Browsing by Author "Powell, Camilah D."
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Item Development of Non-conventional Iron-based Nanomaterials for Water Treatment(2020-01-29) Powell, Camilah D.; Wong, Michael S.Magnetic particles, generally nanostructured and magnetite-based, have been used extensively to remove drinking water contaminants via adsorption or catalytic degradation. Compositions alternative to Fe3O4 could address long-standing issues of magnetic recoverability and material integrity in real waters. Two alternative compositions of magnetic nanoparticles (Fe3C@C and AuFe) are studied as nano-absorbents and nano-catalysts, respectively. The stability, magnetic separability, and adsorptive properties of nanostructured carbon-coated iron carbide (Fe3C@C) were compared to those of Fe3O4 and other common iron oxide-based nanomaterials. Experimental results show that (i) Fe3C@C is chemically stable in simulated drinking water, (ii) can be separated from water magnetically under flow with >99% recovery, and (iii) is capable of removing organics (1.60 mg-MB/m2) or oxo-anions (6.75 µg-As/m2) from simulated drinking water. In terms of scale up, an optimized permanent magnetic nanoparticle recovery device (i.e., the MagNERD) was developed and operated to separate, capture and reuse superparamagnetic nanoparticles from treated water in-line under continuous flow conditions. Experimental data and computational modeling demonstrate how the MagNERD’s efficiency to recover nanoparticles depends upon reactor configuration, including the integration of stainless-steel wool around permanent magnets, hydraulic flow conditions, and magnetic nanoparticle uptake. The MagNERD efficiently removes high concentrations (500 ppm) of magnetic nanopowder (e.g., >95% removal) under scalable and process-relevant flow rates (e.g., 1 L/min through a 1.11-L MagNERD reactor) from varying water matrices (e.g., ultrapure water, brackish water) and after treatment of As contaminated simulated drinking water (e.g., >94% removal of arsenic-bound Fe3O4). Additionally, we investigate nano-magnetism for the purposes other than magnetic removal – magnetic nanoparticle heating – and explore the structure property relationship between a classically non-magnetic material (e.g., nano-hematite) and magnetic nanoparticle heating. Lastly, the legitimacy of using a magnetic and environmentally bengin AuFe bimetallic catalyst for environmental remediation is explored. Using nitroarene reduction – a simple model environmental reaction – as a probe reaction and AuFe bimetallic catalyst, we found applying an alternating magnetic field (AMF) increased nitroarenes reduction reaction rates by 200%, via localized particle surface heating. This rate constant was equivalent to a ~27C bulk reaction temperature, suggesting AMF exposure raised the AuFe NP surface temperature ~4C above ambient.Item Highly Defective UiO-66 Materials for the Adsorptive Removal of Perfluorooctanesulfonate(American Chemical Society, 2019) Clark, Chelsea A.; Heck, Kimberly N.; Powell, Camilah D.; Wong, Michael S.; Nanosystems Engineering Research Center for Nanotechnology-Enabled Water TreatmentPerfluorooctanesulfonate (PFOS) is a persistent organic pollutant that is bioaccumulative and toxic. While its use in most countries has been restricted to certain industrial applications due to environmental and health concerns, chrome plating and semiconductor manufacturing facilities are industrial point sources of PFOS-containing wastewater. Current remediation technologies are ineffective at treating these highly concentrated industrial effluents. In this work, UiO-66 metal–organic frameworks (MOFs) of several defect concentrations were studied as sorbents for the removal of PFOS from concentrated aqueous solutions. PFOS sorption isotherms indicated that defective UiO-66, prepared with HCl as a modulator, had a maximum Langmuir sorption capacity of 1.24 mmol/g, which was ∼2× greater than powdered activated carbon (PAC), but ∼2× less than that of a commercial ion-exchange resin. Defective UiO-66 adsorbed PFOS 2 orders of magnitude faster than the ion-exchange resin. Large pore defects (∼16 and ∼20 Å) within the framework were critical to the increased adsorption capacity due to higher internal surface area and an increased number of coordinatively unsaturated Zr sites to bind the PFOS head groups. Of the common co-contaminants in chrome plating wastewaters, chloride ions have a negligible effect on PFOS sorption, while sulfate and hexavalent chromium anions compete for cationically charged adsorption sites. These materials were also effective adsorbents for the shorter-chain homologue, perfluorobutanesulfonate (PFBS). The enhanced PFOS and PFBS adsorptive properties of UiO-66 highlight the advantage of structurally defective MOFs as a water treatment approach toward environmental sustainability.Item Room-Temperature Catalytic Treatment of High-Salinity Produced Water at Neutral pH(American Chemical Society, 2020) Yin, Y. Ben; Coonrod, Christian L.; Heck, Kimberly N.; Said, Ibrahim A.; Powell, Camilah D.; Guo, Sujin; Reynolds, Michael A.; Wong, Michael S.Produced waters from hydraulic fracturing (HFPW) operations greatly challenge traditional water treatment technologies due to the high concentrations of total dissolved solids (TDS), highly complex and variable water matrices, and significant residual hydrocarbon content. We recently reported the unusual ability of a PdAu catalyst to degrade phenol in simulated HFPW at room temperature by generating H2O2 in situ from formic acid and air. Phenol removal occurred at TDS levels as high as ∼10 000 ppm (ionic strength I = 0.3 M), but the catalytic reaction required pH < 4 to proceed. Here, we find that PdAu, Pd, and Au degraded phenol in the pH 5–8 range by using hydroxylamine as the hydrogen source in place of formic acid. Pd exhibited the highest activity, and Au the least. Activity of the monometallic catalysts decreased >70% as TDS increased from 0 to ∼100 000 ppm (I = 3 M), whereas the PdAu was comparatively less affected (∼50% activity decrease). All catalysts remained active at TDS levels as high as 100 000 ppm. The majority of the hydroxylamine formed N2, however this reaction generated additional nitrite/nitrate anion byproducts with nitrogen selectivities ranging from 0.5% to 11.5%, depending on the catalyst identity and reaction salinity. To demonstrate one possible flow treatment process concept, we constructed and tested a recirculating trickle bed reactor that removed 28% phenol from simulated HFPW over 48 h. These results show the potential of oxidation catalysis as a treatment approach for produced water and other high-salinity industrial wastewaters.Item Superparamagnetic nanoadsorbents for the removal of trace As(III) in drinking water(Elsevier, 2021) Marcos-Hernández, Mariana; Arrieta, Roy A.; Ventura, Karen; Hernández, José; Powell, Camilah D.; Atkinson, Ariel J.; Markovski, Jasmina S.; Gardea-Torresdey, Jorge; Hristovski, Kiril D.; Westerhoff, Paul; Wong, Michael S.; Villagrán, DinoA series of novel zeolitic imidazolate framework (ZIF) decorated superparamagnetic graphene oxide hybrid nanoadsorbents were synthesized, characterized, and tested for their As(III) adsorbed amount in simulated drinking water. The three composite nanomaterials are based each on three isostructural and water stable ZIFs, (C-1 based on ZIF-8, C-2 based on ZIF-67, and C-3 based on ZIF-Zn/Co). The composite nanomaterials and there parent materials were characterized through pXRD, TEM, FTIR, BET and magnetometry methods (SQUID), and were tested as adsorbents in a representative drinking water matrix containing arsenite (As(III)) at an initial trace concentration (realistic in some natural drinking water sources) of 35 µg/L. The nanoadsorbents were magnetically captured and removed after adsorption in batch conditions. Out of the three composites, C-2 shows the highest As(III) adsorbed amount at an initial concentration of 35 µg/L (q0) of 202 µg/g, followed by C-3 with 102 µg/g and C-1 with 82 µg/g.