Facile synthesis and characterization of folic acid-modified silica nanoparticles and its exploration for adsorptive removal of aluminum(III) from aqueous media

Abstract

In the current study, folic acid-modified silica nanoparticles (FA-SNPs) were fabricated and used for the removal of Al(III) from aqueous media via solid-phase extraction (SPE) procedure before its spectrometric determination using flame atomic absorption spectrometry (FAAS). The prepared adsorbent was characterized by elemental analysis, infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray powder diffraction (XRD), Brunauer-Emmett-Teller (BET) surface area measurement, and pH at a point of zero charge (pH_pzc). Thermogravimetric analysis (TGA) was used to prove the thermal stability of the prepared adsorbent. The influence of several parameters including initial pH, amount of adsorbent, time of contact, initial adsorbate concentration, and the effect of foreign ions was studied. The outcomes presented that optimum adsorption of Al(III) was achieved at pH 3.5, contact time of 30 min, adsorbent dosage of 25 mg, and 25 °C. The experimental data agreed well with the pseudo-2^nd order model and was fitted by the Langmuir model with adsorption capacity equal to 17.52 ± 0.122 mg/g. Thermodynamic analysis revealed that the adsorption of Al(III) was spontaneous and exothermic. The procedure was successfully applied for the recovery of Al(III) spiked to some real water samples. The regeneration study using HNO₃ indicated the excellent regenerative power of the prepared adsorbent. Moreover, pH-metric titration was used to prove the complexation between Al(III) and the surface of the prepared adsorbent. The obtained results showed that FA-SNPs is an effective, eco-friendly, and low-cost adsorbent that can be used for the removal of Al(III) from aqueous solution.

Graphical Abstract

Keywords:

• Adsorption
• isotherms
• kinetics
• thermodynamics
• water treatment