Lead and cadmium decontamination from water media by CNT/Starch/Fe₃O₄, as reclaimable magnetic nanocomposite

In the current work, a magnetic nanocomposite containing carbon nanotubes (CNT), starch, and Fe₃O₄ was synthesized to decontaminate lead (Pb²⁺) and cadmium (Cd²⁺) ions from water. The properties of magnetic nanocomposite (CNT/starch/Fe₃O₄) were determined using X-ray diffraction (XRD), vibrating sample magnetometer (VSM), Brunauer–Emmett–Teller (BET), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy dispersive X-ray (EDX), and mapping techniques. The value of the BET area and magnetic saturation for the nanocomposite were 54.18 m²/g and 28.36 emu/g, respectively. The maximum removal of Pb²⁺ (99.74%) and Cd²⁺ (98.76%) was attained at 25 °C, decontamination duration of 50 min, a metal content of 10 mg/L, composite mass of 1 g/L, and pH 6 (for Pb²⁺) and 7 (for Cd²⁺). The pseudo quadratic model had a more significant potential to describe the metal removal behavior as it has a lower RMSE and a higher R² than other models. The intraparticle penetration model revealed that more than one mechanism is effective in adsorption. The adsorption process data obeyed the Langmuir model with a q_m factor of 50.36 mg/g (Pb²⁺) and 44.72 mg/g (Cd²⁺). The E value was determined to be < 8 kJ/mol, which indicates that the process is physical. The metal removal using the CNT/starch/Fe₃O₄ composite was spontaneous and exothermic, and during adsorption, the random interactions between the composite and metal ions were reduced. The outcomes showed that the desired adsorbent can absorb and desorb Pb²⁺ and Cd²⁺ and can be used as an effective adsorbent in cleaning aqueous solutions containing heavy metal.