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In the current research water-soluble functional polymers (WSFP) were prepared via radical polymerization and purified by fractionation through ultrafiltration membranes with different molecular weights cut off (MWCO) of 30 and 100 kDa. The WSFPs were poly(3-acrylamide propyl) trimethyl ammonium chloride, P(ClAPTA), poly(2-acrylamido-2-methyl-1-propane sodium sulfonate, P(AMPSNa), and poly(3-methacrylamino propyl) dimethyl 3-sulfopropyl ammonium hydroxide, P(HMPDSPA). These polymers were characterized by Fourier transformed infrared spectroscopy (FT-IR) and thermogravimetry analysis (TGA). Using liquid-phase polymer-based retention technique (LPR), chromium [Cr(III) and Cr(VI)] retention was studied as a function of pH, polymer and chromium concentration, selectivity, maximum retention capacity, chromium elution capacity, and polymer regeneration through sorption and desorption studies. Results of FT-IR showed the characteristic absorption bands of the synthesized polymers. The decomposition temperatures of P(ClAPTA) were at 303.1 °C, and for P(AMPSNa) three decompositions temperatures were registered at 190.5 °C, 223.2 °C, and 304.8 °C. P(HMPDSPA) presented two important decomposition temperatures at 292.4 °C and 391.7 °C, respectively. Concerning to the retention of Cr(VI), it was maximal (100 %) when P(ClAPTA) was studied at pH 6. The maximum retention of Cr(III) (100 %) was achieved by P(AMPSNa) at pH 3. The optimum polymer:Cr mole ratio obtained was 10:1 for both Cr(VI) and Cr(III). The retention of Cr(VI) decreased due to the presence of interfering ions, and the hydrodynamic flow was almost constant during the ultrafiltration of polymer-Cr macromolecule.

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The current problem of contamination caused by colored industrial effluents has led to the development of different techniques to remove these species from water. One of them, polymer-enhanced ultrafiltration (PEUF), has been systematically studied in this mini review, in which research works from 1971 to date were found and analyzed. Dye retention rates of up to 99% were obtained in several cases. In addition, a brief discussion of different parameters, such as pH, interfering salts, type of polymer, dye concentration, and membrane type, and their influence in dye removal is presented. It was concluded from the above that these factors can be adapted depending on the pollutant to be remediated, in order to optimize the process. Finally, theoretical approaches have been used to understand the intermolecular interactions, and development of the studied technique. In this revision, it is possible to observe that molecular docking, molecular dynamics simulations, density functional theory calculations, and hybrid neural-genetic algorithms based on an evolutionary approach are the most usual approximations used for this purpose. Herein, there is a detailed discussion about what was carried out in order to contribute to the research development of this important science field.

In the present work, three hydrogels of poly(2-hydroxyethyl methacrylate-co-itaconic acid), p(HEMA-co-IA), poly(2-hydroxyethyl methacrylate-co-acrylic acid), p(HEMA-co-AA) and poly(2-hydroxyethyl methacrylate-co-(1-vinyl-2-pyrrolidone)), p(HEMA-co-NVP) were prepared by free radical polymerization in aqueous solution (1:1 monomer mole ratio) using ammonium persulfate as initiator and N,N´-methylenebisacrylamide as crosslinking agent at two different amount (0.3 and 0.9 mol%). The obtained hydrogels were characterized by Fourier transform infrared spectroscopy (FT-IR), which allowed to verify the structural composition. Thermal analysis of the hydrogels was carried out by thermogravimetric analysis (TGA). In addition, hydration capacity (U%) was studied at different experimental conditions such as: time, pH, concentrations of interfering salts (KCl, NaCl and LiCl). The results showed a good polymerization yield (95%). FTIR characterization shows the absorption bands of the functional groups of copolymers. TGA exhibited the characteristic thermal stability of this type of hydrogels. The presence of comonomer AI, AA or NVP in copolymer determine the thermal behavior. Hydration experiments revealed a higher U% in copolymer containing more carboxylic acid groups. The maximum U% values in water were 400% and 250% for p(HEMA-co-AI) and p(HEMA-co-AA), respectively. For P(HEMA-co-NVP) a maximum of U% value was only 74% in water. The effect of interferent salts affects the hydration capacity decreasing U% when the concentration of salts increase.

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