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A number of different nanoscale zero-valent iron (nZVI) materials have been prepared and compared depending on the desired properties for the particular application, but different physicochemical properties of this prepared nZVI make it difficult to universally compare and standardize them to the same scale. In this study, we aimed to demonstrate a simple microplate-based colorimetric assay using 4-chlorophenol as an indicator with respect to the remediation of real treatment targets, such as trichloroethylene (TCE), 1,1,1-trichloroethane (TCA), and atrazine. Effect of nickel contents on 4-chlorophenol reduction was successfully investigated by the miniaturized colorimetric assay. In the same manner, the effect of nickel contents on dehalogenation of TCE, TCA, and atrazine was investigated and the pseudo-first-order kinetic constants were compared with the results for 4-chlorophenol. The similar pattern could be observed between 4-chlorophenol reduction obtained by colorimetric assay and TCE, TCA, atrazine reduction obtained by a traditional chromatographic method. The reaction kinetics does not match perfectly, but the degree of reaction can be estimated. Therefore, the colorimetric assay can be a useful and simple screening tool to determine nZVI reactivity toward halogenated organics before it is applied to a particular remediation site.

The recent discovery of completely nitrifying Nitrospira demands a re‐examination of nitrifying environments to evaluate their contribution to nitrogen cycling. To approach this challenge, tools are needed to detect and quantify comammox Nitrospira. We present primers for the simultaneous quantification and diversity assessement of both comammox Nitrospira clades. The primers cover a wide range of comammox diversity, spanning all available high quality sequences. We applied these primers to 12 groundwater‐fed rapid sand filters, and found comammox Nitrospira to be abundant in all filters. Clade B comammox comprise the majority (∼75%) of comammox abundance in all filters. Nitrosomonadaceae were present in all filters, although at low abundance (mean = 1.8%). Ordination suggests that temperature impacts the structure of nitrifying communities, and in particular that increasing temperature favours Nitrospira. The nitrogen content of the filter material, sulfate concentration and surface ammonium loading rates shape the structure of the comammox guild in the filters. This work provides an assay for simultaneous detection and diversity assessment of clades A and B comammox Nitrospira, expands our current knowledge of comammox Nitrospira diversity and demonstrates a key role for comammox Nitrospira in nitrification in groundwater‐fed biofilters.

The use of nanoscale zero valent iron (nZVI) has quickly become a leading research material for the treatment of typically hard to degrade contaminants found in groundwater. These contaminants include antibiotics, pesticides, halogenated organics, heavy metals, among others. However, the effectiveness of nZVI has its limitations, due to its high reactivity and subsequent loss of degradative ability. Therefore, nZVI must be stabilized in a matrix allowing for the maintaining of reactivity, as well as the protection from the effects of the surrounding environment. By employing a nanoporous polymeric network already previously proven to stabilize nZVI and a long-standing water treatment material,1 activated carbon; we have developed an advanced material that allows for the not only the stabilization of nZVI, but also the improved degradation of various water contaminants. This was done by performing a series of surface modification techniques to the surface of the activated carbon, then physically grafting the covalent organic polymer to the carbon in a shell-like manner, and ultimately synthesizing nZVI in situ within the pores of both the activated carbon and the polymeric network. Not only does this enhanced version of activated carbon utilize the outstanding adsorptive properties of both activated carbon and the polymeric network, but it also employs the degradation capability of nZVI. In this way, a new breed of materials is being developed, working in a synergistic manner for the purpose of the remediation of contaminants found in the groundwater. We confirmed the existence of the polymeric shell with a variety of chemical characterization techniques; including Fourier transform infrared spectroscopy (FTIR), elemental analysis, X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and scanning electron microscopy (SEM). We also monitored the degradation and/or adsorption of various contaminants (e.g. chlorinated organics like trichloroethylene and trichloroethane, and heavy metals like cadmium and nickel) to produce the kinetics of the interactions.

Grundvand er en vigtig kilde til drikkevand alle steder på Jorden, og steder som Danmark er det dén primære kilde til drikkevand. Klimaændringer og befolkningstilvækst vil kun betyde en større afhængighed af grundvand som kilde til drikkevand. Men den voksende befolkning og industrialisering af jordens befolkede arealer har miljømæssige konsekvenser for de naturlige grundvandsressourcer. Stormvand og afstrømning fra landbrug, spild og dumping fra industrien, syreholdig afstrømning fra minebrug og perkolat fra lossepladser er primære eksempler på måder hvordan forurenende stoffer trænger ned i grundvandet. For at gøre dette forurenede vand brugbart til menneskeligt indtag benytter man reaktivt jern og i særdeleshed nano-zero-valent jern (nZVI) for at nedbryde og/eller absorbere mange af disse forurenende stoffer. Imidlertid har den nuværende anvendelse af nZVI begrænsninger. Disse begrænsninger er primært hurtig oxidering og aggregering, der medfører nedsat reaktivitet og anvendelighed. Derfor er udviklingen af nye materialer med inkorporeret nZVI og forbedring af strategien for syntese for at forbedre anvendeligheden af nZVI afgørende for den fremtidige succes for brug af nZVI som rensningsteknik. Dette ph.d.-studie har undersøgt forskellige materialer hvis formål er at løse tabet af reaktivitet af nZVI for dermed at skabe et robust behandlingssystem der er i stand til at håndtere det forurenede vand. Dette ph.d.-studie har også undersøgt og udviklet en fremgangsmåde til hensigtsmæssigt at måle reaktiviteten af det reaktive jern som en universel testmetode. Overflademodifikation af nZVI er en almindelig løsning til at modvirke begrænsningen af materialet, da overflademodifikationen kan indfatte nZVI-partiklen og forhindre den i at interagere med andre partikler men stadigt tillade partiklen at interagere med den vandopløste forurening. I denne undersøgelse anvendtes en syntetisk fremstillet organo-funktionaliseret magnesiumbaseret aminoler (MgAC) til netop dette formål. Ved at variere forholdet af MgAC til nZVI og overvåge forandringen af den fysiske fremtræden og reaktivitet, blev der fremstillet et komposit materiale, der forbedrede den generelle virkning af nZVI. Det blev fastslået, at det reaktive jern indhold, dets kolloide stabilitet, partikelstørrelse og evne til at reducere nitrat (i modsætning til det oxiderede jern) var optimalt ved en støkiometrisk ratio på 7½:1 af MgAC:Fe. En alternativ, men mindre anvendt løsning, er at indbygge eller imprægnere et porøst materiale med nZVI. Denne metode fungerer på tilsvarende måde, med undtagelse af, at nZVI er fanget i en kompleks indlejringsmasse i modsætning til at være belagt med en beskyttende barriere. Forskellige porøse polymerer, samlet betegnet som kovalente organiske polymere (COP), blev imprægneret med nZVI og undersøgt på samme måde som MgAC. Alle COP udviste et højt optag af nZVI på omtrent 10 % på vægtbasis. Kvantificering af reaktiviteten viste sig at være vanskelig i forbindelse med nedbrydning af et azo-farvestof pga. COP materialernes meget høje tilbøjelighed til at adsorbere både farvestoffet og dets nedbrydningsprodukt. Imidlertid var disse COP ekstremt effektive bærere af nZVI med henblik på at opretholde kolloid stabilitet. I et tilfælde fordoblede den anvendte COP (COP-19) den kolloide stabilitet. For at udvide anvendelsesmulighederne for disse komposit materialer, kan en undersøgelse af hvordan man optimalt håndterer disse syntetiske materialer bruges til at forlænge deres levetid. For at gøre dette blev tre vaske- og opbevaringsmetoder for nZVI belagt med MgAC undersøgt. Metoderne var: Vask af partiklerne umiddelbart efter syntese med en NaHCO3-opløsning, vask af partiklerne med en NaHCO3-opløsning efter opbevaring og vask af partiklerne umiddelbart efter syntese med en MgAC-opløsning. Det var tydeligt ved alle reaktivitetstestene af partiklerne, at vask af partiklerne efter opbevaring var ødelæggende for materialet. Kolloidstabilitet, indhold af reaktivt jern og aktiviteten overfor nitrat faldt hurtigt i løbet af en uges opbevaring. De andre metoder hvor vask af partikler skete umiddelbart efter brug, evnede at fastholde de tre førnævnte egenskaber langt mere effektivt ved en uges opbevaring, og partiklerne vasket med MgAC-opløsningen klarede sig bedst i forhold til NaHCO3 opløsningen. Denne præ-opbevaring-vask-teknik fjernede tilbageblevne reaktanter i syntese-blandingen som kan korrodere jernet, og ydermere tilfører præ-opbevaring-vask med MgAC endnu mere stabilitet til materialet, der beskytter nZVI’en. Herudover, var det muligt at undersøge karakteristikken af den ikke-overflademodificerede nZVI og dermed at få en større indsigt i de ændringer, der opstår ved opbevaring af stoffet. Det blev observeret at ved at vaske nZVI med MilliQ vand efter syntese blev der skabt et miljø, hvor partiklerne var en smule mere oxiderede fra begyndelsen, hvilket betød en forøget dannelse af en jern-hydroxid skal ved opbevaring. Ved ikke at vaske nZVI sammenlignet med vask med reduktionsmidlet NaBH4 forhindredes en initial oxidering, der medfører en efterfølgende jernoxid dannelse ved opbevaring. Dette har betydning da hydroxidskallen fremmer en større elektron-overførsel, hvorimod den oxiderede skal fungerer som et passiverende lag. Den forhøjede elektron-overførsel medførte en højere reaktivitet i op til en uge ved opbevaring.Til brug for sammenligning og kvantificering for forskere er det utroligt vigtigt med en simpel og effektiv metode til at vurdere nZVI’s reaktivitet. Nu er de fleste metoder til at karaktisere reaktiviteten af nZVI ofte analytiske tunge, kræver dyrt udstyr og mangler en standardiseret måde at udføre behandlingen på. Dette studie har forsøgt at løse denne problemstilling ved at udvikle en simpel kolorimetrisk karakteriseringsmetode, der gør det muligt at detektere et nedbrydelsesprodukt produceret af nZVI og ved at tilsætte en kemisk forbindelse skabe en farve-reaktion, der er mulig at aflæse med et simpelt spektrofotometer. Dette blev opnået ved at anvende indophenol-reaktionen, der benytter fenol og andre udvalgte reagenser til at skabe en blå farve. Fenol kan produceres ved dehalogenering af 4-chlorphenol med nZVI, og endnu lettere ved reaktion med bi-metallisk nikkel-nZVI. Denne simple metode blev herefter optimeret for at reducere reagent voluminerne og nikkelkoncentrationen og for at udvide rækken af detekterede reduktionsreaktionsprodukter. De forbindelser, der kunne anvendes i farve-analysen med de samme reagenter var slutteligt anilin, ammonium og fenol, som alle kan blive produceret ved reduktiv nedbrydning af passende reagenser med nZVI. Til sidst, for at sammenligne anvendeligheden af den kolorimetriske analyse med almindelige halogenerede grundvandsforureningsstoffer, blev resultatet sammenlignet med dehalogenering af TCE, TCA og atrazin. Den kolorimetriske analyse fungerede også i forhold til nedbrydningen af disse klor-forbindelser, hvilket betyder at analysemetoden kan fungere som et simpelt værktøj til at måle reaktiviteten af al slags nZVI, når det endelige behandlingsmål er vanskeligt analyserbare forbindelser i reelle vandmatricer.I den sidste ende var det primære mål for dette ph.d.-projekt at udvikle et robust nano-komposit materiale indeholdende nZVI til brug i vandbehandlingssystemer. Belært af de tidlige erfaringer med komposit materialet, hvor MgAC og COP blev anvendt, blev slutresultatet en kombination af granulært aktivt kul, COP og nZVI. Efter en længere proces for at udvikle en metode til kemisk at binde COP-materialet til overfladen af aktivt kul, blev det muligt at imprægnere komposit materialet med nZVI. På grund af hovedbestanddelen af aktivt kul i det endelige materiale, viste det sig at være ekstremt robust med en strukturel som kunne anvendes i et gennemstrømningsfilter som er det almindelige, når man behandler store mængder af vand. Selvom en fortsat optimering af materialet er nødvendig, viser de første resultater for adsorbering og nedbrydning af forureningen meget lovende resultater, langt bedre end aktivt kul alene og også bedre end kul imprægneret med nZVI. Endvidere medførte processen en uventet bonus, da det kompositte materiale, og i særdeleshed når kullet blev imprægneret med COP, fungerede som en beskyttende barriere mod effekterne af oxidering. Kompositionen af aktivt kul-COP-nZVI udviste tæt på 100 % reaktivt jern efter syntesen, sammenlignet med meget lavere mængder i andre kendte nZVI-kompositter eller aktivt kul-nZVI-kompositionen anvendt i dette forsøg, hvor der kun var 80 % reaktivt jern indhold.Resultaterne af dette ph.d.-projekt konkluderer i forskellige fremskridt i anvendelsen og analysen af nZVI og nZVI-kompositte materialer. Forskellige kompositte materialer udviste forhøjet kolloid stabilitet og reagerede på nZVI. Forskellige vaske- og opbevaringsteknikker belyste bedre metoder for at anvende nZVI til vandforureningen og de underliggende (sekundære) mekanismer, der opstår i korrosionen af nZVI. Slutteligt, så blev der ved at kombinere tre forskellige teknologier udviklet nye materialer, der med tiden kan føre til et mere robust vandbehandlingssystem i stand til at nedbryde typiske problematiske forureningsstoffer i vand. Groundwater is an important source for drinking water in all corners of the globe, and in places like Denmark, it is the primary source for drinking water. Climate change and population growth will only lead to further dependence on groundwater as the supply for drinking water. However, the expanding population and industrialization of human civilization also leads to environmental consequences affecting groundwater sources. Storm-water and agricultural runoff, industrial spillage and dumping, acid mine drainage, and leakage from landfills are a few prime examples of routes of contamination for pollutants to enter groundwater systems. In order to make these contaminated water sources viable for human consumption, the use of reactive iron (i.e. Fe0 or zero-valent iron), and in particular nanoscale zero-valent iron (nZVI), is being employed to reductively degrade and/or adsorb many of these pollutants. However, the use of nZVI, as it currently stands, has its limitations. These limitations are primarily rapid oxidation and aggregation, resulting in loss of reactivity and applicability. Therefore, development of new materials incorporating nZVI and improving synthesis strategies to increase the applicability of nZVI is paramount to its future success as a remediation technique. This PhD project has investigated various materials aimed at solving the reactivity loss of reactive iron to create a robust treatment system capable of treating polluted waters. This PhD project also investigated and developed a procedure to appropriately measure the reactivity of reactive iron for a universal testing method.Coating of nZVI is a common solution to combatting the limitations of the material, in that the coating can surround the nZVI particle and prevent it from interacting with other particles while still allowing for interaction with the aqueous pollutant. This study employed a synthetic organo-functionalized magnesium-based aminoclay (MgAC) for this exact purpose. By varying the ratio of MgAC to nZVI and monitoring the change in physical characteristics and reactivity, a composite material was formed that improved the overall functionality of nZVI. It was determined that the reactive iron (vs. oxidized iron) content, colloidal stability, particle size, and nitrate degradation could all be best enhanced at a weight ratio of 7.5:1 of MgAC:Fe. Another solution, although less common, to combatting the limitations, is to entrap or impregnate a porous material with nZVI. This way acts in a similar manner, except that the nZVI is bound within a complex matrix rather than coated with a protective barrier. A variety of porous polymeric networks, termed covalent organic polymers (COPs), were impregnated with nZVI and evaluated similarly as with the MgAC. All COPs exhibited high uptake of nZVI, approximately 10% by mass. Reactivity quantification proved to be difficult when degrading an azo dye, due to the very high propensity of the COPs to adsorb both the dye and its degradation products. However, these COPs acted as extremely efficient carriers of nZVI for maintaining colloidal stability. In one case, the COP used (COP-19) increased the colloidal stability of nZVI by two orders of magnitude. Building on the application of these composite materials, investigating how best to handle the synthesized materials can prolong their lifetime. To do this, three washing and storage strategies of the MgAC coated nZVI were investigated. They were: washing the particles immediately after synthesis with a NaHCO3 buffer, washing the particles after storing with a NaHCO3 buffer, and washing the particles immediately after synthesis with a MgAC solution. For all the particle reactivity tests done, it was apparent that washing the particles after storing was detrimental to the material. The colloidal stability, reactive iron, and reactivity towards nitrate dropped rapidly through one week of storage. The other strategies, where washing was done immediately was able to preserve the three aforementioned properties much more efficiently though one week of storage, with MgAC washed particles faring better of the two. This pre-washing technique removes residual reactants in the synthesis mixture that can corrode the iron, and furthermore, pre-washing with MgAC adds more of the stabilizer to the material that protects the nZVI even more. Moreover, by looking deeper into the characteristics of uncoated nZVI, depending on the washing method, allowed for more insight to the nature of the mechanisms taking place during storage. It was observed that washing nZVI with MilliQ water after synthesis created an environment where the particles were slightly more oxidized from the start, which led to an increased formation of an iron-hydroxide shell during storage. Not washing nZVI or washing with the reductant NaBH4 prohibited initial oxidation, leading to subsequent iron-oxide formation during storage. This is important, because the hydroxide shell promotes more electron transfer, whereas the oxide shell acts as a depassivation layer. The increased electron transfer then allowed for higher reactivity during storage, up to one week.To make comparison and quantification for researchers, a simple and effective method to assess the reactivity of nZVI is extremely important. And, as it is now, most of the reactivity characterization methods are often analytically intensive, requiring expensive equipment, and often don’t respond uniformly to different nZVI-based materials. This study sought to solve this problem, by developing a simple colorimetric assay that is capable to taking a degradation product produced by nZVI reacting with a compound, and creating a color reaction detectable with a simple spectrophotometer. This was done by utilizing the indophenol reaction, which uses phenol and selected other reagents to produce a blue color. Phenol can be produced from the dehalogenation of 4-chlorophenol by nZVI, and to a greater extent by bimetallic nickel-nZVI. That simple method was then optimized to reduce reagent volumes, nickel concentration, and to broaden the range of detectable compounds. These compounds capable of being used in the color assay with the same set of reagents were ultimately aniline, ammonium, and phenol; all of which can be produced by the degradation reaction from nZVI. Finally, to compare the applicability of the colorimetric assay to common halogenated groundwater contaminants; it was compared to the dehalogenation of TCE, TCA, and atrazine. The colorimetric assay performed similarly to the degradation of those chlorinated compounds; meaning the assay can be a simple tool to assess the reactivity of any nZVI when ultimately targeting more difficult to analyze compounds in real-world sources.Ultimately, the primary goal of this PhD study was to develop a robust nanocomposite material containing nZVI for water treatment systems. Taking the lessons learned from initial composite work using MgAC and COPs, the final material combined granular activated carbon with COP and nZVI. After a lengthy process in developing a method to chemically graft COP material to the surface of activated carbon, it was possible to impregnate that composite material with nZVI. Because of the activated carbon backbone, the final material proved to be an extremely robust material with the structural integrity to be used in a packed-bed column that is common when treating high volumes of water. Although, continued optimization of the material is necessary, preliminary results when adsorbing and degrading contaminants were very promising, outperforming activated carbon alone and just the carbon impregnated with nZVI. Also, a bonus effect was achieved in the process. In that the entire composite material, in particular the COP attached to the surface of the carbon, acted as a protective barrier from the effects of oxidation. The carbon-COP-nZVI composites exhibited nearly 100% reactive iron content upon synthesis, compared to much lower amounts in other reported nZVI composites or the carbon-nZVI produced in this study having only 80% reactive iron content.The results of this PhD concluded in various advances in the application and assessment of nZVI and nZVI composite materials. Various composite materials provided increased colloidal stability and reactivity for nZVI. Various washing and storage strategies elucidated better methods for delivering nZVI to a water contaminant and the underlying mechanisms taking place in the nZVI corrosion process. Finally, novel materials combining three different technologies were developed to eventually lead to a robust water treatment system capable of degrading typically hard to remediate water pollutants.

Nanoscale zero valent iron (nZVI) has been intensively studied for the treatment of a plethora of pollutants through reductive reaction, however, the nano size should be of concern when nZVI is considered for water treatment, due to difficulties in recovery. The loss of nZVI causes not only economical loss, but also potential risk to human health and environment. Thus, the immobilization onto coarse or structured support is essential. In this study, two representative processes for nZVI immobilization on granular activated carbon (GAC) were evaluated, and optimized conditions for synthesizing Fe/GAC composite were suggested. Both total iron content and Fe0 content can be significantly affected by preparation processes, therefore, it was important to avoid oxidation during preparation to achieve higher reduction capacity. Synthesis conditions such as reduction time and existence of intermediate drying step were investigated to improve Fe0 content of Fe/GAC composites. The optimal condition was two hours of NaBH4 reduction without intermediate drying process. The prepared Fe/GAC composite showed synergistic effect of the adsorption capability of the GAC and the degradation capability of the nZVI, which make this composite a very effective material for environmental remediation.

Covalent organic polymers (COPs) have emerged as one of the leading advanced materials for environmental applications, such as the capture and recovery of carbon dioxide and the removal of contaminants from polluted water.1–4 COPs exhibit many remarkable properties that other leading advanced materials do not all-encompassing possess. Moreover, COPs have proven to be extremely stable in a wide variety of conditions, i.e. extremely high temperatures and boiling water for weeks at a time, which make them ideal for environmental applications;1 ranging from CO2 capture and recovery to organic solvent uptake in concentrated streams to metal and organic pollutant adsorption in contaminated waters.2 However, given the nanoscale structure of these COPs, real-world application has yet remained elusive for these materials. By creating a material large and robust enough to be used in a full-scale operation, and by retaining the unique properties that only nanomaterials can offer; this novel class of carbon-based materials promises to be a practical and efficient solution to many environmental applications. Herein, we report the functionalization of COPs onto the surface of activated carbon granules; through a series of surface modification techniques, followed by the synthesis of a COP “shell” around the carbon granule. Activated carbon, established as one of the cheapest, robust, and most effective environmental remediation materials of all time, provides the ideal base material for the grafting of COPs onto a material large enough to be able to be used in a packed-bed column. These columns can then be applied in biogas purification to remove CO2 and up-concentrate methane, in the exhaust flue gas stream from a power plant. Furthermore, by impregnating nanoscale zero valent iron (nZVI) inside the COP matrix, these columns can subsequently degrade organic contaminants, e.g. halogenated solvents, azo dyes, antibiotics, etc., during the water treatment process as a flow-through water treatment column that can syngergistically adsorb and degrade various pollutants in various water sources. A first of its kind, activated carbon with a COP-functionalized shell provides a robust and regenerate-able material with the durability and versatility for a wide range of environmental applications.

Even though nanoscale zero valent iron (nZVI) has been intensively studied for the treatment of a plethora of pollutants through reductive reaction, a quantification of nZVIreactivity has not been standardized. Here, we developed series of colorimetric assays for determining reductive activity of nZVI and its composite with granular activated carbon(GAC). The assay focused on analysis of reaction products rather than its mother compounds, which gives more accurate quantification of reductive activity. The colorimetric assays were developed to quantify three reaction products, ammonia, phenol, and aniline, generated as results of reduction of nitrate, halophenols, and nitrobenzene, respectively. The color reactions are simple and versatile since same types of reagents are able to be applied for all reactions. The colorimetric assays were further miniaturizedand optimized into 96-well microplate having 230 μL of sample volume and 2 h of reaction time. The three groups of compounds, nitrate, nitrobenzene, and para-positionedhalogenated phenols, showed graduated reactivity and were possible to distinguish a reaction mechanism between normal reduction and catalytic behaviour of second metal.The applicability was successfully proven by determining reactivity of GAC/Fe(0) composite prepared in various reduction conditions. It was shown that reactivity of GAC/Fe(0) was significantly influenced by reduction conditions, i.e. pH and reduction time, and addition of second metal further increased its reactivity. The preliminary results of GAC/Fe(0) reactivity obtained by suggested assay would be useful to determine suitable reaction condition for remediation work and estimate efficiency and required time.Therefore, suggested reactivity test with different compound combined with multiwell microplate based color assay will be useful and simple tool in various nZVI relatedresearch topics, e.g. different stabilization, immobilization, etc.

The project aims to investigate the benefits for health and environment that the use of nanomaterials in products and technologies may have. More specifically, the project provides an overview of the most relevant nano-enabled environmental technologies, different types of products and technologies on the (Danish) market, as well as products and technologies, which are still in R&D and it will provide a qualitative overview of health and environmental pros and cons of these technologies. The project has focused on technologies applied in: 1) purification of water and wastewater, 2) remediation of soil and groundwater, 3) cleaning of air, 4) reduction of energy consumption and 5) for improving hygiene in the health care sector by utilizing the antibacterial properties of certain nanomaterials.

Covalent organic polymers (COPs) have emerged as one of the leading advanced materials for environmental applications, such as the capture and recovery of carbon dioxide and the removal of contaminants from polluted water. COPs exhibit many remarkable properties that other leading advanced materials do not all-encompassing possess. Moreover, COPs have proven to be extremely stable in a wide variety of conditions, i.e. extremely high temperatures and boiling water for weeks at a time, which make them ideal for environmental applications; ranging from CO2 capture and recovery to organic solvent uptake in concentrated streams to metal and organic pollutant adsorption in contaminated waters. However, given the nanoscale structure of these COPs, real-world application has yet remained elusive for these materials. Herein, we report the functionalization of COPs onto the surface of activated carbon granules; through a series of surface modification techniques, followed by the synthesis of a COP “shell” around the carbon granule. Activated carbon, established as one of the cheapest and most effective environmental remediation materials of all time, provides the perfect base material for the attachment of COPs onto a material large enough to be able to be used in a packed-bed column. These columns can then be applied to the exhaust flue gas stream from a power plant or as a flow-through water treatment column. Furthermore, by impregnating nanoscale zero valent iron (nZVI) inside the COP matrix, these columns can subsequently degrade organic contaminants, e.g. halogenated solvents, azo dyes, antibiotics, etc., during the water treatment process. A first of its kind, activated carbon with a COP-functionalized shell provides a robust and regenerate-able material with the durability and versatility for a wide range of environmental applications.

Zero valent iron is commonly used in a variety of treatment technologies (e.g. permeable reactive barriers), though recently a heavier focus has been placed on nano-sized zero valent iron (nZVI). Having superior reductive properties and large surface areas, nZVI is ideal for the degradation of chemicals such as azo dyes and trichloroethylene (TCE). However, stabilization and immobilization of nZVI is a key parameter in its effectiveness as a chemical degradation agent for both in-situ and ex-situ applications. Most importantly, this inhibits unwanted iron oxidation from the environment and prevents particle agglomeration; but also still allows for contaminant diffusion into the composite matrix, leading to degradation. In this study, the effect of various covalent organic polymers (COPs) as effective supporting materials for nZVI for optimal pollutant degradation was assessed. These COPs demonstrate promising results for the ability to adsorb and remove carbon dioxide, yielding the notion that they are capable of groundwater contaminant removal. Composites of nZVI impregnated within COPs of high surface areas exhibit effective ability to degrade azo dyes, up to 95%, over a 30-minute reaction period. Dye decolorization results were designated a precursor for effectiveness of pollutant decontamination; pollutants ranging in chlorinated organics, heavy metals, and various other groundwater contaminants.Using transmission electron microscopy (TEM), dimensional extrapolation of composite widths were on average approximately 6nm, with extremes at 2.5nm and 24nm. Composite lengths exhibited much more variance, and although the average was approximately 110nm, many lengths were observed as low as 50-70nm and as high as 260-280nm ranges.BET surface areas of the polymers were as small as 1.8m2/g using COP47, and as large as 600m2/g using COP19. Degradation of acid black I exhibited very fast kinetics within the first 2.5 minutes, with a strong plateau effect thereafter for 30 minutes, plotted in Figure 1. Ultimately, dye removal rates were as high as 95% in COP19 and as low as 42% in COP48. Removal efficiency was determined to be a function of the BET surface area, as well as individual properties of the core/linker molecular make-up of each COP. The parallel control experiment with nZVI and COPs clearly indicated the azo dye removal mechanism by COP-nZVI-composite, the synergistic effect of adsorption onto COPs and reduction by impregnated nZVI. This translates well for treatment of many groundwater pollutants, with similar trends in abilities of each composite to degrade pollutants.

Despite the large surface area and superior reactivity of nZVI, its limited stability is a major obstacle for in situ subsurface remediation. In this study, Mg-aminoclay (MgAC) was applied for the first time as a stabilizer in nZVI synthesis. With increased doses of Mg-aminoclay, nZVI particle growth was inhibited and thin sheathed grape-like nZVI particles with higher crystallinity were produced. The coated nZVI were smaller and non-aggregating, and it can reduced nitrate 350-fold faster than uncoated. The higher stability of MgAC coated nZVI was achieved by electrostatic repulsion from the positively charged MgAC coating. Moreover, the proper washing strategy is essential to keep stability and reactivity during preparation and transport.

Having superior reductive properties and large surface areas, nanosized zero valent iron (nZVI) is ideal for the degradation of chemicals such as azo dyes and trichloroethylene (TCE). However, immobilization of nZVI is a key parameter in its effectiveness as a chemical degradation agent. In this study, the effect of various covalent organic polymers (COPs) as effective supporting materials for nZVI for optimal pollutant degradation was assessed. These COPs demonstrate promising results for the ability to adsorb and remove carbon dioxide, yielding the notion that they are capable of groundwater contaminant removal. Composites of nZVI impregnated within COPs of high surface areas exhibit effective ability to degrade azo dyes, up to 95%, over a 30-minute reaction period. Dye decolorization results were designated a precursor for effectiveness of pollutant decontamination; pollutants ranging in chlorinated organics, heavy metals, and various other groundwater contaminants.