Reactional Processes on Osmium–Polymeric Membranes for 5–Nitrobenzimidazole Reduction
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membranes Article Reactional Processes on Osmium–Polymeric Membranes for 5–Nitrobenzimidazole Reduction 1 1 2, 1 Aurelia Cristina Nechifor , Alexandru Goran , Vlad-Alexandru Grosu * , Andreia Pîrt, ac , 3 4 1, 1 Paul Constantin Albu , Ovidiu Oprea , Alexandra Raluca Grosu * , Dumitru Pas, cu , Florentina Mihaela Păncescu 1 , Gheorghe Nechifor 1 , Szidonia-Katalin Tanczos 5 and Simona Gabriela Bungău 6 1 Analytical Chemistry and Environmental Engineering Department, University Politehnica of Bucharest, 1-7 Polizu Street, 011061 Bucharest, Romania; [email protected] (A.C.N.); [email protected] (A.G.); [email protected] (A.P.); [email protected] (D.P.); fl[email protected] (F.M.P.); [email protected] (G.N.) 2 Department of Electronic Technology and Reliability, Faculty of Electronics, Telecommunications and Information Technology, University Politehnica of Bucharest, Bulevardul Iuliu Maniu, nr. 1-3, 061071 Bucharest, Romania 3 IFIN Horia Hulubei, Radioisotopes and Radiation Metrology Department (DRMR), 30 Reactorului Street, 023465 Măgurele, Romania; [email protected] 4 Department of Inorganic Chemistry, Physical Chemistry and Electrochemistry, University Politehnica of Bucharest, 1-7 Polizu Street, 011061 Bucharest, Romania; [email protected] 5 Department of Bioengineering, Sapientia Hungarian University of Transylvania, Libertatii Street, 500104 Miercurea-Ciuc, Romania; [email protected] 6 Department of Pharmacy, Faculty of Medicine and Pharmacy, University of Oradea, 410028 Oradea, Romania; [email protected] * Correspondence: [email protected] (V.-A.G.); [email protected] (A.R.G.) Citation: Nechifor, A.C.; Goran, A.; Grosu, V.-A.; Pîrt,ac, A.; Albu, P.C.; Oprea, O.; Grosu, A.R.; Pas, cu, D.; Abstract: Membranes are associated with the efficient processes of separation, concentration and P˘ancescu,F.M.; Nechifor, G.; et al. purification, but a very important aspect of them is the realization of a reaction process simulta- Reactional Processes on neously with the separation process. From a practical point of view, chemical reactions have been Osmium–Polymeric Membranes for introduced in most membrane systems: with on-liquid membranes, with inorganic membranes 5–Nitrobenzimidazole Reduction. or with polymeric and/or composite membranes. This paper presents the obtaining of polymeric Membranes 2021, 11, 633. https:// membranes containing metallic osmium obtained in situ. Cellulose acetate (CA), polysulfone (PSf) doi.org/10.3390/membranes11080633 and polypropylene hollow fiber membranes (PPM) were used as support polymer membranes. The metallic osmium is obtained directly onto the considered membranes using a solution of osmium Academic Editor: Isabel C. Escobar tetroxide (OsO4), dissolved in tert–butyl alcohol (t–Bu–OH) by reduction with molecular hydrogen. The composite osmium–polymer (Os–P)-obtained membranes were characterized in terms of the Received: 30 July 2021 Accepted: 13 August 2021 morphological and structural points of view: scanning electron microscopy (SEM), high-resolution Published: 17 August 2021 SEM (HR–SEM), energy-dispersive spectroscopy analysis (EDAX), Fourier Transform Infra-Red (FTIR) spectroscopy, thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). Publisher’s Note: MDPI stays neutral The process performance was tested for reduction of 5–nitrobenzimidazole to 5–aminobenzimidazole with regard to jurisdictional claims in with molecular hydrogen. The paper presents the main aspects of the possible mechanism of transfor- published maps and institutional affil- mation of 5–nitrobenzimidazole to 5–aminobenzimidazole with hydrogen gas in the reaction system iations. with osmium–polymer membrane (Os–P). Keywords: composite membranes; osmium polymer membrane; nitro derivatives reduction; re- actional processes; 5–nitrobenzimidazole; cellulose acetate membranes; polysulfone membranes; Copyright: © 2021 by the authors. polypropylene hollow fiber membranes Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons 1. Introduction Attribution (CC BY) license (https:// The membranes and membrane processes represent one of the most viable variants creativecommons.org/licenses/by/ of separation, concentration and purification of the chemical compounds from solutions 4.0/). Membranes 2021, 11, 633. https://doi.org/10.3390/membranes11080633 https://www.mdpi.com/journal/membranes MembranesMembranes 20212021,, 1111,, x 633 FOR PEER REVIEW 2 2of of 29 28 andand complex complex mixtures mixtures [1,2]. [1,2]. The The characteristics characteristics that that recommend recommend the the membrane membrane systems systems forfor implementation implementation are: high selectivity,selectivity, flows flows driven driven by by accessible accessible operational operational parameters parame- ters(pressure, (pressure, temperature temperature and and potential potential difference), difference), simplicity simplicity of of thethe modulesmodules and their their repeatabilityrepeatability in in large large installations, installations, favorable favorable ratio ratio of of useful useful area/installation area/installation volume volume [3 [3––55].]. TheseThese definite definite advantages advantages of of the the membrane membrane p processesrocesses have have led led to to extensive extensive research research on on variousvarious kinds kinds of of membranes: membranes: liquid, liquid, polymeric, polymeric, inorganic inorganic or or composite composite [6 [6––88].]. AtAt the the same same time, time, in in order order to to improve improve the the separation separation of of various various chemical chemical species, species, attemptsattempts were were made made to to use use their their most most varied varied characteristics: characteristics: dimension, dimension, diffusion diffusion speed, speed, volatility,volatility, surface surface activity, activity, electric charge, thermal or magnetic fieldfield behaviorbehavior [[99––1111].]. However,However, sometimes sometimes there there are are problems problems in in choosing choosing the the membrane membrane so so as as to to ensure ensure a a selectiveselective and and high high flow flow separation, especiallyespecially ifif thethe chemical chemical species species to to be be separated separated are are in invery very small small concentrations concentrations or or have have similar similar characteristics characteristics [12 [12,13].,13]. TheThe separ separationation ofof chemicalchemical species species with with similar similar physical–chemical physical–chemical properties properties has beenhas beenapproached approached with with great great insistence insistence and remarkableand remarkable results results in the in case the ofcase liquid of liquid membranes, mem- branes,by introducing by introducing a new anda new versatile and versatile variable, variable, the reaction the reaction or the or chemical the chemical interaction interac- of tioncompounds of compounds to separate to separate with the with membrane the membrane components components (Figure (Figure1): 1): • Specific complexants [14,15]; • Specific complexants [14,15]; • Ions exchangers [16]; • Ions exchangers [16]; • Surfactants and microemulsions [17,18]; • Surfactants and microemulsions [17,18]; • Ionic liquids [19]; • Ionic liquids [19]; • Adsorbent nanoparticles (polymeric, metallic, oxide) [20–22]; • Adsorbent nanoparticles (polymeric, metallic, oxide) [20–22]; • Magnetic nanoparticles [23,24]; • Magnetic nanoparticles [23,24]; • Proteins and enzymes [25,26]. • Proteins and enzymes [25,26]. Figure 1. Membrane reaction systems: A—target chemical species; C—carrier; R—reagent. Figure 1. Membrane reaction systems: A—target chemical species; C—carrier; R—reagent. Starting from these results, in the last decade, various membrane reaction systems were addressed,Starting based from onthese polymer results, and in inorganicthe last decade membranes,, various but membrane especially reaction on the composite systems wereones, addressed, which improve based theon membranepolymer and efficiency inorganic in membranes the separation, but processes, especially buton the also com- add positethe chemical ones, which transformation improve the of themembrane chemical efficiency species of in interest the separation and developing processes, catalytic but also or addbio-catalytic the chemical membrane transformation reactors [of27 the–30 ].chemical species of interest and developing cata- lytic orThe bio basic-catalytic element membrane of a membrane reactors [27 reactor–30]. is the membrane that ensures both the transformationThe basic element of the chemical of a membrane species and reactor their is separation the membrane [31,32]. that ensures both the transformationWhen the chemicalof the chemical species species for such and a process their separation is an organic [31,32]. substance, then the selective transformationWhen the chemical and its preferential species for transfersuch a process into the is receivingan organic phase substance, are considered then the [selec-33]. tive transformation and its preferential transfer into the receiving phase are considered [33]. MembranesMembranes 20212021, 11, 11, x, 633FOR PEER REVIEW 3 of3 of29 28 ConventionalConventional membrane membrane reactors reactors have have ensured ensured esterification, esterification, etherification, etherification, dehy- dehy- drogenation,drogenation, alky alkylation,lation, synthesis synthesis