Central composite design for optimization of removal of trace amounts of toxic heavy metal ions from aqueous solution using magnetic Fe ₃ O ₄ functionalized by guanidine acetic acid as an efficient nano-adsorbent

In this study, a novel and effective preconcentration and removal technique based on the use of magnetic Fe ₃ O ₄ functionalized by guanidine acetic acid (Fe ₃ O ₄ @GAA) as a nano-adsorbent were introduced. The application of synthesized nano-adsorbent was investigated for the adsorption and removal of a trace amount of some heavy metals, such as Hg (II), Zn (II), Cu (II) and Ag (I), from aqueous samples. The synthesized nano-adsorbents were analyzed by scanning electron microscopy (SEM), Fourier transforms infrared spectroscopy (FT-IR) and X-ray powder diffraction (XRD). The diameter of the magnetic nano-adsorbents was in the range of 20–30 nm. In order to obtain maximum removal efficiency, the effects of effective parameters were optimized using a central composite chemometric design. The optimum conditions were pH of 7, nano-adsorbent amount of 14 mg and contact time of 10 min. The Fe ₃ O ₄ @GAA nano-adsorbent could be simply separated from the solution with the assistance of an external magnetic field, eluted with proper eluent and reused for twenty runs without a significant loss of its adsorbent activity. The adsorption efficiencies and preconcentration factors of developed procedure for target ions were in the range of 95–100% and 112–125, respectively, under the optimum condition. The obtained results revealed that the Fe ₃ O ₄ @GAA nano-adsorbent could be applied as a novel, simple, highly effective, reusable and cost-consuming material for the preconcentration and removal of the target toxic heavy metal ions from the aqueous solution.