Chemical and Biomolecular Engineering

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Browsing Chemical and Biomolecular Engineering by Subject "Adsorption"

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    Characterizing adsorption of associating surfactants on carbonates surfaces
    (Elsevier, 2018) Jian, Guoqing; Puerto, Maura; Wehowsky, Anna; Miller, Clarence; Hirasaki, George J.; Biswal, Sibani L.
    HYPOTHESIS: The adsorption of anionic surfactants onto positively charged carbonate minerals is typically high due to electrostatic interactions. By blending anionic surfactants with cationic or zwitterionic surfactants, which naturally form surfactant complexes, surfactant adsorption is expected to be influenced by a competition between surfactant complexes and surfactant-surface interactions. EXPERIMENTS: The adsorption behavior of surfactant blends known to form complexes was investigated. The surfactants probed include an anionic C15-18 internal olefin sulfonate (IOS), a zwitterionic lauryl betaine (LB), and an anionic C13-alcohol polyethylene glycol ether carboxylic acid (L38). An analytical method based on high-performance liquid chromatography evaporative light scattering detector (HPLC-ELSD) was developed to measure three individual surfactant concentrations from a blended surfactant solution. The adsorption of the individual surfactants and surfactant blends were systematically investigated on different mineral surfaces using varying brine solutions. FINDINGS: LB adsorption on calcite surfaces was found to be significantly increased when blended with IOS or L38 since it forms surfactant complexes that partition to the surface. However, the total adsorption of the LB-IOS-L38 solution on dolomite decreased from 3.09 mg/m2 to 1.97 mg/m2 when blended together compared to summing the adsorption values of individual surfactants, which highlights the importance of mixed surfactant association.
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    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 Treatment
    Perfluorooctanesulfonate (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.