STAGE 1. Establishing the conditions for the synthesis of composite membranes based on terpolymers and functionalized carbon nanotubes (MWCNTs) and their complex characterization

PERIOD: 13.05.2022-31.12.2022

OBJECTIVES

Act 1.1. – Studies on the synthesis and characterization of simple membranes based on terpolymer formulations.

Act 1.2. – Functionalization of carbon nanotubes (MWCNTs) using non-covalent methods.

Act 1.3. – Synthesis and characterization of composite membranes based on recipes of terpolymers and functionalized carbon nanotubes (MWCNTs).

Act 1.4. – Communication activities and writing of scientific papers in compliance with Open Access conditions.

SUMMARY

The I-ON-MEM project aims is to identify suitable solutions for treating metal-contaminated diluted water streams with removal efficiencies above 90%, relying only membrane technologies. The research study’s main objective will be synthesizing original composite membranes for the advanced retention of heavy metals in electrodialysis wastewater. In this sense, the following secondary objectives were established:

OS1. Studies regarding the synthesis and characterization of simple membranes based on terpolymer formulations.

OS2. Carbon nanotubes functionalization (MWCNT) using non-covalent methods.

OS3. Synthesis and complex characterization of composite membranes based on terpolymers and functionalized carbon nanotubes (MWCNT).

OS1. In order to obtain simple synthetic membranes, several polymer solutions of different concentrations were prepared. Moreover, it was also investigated the effect of changing the ratio between terpolymers. The membranes were prepared by the wet phase inversion method. The synthetic membranes were analyzed in terms of their rheological behavior and also the permeability point of view in order to choose the optimal composition. Synthetic membrane with the composition of 70% Acrylonitrile-acrylic acid copolymer (AN-AA), 7.5% polyvinyl alcohol (PVA) and 22.5% polysulfone (PSf) and biomembrane with the composition 0.2% sodium alginate (SA), 0.65% polyvinyl alcohol (PVA) and 0.05% biocellulose (BC) were chosen to be used in subsequent experiments in order to get composite membranes.

OS2. In order to functionalize MWCNTs with surfactants, two surfactants, i.e. cetrimonium bromide (CTAB) and behentrimonium chloride (BTAC), were tested. MWCNTs thus functionalized were characterized by Dynamic Light Scattering (DLS) and Raman Spectroscopy, which indicated that in the case of samples functionalized with surfactant the I_D/I_G ratio increased significantly due to good functionalization process and the attachment of surfactant molecules to CNTs by electrostatic forces or Van der Waals, but also due to the increase in the degree of disorder of the structure. In order to functionalize carbon nanotubes by covering them with organosilanes, silanes bearing different functional groups (amino, carboxy, sulfur) were used such as 3-Aminopropyltriethoxysilane (APTES), 3-(Trimethoxy silyl)propyl methacrylate (MAPTES) and (3-Mercaptopropyl)trimethoxy silane (MPTMS). This type of functionalization was achieved by 2 methods, which were differentiated by the presence and absence of the reaction medium. The functionalized MWCNT products obtained were intensively characterized by FTIR, XPS, XRD, Raman, TGA/DTG and SEM. All analyzes demonstrated that the functionalization process led to a less disordered network, leading to the attachment or interpenetration of surfactant/silane molecules with CNTs.

OS3. In order to obtain composite membranes, a percentage of 0.5% non-modified CNT or functionalized by both methods was chosen as optimal. Thus, the composite membranes were characterized in terms of chemical composition (FTIR), hydrophilicity (contact angle), permeability (water flow), thermal stability (TGA/DTG), morphology (SEM) and showed improved characteristics compared to the reference membranes and a significant improvement in final properties by introducing some functionalized MWCNTs.

Experimental models were developed for obtaining simple synthetic membranes and based on biopolymers, for functionalizing MWCNTs by non-covalent methods and for obtaining composite membranes based on synthetic polymers and from bio sources and functionalized nanotubes. The original results were disseminated by attending 2 conferences (1 national and 1 international), but also by publishing 2 ISI articles (published in journals indexed in Web of Science from the red zone (Q1), classified as article and review). The website of the I-ON-MEM project was also created.

The degree of achievement of the objectives was 100%.

DISSEMINATION

In the framework of stage I/2022, for the fulfillment of the deliverables from the implementation plan and for the presentation of the obtained results, the following dissemination actions were carried out, 2 published articles, which present the research that was the basis of the project’s activities and 2

participations in the form of poster-type communications or oral communications in international and national conferences, with exceptional visibility:

Published articles

1. Miron, A.; Sarbu, A.; Zaharia, A. Sandu, T.; Iovu, H.; Fierascu, R.C.; Neagu, A.-L.; Chiriac, A.-L.*; Iordache, T.-V. A Top-Down Procedure for Synthesizing Calcium Carbonate-Enriched Chitosan from Shrimp Shell Wastes. Gels 2022, 8(11), 742. https://doi.org/10.3390/gels8110742

2. Teodor Sandu, Andrei Sârbu, Simona Căprărescu, Elena-Bianca Stoica Tanța-Verona Iordache, Anita-Laura Chiriac*, Polymer Membranes as Innovative Means of Quality Restoring for Wastewater Bearing Heavy Metals. Membranes 2022, 12(12), 1179. https://doi.org/10.3390/membranes12121179

Scientific communications at national/international conferences

1. Verona Iordache, Anamaria Zaharia, Ana-Mihaela Gavrila, Bianca Elena Stoica, Ana Lorena Ciurlica, Marinela Dumitru, Andreea Olaru, Andrei Sarbu, Laura Anita Chiriac, Quaternary Ammonium Functionalized-Clay Microparticles with Bactericidal Activity Applied for Wastewater Treatment, 22nd Romanian International Conference on Chemistry and Chemical Engineering, Sinaia, ROMANIA – 7th-9thSeptember, 2022. Poster

2. Andreea Miron, Ana-Lorena Neagu, Sorin Dolana, Anamaria Zaharia, Ana-Mihaela Gavrila, Andrei Sarbu, Tanta-Verona Iordache, Anita-Laura Chiriac, Beads based on sodium alginate and titania composites for heavy metals removal from simulated waste waters, NATIONAL CHEMISTRY CONFERENCE, XXXVI EDITION, Călimănești-Căciulata, 4th-7th October 2022. Oral presentation

For better visibility, the idea of the I-ON-MEM Project was exposed to radio listeners in the show “Stiinta 360” on Radio Romania Cultural https://www.radioromaniacultural.ro/stiinta-360-30-noiembrie-2022-proiecte-complexe-derulate-la-icechim/