Role of Zn And Polyaniline In Magnetic Nanocomposites And Enhanced Arsenic Adsorption Capacity In Wastewater

Polyaniline/Fe0.90Zn0.10Fe2O4 (PANI/Zn0.10Fe2.90O4) nanocomposites were synthesized by a chemical method and an onsite polymerization method. XRD patterns showed that the Zn0.10Fe2.90O4 grain size about 12 nm, while TEM image showed grain size from 10 to 20 nm. The results of Raman spectra and DTA analyses showed that PANI participated in part of the PANI/Zn0.10Fe2.90O4 nanocomposite samples. The grain size of PANI/Zn0.10Fe2.90O4 samples measured by SEM was about 35–50 nm. These results demonstrated the shell–core structures of the nanocomposite material. The magnetization measurements at room temperature showed that in 1250 Oe magnetic field, the saturation magnetic moment of PANI/Zn0.10Fe2.90O4 samples decreased from 71.2 to 42.3 emu/g when the PANI concentration increased from 0 % to 15 %. The surface area and porous structure of nanoparticles were investigated by the BET method at 77 K and a relative pressure P/P0 of about 1. The arsenic adsorption capacity of the PANI/Zn0.10Fe2.90O4 sample with the PANI concentration of 5 % was better than that of Fe3O4 and Zn0.10Fe2.90O4 in a solution of pH 7. In the solution with pH P14, the arsenic adsorption of magnetic nanoparticles was insignificant. Due to substitution of Fe ions by Zn transition metal and coating polyaniline, these materials could be reabsorbed and reused.

Adsorptive Removal of Arsenic by Synthetic Iron-loaded Goethite: Isotherms, Kinetics, and Mechanism

Arsenic contamination in the groundwater is a worldwide concern. Therefore, this study was designed to use synthetic iron-loaded goethite to remove arsenic. Adsorption was significantly pH-dependent; hence, pH values between 5.0 and 7.0 resulted in the highest removal of arsenate and arsenite. Langmuir and Freundlich isotherms were almost perfectly matched in terms of strong positive coefficient of determination “R2” arsenate – 0.941 and 0.992 and arsenite – 0.945 and 0.993. The adsorption intensity “n” resulted as arsenate – 2.542 and arsenite – 2.707; besides separation factor “RL” found as arsenate – 0.1 and arsenite – 0.5, respectively. However, both “n” and “RL” leads to a favourable adsorption process. Temkin isotherm yielded in equal binding energies “bt” showing as 0.004 (J/μg) for both arsenate and arsenite. Jovanovic monolayers isotherm was dominated by the Langmuir isotherm. This resulting in maximum adsorption capacity “Qmax” of arsenate – 1369.877 and arsenite – 1276.742 (μg/g), which approaches to the saturated binding sites. Kinetic data revealed that adsorption equilibrium was achieved in 240 – arsenate and 360 – arsenite (minutes), respectively. Chemisorption was found effective with high “R2” values 0.981 ­– arsenate and 0.994 – arsenite, respectively, with the best fitting of pseudo-second order. Moreover, Brunauer Emmett Teller (BET), Scanning Electron Microscopy (SEM), X-ray diffraction (XRD), and Fourier Transform Infrared Spectroscopy (FTIR) were used to determine the morphological content, surface area, crystalline structure, and chemical characteristics of the adsorbent. It is anticipated that optimal arsenic removal was achieved by the porosity, chemical bindings, and surface binding sites of the adsorbent.