Effective separation of chromium species in technological solutions using amino-immobilized silica prior to their determination

Amino-immobilized (poly(4,9-dioxadodecane-1,12-guanidine, polydiallyldimethylammonium, hexadimethrin bromide, polyhexamethylene guanidine) silicas were proposed for chromium speciation for the first time. Adsorbents surface was characterized by TGA-DSC, FT-IR, CHN, XRD and SEM analysis. Polyamines were strongly fixed on the silica surface and were not washed off with solutions of 3M HNO3 and 20 g L-1 NaCl. Amino-immobilized silica quantitatively removed (R >= 99%) Cr(VI) from solutions at pH 4-7. Cr(III) was not recovered in this pH range, which makes it possible to separate Cr(VI) from Cr(III). The separation factor (K-Cr(VI)/Cr(III)) was >= 1.10(4). Silica-based adsorbents layer-by-layer immobilized with polyamines and 2-(1,8-dihydroxy-3,6-disulfo-2-naphthylazo)benzenearsonic acid were proposed for quantitative removal of Cr(III) from aqueous solutions with pH 4-6 at 90 degrees C. A system of sequentially connected columns filled with selective adsorbents was used to separate the chromium species in stream at pH = 5 and a flow rate of 1 mL min(-1). Chromium was determined after its elution with 5 mL of 2 M HNO3 at a flow rate of 1 mL min(-1) using ICP-OES or ICP-MS. The preconcentration factors for Cr(VI) and Cr(III) was 60. A two-column system was used for chromium speciation in technological solutions. The efficiency of chromium speciation was confirmed by state standard procedure.

Automated summary

Amino-immobilized silicas were used for the first time for chromium speciation. The results showed that this method can effectively separate Cr(VI) and Cr(III) with good application prospects in technological solutions.