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    Item type:Publication, Access status: with files ,
    Characterizing macroporous ion exchange membrane adsorbers for natural organic matter (NOM) removal-adsorption and regeneration behavior
    (Multidisciplinary Digital Publishing Institute (MDPI), 2024-06)
    Wullenweber, Jon
    ;
    Bennert, Julia
    ;
    Mantel, Tomi Jonathan
    ;
    Ernst, Mathias
    Addressing the characterization of Natural Organic Matter (NOM) removal by functionalized membranes in water treatment, this study evaluates the effectiveness of two commercial ion-exchange membrane adsorbers: Sartobind® Q (with quaternary amines) and D (with tertiary amines). Using Suwannee River NOM (SRNOM) as a surrogate, Langmuir adsorption isotherms revealed maximum capacities (Qmax) of 2966 ± 153 mg C/m2 and 2888 ± 112 mg C/m2, respectively. Variations in flux from 50 to 500 LMH had a minimal impact on breakthrough times, proving low diffusion limitations. The macroporous (3-5 µm) functionalized cellulose-based membranes exhibited high permeabilities of 10,800 L/(h m2 bar). Q maintained positive zeta potential vs. pH, while D's zeta potential decreased above pH 7 due to amine deprotonation and turning negative above an isoelectric point of 9.1. Regeneration with 0.01 M NaOH achieved over 95% DOC regeneration for Sartobind® D, characterizing reversibility through a pH-swing. Cyclic adsorption showed that Q maintained its capacity with over 99% DOC regeneration, while D required acidic conditioning after the first regeneration cycle to mitigate capacity reduction and re-deprotonate the adsorber. These results have demonstrated the potential suitability of adsorber membranes, designed originally for biotechnological purposes, for the possible removal of disinfection byproduct precursors in drinking water treatment.
    Publicationtype: Journal Article
      36  31
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    Item type:Publication, Access status: with files ,
    Electro-sorption and -desorption characteristics of electrically conductive polyacrylonitrile membranes to remove aqueous natural organic matter in dead-end ultrafiltration system
    (Elsevier, 2024-02)
    Usman, Muhammad
    ;
    Glaß, Sarah
    ;
    Mantel, Tomi Jonathan
    ;
    Filiz, Volkan
    ;
    Ernst, Mathias
    Electrically conductive (EC) membranes have emerged as an innovative approach in removing natural organic matter (NOM) by electro-sorption (e-sorption) when external anodic potential (AP) is applied. In this study, the EC membranes were established by a forming a porous nanolayer of Pt nanoparticles via magnetron sputtering on both sides of virgin and chemically modified PAN ultrafiltration (UF) membranes. The modified PAN membranes were functionalized with ethylenediamine (PAN-EDA) and sodium hydroxide (PAN-NaOH). The virgin PAN membrane material contains nitrile group and demonstrated a negative zeta potential in the analyzed pH range. The PAN-EDA membrane owned amidine and amine groups, whereas PAN-NaOH membrane possessed carboxyl and amide groups in the membrane matrix. The PAN-NaOH and PAN-EDA membranes exhibited isoelectric points at 3.7 and 7.8, respectively. Electrical field-assisted UF experiments were conducted with Suwannee River NOM in dead-end mode and NOM removal was monitored using different methods of NOM characterization (e.g., SEC, DOC and UV254 absorbance). The results revealed that the non-electrically conductive (NEC) and EC virgin PAN membranes exhibited almost no intrinsic adsorption (at 0 V external potential) and e-sorption of NOM at 2.5 V AP respectively. However, NEC PAN-NaOH and PAN-EDA membranes showed DOC intrinsic sorption loadings of 17 mg·m−2 and 258 mg·m−2 at permeate flux 100 L·m−2·h−1 and pH 7 respectively. In comparison, the DOC e-sorption loadings of the EC PAN-NaOH and EC PAN-EDA membranes at 2.5 V AP were 197 mg·m−2 and 525 mg·m−2 under same test conditions respectively. The NOM e-desorption characteristics of the EC modified PAN membranes were also investigated to regenerate membranes for a sustainable filtration process. The results indicated that the EC PAN-NaOH and PAN-EDA membranes can be regenerated by reversing the electrical polarity almost completely. In conclusions, the outcomes of this work confirm that the presence of the derivatives of amines (e.g., amines, amidine and amide groups) and carboxyl group are necessary in the membrane matrix to induce e-sorption and -desorption characteristics.
    Publicationtype: Journal Article
    Scopus© Citations 1  28  112
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    Item type:Publication, Access status: with files ,
    Surface grafted N-Oxides have low-fouling and antibacterial properties
    (Wiley, 2023-12-13)
    Burmeister, Nils
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    Zorn, Eilika
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    Farooq, Aneeq
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    Preuss, Lena
    ;
    Vollstedt, Christel
    Low-fouling materials are often generated by surface zwitterionization with polymers. In this context, poly-N-oxides have recently attracted considerable attention as biomimetic stealth coatings with low protein adsorption. Herein, this study reports that poly-N-oxides can be grafted from plasma-activated plastic base materials. The resulting hydrophilic surfaces have low-fouling properties in bacterial suspensions and suppress the formation of biofilms. Moreover, efficient antibacterial activity against Gram-negative and Gram-positive bacteria caused by release of reactive oxygen species is observed. The latter effect is specific for polymeric N-oxides and is most likely triggered by a reductive activation of the N-oxide functionality in the presence of bacteria. In contrast to other zwitterionic polymers, N-oxides combine thus low-fouling (stealth) properties with antibacterial activity. The bioactive N-oxide groups can be regenerated after use by common oxidative disinfectants. Poly-N-oxides are thus attractive antibacterial coatings for many base materials with a unique combined mechanism of action.
    Publicationtype: Journal Article
    Scopus© Citations 4  21  66