Synthesis and characterization of magnetic clay-based carboxymethyl cellulose-acrylic acid hydrogel nanocomposite for methylene blue dye removal from aqueous solution.

Carboxymethyl cellulose/poly(acrylic acid) (CMC-cl-pAA) hydrogel and its magnetic hydrogel nanocomposite (CMC-cl-pAA/Fe3O4-C30B) were prepared via a free radical polymerization method and used as adsorbents for adsorption of methylene blue (MB) dye. The samples were characterized using Fourier transform infrared, X-ray diffraction, thermogravimetric analysis, scanning electron microscopy coupled with energy-dispersive X-ray spectrometer, high-resolution transmission electron microscope, and dynamic mechanical analysis. The adsorption performance of the prepared adsorbents was studied in a batch mode. Adsorption kinetics and isotherm models were applied in the experimental data to evaluate the nature as well as the mechanism of adsorption processes. It was deduced that the adsorption followed the pseudo-second-order rate equation and Langmuir isotherm models. The maximum adsorption capacities were found to be 1109.55 and 1081.60 mg/g for CMC-cl-pAA hydrogel and CMC-cl-pAA/Fe3O4-C30B hydrogel nanocomposite, respectively. The adsorption thermodynamic studies suggested that the adsorption process was spontaneous and endothermic for CMC-cl-pAA/Fe3O4-C30B hydrogel nanocomposite. The homogeneous dispersion of the Fe3O4-C30B nanocomposite in the CMC-cl-pAA hydrogel significantly improved the thermal stability, mechanical strength, and excellent regeneration stability. This study demonstrates the application potential of the fascinating properties of CMC-cl-pAA/Fe3O4-C30B hydrogel nanocomposite as a highly efficient adsorbent in the removal of organic dyes from aqueous solution.

Poly(3-aminobenzoic acid) Decorated with Cobalt Zeolitic Benzimidazolate Framework for Electrochemical Production of Clean Hydrogen.

A novel composite of poly(3-aminobenzoic acid) (PABA) and a cobalt zeolitic benzimidazolate framework (CoZIF) has been studied for the production of hydrogen through the hydrogen evolution reaction (HER). The structural characteristics and successful synthesis of PABA, CoZIF and the PABA/CoZIF composite were confirmed and investigated using different techniques. Probing-ray diffraction for phase analysis revealed that the composite showed a decrease and shift in peak intensities, confirming the incorporation of CoZIF on the PABA backbone via in situ polymerization, with an improvement in the crystalline phase of the polymer. The thermal stability of PABA was enhanced upon composite formation. Both scanning electron microscopy and transmission electron microscopy showed that the composite had a rough surface, owing to an interaction between the CoZIF and the external surface of the PABA. The electrochemical hydrogen evolution reaction (HER) performance of the synthesized samples was evaluated using cyclic voltammetry and Tafel analysis. The composite possessed a Tafel slope value of 156 mV/dec and an α of 0.38, suggesting that the Volmer reaction coupled with either the Heyrovsky or Tafel reaction as the rate determining step. The fabricated composite showed high thermal stability and excellent tolerance as well as high electroactivity towards the HER, showing it to be a promising non-noble electrocatalyst to replace Pt-based catalysts for hydrogen generation.

Influence of Magnetic Nanoparticles on Modified Polypyrrole/m-Phenylediamine for Adsorption of Cr(VI) from Aqueous Solution.

A novel, modified polypyrrole/m-phenylediamine (PPy-mPD) composite, decorated with magnetite (Fe3O4) nanoparticles, and prepared via an in-situ oxidative polymerisation, was investigated. The PPy-mPD/Fe3O4 nanocomposite was employed for the removal of highly toxic oxyanion hexavalent chromium Cr(VI) from an aqueous solution. The structure and successful formation of the PPy-mPD/Fe3O4 nanocomposite was confirmed and investigated using various techniques. The presence of Fe3O4 was confirmed by high resolution transmission electron microscopy, with an appearance of Fe lattice fringes. The estimation of the saturation magnetisation of the nanocomposite, using a vibrating sample magnetometer, was observed to be 6.6 emu/g. In batch adsorption experiments, PPy-mPD/Fe3O4 nanocomposite (25 mg) was able to remove 99.6% of 100 mg/L of Cr(VI) at pH 2 and 25 °C. Adsorption isotherms were investigated at different Cr(VI) concentration (100-600 mg/L) and temperature (15-45 °C). It was deduced that adsorption follows the Langmuir model, with a maximum adsorption capacity of 555.6 mg/g for Cr(VI) removal. Furthermore, isotherm data were used to calculate thermodynamic values for Gibbs free energy, enthalpy change and entropy change, which indicated that Cr(VI) adsorption was spontaneous and endothermic in nature. Adsorption-desorption experiments revealed that the nanocomposite was usable for two consecutive cycles with no significant loss of adsorption capacity. This research demonstrates the application potential for the fascinating properties of PPy-mPD/Fe3O4 nanocomposite as a highly efficient adsorbent for the removal of heavy metal ions from industrial wastewater.