Magnetically recyclable core–shell structured Co0.5Zn0.5Fe2O4@polyaniline nanocomposite: high stability and rapid photocatalytic degradation of commercial azo dyes and industrial effluents

Chitosan-based nano-sorbents: synthesis, surface modification, characterisation and application in Cd (II), Co (II), Cu (II) and Pb (II) ions removal from wastewater

In contemplation of treating hazardous industrial wastewater, sodium tripolyphosphate (TPP) and vanillin (V)-modified chitosan-based magnetic nano-sorbents (TPP-CMN and V-CMN) were prepared, and the physical and surface properties of both nano-sorbents were characterised. The results of FE-SEM and XRD showed an average size of between 6.50 and 17.61 nm for Fe₃O₄ magnetic nanoparticles. The Physical Property Measurement System (PPMS) was carried out, and the saturation magnetisations for chitosan, Fe₃O₄ nanoparticles, TPP-CMN, and V-CMN were 0.153, 67.844, 7.211, and 7.772 emu.g^-1, respectively. By using multi-point analysis, the BET surface areas of the synthesised TPP-CMN and V-CMN nano-sorbents were found to be 8.75 and 6.96 m²/g, respectively. The synthesised TPP-CMN and V-CMN were investigated as effective nano-sorbents to uptake Cd (II), Co (II), Cu (II), and Pb (II) ions, and the results were investigated by AAS. The adsorption process of heavy metals was investigated by the batch equilibrium technique, and the sorption capacity values of Cd (II), Co (II), Cu (II), and Pb (II) ions by TPP-CMN were 91.75, 93.00, 87.25, and 99.96 mg/g. By V-CMN, the values were 92.5, 94.00, 88.75, and 99.89 mg/g, respectively. The equilibrium times for adsorption were found to be 15 minutes for TPP-CMN and 30 minutes for V-CMN nano-sorbents. The adsorption isotherms, kinetics, and thermodynamics were studied to understand the adsorption mechanism. Furthermore, the adsorption of two synthetic dyes and two real wastewater samples was studied and obtained significant results. These nano-sorbents' simple synthesis, high sorption capability, excellent stability, and recyclability may provide highly efficient and cost-effective nano-sorbents for wastewater treatment.

Hydrothermal synthesis of cobalt substitute zinc-ferrite (Co1-xZnxFe2O4) nanodot, functionalised by polyaniline with enhanced photocatalytic activity under visible light irradiation

Fabrication and development of effective visible-light-responsive photocatalysts are required to tackle critical environmental issues. The aim of this study was to develop a nanocomposite material with improved photocatalytic activity for the degradation of industrial dyes such as Reactive Orange-16 (RO-16), Reactive Blue (RB-222), Reactive Yellow-145 (RY-145), and Disperse Red-1 (DR-1) without the need for a post-separation process after use. Here we report the hydrothermal synthesis of nanodots of Co_1-xZn_xFe₂O₄ (x = 0.3, 0.5 and 0.7), coated with polyaniline, by in situ polymerization. The Co_1-xZn_xFe₂O₄ nanodots, coated with polyaniline (PANI) nanograins, facilitated optical properties by easily capturing visible light. X-ray Diffraction (XRD) patterns and Scanning Electron Microscopy (SEM) images have confirmed the single-phase spinel structure of Co_1-xZn_xFe₂O₄ nanodot and nano-pore size of the Co_1-xZn_xFe₂O₄/PANI nanophotocatalyst. The specific surface area of the Brunauer-Emmett-Teller (BET) of the Co_1-xZn_xFe₂O₄/PANI photocatalyst was determined to be 24.50 m²/g by multipoint analysis. The final Co_1-xZn_xFe₂O₄/PANI (x = 0.5) nanophotocatalyst showed high efficiency in the catalytic degradation of toxic dyes (∼98% within 5 min), with good mechanical stability and recyclability under visible light irradiation. The nanophotocatalyst was re-used and its efficiency was largely maintained, even after seven cycles (∼82%) of degradation. The effects of various parameters, such as initial dye concentration, nanophotocatalyst concentration, initial pH of dye solution, and reaction kinetics were studied. According to the Pseudo-first-order kinetic model, photodegradation data followed the first-order reaction rate (R² > 0.95) of degradation of dyes. In conclusion, a simple and low-cost synthesis process, speedy degradation and excellent stability of polyaniline-coated Co_1-xZn_xFe₂O₄ nanophotocatalyst could be used as a promising photocatalyst for dye-wastewater treatment.

Recent Advances in the Removal of Organic Dyes from Aqueous Media with Conducting Polymers, Polyaniline and Polypyrrole, and Their Composites

Water pollution by organic dyes, and its remediation, is an important environmental issue associated with ever-increasing scientific interest. Conducting polymers have recently come to the forefront as advanced agents for removing dye. The present review reports on the progress represented by the literature published in 2020–2022 on the application of conducting polymers and their composites in the removal of dyes from aqueous media. Two composites, incorporating the most important polymers, polyaniline, and polypyrrole, have been used as efficient dye adsorbents or photocatalysts of dye decomposition. The recent application trends are outlined, and future uses also exploiting the electrical and electrochemical properties of conducting polymers are offered.