Magnetic ion‐imprinted microspheres for the removal of heavy metal ions from aqueous solution

Abstract

Magnetic ion-imprinted microspheres (IIM) with core-shell structure were successfully prepared by reverse emulsion polymerization and applied to adsorb heavy metal ions from sewage. The semi-interpenetrating polymer network composed of cross-linked polyacrylamide (PAM) and linear chitosan (CTS) was used as the microgel shell of microspheres, which can not only fully retain the active sites of CTS but also tightly encapsulate magnetic particle nuclei. In addition, ion imprinting technology was used to further improve the adsorption capacity. In this study, the effects of PAM to CTS ratio on the thermal stability, magnetic properties, and microstructure of microspheres were investigated. Adsorption studies showed that IIM exhibited excellent selective adsorption of Cu(II), and the effects of initial concentration of metal ions, adsorption time, adsorbent dosage, pH, ionic strength, and cycle times on adsorption of Cu(II) by IIM-2 were also studied. In addition, it was revealed that pseudo-second-order kinetic model and Langmuir isotherm model could better simulate the adsorption kinetic and isotherm of IIM-2 for Cu(II), respectively. At 30 C and pH 5.0, the theoretical maximum adsorption capacities for Cu(II) by IIM-2 were 151.13 mg/g. X-ray photoelectron spectroscopy and Zeta potential study showed that the adsorption mechanism of IIM-2 was a combination of electrostatic interaction and ion exchange.

Exploring microgel adsorption: synthesis, classification, and pollutant removal dynamics

“…The adsorption capacity of the core–shell systems decreased when the content of NaCl increased from 0 mol L −1 to 1.00 mol L −1 . Similar behavior was observed by Zhao et al 113 They used different contents of NaNO 3 during the adsorption of heavy metal ions. The adsorption capacity of the microgels decreased with an increase in the content of NaNO 3 from 0 mol L −1 to 0.1 mol L −1 .…”

“…This porosity increases the adsorption capacity of the systems. Zhao et al 113 reported the synthesis of a core–shell system, in which the core consisted of Fe 3 O 4 and shell chitosan-poly(acrylamide) CSa-P(AAm) together with Ca 2+ ions. The adsorption quantity of Cr 3+ , Cd 2+ , Pd 2+ , and Cu 2+ ions from water by the synthesized systems was 4.64, 8.20, 18.56, and 37.84 mg g −1 , respectively.…”

Construction of double cross‐linked networks in calcium alginate/poly‐N‐isopropylacrylamide hydrogel with photothermal responsiveness for absorbing heavy metal ions

“…In addition, the bending vibration peak of NH 2 located at 1604 cm −1 shifted toward the high wave number, indicating the presence of adsorption of the amino group on Cr(III). The shift of this peak was mainly caused by the increase in the bonding constant due to the more uniform distribution of the NH electron cloud density after the nitrogen atom on the amino group shared the lone pair of electrons with Cr(III) 59 . Meanwhile, the OH and NH 2 stretching vibrational peaks at 3600–3100 cm −1 became significantly wider and weaker after the adsorption of Cr(III).…”

“…The shift of this peak was mainly caused by the increase in the bonding constant due to the more uniform distribution of the N H electron cloud density after the nitrogen atom on the amino group shared the lone pair of electrons with Cr(III). 59 Meanwhile, the OH and NH 2 stretching vibrational peaks at 3600-3100 cm À1 became significantly wider and weaker after the adsorption of Cr(III). The decrease in electron cloud density of O H and N H functional groups during their coordination with Cr(III) could be explained by the sharing of lone pair electrons between O and N.…”