Synthesis of a chelating cellulose filter with 2,2′‐diaminodiethylamine functional groups

For the purpose of preconcentrations of trace transition metals from solutions containing important quantities of alkali and alkaline earth ions, the synthesis of cellulose filters containing 2,2′‐diaminodiethylamine functional groups was studied. The optimized synthesis procedure consists of heating Whatman‐41 cellulose filters during 15 min at 90°C in a mixture of 200 ml purified and dried dimethylformamide and 6 ml POCl3, and by heating the resulting chlorodeoxycellulose filters in a subsequent step to 130°C during at least two hours in an excess of purified 2,2′‐diaminodiethylamine. The resulting chelating filters exhibit a capacity for transition metal collection of 2.4 μeq/cm2 for 1 ml/min · cm2 filtering experiments and of 10 μeq/cm2 for batch experiments with long equilibration times. The lateral filter homogeneities are better than 18% on all studied specimen. The blank impurities correspond to detection limits in 11 water samples of e.g. 1.5 ppb for Fe, 0.5 ppb for Zn and 0.2 ppb for Cu. In preliminary experiments, the influence of Ca2+ on the transition metal collection yield was proven to be insignificant.