PEI modified magnetic porous cassava residue microspheres for adsorbing Cd(II) from aqueous solution

Abstract

• PEI modified porous magnetic microspheres prepared from cassava residue were prepared. • Cd(II) adsorption amount was increased from 29.2 mg/g to 42.6 mg/g after PEG2000 addition. • It is easily separated after adsorption in aqueous solution and is recyclable. • Cd(II) adsorption process on PEI/HMPCR was controlled by chemical adsorption and diffusion. Polyethyleneimine modified magnetic porous cassava residue microspheres (PEI/HMPCR) were prepared by reverse emulsion polymerization with pretreated cassava residue (PCR) as raw material, modified by linear polyethyleneimine (PEI) and polyethylene glycol (PEG2000) as the porogen, which was applied for the adsorption remove of the cadmium ions (Cd(II)) from the simulated wastewater. The results showed the specific surface area increased from 8.08 m 2 /g to 17.06 m 2 /g for the magnetic microspheres of cassava residue (HMPCR) after the PEG2000 was added, and the PEI was successfully graft-modified onto the PCR surface. However, After the PEI was added, the specific surface area was reduced to 14.86 m 2 /g with a pore diameter size of 14.24 nm. X-ray photoelectron spectroscopy (XPS) and Fourier-transform infrared spectroscopy (FT-IR) analysis demonstrated the Cd(II) was adsorption mainly with the –NH and –NH 2 groups on the PEI/HMPCR surface, and the PEI/HMPCR adsorbent exhibited superparamagnetic with a saturation magnetic susceptibility of 9.5 emu/g. Furthermore, the effects of the pH, amounts of PEG2000 and PEI, and optimize conditions on the adsorption process were also studied. The adsorption results showed the adsorption capacity of Cd(II) on the PEI/HMPCR increased from 29.1 mg/g to 42.6 mg/g compared with the sample without porogen. The maximum adsorption capacity was 143.6 mg/g at the pH of 6.0, temperature of the 35 °C, and a Cd(II) initial concentration of 250 mg/L. The addition of PEI provided more –NH and –NH 2 groups as adsorption sites for Cd(II). The thermodynamics and kinetic studies showed the adsorption of Cd(II) on PEI/HMPCR could be fitted by a Langmuir isothermal and a pseudo-second-order model, and a possible reaction mechanism was proposed.