This research was supported by the JSPS KAKENHI Grant Number (26420764, JP17K06892). The contribution of Ministry of Land, Insfrastructure, Transport and Tourism (MLIT), Government of Japan under &#8216;Construction Technology Research and Development Subsidy Program&#8217; to this research is also recognized. &#160;We also acknowledge the contribution of Mr. Kiyotaka Senmoto to this research. Ms. Adele Pitkeathly, Senior Writing Advisor Fellow from Writing Center of Hiroshima University is also acknowledged for English corrections and suggestions. This research was selected for oral presentation in 7th IWA-Aspire Conference, 2017 and Water and Environment Technology Conference, 2018.

CAUTION: Arsenic is extremely toxic. Please use gloves, long sleeve clothing, and experimental goggles at all times during the experiment to prevent any contact of arsenic solution with the skin and eyes. If arsenic comes into contact with any part of your body, wash it immediately with soap. Additionally, please clean up the experimental surroundings regularly so that you and others do not come into contact with arsenic, even when the experiment is not being performed. The symptoms of arsenic exposure may appear after a long period of time. Prior to cleaning the equipment, first rinse it with clean water and dispose the water separately into an experimental waste container designated for arsenic. Then, clean the equipment well with detergent. To prevent arsenic contamination of the environment, take precautions while disposing of arsenic samples. Dispose of them separately into experimental waste containers designated for arsenic. After the adsorption or desorption experiment is performed, the gels contain a high amount of arsenic. Therefore, dispose of the gels separately to a designated experimental waste bin for only arsenic-containing gels.
1. Synthesis of the DMAPAAQ+FeOOH gel composite
<ol>
	<li>Dry two 20 mL measuring flasks and two 20 mL beakers equipped with magnetic stir bars.</li>
	<li>Transfer 2.07 g of DMAPAAQ (75%), 0.15 g of N,N&#8217;-methylene bisacrylamide (MBAA), 0.25 g of sodium sulfite and 1.68 g of NaOH to one 20 mL beaker.</li>
	<li>Dissolve the solution wholly in distilled water as &#8216;solvent&#8217; and stirring it for 30 min with a magnetic stir bar.</li>
	<li>Transfer the mixture from the beaker to one 20 mL measuring flask and add distilled water to generate a 20 mL solution. Label the solution as the &#8220;monomer solution&#8221;.</li>
	<li>Similarly, take 0.27 g of ammonium peroxodisulfate (APS) and 3.78 g of FeCl3 in another 20 mL beaker.</li>
	<li>Dissolve the solution completely in distilled water and stirring it for 30 min with a magnetic stir bar.</li>
	<li>Transfer the mixture from the beaker to another 20 mL measuring flask and add distilled water to compose a 20 mL solution. Label the solution as the &#8220;initiator solution&#8221;.</li>
	<li>Prepare the experimental setup as shown in Figure 1.</li>
	<li>Transfer the solutions into the respective 20 mL separating funnels.</li>
	<li>Purge the solutions with N2 gas for 10 min.</li>
	<li>Mix the solutions together, stir them in a 50 mL test tube with an electric stirrer, and then place the mixture into a chiller maintained at 10 &#176;C for 40 min.</li>
	<li>Take out the gel block from the test tube and place it on a flat cutting board.</li>
	<li>Cut the gel block into a cubic shape, 5 mm in length.</li>
	<li>Soak the gel slices with de-ionized water for 24 h to remove the impurities.</li>
	<li>After 12 h, replace the water and soak the gel slices again.</li>
	<li>Spread the gel slices onto a Petri dish and dry them at room temperature for 24 h.</li>
	<li>Place the Petri dish with the gel slices in the oven at 50 &#176;C for 24 h.</li>
</ol>
2. pH sensitivity analyses
<ol>
	<li>Dry nine 40 mL plastic containers.</li>
	<li>Measure nine 20 mg dried gel pieces and put each of them in a separate 40 mL plastic container.</li>
	<li>Add 20 mL of a 4 mM disodium hydrogenarsenate heptahydrate (Na2HAsO4&#183;7H2O) solution to each container.</li>
	<li>To control the pH levels, add 20 mL of NaOH solution or HCL solution with different concentrations (0.1, 0.01, 0.001, 0.0001 M) in the respective containers to maintain pH levels of 2, 6, 8, 10, 12, 13 and label them.</li>
	<li>Keep the containers in the stirrer at 20 &#176;C and 120 rpm for 24 h.</li>
	<li>Collect a 5 mL sample from each container and place each sample in a plastic tube using a micropipette.</li>
	<li>Measure the equilibrium pH for all the samples.</li>
	<li>Measure the remaining concentration of arsenic in the solution using a high performance liquid chromatography (HPLC). Use an analytical column (4 x 200 mm), a guard column (4 x 50 mm) and a 4 mm suppressor with the following conditions: 
	Flowrate: 1.5 mL/min; 
	Amount of injected sample: 10 &#956;L; 
	Column temperature: 30 &#176;C; 
	Eluent solution: 2.7 mM Na2CO3 and 0.3 mM NaHCO3; 
	Pump pressure: 2000 psi; 
	Electric conductivity detection: Suppressor method. 
	NOTE: We procured 1 mL of the sample into a 1 mL single-use syringe. The syringe was coupled with a syringe membrane filter (pore size: 0.22 &#956;m, diameter: 13 mm) to discrete the microscopic fragments of the gel from the sample. About 0.7 mL of sample was instilled into the column. Distilled water was infused before the inception of injecting the samples as blank sample. Peaks denoting the existence of arsenic in the sample was detected at 13 min. 
	CAUTION: After injecting the sample, please leave the syringe into the suction head of HPLC for nearly 2 min with roughly 0.2-0.3 mL of sample remaining in it. Because the dust and air could penetrate the column and alter its adeptness, which possibly will result in erroneous outcome.</li>
</ol>
3. Arsenic adsorption experiment
<ol>
	<li>Dry five 40 mL plastic containers.</li>
	<li>Measure and place 20 mg of dried gel in each 40 mL plastic container.</li>
	<li>Add 40 mL of disodium hydrogenarsenate heptahydrate (Na2HAsO4&#183;7H2O) solution to each container at the following concentrations: 0.1, 0.2, 0.5, 1, 2 mM.</li>
	<li>Keep the containers in the stirrer at 20 &#176;C and 120 rpm for 24 h.</li>
	<li>Collect a 5 mL sample from each container and place in a plastic tube using a micropipette.</li>
	<li>Follow step 2.8 to assess the equilibrium arsenic levels in the solutions using HPLC.</li>
</ol>
4. Selectivity analyses of the DMAPAAQ+FeOOH gel
<ol>
	<li>Dry five 40 mL plastic containers.</li>
	<li>Place 20 mg of dried gel in each of the five 40 mL plastic containers.</li>
	<li>Add 20 mL of a 0.4 mM disodium hydrogenarsenate heptahydrate (Na2HAsO4&#183;7H2O) solution to each container.</li>
	<li>Add 20 mL at concentrations of 0.5, 1, 2, 5, 10 mM Na2SO4 to the five containers.</li>
	<li>Keep the containers in the stirrer at 20 &#176;C and 120 rpm for 24 h.</li>
	<li>Collect a 5 mL sample from each container and place into separate plastic tubes using micropipettes.</li>
	<li>Follow step 2.8 to quantify the remaining concentration of arsenic in the solution using HPLC.</li>
</ol>
5. Equilibrium rate analyses
<ol>
	<li>Dry seven 40 mL plastic containers.</li>
	<li>Place 20 mg of dried gel in each of the 40 mL plastic containers.</li>
	<li>Add 40 mL of a 0.2 mM disodium hydrogenarsenate heptahydrate (Na2HAsO4&#183;7H2O) solution to each of the containers.</li>
	<li>Keep the containers in the stirrer at 20 &#176;C at 120 rpm for the duration of their designated times.</li>
	<li>Collect 5 mL samples in plastic tubes using micropipettes after 0.5, 1, 3, 7, 11, 24, and 48 h.</li>
	<li>Follow step 2.8 to determine the equilibrium arsenic level in each solution using HPLC.</li>
</ol>
6. Regeneration analysis
<ol>
	<li>Adsorption analysis
	<ol>
		<li>Dry a 40 mL plastic container.</li>
		<li>Take 20 mg of dried gel and place it in the 40 mL plastic container.</li>
		<li>Add 40 mL of a 0.2 mM disodium hydrogenarsenate heptahydrate (Na2HAsO4&#183;7H2O) solution to the container.</li>
		<li>Keep the container in the stirrer at 20 &#176;C and 120 rpm for 24 h.</li>
		<li>Collect a 5 mL sample in a plastic tube using a micropipette.</li>
		<li>Refer to step 2.8 to evaluate the equilibrium arsenic level in the solution using HPLC.</li>
	</ol>
	</li>
	<li>Cleaning the gel
	<ol>
		<li>Obtain a mesh sieve.</li>
		<li>Carefully collect the gel pieces one at a time so that they do not break and place them in the mesh sieve.</li>
		<li>Wash the gel several times (minimum five times) using de-ionized water so that any remaining arsenic on the surface of the gel is washed away. 
		CAUTION: The gel pieces are fragile. Handle them with care while washing and transferring them from the arsenic solution to the NaCl solution.</li>
	</ol>
	</li>
	<li>Desorption analyses
	<ol>
		<li>Dry a 40 mL plastic container.</li>
		<li>Put the gel pieces from step 6.2 into a 40 mL plastic container.</li>
		<li>Add 40 mL of a 0.5 M NaCl solution to the container.</li>
		<li>Keep the container in the stirrer at 20 &#176;C and 120 rpm for 24 h.</li>
		<li>Collect a 5 mL sample in a plastic tube using a micropipette.</li>
		<li>Follow the step 2.8 to evaluate the equilibrium arsenic level in the solution using HPLC.</li>
	</ol>
	</li>
	<li>Repetition of the process
	<ol>
		<li>After collecting the gel from step 6.3, repeat the process in the following sequence for eight complete cycles: 6.2 &#62; 6.1 &#62; 6.2 &#62; 6.3 &#62; 6.2 &#62; 6.1 &#62; 6.2 &#62; 6.3.</li>
	</ol>
	</li>
</ol>

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The authors have nothing to disclose.

The main advancement of our developed method is the unique design strategy of the gel composite. The purpose of our gel preparation method was to maximize the amount of iron content in the gel. During the preparation, we added FeCl3 and NaOH to the &#8220;initiator solution&#8221; and the &#8220;monomer solution,&#8221; respectively. Once the monomer solution was mixed with the initiator solution, there was a reaction between FeCl3 and NaOH, producing FeOOH inside the gel. This phenomenon ensured ma...

Water pollution is a great environmental concern, motivating researchers to develop methods for removing contaminants such as arsenic from wastewaster1. Among all the reported methods, adsorption processes are a relatively low cost approach for heavy metal removal2,3,4,5,6,7. Iron oxyhydroxide powders are considered to be one of the most efficient adsorbents for extracting arsenic from aqueous solutions8,9. Still, these materials suffer from a number of drawbacks, including early saturation times and toxic synthetic precursors. Additionally, there is a severe adverse effect in the water quality when these adsorbents are used for a long period of time10. An additional separation process, such as sedimentation or filtration, is then needed to purify the contaminated water, which increases the cost of the production further8,11.
Recently, researchers have developed polymer gels such as cationic hydrogels, microgels, and cryogels that have demonstrated efficient adsorption properties. For example, an arsenic removal rate of 96% was achieved by the cationic cryogel, poly(3-acrylamidopropyl) trimethyl ammonium chloride [p(APTMACl)]12. Additionally, at pH 9, approximately 99.7% removal efficiency was achieved by this cationic hydrogel13. At pH 4, 98.72 mg/g of maximum arsenic adsorption capacity was achieved by the microgel, based on tris(2-aminoethyl) amine (TAEA) and glyceroldiglycidyl ether (GDE), p(TAEA-co-GDE)14. Although these gels demonstrated good adsorption performances, they failed to effectively remove arsenic from water at neutral pH levels, and their selectivities in all studied environments were not reported15. A maximum adsorption capacity of 227 &#956;g/g of was measured when Fe(III)-Sn(IV) mixed binary oxide-coated sand was used at a temperature of 313 K and a pH of 716. Alternatively, Fe-Zr binary oxide-coated sand (IZBOCS) has also been used to remove arsenic and achieved a maximum adsorption capacity of 84.75 mg/g at 318 K and a pH of 717. Other reported adsorbents suffer from low adsorption performances, lack of recyclability, low stability, high operational and maintenance costs, and the use of hazardous chemicals in the synthesis process4.
We sought to address the above limitations by developing a material with improved arsenic adsorption performance, high selectivity in complex environments, recycling capability, and efficient activity at neutral pH levels. Therefore, we developed a cationic gel composite of N,N-dimethylamino propylacrylamide methyl chloride quaternary (DMAPAAQ) gel and iron(III) hydroxide (FeOOH) particles as an adsorbent for arsenic removal. We chose to combine FeOOH with our gel because FeOOH increases the adsorption of both forms of arsenic18. In this study, our gel composite was designed to be non-porous and was impregnated with FeOOH during preparation. In the next section, the details of the gel preparation method, including our strategy for maximizing the content of FeOOH is discussed further.

<table><tbody><tr><td>&lt;em&gt;N,N&amp;rsquo;&lt;/em&gt;-dimethylamino propylacrylamide, methyl chloride quaternary (DMAPAAQ) (75% in H&lt;sub&gt;2&lt;/sub&gt;O)</td><td>KJ Chemicals Corporation, Japan</td><td>150707</td><td></td></tr><tr><td>&lt;em&gt;N,N&amp;rsquo;&lt;/em&gt;-Methylene bisacrylamide (MBAA)</td><td>Sigma-Aldrich, USA</td><td>1002040622</td><td></td></tr><tr><td>Sodium sulfite (Na&lt;sub&gt;2&lt;/sub&gt;SO&lt;sub&gt;3&lt;/sub&gt;)</td><td>Nacalai Tesque, Inc., Japan</td><td>31922-25</td><td></td></tr><tr><td>Sodium sulfate (Na&lt;sub&gt;2&lt;/sub&gt;SO&lt;sub&gt;4&lt;/sub&gt;)</td><td>Nacalai Tesque, Inc., Japan</td><td>31916-15</td><td></td></tr><tr><td>Di-sodium hydrogenarsenate heptahydrate(Na&lt;sub&gt;2&lt;/sub&gt;HAsO&lt;sub&gt;4&lt;/sub&gt;.7H&lt;sub&gt;2&lt;/sub&gt;0)</td><td>Nacalai Tesque, Inc., Japan</td><td>10048-95-0</td><td></td></tr><tr><td>Ferric chloride(FeCl&lt;sub&gt;3&lt;/sub&gt;)</td><td>Nacalai Tesque, Inc., Japan</td><td>19432-25</td><td></td></tr><tr><td>Sodium hydroxide(NaOH)</td><td>Kishida Chemicals Corporation, Japan</td><td>000-75165</td><td></td></tr><tr><td>Ammonium peroxodisulfate (APS)</td><td>Kanto Chemical Co. Inc., Japan</td><td>907W2052</td><td></td></tr><tr><td>Hydrochloric acid (HCl)</td><td>Kanto Chemical Co. Inc., Japan</td><td>18078-01</td><td></td></tr><tr><td>Sodium Chloride (NaCl)</td><td>Nacalai Tesque, Inc., Japan</td><td>31320-05</td><td></td></tr></tbody></table>

removal of arsenic using a cationic polymer gel impregnated with iron hydroxide

In this work, we prepared an adsorbent composed of a cationic polymer gel containing iron hydroxide in its structure designed to adsorb arsenic from groundwater. The gel we selected was the N,N-dimethylamino propylacrylamide methyl chloride quaternary (DMAPAAQ) gel. The objective of our preparation method was to ensure the maximum content of iron hydroxide in the structure of the gel. This design approach enabled simultaneous adsorption by both the polymer structure of the gel and the iron hydroxide component, thus, enhancing the adsorption capacity of the material. To examine the performance of the gel, we measured reaction kinetics, carried out pH sensitivity and selectivity analyses, monitored arsenic adsorption performance, and conducted regeneration experiments. We determined that the gel undergoes a chemisorption process and reaches equilibrium at 10 h. Moreover, the gel adsorbed arsenic effectively at neutral pH levels and selectively in complex ion environments, achieving a maximum adsorption volume of 1.63 mM/g. The gel could be regenerated with 87.6% efficiency and NaCl could be used for desorption instead of harmful NaOH. Taken together, the presented gel-based design method is an effective approach for constructing high-performance arsenic adsorbents.

Figure 1 describes the experimental setup for the preparation of the DMAPAAQ+FeOOH gel. Table 1 illustrates the compositions of the materials involved in the preparation of the gel.
Figure 2 shows the relation of contact time with the adsorption of arsenic by the DMAPAAQ+FeOOH gel. In the figure, the amount of adsorption of arsenic was examined at 0.5, ...

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Removal of Arsenic Using a Cationic Polymer Gel Impregnated with Iron Hydroxide

In this work, we prepared an adsorbent composed of the cationic N,N-dimethylamino propylacrylamide methyl chloride quaternary (DMAPAAQ) polymer gel and iron hydroxide for adsorbing arsenic from groundwater. The gel was prepared via a novel method designed to ensure the maximum content of iron particles in its structure.

In this work, we prepared an adsorbent composed of a cationic polymer gel containing iron hydroxide in its structure designed to adsorb arsenic from ...

removal-arsenic-using-cationic-polymer-gel-impregnated-with-iron

Research

JoVE Journal

Environment

7.5K Views.  Hiroshima University. De belangrijkste voordelen van deze procedure zijn dat de gel selectief arseen adsorbeert uit grondwater bij hogere arseenconcentraties dan de andere technieken en de gel kan worden geregenereerd. Demonstratie van deze methode is van cruciaal belang omdat de voorbereiding van de gel en de absorptie-experimenten moeten worden gevisualiseerd om de experimenten te repliceren. Arseen wordt gevonden in het grondwater van meer dan 20 landen.De implicatie van deze techniek kan worden uitgebre...

Video: Removal of Arsenic Using a Cationic Polymer Gel Impregnated with Iron Hydroxide

Removal of Trace Elements by Cupric Oxide Nanoparticles from Uranium In Situ Recovery Bleed Water and Its Effect on Cell Viability

In situ recovery (ISR) is the predominant method of uranium extraction in the United States. During ISR, uranium is leached from an ore body and extracted through ion exchange. The resultant production bleed water (PBW) contains contaminants such as arsenic and other heavy metals. Samples of PBW from an active ISR uranium facility were treated with cupric oxide nanoparticles (CuO-NPs). CuO-NP treatment of PBW reduced priority contaminants, including arsenic, selenium, uranium, and vanadium. Untreated and CuO-NP treated PBW was used as the liquid component of the cell growth media and changes in viability were determined by the MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay in human embryonic kidney (HEK 293) and human hepatocellular carcinoma (Hep G2) cells. CuO-NP treatment was associated with improved HEK and HEP cell viability. Limitations of this method include dilution of the PBW by growth media components and during osmolality adjustment as well as necessary pH adjustment. This method is limited in its wider context due to dilution effects and changes in the pH of the PBW which is traditionally slightly acidic&#160;however; this method could have a broader use assessing CuO-NP treatment in more neutral waters.

Removal of Trace Elements by Cupric Oxide Nanoparticles from Uranium In Situ Recovery Bleed Water and Its Effect on Cell Viability

Production bleed water (PBW) was treated with cupric oxide nanoparticles (CuO-NPs) and cellular toxicity was assessed in cultured human cells. The goal of this protocol was to integrate the native environmental sample into a cell culture format assessing the changes in toxicity due to CuO-NP treatment.

In situ recovery (ISR) is the predominant method of uranium extraction in the United States. During ISR, uranium is leached from an ore body and extracted ...

Preparation of Highly Porous Coordination Polymer Coatings on Macroporous Polymer Monoliths for Enhanced Enrichment of Phosphopeptides

We describe a protocol for the preparation of hybrid materials based on highly porous coordination polymer coatings on the internal surface of macroporous polymer monoliths. The developed approach is based on the preparation of a macroporous polymer containing carboxylic acid functional groups and the subsequent step-by-step solution-based controlled growth of a layer of a porous coordination polymer on the surface of the pores of the polymer monolith. The prepared metal-organic polymer hybrid has a high specific micropore surface area. The amount of iron(III) sites is enhanced through metal-organic coordination on the surface of the pores of the functional polymer support. The increase of metal sites is related to the number of iterations of the coating process.
The developed preparation scheme is easily adapted to a capillary column format. The functional porous polymer is prepared as a self-contained single-block porous monolith within the capillary, yielding a flow-through separation device with excellent flow permeability and modest back-pressure. The metal-organic polymer hybrid column showed excellent performance for the enrichment of phosphopeptides from digested proteins and their subsequent detection using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. The presented experimental protocol is highly versatile, and can be easily implemented to different organic polymer supports and coatings with a plethora of porous coordination polymers and metal-organic frameworks for multiple purification and/or separation applications.

A procedure for the preparation of porous hybrid separation media composed of a macroporous polymer monolith internally coated by a high surface area microporous coordination polymer is presented.

We describe a protocol for the preparation of hybrid materials based on highly porous coordination polymer coatings on the internal surface of macroporous ...

Chemistry

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

Determination of Inorganic Arsenic in a Wide Range of Food Matrices using Hydride Generation - Atomic Absorption Spectrometry.

The European Food Safety Authority (EFSA) underlined in its Scientific Opinion on Arsenic in Food that in order to support a sound exposure assessment to inorganic arsenic through diet, information about distribution of arsenic species in various food types must be generated. A method, previously validated in a collaborative trial, has been applied to determine inorganic arsenic in a wide variety of food matrices, covering grains, mushrooms and food of marine origin (31 samples in total). The method is based on detection by flow injection-hydride generation-atomic absorption spectrometry of the iAs selectively extracted into chloroform after digestion of the proteins with concentrated HCl. The method is characterized by a limit of quantification of 10 &#181;g/kg dry weight, which allowed quantification of inorganic arsenic in a large amount of food matrices. Information is provided about performance scores given to results obtained with this method and which were reported by different laboratories in several proficiency tests. The percentage of satisfactory results obtained with the discussed method is higher than that of the results obtained with other analytical approaches.

The usefulness of an analytical method to determine inorganic arsenic in a wide range of food matrices is demonstrated. The method consists of selective extraction of inorganic arsenic into chloroform with a final determination by hydride generation-atomic absorption spectrometry.

The European Food Safety Authority (EFSA) underlined in its Scientific Opinion on Arsenic in Food that in order to support a sound exposure assessment to ...

Experimental Column Setup for Studying Anaerobic Biogeochemical Interactions Between Iron (Oxy)Hydroxides, Trace Elements, and Bacteria

Fate and speciation of trace elements (TEs), such as arsenic (As) and mercury (Hg), in aquifers are closely related to physio-chemical conditions, such as redox potential (Eh) and pH, but also to microbial activities that can play a direct or indirect role on speciation and/or mobility. Indeed, some bacteria can directly oxidize As(III) to As(V) or reduce As(V) to As(III). Likewise, bacteria are strongly involved in Hg cycling, either through its methylation, forming the neurotoxin monomethyl mercury, or through its reduction to elemental Hg&#176;. The fates of both As and Hg are also strongly linked to soil or aquifer composition; indeed, As and Hg can bind to organic compounds or (oxy)hydroxides, which will influence their mobility. In turn, bacterial activities such as iron (oxy)hydroxide reduction or organic matter mineralization can indirectly influence As and Hg sequestration. The presence of sulfate/sulfide can also strongly impact these particular elements through the formation of complexes such as thio-arsenates with As or metacinnabar with Hg.
Consequently, many important questions have been raised on the fate and speciation of As and Hg in the environment and how to limit their toxicity. However, due to their reactivity towards aquifer components, it is difficult to clearly dissociate the biogeochemical processes that occur and their different impacts on the fate of these TE.
To do so, we developed an original, experimental, column setup that mimics an aquifer with As- or Hg-iron-oxide rich areas versus iron depleted areas, enabling a better understanding of TE biogeochemistry in anoxic conditions. The following protocol gives step by step instructions for the column set-up either for As or Hg, as well as an example with As under iron and sulfate reducing conditions.

Experimental Column Setup for Studying Anaerobic Biogeochemical Interactions Between Iron OxyHydroxides, Trace Elements, and Bacteria

Fate and speciation of arsenic and mercury in aquifers are closely related to physio-chemical conditions and microbial activity. Here, we present an original experimental column setup that mimics an aquifer and enables a better understanding of trace element biogeochemistry in anoxic conditions. Two examples are presented, combining geochemical and microbiological approaches.

Fate and speciation of trace elements (TEs), such as arsenic (As) and mercury (Hg), in aquifers are closely related to physio-chemical conditions, such as ...

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 ...

A Dual-Functional Electroactive Filter Towards Simultaneously Sb(III) Oxidation and Sequestration

We have designed a facile method to synthesize a dual-functional electrochemical filter consisting of two 1-D materials: titanate nanowires and carbon nanotubes. The hybrid titanate-CNT filter was prepared by a sonication coupled with a post-filtration route. Due to the synergistic effects of the increased number of exposed sorption sites, electrochemical reactivity, small pore size of the titanate-CNT network coupled with a flow-through design, simultaneous Sb(III) oxidation and sequestration can be readily achieved. Atomic fluorescence spectrometer technology demonstrated that the applied electrical field accelerates the Sb(III) conversion rate and the as-obtained Sb(V) were adsorbed effectively by the titanate nanowires due to their Sb specificity. This protocol provides a practical solution for the removal of highly toxic Sb(III) and other similar heavy metal ions.

A Dual-Functional Electroactive Filter Towards Simultaneously SbIII Oxidation and Sequestration

A protocol for the rational design of a dual-functional electroactive filter consisting of carbon nanotubes and titanate nanowires is reported and their environmental applications towards Sb(III) oxidation and sequestration is presented.

We have designed a facile method to synthesize a dual-functional electrochemical filter consisting of two 1-D materials: titanate nanowires and carbon ...

A Method to Preserve Wetland Roots and Rhizospheres for Elemental Imaging

Roots extensively interact with their soil environment but visualizing such interactions between roots and the surrounding rhizosphere is challenging. The rhizosphere chemistry of wetland plants is particularly challenging to capture because of steep oxygen gradients from the roots to the bulk soil. Here a protocol is described that effectively preserves root structure and rhizosphere chemistry of wetland plants through slam-freezing and freeze drying. Slam-freezing, where the sample is frozen between copper blocks pre-cooled with liquid nitrogen, minimizes root damage and sample distortion that can occur with flash-freezing while still minimizing chemical speciation changes. While sample distortion is still possible, the ability to obtain multiple samples quickly and with minimal cost increases the potential to obtain satisfactory samples and optimizes imaging time. The data show that this method is successful in preserving reduced arsenic species in rice roots and rhizospheres associated with iron plaques. This method can be adopted for studies of plant-soil relationships in a wide variety of wetland environments that span concentration ranges from trace-element cycling to phytoremediation applications.

We describe a protocol to sample, preserve, and section intact roots and the surrounding rhizosphere soil from wetland environments using rice (Oryza sativa L.) as a model species. Once preserved, the sample can be analyzed using elemental imaging techniques, such as synchrotron X-ray fluorescence (XRF) chemical speciation imaging.

Roots extensively interact with their soil environment but visualizing such interactions between roots and the surrounding rhizosphere is challenging. The ...

An Efficient Method for Selective Desalination of Radioactive Iodine Anions by Using Gold Nanoparticles-Embedded Membrane Filter

Here, we demonstrate a detail protocol for the preparation of nanomaterials-embedded composite membranes and its application to the efficient and ion-selective removal of radioactive iodines. By using citrate-stabilized gold nanoparticles (mean diameter: 13 nm) and cellulose acetate membranes, gold nanoparticle-embedded cellulose acetate membranes (Au-CAM) have easily been fabricated. The nano-adsorbents on Au-CAM were highly stable in the presence of high concentration of inorganic salts and organic molecules. The iodide ions in aqueous solutions could rapidly be captured by this engineered membrane. Through a filtration process using an Au-CAM containing filter unit, excellent removal efficiency (&gt;99%) as well as ion-selective desalination result was achieved in a short time. Moreover, Au-CAM provided good reusability without significant decrease of its performances. These results suggested that the present technology using the engineered hybrid membrane will be a promising process for the large-scale decontamination of radioactive iodine from liquid wastes.

An efficient method for the rapid and ion-selective desalination of radioactive iodine in several aqueous solutions is described by using gold nanoparticles-immobilized cellulose acetate membrane filters.

Here, we demonstrate a detail protocol for the preparation of nanomaterials-embedded composite membranes and its application to the efficient and ...

Cell Labeling and Targeting with Superparamagnetic Iron Oxide Nanoparticles

Targeted delivery of cells and therapeutic agents would benefit a wide range of biomedical applications by concentrating the therapeutic effect at the target site while minimizing deleterious effects to off-target sites. Magnetic cell targeting is an efficient, safe, and straightforward delivery technique. Superparamagnetic iron oxide nanoparticles (SPION) are biodegradable, biocompatible, and can be endocytosed into cells to render them responsive to magnetic fields. The synthesis process involves creating magnetite (Fe3O4) nanoparticles followed by high-speed emulsification to form a poly(lactic-co-glycolic acid) (PLGA) coating. The PLGA-magnetite SPIONs are approximately 120 nm in diameter including the approximately 10 nm diameter magnetite core. When placed in culture medium, SPIONs are naturally endocytosed by cells and stored as small clusters within cytoplasmic endosomes. These particles impart sufficient magnetic mass to the cells to allow for targeting within magnetic fields. Numerous cell sorting and targeting applications are enabled by rendering various cell types responsive to magnetic fields. SPIONs have a variety of other biomedical applications as well including use as a medical imaging contrast agent, targeted drug or gene delivery, diagnostic assays, and generation of local hyperthermia for tumor therapy or tissue soldering.

Targeted cell delivery is useful in a variety of biomedical applications. The goal of this protocol is to use superparamagnetic iron oxide nanoparticles (SPION) to label cells and thereby enable magnetic cell targeting approaches for a high degree of control over cell delivery and localization.

Targeted delivery of cells and therapeutic agents would benefit a wide range of biomedical applications by concentrating the therapeutic effect at the ...

Removal of Arsenic Using a Cationic Polymer Gel Impregnated with Iron Hydroxide

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