Aminated cassava residue-based magnetic microspheres for Pb(II) adsorption from wastewater

Aminated cassava residue magnetic microspheres (ACRPM) were synthesized via an inverse emulsion method by using chemically modified cassava residue as a crude material, and acrylic acid (AA), acrylamide (AM), and methyl methacrylate (MMA) as monomers and a polyethylene glycol/methanol system (PEG/MeOH) as the porogen. Fourier-transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), N 2 adsorption-desorption and vibrating sample magnetometry (VSM) were used to characterize the ACRPM. The results indicated that amino groups were grafted to the cassava residue magnetic microspheres, and the Fe 3 O 4 nanoparticles were encapsulated in the microspheres. After porogen was added, the particle size of the ACRPM decreased from 16.5 μm to 150 nm with a pore volume of 0.05510 m 3 /g, and the specific surface area of the ACRPM increased from 3.02 to 12.34 m 2 /g. The ACRPM were superparamagnetic, and the saturation magnetization was 9.8 emu/g. The maximum adsorption capacity of Pb(II) on the ACRPM was 390 mg/g. The ACRPM exhibited a large specific surface area and provided many adsorption sites for metal ion adsorption, which favored a high adsorption capacity. Additionally, the Pb(II) adsorption process was fitted to pseudo-second-order kinetic and Langmuir isothermal adsorption models. This suggests that the Pb(II) adsorption process was dominated by a chemical reaction process and that chemisorption was the rate-controlling step during the Pb(II) removal process. In addition, the adsorbent exhibited good stability after six consecutive reuses.