Removal of Cd(II) by poly(styrenesulfonic acid)-impregnated alginate capsule

• PSSA-AC was successfully developed using a simple and moderate method.
• The maximum Cd(II) uptake was 184.12 ± 6.30 mg/g using Langmuir isotherm model.
• The Cd(II)-loaded PSSA-AC was easily regenerated by using 2% CaCl2 solution.
• The overall sorption/desorption mechanism was cation ion-exchange between Cd(II) and Ca(II).

In this study, a capsule type sorbent of poly(styrenesulfonic acid)-impregnated alginate capsule (PSSA-AC) was developed by using a simple and moderate method. PSSA was used as a model encapsulated material because of its large number of sulfonic acid groups which have high affinity toward Cd(II). PSSA-AC was prepared by dropping solution A (mixture of 10% (w/v) PSSA + 1% CaCl2) into B solution (0.6% (w/v) sodium alginate). Microscope images revealed that PSSA was well encapsulated inside of the alginate shell. The pH edge experiment indicated that Cd(II) sorption was influenced marginally by the experimental pH range. The maximum Cd(II) uptake by PSSA-AC was as high as 184.12 ± 6.30 mg/g. The kinetic and FTIR studies demonstrated that ion-exchange was the main sorption mechanism. The PSSA-AC could be regenerated by using 2% CaCl2 as a desorbing agent.

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