Selective adsorption behavior of Cd2+ imprinted acrylamide-crosslinked-poly(alginic acid) magnetic polymers: fabrication, characterization, adsorption performance and mechanism.

Abstract

Poly(acrylamide) grafted and glutaraldehyde-crosslinked alginic acid nano-magnetic adsorbent (AAMA) was prepared by selecting Cd2+ as a template ion. Scanning electron microscope (SEM), thermo-gravimetric analyzer (TGA), vibrating sample magnetometer (VSM) and infrared spectroscopy (IR) were used to characterize the morphology and structure of AAMA. The adsorption of AAMA for different metal ions was compared and the impact of various factors for adsorption of Cd2+ was systematically investigated. These results suggested that the AAMA was the aggregates of Fe3O4 nanoparticles with a diameter of about 50-100 nm and had selectivity for Cd2+ adsorption. The maximum adsorption capacity for Cd2+ is 175 mg/g at pH 5.0 and 303 K. The experimental data were well described by the Langmuir isotherm model and pseudo-second-order model. The parameters of adsorption thermodynamics concluded that the adsorption progress is spontaneous and endothermic in nature. The parameters of adsorption activation energy suggested that there is physical adsorption and chemisorption on the adsorption of metal ions. AAMA could be regenerated by EDTA and still keep 71% adsorption capacity in the fifth consecutive adsorption-regeneration cycle. Therefore, AAMA would be useful as a selective and high adsorption capacity nano-magnetic adsorbent in the removal of Cd2+ from wastewater.