Preparation of hydrogel composites using Ca2+ and Cu2+ ions as crosslinking agents

The aim of this work was to investigate the influence of the crosslinking agent on the production of biopolymer composites with immobilized eggshells. Capsules with various chemical composition were produced: pure alginate (ALG) and alginate with carboxymethylcellulose and different content of biosorbent (5 wt% and 10 wt%). Two crosslinking agents have been used for the production of composites, i.e. Cu2+ ions and Ca2+ ions. Physicochemical properties (drying kinetics, swelling) and sorption properties of the structures were examined. Composite functional groups responsible for binding Cu2+ cations using Fourier transform infrared spectroscopy were located. Desorption of Cu2+ ions was performed to investigate the effect of crosslinkers on the release of cations (composites crosslinked with Ca2+ ions slower desorb the Cu2+ ions). The results showed that the type of the crosslinking agent has a significant influence on the physicochemical properties of biocomposites, as well as the binding and release of Cu2+ ions. Based on the result, biocomposites with immobilized biomass crosslinked with Ca2+ ions could be used in the future as controlled release fertilizers.