Exploitation of Egyptian insecticide cans in the fabrication of Si/Fe nanostructures and their chitosan polymer composites for the removal of Ni(II), Cu(II), and Zn(II) ions from aqueous solutions

Si/Fe nanostructures (F1, F2, F3, and F4) with different crystallite sizes (25.98, 18.07, 17.23, and 8.97 nm, respectively) were hydrothermally synthesized from Egyptian insecticide cans as an iron source. Also, different mmoles of fumed silica (50.00, 58.33, 66.67, and 75.00, respectively) were utilized as a silicon source. In addition, chitosan composites of the aforementioned nanostructures were synthesized (CF1, CF2, CF3, and CF4, respectively). XRD, EDS, and FT-IR were used to identify the synthesized products and their functional group. Besides, HR-TEM, FE-SEM, and BET techniques were used to identify the morphology and surface texture of the synthesized products. Moreover, Ni(II), Cu(II), and Zn(II) ions were successfully removed from aqueous solutions using the synthesized products. In the case of Ni(II), maximum adsorption capacities of F1, F2, F3, and F4 were 47.348, 49.188, 51.679, and 55.586 mg/g, respectively. But, their values for CF1, CF2, CF3, and CF4 were 59.880, 65.789, 70.922, and 77.519 mg/g, respectively. In the case of Cu(II), maximum adsorption capacities of F1, F2, F3, and F4 were 46.211, 50.251, 52.383, and 56.306 mg/g, respectively. But, their values for CF1, CF2, CF3, and CF4 were 55.249, 60.976, 64.935, and 72.464 mg/g, respectively. In the case of Zn(II), maximum adsorption capacities of F1, F2, F3, and F4 were 41.982, 43.898, 46.404, and 53.333 mg/g, respectively. But, their values for CF1, CF2, CF3, and CF4 were 52.356, 57.471, 59.880, and 68.027 mg/g, respectively. Kinetic study showed that the intra-particle diffusion and pseudo-second-order models are more suitable to describe Ni(II), Cu(II), and Zn(II) ions adsorption processes. Besides, equilibrium study proved that Langmuir isotherm outperforms Freundlich in the description of the adsorption processes. Moreover, reusability study revealed these adsorbents are promising, stable, and can possibly be utilized repeatedly without giving up its adsorption capacity towards Ni(II), Cu(II), or Zn(II) ions.