High-impact polystyrene/polyaniline membranes for acid solution treatment by electrodialysis: preparation, evaluation, and chemical calculation

Donnan Dialysis for Recovering Ammonium from Fermentation Solutions Rich in Volatile Fatty Acids

For the production of polyhydroxyalkanoates (PHA) using nitrogen-rich feedstocks (e.g., protein-rich resources), the typical strategy of restricting cell growth as a means to enhance overall PHA productivity by nitrogen limitation is not applicable. In this case, a possible alternative to remove the nitrogen excess (NH₄⁺/NH₃) is by applying membrane separation processes. In the present study, the use of Donnan dialysis to separate ammonium ions from volatile fatty acids present in the media for the production of PHA was evaluated. Synthetic and real feed solutions were used, applying NaCl and HCl receiver solutions separated by commercial cation-exchange membranes. For this specific purpose, Fumasep and Ralex membranes showed better performance than Ionsep. Sorption of ammonium ions occurred in the Ralex membrane, thus intensifying the ammonium extraction. The separation performances with NaCl and HCl as receiver solutions were similar, despite sorption occurring in the Ralex membrane more intensely in the presence of NaCl. Higher volumetric flow rates, NaCl receiver concentrations, and volume ratios of feed:receiver solutions enhanced the degree of ammonium recovery. The application of an external electric potential difference to the two-compartment system did not significantly enhance the rate of ammonium appearance in the receiver solution. The results obtained using a real ammonium-containing solution after fermentation of cheese whey showed that Donnan dialysis can be successfully applied for ammonium recovery from such solutions.

Electroactive macromolecular motors as model materials of ectotherm muscles

The electrochemical reaction in liquid electrolytes of conducting polymers, carbon nanotubes, graphenes, among other materials, replicates the active components (macromolecular electro-chemical motors, ions and solvent) and volume variation of the sarcomere in any natural muscles during actuation, allowing the development of electro-chemo-mechanical artificial muscles. Materials, reactions and artificial muscles have been used as model materials, model reactions and model devices of the muscles from ectotherm animals. We present in this perspective the experimental results and a quantitative description of the thermal influence on the reaction extension and energetic achievements of those muscular models using different experimental methodologies. By raising the temperature for 40 °C keeping the extension of the muscular movement the cooperative actuation of the macromolecular motors harvest, saving chemical energy, up to 60% of the reaction energy from the thermal environment. The synergic thermal influence on either, the reaction rate (Arrhenius), the conformational movement rates of the motors (ESCR model) and the diffusion coefficients of ions across polymer matrix (WLF equation) can support the physical chemical foundations for the selection by nature of ectotherm muscles. Macromolecular motors act, simultaneously, as electro-chemo-mechanical and thermo-mechanical transducers. Technological and biological perspectives are presented.

Permselectivity of Cation Exchange Membranes Modified by Polyaniline

This work discusses the applicability of polyaniline-modified cation exchange membranes for the separation of monovalent/divalent cations by electrodialysis. A novel method of membrane modification directly in the electrodialysis unit is used to prepare permselective membranes. Complex characterization of the membranes before and after modification allows revealing the influence of membrane matrix on the modification efficiency. The characterization of the membranes includes determination of the diffusion permeability, specific conductivity and current-voltage curves in HCl, NaCl and CaCl₂ solutions, as well as transport-structural parameters of the extended three-wire model. The characterization results are used to predict the influence of the modification on membrane permselectivity. The competitive mass transfer of singly and doubly charged cations in the electrodialysis process is investigated in underlimiting and overlimiting currents. Electrodialysis desalination of a solution containing Na⁺/Ca²⁺ or H⁺/Ca²⁺ cations shows that the modification leads to an increase in membrane permselectivity to single-charged cations due to the repulsion of Ca²⁺ ions from the positively charged membrane surface. The permselectivity of the polyaniline-modified perfluorinated membrane to H⁺ in the mixture of H⁺/Ca²⁺ cations is observed in all current regimes.

Polyaniline–polystyrene membrane for simple and efficient retrieval of double-stranded DNA from aqueous media

Extraction of nucleic acids from biological samples is a necessary step in almost all biotechnological procedures.

Facile synthesis of fluorescent polyaniline microspheres and their use for the detection of mercury ions

Bright blue fluorescent polyaniline microspheres were prepared by a simple controlled oxidation under mild conditions. A simple, highly sensitive fluorometric Hg²⁺ probe has been constructed.

Facile synthesis of polyaniline/carbon dot nanocomposites and their application as a fluorescent probe to detect mercury

Novel polyaniline/carbon dot nanocomposites have been synthesized using a simple method, and a PANI/Cdot “off–on” fluorescent probe has been constructed for the simple, ultrasensitive and selective detection of Hg²⁺ in aqueous media.

Study of Chromium Removal by the Electrodialysis of Tannery and Metal-Finishing Effluents

The metal-finishing and tannery industries have been under strong pressure to replace their current wastewater treatment based on a physicochemical process. The electrodialysis process is becoming an interesting alternative for wastewater treatment. Electrodialysis is a membrane separation technique, in which ions are transported from one solution to another through ion-exchange membranes, using an electric field as the driving force. Blends of polystyrene and polyaniline were obtained in order to produce membranes for electrodialysis. The produced membranes were applied in the recovery of baths from the metal-finishing and tannery industries. The parameter for electrodialysis evaluation was the percentage of chromium extraction. The results obtained using these membranes were compared to those obtained with the commercial membrane Nafion 450.

Desenvolvimento de membranas e filmes auto-suportados a partir de polianilina: síntese, caracterização e aplicação

Polímeros condutores são uma nova classe de polímeros que tem recebido especial interesse para a produção de membranas e filmes. A polianilina (PANI) destaca-se entre eles por sua elevada estabilidade química, fácil polimerização e baixo custo. O objetivo deste trabalho foi desenvolver uma blenda de polímero convencional (HIPS) com polímero condutor (PANI-CSA) e um filme de polianilina auto-suportado, usando ácido canforsulfônico (CSA) como dopante primário e 4-cloro-3-metil fenol (CMC) como dopante secundário. Estes dois materiais foram empregados como membranas íon-seletivas em um sistema de eletrodiálise para remoção de níquel de soluções. A membrana e o filme foram caracterizados por condutividade elétrica, MEV, espectroscopia FTIR, Raman e TGA. Os resultados obtidos apontam para a possibilidade de aplicação da membrana seletiva para eletrodiálise. A extração de níquel para a membrana sintetizada se mostrou semelhante à extração para a membrana comercial. O filme auto-suportado apesar de exibir boa resistência mecânica no estado sólido apresentou comportamento pouco satisfatório quando colocado em imersão com a solução de trabalho para eletrodiálise, devido ao seu estado quebradiço.