Effective Removal of Calcium and Magnesium Ions from Water by a Novel Alginate-Citrate Composite Aerogel.

In this work, a novel alginate/citrate composite aerogel (CA-SC) was synthesized by chemical grafting technology combined with vacuum freeze-drying method, and CA-SC was used for removing calcium (Ca2+) and magnesium (Mg2+) ions from water. The experimental results indicate that the as-prepared CA-SC has a high affinity for Ca2+ and Mg2+ and can remove 96.5% of Ca2+ (or 96.8% of Mg2+) from the corresponding solution. The maximum adsorption capacities of CA-SC for Ca2+ and Mg2+ are 62.38 and 36.23 mg/g, respectively. These values are higher than those of the most reported Ca2+-sorbents and Mg2+-sorbents. The CA-SC adsorbent can be regenerated through a simple pickling step, and its adsorption performance keeps stable after repeated use. Analysis of the adsorption mechanism shows that the CA-SC combines Ca2+ and Mg2+ in water mainly through coordination effect.