm 20</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Magnetic stirrer</td>
			<td style="width:87px;">Stuart</td>
			<td style="width:119px;">CD162</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Analytical balance</td>
			<td style="width:87px;">Kern</td>
			<td style="width:119px;">ALS 220-4N</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Analytical balance</td>
			<td style="width:87px;">Mettler Toledo</td>
			<td style="width:119px;">NewClassic MF MS 2045</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Laboratory balance</td>
			<td style="width:87px;">Shimadzu</td>
			<td style="width:119px;">ELB 3000</td>
			<td></td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;width:216px;">Electrodes from 316 stainless steel sheet</td>
			<td style="width:87px;">RS Components</td>
			<td style="width:119px;">559-199</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Sanding sheets, P1000 grade</td>
			<td style="width:87px;">Norton</td>
			<td style="width:119px;">No-Fil A275</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Multi-walled carbon nanotubes</td>
			<td style="width:87px;">Hanwha</td>
			<td style="width:119px;">CM-95</td>
			<td>http://hcc.hanwha.co.kr/eng/business/bus_table/nano_02.jsp</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Graphene nanoplatelets</td>
			<td style="width:87px;">XG Sciences</td>
			<td style="width:119px;">XGNP Grade C</td>
			<td>http://xgsciences.com/products/graphene-nanoplatelets/grade-c/</td>
		</tr>
	</tbody>
</table>

functionalization and dispersion of carbon nanomaterials using an environmentally friendly ultrasonicated ozonolysis process

Functionalization of carbon nanomaterials is often a critical step that facilitates their integration into larger material systems and devices. In the as-received form, carbon nanomaterials, such as carbon nanotubes (CNTs) or graphene nanoplatelets (GNPs), may contain large agglomerates. Both agglomerates and impurities will diminish the benefits of the unique electrical and mechanical properties offered when CNTs or GNPs are incorporated into polymers or composite material systems. Whilst a variety of methods exist to functionalize carbon nanomaterials and to create stable dispersions, many the processes use harsh chemicals, organic solvents, or surfactants, which are environmentally unfriendly and may increase the processing burden when isolating the nanomaterials for subsequent use. The current research details the use of an alternative, environmentally friendly technique for functionalizing CNTs and GNPs. It produces stable, aqueous dispersions free of harmful chemicals. Both CNTs and GNPs can be added to water at concentrations up to 5 g/L and can be recirculated through a high-powered ultrasonic cell. The simultaneous injection of ozone into the cell progressively oxidizes the carbon nanomaterials, and the combined ultrasonication breaks down agglomerates and immediately exposes fresh material for functionalization. The prepared dispersions are ideally suited for the deposition of thin films onto solid substrates using electrophoretic deposition (EPD). CNTs and GNPs from the aqueous dispersions can be readily used to coat carbon- and glass-reinforcing fibers using EPD for the preparation of hierarchical composite materials.

Figure 3 shows the XPS wide-scan characterization of CNTs that had undergone USO treatment. CNTs that had not undergone USO show almost no oxygen content. As the USO time increases, the surface oxygen level increases. Figure 4 charts the oxygen-to-carbon ratio increases as a function of USO time. Table 1 shows the deconvoluted carbon species atomic concentrations of GNP treated with USO. The peak fitting used a combination of constrained ...

Watch this Scientific Journal Video about Functionalization and Dispersion of Carbon Nanomaterials Using an Environmentally Friendly Ultrasonicated Ozonolysis Process at JoVE.com

Functionalization and Dispersion of Carbon Nanomaterials Using an Environmentally Friendly Ultrasonicated Ozonolysis Process

Here, a novel method for the functionalization and stable dispersion of carbon nanomaterials in aqueous environments is described. Ozone is injected directly into an aqueous dispersion of carbon nanomaterial that is continuously recirculated through a high-powered ultrasonic cell.

Functionalization of carbon nanomaterials is often a critical step that facilitates their integration into larger material systems and devices. In the ...

The overall goal of this Ultrasonic Ozonolysis and Electrophoretic Deposition processes is to achieve a stable dispersion of carbon nanomaterials which can then be used for the preparation of hierarchichal composite materials. This method can answer key questions in the hierarchichal composites field. By providing a convenient method to controllably coat microfiber fabrics with carbon nanomaterials.The main advantage of this technique is that carbon nanomaterials such as nanotubes and nanoplatelets can be functionalized made compatible with polymeric resin systems without the use of harsh chemicals. To begin this procedure, transfer all needed materials into a glove box inside a hepa-filter equipped fume cupboard. Weigh the desired quantity of nanomaterials into a bottle and add water so that the final nanoparticle concentration is one gram per liter.Seal the bottle with a lid. Ultrasonicate for 30 minutes at 43 kilohertz and 60 watts to disperse the CNTs and GNPs. Next, carefully pour the nanoparticles suspension into a reactor flask containing a magnetic stir-bar.Assemble the experimental set-up as detailed in the text protocol. After this, insert the ozone bubbler and connect it to the ozone generator. Then, place the reactor flask into the refrigerated bath.Stir the solution to prevent the CNTs from settling out of the suspension. Turn on the cooling water recirculation unit to cool the ozone reactor and ultrasonic cell. Then, turn on the oxygen supply to the ozone generator.Adjust the flow rate to zero point five litters per minute. Turn on the ozone generator and allow it to run for 30 to 60 minutes. The use of a bubbler on the other side of the ozone destruct unit enables a quick check that the ozone generator is connected and flowing properly.After this, turn on the peristaltic pump and adjust it to zero point six seven hertz. Turn on the ultrasonic horn and adjust the power to 60 watts. Observe the sonication process for at least 30 minutes, to ensure the pumping and ultrasonic horn operation is stable.After the desired ultrasonicated ozonolysis processing time has elapsed, turn off the ozone generator, sonicator, and pump. Stir the carbon nanomaterial dispersion for one hour to allow the ozone and solution to decompose. To begin, sonicate the nanomaterial suspension if electrophoresis is not performed within 24 hours of the ultrasonicated ozonolysis processing.Then, prepare three stainless steel electrodes as outlined in the text protocol. Using P1000 aluminum oxide sandpaper abrade the electrodes. Clean the abraded electrodes in an ultrasonic cleaning bath for 10 minutes in ultra pure water.Place the electrodes in a clean oven to dry for 10 minutes at 100 degrees celsius. After this, move the eletrodes to a desicator to cool. When cooled, weigh the electrodes to be used for anotic deposition on a four figure analytical balance.Then assemble the electrodes as outlined in the text protocol. Transfer 35 milliliters of carbon nanomaterial dispersion to a 50 milliliter beaker. Secure the electrode fixture to a retort-stand.After this, slowly lower the electrodes to the bottom of the beaker. Attach the positive terminal of the DC power supply to the central anode. Next, attach the negative terminal to one of the outer cathodes.Using a lid with alligator clips, connect the two outer cathodes. With the power supply turned off, adjust the current to the maximum setting. Adjust the voltage to the required value for the desired study.Then, prepare a stopwatch and turn on the power supply for the required coding duration. After this, switch off the power supply. Slowly raise the electrode fixture out of the dispersion, ensuring that the film is not disturbed.Disconnect the terminals from the electrodes. Next, slowly rotate the electrode fixture to a horizontal orientation. Allow the film on the anode to dry evenly.After this, disassemble the fixture and dry the anode in an oven for one hour at 100 degrees celsius. Place the dried anode in the desicator to cool. Using an analytical scale, record the weight to four decimal places.Photograph the coded anode and repeat the coding and weighing process for each deposition time. Then, perform characterization and analysis as outlined in the text protocol. In this study, a novel method is used to functionalize and stably disperse carbon nanomaterials in an aqueous environment.X-ray photoelectron spectroscopy widescan characterization shows that CNTs that did not undergo USO treatment contain almost no oxygen. However, the surface oxygen level is seen to increase as the USO treatment time increases. A raman spectrum reveals the presence of defects in the CNTs which existed even before USO treatment.The G band is seen to shift from a wavenumber of 1, 576 to a wavenumber of 1, 582 with the second component becoming more pronounced at a wavenumber of 1, 618 as USO time increases. Noticeable differences are also seen in the intensity of the two D band at a wavenumber of 2, 698. And then the D and G band at a wavenumber of 2, 941 as USO time increases.These changes all correspond with an increase in the oxidation level of the CNTs. Scanning electron microscopy shows that while untreated CNTs are highly compt, CNTs treated with USO are much more evenly distributed across the surface. This indicates that USO treatments has helped to reduce agglomirates present in the as received material.The USO treated CNTs are then electrophorically deposited using a variety of conditions, thicker films are produced as electrophoresis time increases. Thicker films are also produced when higher CNT concentrations are used. After its development, this technique paved the way for researchers in the field of hierarchical composites to explore whether Ultrasonic Ozonolysis can be used to functionalize other nanomaterials for eletrophoretic deposition.Different coating levels of carbon nanomaterials can have a significant effect on the macroscale composite properties such as strength and toughness. Because the method is water based after funtionalization, the ozone breaks down into harmless oxygen. And there is no need to remove chemicals from the dispersion before using the nanomaterials.Don't forget to run the ozone for one hour before turning on the peristaltic pump. Otherwise, you'll get clumping of nanomaterials in the tube.

functionalization-dispersion-carbon-nanomaterials-using-an

Research

JoVE Journal

Environment

The Use of an Automated System (GreenFeed) to Monitor Enteric Methane and Carbon Dioxide Emissions from Ruminant Animals

Ruminant animals (domesticated or wild) emit methane (CH4) through enteric fermentation in their digestive tract and from decomposition of manure during storage. These processes are the major sources of greenhouse gas (GHG) emissions from animal production systems. Techniques for measuring enteric CH4 vary from direct measurements (respiration chambers, which are highly accurate, but with limited applicability) to various indirect methods (sniffers, laser technology, which are practical, but with variable accuracy). The sulfur hexafluoride (SF6)&#160;tracer gas method is commonly used to measure enteric CH4 production by animal scientists and more recently, application of an Automated Head-Chamber System (AHCS) (GreenFeed, C-Lock, Inc., Rapid City, SD), which is the focus of this experiment, has been growing. AHCS is an automated system to monitor CH4 and carbon dioxide (CO2) mass fluxes from the breath of ruminant animals. In a typical AHCS operation, small quantities of baiting feed are dispensed to individual animals to lure them to AHCS multiple times daily. As the animal visits AHCS, a fan system pulls air past the animal&#8217;s muzzle into an intake manifold, and through an air collection pipe where continuous airflow rates are measured. A sub-sample of air is pumped out of the pipe into non-dispersive infra-red sensors for continuous measurement of CH4 and CO2 concentrations. Field comparisons of AHCS to respiration chambers or SF6 have demonstrated that AHCS produces repeatable and accurate CH4 emission results, provided that animal visits to AHCS are sufficient so emission estimates are representative of the diurnal rhythm of rumen gas production. Here, we demonstrate the use of AHCS to measure CO2 and CH4 fluxes from dairy cows given a control diet or a diet supplemented with technical-grade cashew nut shell liquid.

The Use of an Automated System GreenFeed to Monitor Enteric Methane and Carbon Dioxide Emissions from Ruminant Animals

Accuracy and precision of the techniques used to measure methane emissions from ruminant animals are critically important for the success of greenhouse gas mitigation efforts. This manuscript describes the principles and operation of an automated system to monitor methane and carbon dioxide mass fluxes from the breath of ruminant animals.

Ruminant animals (domesticated or wild) emit methane (CH4) through enteric fermentation in their digestive tract and from decomposition of manure during ...

Measuring Carbon-based Contaminant Mineralization Using Combined CO2 Flux and Radiocarbon Analyses

A method is described which uses the absence of radiocarbon in industrial chemicals and fuels made from petroleum feedstocks which frequently contaminate the environment. This radiocarbon signal &#8212; or rather the absence of signal &#8212; is evenly distributed throughout a contaminant source pool (unlike an added tracer) and is not impacted by biological, chemical or physical processes (e.g., the 14C radioactive decay rate is immutable). If the fossil-derived contaminant is fully degraded to CO2, a harmless end-product, that CO2 will contain no radiocarbon. CO2 derived from natural organic matter (NOM) degradation will reflect the NOM radiocarbon content (usually &#60;30,000 years old). Given a known radiocarbon content for NOM (a site background), a two end-member mixing model can be used to determine the CO2 derived from a fossil source in a given soil gas or groundwater sample. Coupling the percent CO2 derived from the contaminant with the CO2 respiration rate provides an estimate for the total amount of contaminant degraded per unit time. Finally, determining a zone of influence (ZOI) representing the volume from which site CO2 is collected allows determining the contaminant degradation per unit time and volume. Along with estimates for total contaminant mass, this can ultimately be used to calculate time-to-remediate or otherwise used by site managers for decision-making.

Measuring Carbon-based Contaminant Mineralization Using Combined CO2 Flux and Radiocarbon Analyses

A protocol is described wherein CO2 mineralized from organic contaminant (derived from petroleum feedstocks) biodegradation is trapped, quantified, and analyzed for 14C content. A model is developed to determine CO2 capture zone's spatial extent. Spatial and temporal measurements allow integrating contaminant mineralization rates for predicting remediation extent and time.

A method is described which uses the absence of radiocarbon in industrial chemicals and fuels made from petroleum feedstocks which frequently contaminate ...

Spotting Cheetahs: Identifying Individuals by Their Footprints

The cheetah (Acinonyx jubatus) is Africa's most endangered large felid and listed as Vulnerable with a declining population trend by the IUCN1. It ranges widely over sub-Saharan Africa and in parts of the Middle East. Cheetah conservationists face two major challenges, conflict with landowners over the killing of domestic livestock, and concern over range contraction. Understanding of the latter remains particularly poor2. Namibia is believed to support the largest number of cheetahs of any range country, around 30%, but estimates range from 2,9053 to 13,5204. The disparity is likely a result of the different techniques used in monitoring.
Current techniques, including invasive tagging with VHF or satellite/GPS collars, can be costly and unreliable. The footprint identification technique5 is a new tool accessible to both field scientists and also citizens with smartphones, who could potentially augment data collection. The footprint identification technique analyzes digital images of footprints captured according to a standardized protocol. Images are optimized and measured in data visualization software. Measurements of distances, angles, and areas of the footprint images are analyzed using a robust cross-validated pairwise discriminant analysis based on a customized model. The final output is in the form of a Ward's cluster dendrogram. A user-friendly graphic user interface (GUI) allows the user immediate access and clear interpretation of classification results.
The footprint identification technique algorithms are species specific because each species has a unique anatomy. The technique runs in a data visualization software, using its own scripting language (jsl) that can be customized for the footprint anatomy of any species. An initial classification algorithm is built from a training database of footprints from that species, collected from individuals of known identity. An algorithm derived from a cheetah of known identity is then able to classify free-ranging cheetahs of unknown identity. The footprint identification technique predicts individual cheetah identity with an accuracy of &gt;90%.

The cheetah (Acinonyx jubatus) is an iconic, endangered species, but conservation efforts are challenged by habitat shrinkage and conflict with commercial farmers. The footprint identification technique, a robust, accurate and cost-effective image classification system, is a new approach to monitoring cheetahs.

The cheetah (Acinonyx jubatus) is Africa's most endangered large felid and listed as Vulnerable with a declining population trend by the IUCN1. It ranges ...

Assessment of Labile Organic Carbon in Soil Using Sequential Fumigation Incubation Procedures

Management practices and environmental changes can alter soil nutrient and carbon cycling. Soil labile organic carbon, a readily decomposable C pool, is highly sensitive to disturbance. It is also the primary substrate for soil microorganisms, which is fundamental to nutrient cycling. Due to these attributes, labile organic carbon (LOC) has been identified as an indicator parameter for soil health. Quantifying the turnover rate of LOC also aids in understanding changes in soil nutrient cycling processes. A sequential fumigation incubation method has been developed to estimate soil LOC and potential C turnover rate. The method requires fumigating soil samples and quantifying CO2-C respired during a 10 day incubation period over a series of fumigation-incubation cycles. Labile organic C and potential C turnover rate are then extrapolated from accumulated CO2 with a negative exponential model. Procedures for conducting this method are described.

Labile organic carbon (LOC) and the potential carbon turnover rate are sensitive indicators of changes in soil nutrient cycling processes. Details are provided for a method based on fumigating and incubating soil in a series of cycles and using the CO2 accumulated during the incubation periods to estimate these parameters.

Management practices and environmental changes can alter soil nutrient and carbon cycling. Soil labile organic carbon, a readily decomposable C pool, is ...

Biofilm Removal Using Carbon Dioxide Aerosols without Nitrogen Purge

Biofilms can cause serious concerns in many applications. Not only can they cause economic losses, but they can also present a public health hazard. Therefore, it is highly desirable to remove biofilms from surfaces. Many studies on CO2 aerosol cleaning have employed nitrogen purges to increase biofilm removal efficiency by reducing the moisture condensation generated during the cleaning. However, in this study, periodic jets of CO2 aerosols without nitrogen purges were used to remove Pseudomonas putida biofilms from polished stainless steel surfaces. CO2 aerosols are mixtures of solid and gaseous CO2 and are generated when high-pressure CO2 gas is adiabatically expanded through a nozzle. These high-speed aerosols were applied to a biofilm that had been grown for 24 hr. The removal efficiency ranged from 90.36% to 98.29% and was evaluated by measuring the fluorescence intensity of the biofilm as the treatment time was varied from 16 sec to 88 sec. We also performed experiments to compare the removal efficiencies with and without nitrogen purges; the measured biofilm removal efficiencies were not significantly different from each other (t-test, p &gt; 0.55). Therefore, this technique can be used to clean various bio-contaminated surfaces within one minute.

Biofilms on surfaces can be effectively and rapidly removed by using a periodic jet of carbon dioxide aerosols without a nitrogen purge.

Biofilms can cause serious concerns in many applications. Not only can they cause economic losses, but they can also present a public health hazard. ...

Measurement of the Rheology of Crude Oil in Equilibrium with CO2 at Reservoir Conditions

A rheometer system to measure the rheology of crude oil in equilibrium with carbon dioxide (CO2) at high temperatures and pressures is described. The system comprises a high-pressure rheometer which is connected to a circulation loop. The rheometer has a rotational flow-through measurement cell with two alternative geometries: coaxial cylinder and double gap. The circulation loop contains a mixer, to bring the crude oil sample into equilibrium with CO2, and a gear pump that transports the mixture from the mixer to the rheometer and recycles it back to the mixer. The CO2 and crude oil are brought to equilibrium by stirring and circulation and the rheology of the saturated mixture is measured by the rheometer. The system is used to measure the rheological properties of Zuata crude oil (and its toluene dilution) in equilibrium with CO2 at elevated pressures up to 220 bar and a temperature of 50 &#176;C. The results show that CO2 addition changes the oil rheology significantly, initially reducing the viscosity as the CO2 pressure is increased and then increasing the viscosity above a threshold pressure. The non-Newtonian response of the crude is also seen to change with the addition of CO2.

Measurement of the Rheology of Crude Oil in Equilibrium with CO2 at Reservoir Conditions

A method for measuring the rheology of crude oil in equilibrium with carbon dioxide at reservoir conditions is presented.

A rheometer system to measure the rheology of crude oil in equilibrium with carbon dioxide (CO2) at high temperatures and pressures is described. The ...

Dispersion of Nanomaterials in Aqueous Media: Towards Protocol Optimization

The sonication process is commonly used for de-agglomerating and dispersing nanomaterials in aqueous based media, necessary to improve homogeneity and stability of the suspension. In this study, a systematic step-wise approach is carried out to identify optimal sonication conditions in order to achieve a stable dispersion. This approach has been adopted and shown to be suitable for several nanomaterials (cerium oxide, zinc oxide, and carbon nanotubes) dispersed in deionized (DI) water. However, with any change in either the nanomaterial type or dispersing medium, there needs to be optimization of the basic protocol by adjusting various factors such as sonication time, power, and sonicator type as well as temperature rise during the process. The approach records the dispersion process in detail. This is necessary to identify the time points as well as other above-mentioned conditions during the sonication process in which there may be undesirable changes, such as damage to the particle surface thus affecting surface properties. Our goal is to offer a harmonized approach that can control the quality of the final, produced dispersion. Such a guideline is instrumental in ensuring dispersion quality repeatability in the nanoscience community, particularly in the field of nanotoxicology.

Here, we present a step-wise protocol for the dispersion of nanomaterials in aqueous media with real-time characterization to identify the optimal sonication conditions, intensity, and duration for improved stability and uniformity of nanoparticle dispersions without impacting the sample integrity.

The sonication process is commonly used for de-agglomerating and dispersing nanomaterials in aqueous based media, necessary to improve homogeneity and ...

Use of Principal Components for Scaling Up Topographic Models to Map Soil Redistribution and Soil Organic Carbon

Landscape topography is a critical factor affecting soil formation and plays an important role in determining soil properties on the earth surface, as it regulates the gravity-driven soil movement induced by runoff and tillage activities. The recent application of Light Detection and Ranging (LiDAR) data holds promise for generating high spatial resolution topographic metrics that can be used to investigate soil property variability. In this study, fifteen topographic metrics derived from LiDAR data were used to investigate topographic impacts on redistribution of soil and spatial distribution of soil organic carbon (SOC). Specifically, we explored the use of topographic principal components (TPCs) for characterizing topography metrics and stepwise principal component regression (SPCR) to develop topography-based soil erosion and SOC models at site and watershed scales. Performance of SPCR models was evaluated against stepwise ordinary least square regression (SOLSR) models. Results showed that SPCR models outperformed SOLSR models in predicting soil redistribution rates and SOC density at different spatial scales. Use of TPCs removes potential collinearity between individual input variables, and dimensionality reduction by principal component analysis (PCA) diminishes the risk of overfitting the prediction models. This study proposes a new approach for modeling soil redistribution across various spatial scales. For one application, access to private lands is often limited, and the need to extrapolate findings from representative study sites to larger settings that include private lands can be important.

Landscape processes are critical components of soil formation and play important roles in determining soil properties and spatial structure in landscapes. We propose a new approach using stepwise principal component regression to predict soil redistribution and soil organic carbon across various spatial scales.

Landscape topography is a critical factor affecting soil formation and plays an important role in determining soil properties on the earth surface, as it ...

Split Point Analysis and Uncertainty Quantification of Thermal-Optical Organic/Elemental Carbon Measurements

Researchers from myriad fields frequently seek to quantify and classify concentrations of carbonaceous aerosols as organic carbon (OC) or elemental carbon (EC). This is commonly accomplished using thermal-optical OC/EC analyzers (TOAs), which enable measurement via controlled thermal pyrolysis and oxidation under specific temperature protocols and within constrained atmospheres. Several commercial TOAs exist, including a semi-continuous instrument that enables on-line analyses in the field. This instrument employs an in-test calibration procedure that requires relatively frequent calibration. This article details a calibration protocol for this semi-continuous TOA and presents an open-source software tool for data analysis and rigorous Monte Carlo quantification of uncertainties. Notably, the software tool includes novel means to correct for instrument drift and identify and quantify the uncertainty in the OC/EC split point. This is a significant improvement on the uncertainty estimation in the manufacturer&#8217;s software, which ignores split point uncertainty and otherwise uses fixed equations for relative and absolute errors (generally leading to under-estimated uncertainties and often yielding non-physical results as demonstrated in several example data sets). The demonstrated calibration protocol and new software tool enabling accurate quantification of combined uncertainties from calibration, repeatability, and OC/EC split point are shared with the intent of assisting other researchers in achieving better measurements of OC, EC, and total carbon mass in aerosol samples.

This article presents a protocol and software tool for the quantification of uncertainties in the calibration and data analysis of a semi-continuous thermal-optical organic/elemental carbon analyzer.

Researchers from myriad fields frequently seek to quantify and classify concentrations of carbonaceous aerosols as organic carbon (OC) or elemental carbon ...

Measuring Phosphorus Release in Laboratory Microcosms for Water Quality Assessment

Phosphorus (P) is a critical limiting nutrient in agroecosystems requiring careful management to reduce transport risk to aquatic environments. Routine laboratory measures of P bioavailability are based on chemical extractions performed on dried samples under oxidizing conditions. While useful, these tests are limited with respect to characterizing P release under prolonged water saturation. Labile orthophosphate bound to oxidized iron and other metals can rapidly desorb to solution in reducing environments, increasing P mobilization risk to surface runoff and groundwater. To better quantify P desorption potential and mobility during extended saturation, a laboratory microcosm method was developed based on repeated sampling of porewater and overlying floodwater over time. The method is useful for quantifying P release potential from soils and sediments varying in physicochemical properties and can improve site-specific P mitigation efforts by better characterizing P release risk in hydrologically active areas. Advantages of the method include its ability to simulate in situ dynamics, simplicity, low cost, and flexibility.

Accurate quantification of phosphorus (P) desorption potential in saturated soils and sediments is important for P modeling and transport mitigation efforts. To better account for in situ soil-water redox dynamics and P mobilization under prolonged saturation, a simple approach was developed based on repeated sampling of laboratory microcosms.

Phosphorus (P) is a critical limiting nutrient in agroecosystems requiring careful management to reduce transport risk to aquatic environments. Routine ...