Silica nanoparticles@folic acid (SNPs@FA) nanocomposite for the effective removal of Hg(II) from aqueous solution: insight into physicochemical properties, adsorption modelling, isotherm, kinetic, and thermodynamic investigations

Abstract

ABSTRACT This study involved the preparation and utilisation of silica nanoparticles functionalised with folic acid (SNPs@FA) nanocomposite in the adsorptive removal of Hg(II) from aqueous solutions before its spectrometric analysis. Different characterisation techniques were employed to comprehensively assess the different physicochemical properties of the prepared adsorbent, such as elemental analysis, FTIR, SEM, TEM, XRD, TGA, BET, and pHpzc. Investigations were conducted into the variables influencing the adsorption process, such as pH, contact duration, adsorbent dosage, and Hg(II) concentration. It was found that a pH of 7 was ideal, while adsorption equilibration took 80 min. The Langmuir model suited the experimental data well, and 129.03 mg/g of Hg(II) was the maximum adsorption capacity. The kinetic data obtained from the experiments exhibited a remarkable alignment with the pseudo-second-order model. Furthermore, the computed thermodynamic characteristics provided compelling evidence that the adsorption process was endothermic and spontaneous. The recommended process was effectively used to recover Hg(II) that had been added to some real water samples. The regeneration investigation using potassium iodide demonstrated the remarkable regenerative power of the manufactured adsorbent. Finally, the obtained results in this work showed that silica nanoparticles@folic acid nanocomposite is a very efficient and environmentally safe adsorbent and can be used for cleaning mercury-contaminated water.