Synthesis of rectorite/Fe3O4-CTAB composite for the removal of nitrate and phosphate from water

A comparative study on Fe(III)-chitosan and Fe(III)-chitosan-CTAB composites for As(V) removal from water: preparation, characterization and reaction mechanism

Fe(III)-chitosan and Fe(III)-chitosan-CTAB composites were prepared using an ionotropic gelation method. Various techniques were used to analyze the morphology, structure, and property of the adsorbents, including SEM, EDS, FT-IR, XPS, and zeta potential. Compared with Fe(III)-chitosan, Fe(III)-chitosan-CTAB was more effective for As(V) adsorption at a wide range of pH (3.0-8.0). The adsorption of As(V) onto Fe(III)-chitosan and Fe(III)-chitosan-CTAB could reach equilibrium in 20 min, and their maximum adsorption capacities were 33.85 and 31.69 mg g^‒1, respectively. The adsorption kinetics was best described by the pseudo-second-order model (R² = 0.998 and 0.992), whereas the adsorption isotherm was fitted well by the Freundlich model (R² = 0.963 and 0.987). The presence of H₂PO₄^- significantly inhibited the adsorption of As(V) onto Fe(III)-chitosan and Fe(III)-chitosan-CTAB, and humic acid also led to a slight decrease in As(V) adsorption by Fe(III)-chitosan-CTAB. Over 94% of As(V) at the initial concentration of no more than 5 mg L^-1 was removed from real water by the two adsorbents. 1% (w/v) NaOH solution was determined to be the most suitable desorption agent. Fe(III)-chitosan and Fe(III)-chitosan-CTAB still maintained their initial adsorption capacities after five adsorption-desorption cycles. Based on different characterization results, both electrostatic attraction and surface complexation mechanisms played important roles in As(V) adsorption on Fe(III)-chitosan and Fe(III)-chitosan-CTAB.

Preparation of ternary amino-functionalized magnetic nano-sized illite-smectite clay for adsorption of Pb(II) ions in aqueous solution

Ternary amino-functionalized magnetic illite-smectite (AMNI/S) nanocomposites were prepared via integrating two-dimensional illite-smectite nanoflakes (NI/S), magnetite nanoparticles (Fe₃O₄), and 3-aminopropyltriethoxysilane (APTES). The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and vibrating sample magnetometry (VSM). The results show that Fe₃O₄ nanoparticles can be well dispersed on NI/S flakes and the hydrolyzed APTES molecules can simultaneously bond to the hydroxyl groups of Fe₃O₄ and NI/S. Due to the synergetic effect, magnetic NI/S composite can graft more amount of APTES molecules rather than Fe₃O₄ nanoparticles or NI/S alone. When the mass ratio of NI/S:Fe₃O₄ is 1:1, the saturation magnetization of AMNI/S-1 is 17.4 emu/g, facilitating the efficient magnetic separation in aqueous solution. Also, AMNI/S-1 shows a maximal adsorption amount of Pb(II) ions of 227.8 mg/g calculated by the Langmuir model. The effects of initial concentration of Pb(II) ions, pH value, adsorption time, and temperature on the adsorption amount of Pb(II) ions were investigated. The adsorption kinetic models and isotherm models were applied to analyze the adsorption of Pb(II) ions, respectively. The thermodynamic analysis reveals that the adsorption of Pb(II) onto AMNI/S-1 is spontaneous and endothermic in nature. The mechanism for the adsorption of Pb(II) ions onto AMNI/S-1 is due to the surface complexation of Fe₃O₄ and NI/S, and the chelation of amine groups (-NH₂). AMNI/S-1 can be efficiently reused and the regenerated AMNI/S-1 remains 82.91% of initial adsorption capacity after 6-cycle adsorption/desorption process. Thus, ternary AMNI/S-1 could be used as a prospective effective adsorbent.

Fabrication of PVA coated PES/PVDF nanocomposite membranes embedded with in situ formed magnetite nanoparticles for removal of metal ions from aqueous solutions

An in situ procedure for the preparation of a coated nanocomposite membrane containing a complexing agent.