Evaluation of novel, cationic electrospun microfibrous membranes as adsorbents in bacteria removal

Abstract

Electrospun microfibrous membranes comprised of poly(methyl methacrylate)-poly((2diethylaminoethyl) methacrylate) random copolymers (PMMA-co-PDEAEMA) of various chemical compositions blended together with a commercially available PMMA have been fabricated with diameters between 4.0-6.4 µm and further evaluated as adsorbents for bacteria removal from aqueous media. The morphology and thermal stability of the membranes were determined by scanning electron microscopy (SEM) and thermal gravimetric analysis (TGA), respectively. Tensile tests were also performed in order to investigate their mechanical properties. Membrane evaluation as adsorbents against two gram-negative bacteria namely Pseudomonas aeruginosa and Advenella species revealed that the membranes containing the highest percentage of the cationic moieties (DEAEMA) exhibited the highest adsorption efficiency. The bacteria removal by the microfibrous membranes was studied by UV-vis spectrophotometry upon measuring the optical density (OD) of the microorganisms. The highest recorded bacteria removal percentages after 8 hr were approximately 70% and 45%, for the Pseudomonas aeruginosa and Advenella species respectively, whereas in both cases complete (100%) bacteria removal was observed after 24 hr of membrane immersion in bacteria-containing aqueous solutions. The experimental adsorption isotherms for P. aeruginosa and Advenella sp. were well-fitted with the Langmuir isotherm model indicating a monolayer adsorption process. SEM was also used to confirm the adhesion of the bacteria onto the electrospun microfibers. Most importantly, these materials exhibited great performance on the removal of microorganisms from urban wastewater as determined via the standard plating technique prepared by agar. Methyl methacrylate (MMA, Fluka, ≥ 99%), poly(methyl methacrylate) (PMMA) (Mw ∼ 350 000, Sigma-Aldrich), n-hexane (Scharlau, 96%), tetrahydrofuran (THF, Scharlau, extra pure) and ethyl acetate (EA, Scharlau, GC grade, 99.8%) were used without further purification. 2-(diethylaminoethyl) methacrylate (DEAEMA, Sigma-Aldrich, 99%) was passed through a basic alumina column prior to the polymerizations and used without further purification. The radical initiator 2,2'-azobis(2-methylpropionitrile) (AIBN, Sigma-Aldrich, 95%) was recrystallized twice from ethanol. Deuterated chloroform (CDCl 3 , Merck), glutaraldehyde (Sigma-aldrich, 25% in water), calcium chloride dihydrate (CaCl 2 .2H 2 O, Scharlau, Reagent grade), ammonium sulfate ((NH 4 ) 2 SO 4 , Scharlau, reagent grade), sucrose (Himedia), potassium phosphate dibasic (K 2 HPO 4 , Sigma-aldrich, ≥98%), magnesium chloride (MgCl 2 , Sigma, ≥98%) and sodium chloride (NaCl, Himedia) were used as received by the manufacturer. The selected gram-negative microorganisms Pseudomonas aeruginosa LVD-10 and Advenella species LVX-4 were provided by the Applied Microbiology Laboratory culture collection of the Cyprus University of Technology. They were previously isolated and deposited in GenBank with accession number KF728673.1 for P. ...

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