Crosslinked carboxymethyl starch: One step synthesis and sorption characteristics

• One-step carboxymethylation and crosslinking.
• Carboxymethyl starch crosslinked with dichloroacetic acid.
• Decreasing degree of carboxymethylation with the crosslinker content.
• Swellability in water, 0.9% NaCl solution, simulated gastric fluid (pH 1.2).
• Sorption experiment for systems: sorbent/metal cation solution in autogenic pH conditions.
• High efficiency of divalent metal cation sorption (Fe, Ca, Cu, Pb, Cd).

Crosslinked carboxymethyl starch (cCMS) hydrogels were synthesized in a simple one step process using various crosslinking agent content – dichloroacetic acid (DCA) with the constant monochloroacetic acid and DCA/anhydroglucosidic unit (AGU) 1.75:1 molar ratio whereas DCA/AGU was changed in a range 0.15–1.0 mol/AGU. The degree of substitution (DS = 0.4–0.9), and reaction efficiency were evaluated. Moreover, swellability in water and aqueous solutions was determined. Adsorption tests for Fe(II) cation as a function of cCMS crosslinking degree, sorbent dose and time were performed in autogenic pH (ca. 7.0). For comparison four other divalent metal cations were tested. Adsorption efficiency was up to 98% for Fe(II), 96% for Ca(II) and above 99.7% for Cu(II), Cd(II) and Pb(II).

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