Preparation and application of phosphinic acid functionalized nanosilica for the effective removal of mercury (II) in aqueous solutions

Abstract: A novel adsorbent was synthesized by functionalizing nanosilica with phosphinic acid groups for the removal of mercury ions from aqueous solutions. The synthesized absorbent was characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), transmission electron microscope (TEM) and thermogravimetric analysis (TGA). Meanwhile, the effects of initial pH, contact time and initial mercury ions concentration on the removal of mercury ions from aqueous solutions were investigated by batch adsorption experiments. The results showed that the removal rate reached 99.11% and the maximum adsorption capacity was up to 274.32 mg/g at pH 2 and the equilibrium time of adsorption was about 1 h. The absorbent presented good selectivity for mercury ions among Zn(II), Ni(II), Mn(II) and Ge(IIII). Moreover, the obtained adsorbent has good reusability and the absorbability decreased only from 98.76 to 94.75% after five cycles. Besides, the adsorption isotherms fitted well to the Langmuir isotherm model and adsorption kinetics followed the pseudo-second-order model. The removal mechanism of mercury via phosphinic acid-functionalized silica nanoparticles was chelation interaction. All the experimental data indicated that the phosphinic acid-functionalized silica nanoparticles are very promising in removal of mercury ions from aqueous solutions. [Figure not available: see fulltext.].