Enhancement of Cd(II) adsorption by polyacrylic acid modified magnetic mesoporous carbon

A novel adsorbent was prepared by chelating magnetic mesoporous carbon with polyacrylic acid (PAA) to improve the performance of Cd(II) adsorption. Structure characterization demonstrated that the composites were successfully modified with carboxyl groups and preserved ordered mesostructure after modification. The high saturation magnetization (9.2 emu/g) of the modified composites indicated easy and fast separation from water under a moderate magnetic field. Batch experiments with variable pH, contact time and ionic strength were conducted to evaluate the adsorption performance. The modification accelerated the cadmium adsorption rate. The adsorption kinetics of the two materials followed pseudo-second-order model and exhibited 3-stage intraparticle diffusion mode. Equilibrium data were best described by Langmuir model, and the estimated maximum adsorption capacity for the modified adsorbent increased to 406.6 mg/g, which was 140.8% higher than the pristine materials. Moreover, the Cd(II) loaded adsorbent could be regenerated using 0.1 M ethylenediaminetetraacetic acid solution, and the regenerated adsorbent after five cycles could retain 85.2% of the adsorption capacity for the fresh adsorbent. The results suggested that PAA modified adsorbents could be considered to be very effective and promising materials for Cd(II) removal from waste water.