Interaction of Heavy Metal Ions with Carbon and Iron Based Particles

Abstract

Due to the rapid development of industry and associated production of toxic waste, especially heavy metals, there is a great interest in creating and upgrading new sorption materials to remove these pollutants from the environment. This study aims to determine the effectiveness of different carbon forms (graphene, expanded carbon, multi-wall nanotubes) and paramagnetic particles (Fe₂O₃) for adsorption of cadmium(II), lead(II), and copper(II) on its surface, with different interaction time from 1 min to 24 h. The main attention is paid to the detection of these metals using differential pulse voltammetry. Based on the obtained results, graphene and Fe₂O₃ are found to be good candidates for removal of heavy metals from the environment.

Keywords: electrochemical detection; expanded carbon; graphene; heavy metal ions; multi-wall nanotubes; paramagnetic particle; voltammetry.

Figure 1.

Calibration curves of individual metals determined by differential pulse voltammetry: (A) cadmium; (B) lead and (C) copper. 0.2 M acetate buffer (pH = 5) was used as an electrolyte. The parameters were chosen as it follows: initial potential −1.3 V, end potential 0.2 V, deposition potential −1.15 V, accumulation time 240 s, pulse amplitude 25 mV, pulse time 0.04 s, voltage step 5.035 mV, voltage step time 0.3 s, and sweep rate 0.0168 V/s. The characteristic peaks for cadmium, lead and copper were measured at potentials of −0.62, −0.40 and −0.03 V, respectively.

Figure 2.

The amount of bounded cadmium (A,D); lead (B,E) and copper (C,F), on various adsorbents: (A,B,C) for Fe₂O₃; (D,E,F) for expanded carbon. All values were related to the applied concentration of metal (100 μM for cadmium, lead and copper). Zero on the x-axis is control.

Figure 3.

The amount of bounded cadmium (A,D); lead (B,E) and copper (C,F), on various adsorbents: (A,B,C) for multiwall nanotubes; (D,E,F) for reduced graphene oxide. All values were related to the applied concentration of metal (100 μM for cadmium, lead and copper). Zero on the x-axis is control.

Figure 4.

The comparison of time interaction of heavy metal with different adsorbents (A) expanded carbon; (B) MPs Fe₂O₃; (C) multi-walled carbon nanotubes and (D) graphene (reduced graphene oxide). All values were related to the applied concentration of heavy metals (100 μM for cadmium, lead, and copper). K on the x-axis is control. * Statistically significant at the significance level of p < 0.05.

Figure 5.

Determination of the concentration of adsorbent capacity of graphene (reduced graphene oxide): concentration capacity (A) for cadmium; (B) for lead and (C) for copper and of Fe₂O₃ MPs: concentration capacity (D) for cadmium; (E) for lead and (F) for copper. Efficiency of adsorption for each metal is plotted on the y-axis %. Applied concentrations of metals (Cd²⁺, Pb²⁺, and Cu²⁺) were 1, 50, 100, 200 and 500 μ M.

Figure 6.

(A) Preparation of samples: (a) weighed adsorbent; (b) pipetting solution of heavy metal; (c) shaking the sample; (d,e) centrifugation of the sample; (f) pipetting of supernatant; (g) filtration with a MF (membrane filter); (h) electrochemical detection of heavy metal using differential pulse voltammetry. (B) Automatic preparation of samples on EpMotion 5075 (Eppendorf, Germany)—scheme of instrumentation workplace. T0 carrier (capacity ≤ 1200g), T1…T4 dosing machines: TS 1000, TS 300, TS 300/8, TS 50, tip1000_1 epTIPS Motion 1000 μ L, tip300_1 epTIPS Motion 300 μ L, tip50_1 epTIPS Motion 50 μ L, Tubs_1 Holder Eppendorf with 7 × 30 mL reservoirs (max volume: 30 mL, working volume: 25 mL, limit of detection: 3000 μL), Tube_1 Rack Eppendorf, Magnetic pad—magnet for MPs, TMX—thermomix with temperature control, VACUUM—vacuum.