Teresa Poerio

Comparison of polyethylenimine, polyacrylic acid and poly(dimethylamine-co-epichlorohydrin-co-ethylenediamme) in Cu2+ removal from wastewaters by polymer-assisted ultrafiltration☆

Some results on metal ions removal from wastewaters using water-soluble polymers such as polyethylenimine (PEI), polyacrylic acid (PAA), polyacrylic acid sodium salt (PAASS) and poly(dimethylamine-co-epichlorohydrin-co-ethylene-diamine) (PDEHED) as chelating agents and the Cu 2+ ion as the model in combination with a polymer-assisted ultrafiltration process (PAUF) are reported. In particular, the performances of these polymers in Cu 2+ removal from wastewaters were compared. Tests of bonding capacity and best operating conditions of the process showed that complexation conditions depend on pH; indeed, copper ions are complexed by PEI, PAA, PAASS and PDEHED at pHs higher than 6, 4.6, 4.6 and 8, respectively. The decomplexation reactions took place at pH <3. Bonding capacity was 0.333 mg Cu 2+ /mg polymer, meaning a ratio of polymer/Cu 2+ = 3 (w/w) for PEI, PAA and PAASS. For the chelating agent PDEHED, a ratio of PDEHED/Cu 2+ = 0.5 (w/w) was determined. UF tests, realised at two trans-membrane pressures (2 and 4 bar) by using five different flat-sheet membranes, showed that the PAA polymer and the PAN GKSS HV2/T membrane can be used when the objective of the purification process is to decrease methal concentration not lower than a certain value. The PDEHED polymer is useful if the objective of wastewater treatment is to obtain complete copper removal. Simple washings with tap water were enough for regeneration and reuse of the membranes.

Influence of protein bulk properties on membrane surface coverage during immobilization

Biomolecules immobilization is a key factor for many biotechnological applications. For this purpose, the covalent immobilization of bovine serum albumin (BSA), lipase from Candida rugosa and protein G on differently functionalized regenerated cellulose membranes was investigated. Dynamic light scattering and electrophoresis measurements carried out on biomolecules in solution indicated the presence of monomers, dimers and trimers for both BSA and protein G, while large aggregates were observed for lipase. The immobilization rate and the surface coverage on functionalized regenerated cellulose membranes were studied as a function of biomolecule concentration. Results indicated that the saturation coverage of BSA and protein G was concentration independent (immobilized protein amount of 2.40±0.03mg/g and 2.65±0.07mg/g, respectively). Otherwise, a different immobilization kinetics trend was obtained for lipase, for which the immobilized amount increases as a function of time without reaching a saturation value. Atomic force microscopy (AFM) micrographs showed the formation of monolayers for both BSA and protein G on the membrane surface, while a multilayer structure is found for lipase, in agreement with the trends observed in the related immobilization kinetics. As a result, the morphology of the proteins layer on the membrane surface seems to be strictly dependent on the proteins behavior in solution. Besides, the surface coverage has been described for BSA and protein G by the pseudo second order models, the results indicating the surface reaction as the controlling step of immobilization kinetics. Finally, enzyme activity and binding capacity studies indicated the preservation of the biomolecule functional properties.

Low temperature synthesis of nanosized NaY zeolite crystals from organic-free gel by using supported seeds

Zeolite crystals having faujasite-type (FAU) topology and particle size distribution in the nanometer range have been successfully prepared by a room temperature, short duration synthesis, in the absence of organic structure directing agents (SDAs). The use of NaX seeds anchored on α-Al2O3 tubular supports, jointly with the optimal composition of the precursor gel system, allowed control of the zeolite nanocrystal size and phase purity, and allowed reaching of a high degree of conversion of the precursor gel system into a nanocrystalline material under near ambient conditions. The X-ray diffraction (XRD) pattern collected on the samples confirmed the structural features reported for a FAU(Y) phase. The particle size of the zeolite nanocrystals was strongly dependent on the amount of seeds anchored on the supports. The mean particle size of different samples was estimated by SEM and measured by DLS, with similar results falling in the range of 35–60 nm. SEM observations also revealed that aggregates of primary crystals are present, whose size is still in the nanometer range. The synthesis approach described in the present study effectively addresses some significant issues related to the classical seeded syntheses and offers good opportunities for industrial applications. In particular, this novel synthetic route allows avoidance of tedious purification procedures and effectively reduces the cost of the zeolite synthesis.

Photo Assisted Fenton in a Batch and a Membrane Reactor for Degradation of Drugs in Water

Abstract Some advanced oxidation processes (AOPs) such as Fenton H2O2/Fe2+, photo assisted Fenton UV/H2O2/Fe2+, UV photolysis, and photo assisted Fenton—like UV/O2/Fe2+ have been tested for the degradation of Gemfibrozil in aqueous solution in a batch system and then in a membrane reactor. A nanofiltration/reverse osmosis type cross‐linked polyamide, UTC‐60 (Toray) membrane (19 cm2) was used. In the batch degradation tests, the gemfibrozil, used at 5 mg/L, was degraded by employing the four AOPs but numerous peaks of intermediates were observed at the HPLC. Indeed DOC analyses showed poor mineralization in the case of photolysis (3.1%) and UV/O2/Fe (10%), while it was 62% using the photo assisted Fenton and 24% using the Fenton. Thus in the membrane reactor only the Fenton and the photo assisted Fenton were tested. Obtained results showed a drug degradation higher than 92%, a mineralization higher than 55%, and a membrane retention of the catalyst in solution higher than 95%.

Pectinases immobilization on magnetic nanoparticles and their anti-fouling performance in a biocatalytic membrane reactor

Enzyme immobilization on commercial superparamagnetic nanoparticles (NPSP) was performed using covalent bonding. The biofunctionalized NPSP was then immobilized on the surface of the membrane using an external magnetic field to form a magneto-responsive biocatalytic membrane reactor (BMRSP). The magnetically formed smart nanolayer can be easily re-dispersed and recovered from the membrane when the enzyme is deactivated or whenever cleaning is required due to substrate over-accumulation. The system was used to hydrolyze pectin contained in different streams. Results are supported with complementary data from hydrodynamic, kinetic and morphological characterization in a flow-through reactive filtration. Wavelength-dispersive X-ray spectroscopy (WDS) elemental mapping revealed that the NPSP are uniformly dispersed on the surface of the membrane forming a thin biocatalytic layer. Both results of hydrodynamic studies and SEM micrographs of the membrane with the enzyme layer under various operating conditions, show that the immobilized enzyme effectively reduced membrane–foulant interaction. Comparison of filtration data using this commercial NPSP reveals good agreement with our previously used home-made NPSP. This implies that the scaling-up and commercialization of the developed BMRSP can be straightforward.

Preparation of Pd-Loaded Hierarchical FAU Membranes and Testing in Acetophenone Hydrogenation

Pd-loaded hierarchical FAU (Pd-FAU) membranes, containing an intrinsic secondary non-zeolitic (meso)porosity, were prepared and tested in the catalytic transfer hydrogenation of acetophenone (AP) to produce phenylethanol (PE), an industrially relevant product. The best operating conditions were preliminarily identified by testing different solvents and organic hydrogen donors in a batch hydrogenation process where micron-sized FAU seeds were employed as catalyst support. Water as solvent and formic acid as hydrogen source resulted to be the best choice in terms of conversion for the catalytic hydrogenation of AP, providing the basis for the design of a green and sustainable process. The best experimental conditions were selected and applied to the Pd-loaded FAU membrane finding enhanced catalytic performance such as a five-fold higher productivity than with the unsupported Pd-FAU crystals (11.0 vs. 2.2 mgproduct gcat−1·h−1). The catalytic performance of the membrane on the alumina support was also tested in a tangential flow system obtaining a productivity higher than that of the batch system (22.0 vs. 11.0 mgproduct gcat−1·h−1).

Synthesis of Nay-Type Nanozeolites and Their Assembling into Microporous Membranes

In this paper we report on a divalent procedure for the synthesis of FAU zeolites with particle size distribution in the nanometer range and for the concomitantly assembling of a uniform layer of a quasi-solid gel containing nanozeolite precursor species on the support surface. The crystallization has been conducted at room temperature, in absence of organic structure directing agents (SDAs). A highly reactive sodium hydroxide rich hydrogel was used as starting synthesis system, while microsized zeolite crystals, preliminarily coated on the support surface before the synthesis, oriented and promoted the nucleation and crystallization processes. Nanosized FAU crystals with particle size of ca. 56 nm have been obtained after 24 hours. Alongside, a thick gel stratum was formed on the support surface, which contains FAU nanoparticles of 20-30 nm. The gel matrix assembled on the support surface was used as starting material for the zeolite membrane synthesis and it was rapidly converted into a nanocrystalline layer upon hydrothermal treatment at higher temperature. The FAU layer has a thickness of ca. 2 μm and is constituted by closely packed nanocrystals, whose dimension is still. 20-30 nm. The mass transport properties of the prepared membranes were probed by feeding dry single gases (N2 and CO2) at ambient temperature, obtaining low permeance and ideal selectivity higher than the corresponding Knudsen value. The results reported in this study indicate that supersaturation as well as the elevate amount of sodium ions are synergistic factors to reach a high degree of conversion of the hydrogel into a nanocrystalline material at near ambient conditions and to induce the assembling of soluble aluminosilicate species on the support surface, thus effectively promoting the heterogeneous nucleation process.

Organic-template-free synthesis of nanosized NaY crystals induced by a FAU membrane

Zeolite NaY nanocrystals with uniform particle size distribution have been prepared with high yield in a short duration, organic-template-free, hydrothermal synthesis by using FAU membranes as structure directing agents.

Development of biohybrid immuno-selective membranes for target antigen recognition

Membranes are gaining increasing interest in solid-phase analytical assay and biosensors applications, in particular as functional surface for bioreceptors immobilization and stabilization as well as for the concentration of target molecules in microsystems. In this work, regenerated cellulose immuno-affinity membranes were developed and they were used for the selective capture of interleukin-6 (IL-6) as targeted antigen. Protein G was covalently linked on the membrane surface and it was successfully used for the oriented site-specific antibody immobilization. The antibody binding capacity of the protein G-coupled membrane was evaluated. The specific anti IL-6 antibody was immobilized and a quantitative analysis of the amount of IL-6 captured by the immuno-affinity membrane was performed. The immobilization procedure was optimized to eliminate the non-specific binding of antigen on the membrane surface. Additionally, the interaction between anti IL-6 antibody and protein G was stabilized by chemical cross-linking with glutaraldehyde and the capture ability of immuno-affinity membranes, with and without the cross-linker, was compared. The maximum binding capacity of the protein G-coupled membrane was 43.8µg/cm2 and the binding efficiency was 88%. The immuno-affinity membranes showed a high IL-6 capture efficiency at very low antigen concentration, up to a maximum of 91%, the amount of captured IL-6 increased linearly as increasing the initial concentration. The cross-linked surface retained the antigen binding capacity demonstrating its robustness in being reused, without antibody leakage or reduction in antibody binding capacity. The overall results demonstrated the possibility of a reliable application of the immuno-affinity membrane developed for biosensors and bioassays also in multiple use.

Chemical Vapor Deposition of Photocatalyst Nanoparticles on PVDF Membranes for Advanced Oxidation Processes

The chemical binding of photocatalytic materials, such as TiO2 and ZnO nanoparticles, onto porous polymer membranes requires a series of chemical reactions and long purification processes, which often result in small amounts of trapped nanoparticles with reduced photocatalytic activity. In this work, a chemical vapor deposition technique was investigated in order to allow the nucleation and growth of ZnO and TiO2 nanoparticles onto polyvinylidene difluoride (PVDF) porous membranes for application in advanced oxidation processes. The thickness of obtained surface coatings by sputtered nanoparticles was found to depend on process conditions. The photocatalytic efficiency of sputtered membranes was tested against both a model drug and a model organic pollutant in a small continuous flow reactor.