Pietro Argurio

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.

Photothermal Membrane Distillation for Seawater Desalination

Thermoplasmonic effects notably improve the efficiency of vacuum membrane distillation, an economically sustainable tool for high-quality seawater desalination. Poly(vinylidene fluoride) (PVDF) membranes filled with spherical silver nanoparticles are used, whose size is tuned for the aim. With the addition of plasmonic nanoparticles in the membrane, the transmembrane flux increases by 11 times, and, moreover, the temperature at the membrane interface is higher than bulk temperature.

Studies on interactions between membranes (RO and NF) and pollutants (SiO2, NO3 - , Mn ++ and humic acid) in water

Abstract The comparison between two membrane separation processes, like reverse osmosis (RO) and nanofiltration (NF), and the interaction between membrane and pollutant in water cleaning-up were studied. The separation efficiency of pollutants like silica, nitrate, manganese and humic acids (HA) by means of RO and NF membranes (both of spiral wound type, in polyamide) was determined. The interaction between the membrane and other ions (e.g. Cu++ casually present in water) also affected membrane cleaning. All pollutants were dissolved in tap water; in some tests they were singularly present, in others they were all together to simulate a polluted water. Particular attention to membrane washing was given testing various washing conditions for different fouling cases. In the separation of silica by RO, fouling problems were not observed in a three hours test at 600 mg/l concentration. In RO tests with water containing all four pollutant species at initial concentrations of 126 mg/l silica, 263.8 mg/l NO3−, 123.9 mg/l Mn++, 129.4 mg/l humic acids at pH=8, rejections equal to 98%, 94%, 99% and 95.5%, respectively, were observed. These values of rejections were identical to that obtained when the pollutants were present separately, showing absence of interactions among them. The permeate flow rate was 530 l/h×module with a recovery equal to 30% at an average transmembrane pressure of 30 bar. In the NF tests both water polluted with all four contaminants and torrent water (from torrent Emoli, Rende (CS)) were used. Obviously the mean rejections were lower than RO membrane, and equal to 35%, 6%, 80%, 35% respectively. Mn++ rejection was the highest owing to the positive charge of the NF membrane. The permeate flow rate was equal to 530 l/h×module at a mean pressure equal to 11 bar and T=25°C and comparable to that obtained using the RO module at 30 bar. The best washing for membrane cleaning was a NH3 aqueous solution 0.4% w/v. A simple washing with water was not able to remove Mn++ and Cu++ ions (owing to acid-base Lewis type interaction with polyamide membrane) and humic acids; the weak basic agent NH3 was able to avoid precipitation of insoluble hydroxides, like Mn(OH)2, and consequent plugging of membrane pores, with respect to the strong base NaOH. The obtained results show the importance to know the type of interaction membrane-pollutants and the chemical behaviour of pollutants to obtain the maximum benefit both in pollutant separation and in membrane cleaning.

Review On Reduction And Partial Oxidation of Organics In Photocatalytic (Membrane) Reactors

Traditional processes for making chemicals are unsustainable in terms of resources and environmental impact. The present pa- per is a review of the most recent advances in the application of selective photocatalytic reactions to organic synthesis, which, in the last years, has attracted the interest of the scientific community addressing on development of environmentally benign synthetic processes. Indeed, selective photocatalysis is operated at ambient temperature and pressure, needs no complex equipments, does not use dangerous chemical reagents and solvents, does not release harmful wastes into the environment and can utilize solar light. Reactions discussed in this paper, as a green approach for valuable fine chemical synthesis, are: i) photocatalytic hydrogenation and/or transfer hydrogenation of ketones and nitrocompounds by using both UV and visible light; ii) photocatalytic hydrogenation and selective partial hydrogenation of unsaturated compounds; iii) selective partial oxidation of alkanes, alkenes, alcohols, aliphatic acids, benzene and other aromatic com- pounds by using both UV and visible light. Use of Photocatalytic Membrane Reactors (PMRs) in reductions (e.g. CO2 to fuels) and in se- lective partial oxidations (e.g. benzene to phenol) is reported, evidencing that opening up of a new avenue is expected in organic synthe- ses, thanks to the synergy of heterogeneous photocatalysis and membrane processes. Nevertheless, these studies are still at nascent stady and much work is needed before taking advantage of PMRs potentiality at industrial level in this interdisciplinary area.

Photocatalytic processes in membrane reactors

Conversion and degradation processes of various substrates in various types of matrices using both artificial and solar light are today very attractive by considering the scarcity and the expensiveness of the conventional energy sources. Coupling of membrane with light has shown to be very powerful and promising hybrid process, especially because a synergistic effect has often been observed.

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%.

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).

Photocatalytic hydrogenation of organic compounds in membrane reactors

Photocatalytic reduction represents an alternative to conventional catalytic hydrogenation, and it appears a more sustainable method to synthesize organic compounds under mild conditions in the presence of suitable photocatalysts. The present chapter first reviews the basic principles of photocatalysis and of membrane photoreactors as membrane and membrane materials. The chapter then discusses photocatalytic hydrogenation of organic compounds with a wide overview on the recent progress in this field, the latest developments of semiconductors, and some possible application in photocatalytic membrane reactors.

Photocatalytic membrane reactors for water treatment

Abstract Heterogeneous photocatalysis is an advanced oxidation process largely studied in the field of environment recovery by the total degradation of organic and inorganic pollutants and for synthesis. In this chapter, the basic principles of photocatalysis are discussed with the advantages related to its coupling with a membrane separation in photocatalytic membrane reactors (PMRs). The types of membranes most widely used and their criteria of selection are briefly discussed. PMRs’ classification based on their configuration and on the type of membrane operation is also discussed, evidencing as their appropriate choice is a key step in view of large-scale implementation. Finally, some case studies in water treatment (i.e. pharmaceutical removal) are discussed, with potentialities, drawbacks, and future trends.

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.