Enhanced adsorption of cationic and anionic dyes from aqueous solutions by polyacid doped polyaniline

A new high surface area polyaniline (PANI) adsorbent was synthesized by matrix polymerization of aniline in the presence of a polyacid, poly(2-acrylamido-2-methyl-1-propanesulfonic acid) (PAMPSA). Morphological and physicochemical properties of PANI-PAMPSA were characterized by field emission scanning electron microscope (FESEM), Fourier transform infrared spectroscopy (FTIR), X-ray powder diffraction (XRD), nitrogen adsorption/desorption and zeta potential measurement. Adsorption properties were evaluated using methylene blue (MB) and rose bengal (RB) as model dyes.The results showed that PANI-PAMPSA obtained a well-defined porous structure with a specific surface area (126 m2 g−1) over 10 times larger than that of the emeraldine base PANI (PANI-EB) (12 m2 g−1). The maximum adsorption capacities were 466.5 mg g−1 for MB and 440.0 mg g−1 for RB, higher than any other PANI-based materials reported in the literature. The FTIR analysis and zeta potential measurement revealed that the adsorption mechanisms involved π-π interaction and electrostatic interaction. The adsorption kinetics were best described by a pseudo-second-order model, and the adsorption isotherms followed the Langmuir model. The thermodynamic study indicated that the adsorption was a spontaneous endothermic process. Overall, the convenient synthesis and the high adsorption capacity make PANI-PAMPSA a promising adsorbent material for dye removal

Exploiting the electrical conductivity of poly-acid doped polyaniline membranes with enhanced durability for organic solvent nanofiltration

We have developed stable organic solvent nanofiltration (OSN) membranes that are electrically conductive. These membranes overcome key issues with current tuneable membranes: molecular weight cut off (MWCO) limited to the UF-range and lack of filtration stability. Polyaniline (PANI) was in-situ doped by poly(2-acrylamido-2-methyl-1-propanesulfonic acid) (PAMPSA) using chemical oxidative polymerization that leads to formation of interpolymer complex. The PANI-PAMPSA membranes were prepared by phase inversion method and the pore sizes were shrunk by annealing the membranes at temperatures lower than the crosslinking temperature. The membranes were systematically evaluated using visual and chemical analysis and in-filtration experiments. The developed membranes were solvent stable, reusable, had a denser structure and lower MWCO and there was no thermal crosslinking as seen by IR. The solvent permeance obtained were: 0.46, 0.60 and 0.74 Lm −2 h −1 bar −1 for acetone, 2-propanol and methanol respectively, with MWCO below 300 Da and 266 Da for methanol. For the tuneability investigation, when applying an electrical potential (20 V) in a custom-made cross-flow membrane cell, an increase in MWCO and permeance (10.4% and 55.6%, respectively) was observed. These results show that this simple in-situ doping method with heat treatment can produce promising and stable PANI membranes, for OSN processes in different solvents, with the distinctive feature of in-situ performance control by applying external electrical potential. </p

Anhydrides from aldehydes or alcohols via oxidative cross-coupling

A novel type of metal-free oxidative cross-coupling for the synthesis of symmetrical and mixed anhydrides from aldehydes or benzylic alcohols has been developed. The aldehydes or alcohols were converted in situ into their corresponding acyl chlorides, which were then reacted with an array of carboxylic acids. The methodology has a general applicability, and was successfully employed to prepare either aromatic or aliphatic symmetrical anhydrides and mixed anhydrides, which are very unstable compounds

Preparation and benchmarking of highly hydrophilic polyaniline poly(2-acrylamido-2-methyl-1-propanesulfonic acid) PANI PAMPSA membranes in the separation of sterols and proteins from fruit juice

A straightforward approach is presented to prepare highly hydrophilic ultrafiltration polyaniline poly(2-acrylamido-2-methyl-1-propanesulfonic acid (PANI PAMPSA) membranes. Their application in the fractionation of phytosterols and proteins from fruit juice is described. Poly(2-acrylamido-2-methyl-1-propanesulfonic (PAMPSA) is added to aniline during the polymer synthesis and the membrane is prepared via phase inversion forming a highly hydrophilic and mechanically stable ultrafiltration membrane of 200 µm thickness and pure water flux of 126 LMH at 1 bar. The membrane so produced is benchmarked against a hydrophilic commercial regenerated cellulose acetate membrane (RCA) for the separation of phytosterols and proteins from orange juice. Cross-flow filtration experiments show comparable protein separation efficiency of the membranes, but better rejection of phytosterols for the commercial RCA membrane. Both commercial and lab prepared membranes are subject to fouling, with the PANI PAMPSA membrane showing higher irreversible fouling. Nevertheless, the PANI PAMPSA membrane showed a good cleaning efficiency of 74% after three fouling-cleaning cycles. Overall, this work has demonstrated the possibility of use PANI PAMPSA for ultrafiltration application and provided a better understanding of its fouling ability when compared to a commercial membrane in a multicomponent system.</p