Simo O. Pehkonen

Lysozyme-coupled poly(poly(ethylene glycol) methacrylate)-stainless steel hybrids and their antifouling and antibacterial surfaces.

An environmentally benign approach to impart stainless steel (SS) surfaces with antifouling and antibacterial functionalities was described. Surface-initiated atom transfer radical polymerization (ATRP) of poly(ethylene glycol) monomethacrylate) (PEGMA) from the SS surface-coupled catecholic L-3,4-dihydroxyphenylalanine (DOPA) with terminal alkyl halide initiator was first carried out, followed by the immobilization of lysozyme at the chain ends of poly(ethylene glycol) branches of the grafted PEGMA polymer brushes. The functionalized SS surfaces were shown to be effective in preventing bovine serum albumin (BSA) adsorption and in reducing bacterial adhesion and biofilm formation. The surfaces also exhibited good bactericidal effects against Escherichia coli and Staphylococcus aureus. The concomitant incorporation of antifouling hydrophilic brushes and antibacterial enzymes or peptides onto metal surfaces via catecholic anchors should be readily adaptable to other metal substrates, and is potentially useful for biomedical and biomaterial applications.

Superhydrophobic CuO nanoneedle-covered copper surfaces for anticorrosion

With unique water-repellency and self-cleaning properties, superhydrophobic surfaces promise a great potential of anticorrosion for engineered metals. The current study reports a facile and controllable anodization approach to fabricate superhydrophobic CuO nanoneedle array (NNA) films for the enhancement of corrosion resistance of copper substrates. The anodic CuO NNA films were grown on copper foils by electrochemical anodization in an aqueous KOH solution for different anodization times. The morphological features and crystalline structures of the anodic CuO NNA were characterized by SEM-EDS and XRD. The superhydrophobicity on the hierarchical CuO NNA films was achieved by chemical modification with fluoroalkyl-silane (FAS-17). The presence of low surface energy fluorosilanized carbon (–CFx) groups on the FAS-modified surfaces was ascertained by EDS, XPS and water contact angle analyses. The wetting behaviour of the FAS-modified surfaces was investigated to elucidate the correlation between the static water contact angles, surface roughness, dynamic water contact angle hysteresis, and anodization time. The FAS-modified copper surfaces demonstrated not only the desirable superhydrophobicity with a water contact angle as high as approximately 169° and contact angle hysteresis as low as about 5°, but also substantially improved corrosion resistance in an aqueous NaCl solution (3.5%) with an inhibition efficiency higher than 90%, as revealed by means of Tafel plots and EIS measurements. The stability and durability of the superhydrophobic FAS-modified surfaces were evaluated by observing the change in surface wettability and geometric microstructures as a function of exposure time in an aqueous NaCl solution.

Inorganic−Organic Hybrid Coatings on Stainless Steel by Layer-by-Layer Deposition and Surface-Initiated Atom-Transfer-Radical Polymerization for Combating Biocorrosion

To improve the biocorrosion resistance of stainless steel (SS) and to confer the bactericidal function on its surface for inhibiting bacterial adhesion and biofilm formation, well-defined inorganic-organic hybrid coatings, consisting of the inner compact titanium oxide multilayers and outer dense poly(vinyl-N-hexylpyridinium) brushes, were successfully developed. Nanostructured titanium oxide multilayer coatings were first built up on the SS substrates via the layer-by-layer sol-gel deposition process. The trichlorosilane coupling agent, containing the alkyl halide atom-transfer-radical polymerization (ATRP) initiator, was subsequently immobilized on the titanium oxide coatings for surface-initiated ATRP of 4-vinylpyridine (4VP). The pyridium nitrogen moieties of the covalently immobilized 4VP polymer, or P(4VP), brushes were quaternized with hexyl bromide to produce a high concentration of quaternary ammonium salt on the SS surfaces. The excellent antibacterial efficiency of the grafted polycations, poly(vinyl-N-pyridinium bromide), was revealed by viable cell counts and atomic force microscopy images of the surface. The effectiveness of the hybrid coatings in corrosion protection was verified by the Tafel plot and electrochemical impedance spectroscopy measurements.

Antibacterial Inorganic−Organic Hybrid Coatings on Stainless Steel via Consecutive Surface-Initiated Atom Transfer Radical Polymerization for Biocorrosion Prevention

To enhance the corrosion resistance of stainless steel (SS) and to impart its surface with antibacterial functionality for inhibiting biofilm formation and biocorrosion, well-defined inorganic-organic hybrid coatings, consisting of a polysilsesquioxane inner layer and quaternized poly(2-(dimethyamino)ethyl methacrylate) (P(DMAEMA)) outer blocks, were prepared via successive surface-initiated atom transfer radical polymerization (ATRP) of 3-(trimethoxysilyl)propyl methacrylate (TMSPMA) and 2-(dimethylamino)ethyl methacrylate (DMAEMA). The cross-linked P(TMASPMA), or polysilsesquioxane, inner layer provided a durable and resistant coating to electrolytes. The pendant tertiary amino groups of the P(DMAEMA) outer block were quaternized with alkyl halide to produce a high concentration of quaternary ammonium groups with biocidal functionality. The so-synthesized inorganic-organic hybrid coatings on the SS substrates exhibited good anticorrosion and antibacterial effects and inhibited biocorrosion induced by sulfate-reducing bacteria (SRB) in seawater media, as revealed by antibacterial assay and electrochemical analyses, and they are potentially useful to steel-based equipment under harsh industrial and marine environments.

Purification of phenol-contaminated water by adsorption with quaternized poly(dimethylaminopropyl methacrylamide)-grafted PVBC microspheres

Cross-linked poly(vinylbenzyl chloride) (PVBC) microspheres tethered with polymer brushes containing quaternary ammonium ions were developed as an anionic adsorbent for the efficient removal of phenol from aqueous solutions. The terminal alkyl chlorine groups on the PVBC microspheres served as anchor sites for the grafting of poly(dimethylaminopropyl methacrylamide) (PDMAPMA) brushes via surface-initiated atom transfer radical polymerization (ATRP). The pendent tertiary amino groups of the PDMAPMA chains were converted into quaternary ammonium ions by N-alkylation reaction to produce anionic adsorption functionality. Success for each reaction step was ascertained by Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). Batch adsorption results demonstrated that solution pH values in a wide range of 3.0–11.0 had no evident effect on phenol adsorption by the quaternized PDMAPMA-grafted PVBC (i.e., PVBC-g-QPDMAPMA) microspheres, and that the adsorption capacity of the microspheres increased with the grafting density of the quaternized PDMAPMA brushes within 6 h. The so-synthesized anionic adsorbents had a rapid pseudo-first-order-adsorption kinetic (equilibrium achieved within 60 min), and the Langmuir model-fitted maximum adsorption capacity of phenol was approximately 2.23 mmol g−1 at pH 6.5 with an initial concentration of 1.05–5.31 mmol L−1 (i.e., 100–500 mg L−1). The calculated thermodynamic parameters revealed an exothermic and spontaneous adsorption process of phenol onto the quaternized QPDMAPMA-grafted microspheres. Desorption and adsorption cycle experiments demonstrated that the anionic adsorbents loaded with phenol were found to be readily regenerated in a 0.1 mol L−1 NaOH solution, and that the adsorption capacity decreased by less than 10% upon five cycles.

Peracids in water treatment: A critical review

ABSTRACT Peracids have gained interest in the water treatment over the last few decades. Peracetic acid (CH3CO3H) has already become an accepted alternative disinfectant in wastewater disinfection whereas performic acid (CHO3H) has been studied much less, although it is also already commercially available. Additionally, peracids have been studied for drinking water disinfection, oxidation of aqueous (micro)pollutants, sludge treatment, and ballast water treatment, to name just a few examples. The purpose of this review paper is to represent comprehensive up-to-date information about the water treatment applications, aqueous reaction mechanisms, and disinfection by-product formation of peracids, namely performic, peracetic, and perpropionic acids.

High efficiency removal of methylene blue using SDS surface-modified ZnFe 2 O 4 nanoparticles

Recent studies have shown that hazardous organic dye substances can be removed from aqueous solutions by spinel ferrite nanomaterials. We found that Sodium Dodecyl Sulfonate (SDS) surface-modified mesoporous ZnFe2O4 nanoparticles (10-50nm) have a remarkably high maximum adsorptive capacity (∼699.30mg/g) for aqueous Methylene Blue (MB) removal at T of 288K and pH of 12. Unmodified ZnFe2O4 nanoparticles suffer from particle agglomeration, which reduces surface area, thus reducing their adsorptive capacity. Here it is shown that when modified with SDS, the specific surface area increased by ∼34%. It is also shown that the anionic SDS surfactant significantly increased the electrostatic attraction to the cationic MB compound. Moreover, it was found that adsorption of MB positively correlated with the aqueous solutions pH, which is attributed to a stronger negative charge on the SDS modified ZnFe2O4 surface at high pHs. The SDS-modified ZnFe2O4 adsorption of MB fitted well with the Langmuir adsorption isotherm model, and kinetic data fitted into a pseudo-second-order model. Thermodynamic parameters indicated that the adsorption was spontaneous and exothermic in nature, and physisorption dominated the adsorption of MB. The findings of this study demonstrate the potential for enhanced removal of MB contamination from aqueous solutions by SDS-modified ZnFe2O4 nanoparticles and, therefore, the potential for them to remove cationic organic dye from wastewater.

Enhanced adsorption of Cu(II) ions on chitosan microspheres functionalized with polyethylenimine-conjugated poly(glycidyl methacrylate) brushes

To enhance the adsorption capacity of crosslinked chitosan (CCS) microspheres towards Cu(II) ions, well-defined poly(glycidyl methacrylate) (PGMA) brushes were grafted onto the surfaces of CCS microspheres via surface-initiated atom transfer radical polymerization (ATRP) for subsequent conjugation of polyethylenimine (PEI). The resultant PEI-grafted CCS (defined as CCS-g-PGMA-c-PEI) microsphere was used as an effective adsorbent to uptake Cu(II) ions from aqueous solution. Success in each functionalization step was ascertained by ATR-FTIR, XPS, SEM and water contact angle measurements. Batch adsorption experiments were performed to determine adsorption kinetics, adsorption isotherms and thermodynamics of Cu(II) ions on the CCS-g-PGMA-c-PEI microspheres. The adsorption equilibrium of Cu(II) ions on the microspheres was found to be rapidly established within 60 min at an optimal solution pH of 5.0, and the adsorption kinetics was well represented by the pseudo-second-order model, together with a significant effect of mass transfer on the Cu(II) adsorption rate. The Langmuir-fitted maximum adsorption capacity was about 3.58 mmol g−1 (229 mg g−1), and the calculated thermodynamic parameters demonstrated an endothermic and spontaneous adsorption process of Cu(II) ions. The PEI-grafted CCS microspheres also exhibited good regenerability and stability for recycle applications. The postulated adsorption mechanism was proposed to account for the adsorption process of Cu(II) ions on the CCS-g-PGMA-c-PEI microspheres.

PCL microspheres tailored with carboxylated poly(glycidyl methacrylate)–REDV conjugates as conducive microcarriers for endothelial cell expansion

Microcarrier cell culture systems provide one of the most promising techniques for cell amplification due to their high surface area-to-volume ratio. In this study, biodegradable polycaprolactone (PCL) microspheres tethered with carboxylated poly(glycidyl methacrylate)-REDV conjugates were developed by a combination of surface-initiated atom transfer radical polymerization (ATRP) and azide-alkyne click chemistry as conducive microcarriers for rapid cell expansion of human umbilical vein endothelial cells (HUVECs). Azido-terminated poly(glycidyl methacrylate) (PGMA-N3) brushes were grafted onto the PCL microspheres by surface-initiated ATRP. Subsequent carboxylation of PGMA-N3 brushes was accomplished by azide-alkyne click reaction with hexynoic acid. REDV peptides were covalently conjugated to the pendent carboxyl groups on the side chain of carboxylated PGMA-COOH brushes via carbodiimide chemistry to enhance the cytocompatibility of the three-dimension (3D) PCL scaffolding system. Success in each functionalization step was ascertained by the measurement of attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and wet laser particle size analysis. In vitro cell-loading assay of HUVECs demonstrated a significant improvement of cell adhesion and proliferation on the REDV-immobilized PCL microsphere surfaces, and a confluent layer of HUVECs was formed after 7 days of incubation. The highly biocompatible and transportable nature of functionalized PCL microcarriers offers significant potential as a cell expansion platform.

Click functionalization of poly(glycidyl methacrylate) microspheres with triazole-4-carboxylic acid for the effective adsorption of Pb(II) ions

Chelating 1,2,3-triazole-4-carboxylic acids were successfully introduced onto the cross-linked PGMA microsphere surfaces by the combination of ring-opening reactions and the click chemistry process between the alkynyl groups of propiolic acid (PA) and the epoxy groups on the surfaces of the PGMA microspheres. The resultant PA-conjugated PGMA microspheres were found to be an effective adsorbent for Pb(II) removal from aqueous solutions. Success in each functionalization step was ascertained by ATR-FTIR, XPS and SEM characterization. Batch and column adsorption experiments were performed to determine the adsorption kinetics, adsorption isotherms and thermodynamics of Pb(II) ions on the as-synthesized microspheres. The Langmuir-fitted maximum adsorption capacity for Pb(II) ions was found to be 69.41 mg g−1 at a solution pH of 5.0, together with the adsorption equilibrium being achieved within 60 min. The thermodynamic studies demonstrated an endothermic and spontaneous adsorption process of Pb(II) ions on the PA-conjugated PGMA microspheres. Column adsorption studies revealed the decrease in the adsorption capacities of the breakthrough and exhaustion points with increasing flow rate. The postulated adsorption mechanism was attributed to the electrostatic interactions from carboxylic groups and chelation or coordination of Pb(II) ions from the triazole moieties, which was facilitated to form a pluralistic potential trap for Pb(II) ions, as confirmed by XPS characterization.