Deionized Milli-Q water (Millipore, USA) was used for the preparation of all solutions. Working standard solutions of chromium were prepared daily by appropriate dilution of the stock standard: Cr(III) (20 g L−1, Merck, Germany) or Cr (VI) (1.001 g L−1, Sigma-Aldrich, Germany). Ammonia solution (25 %) supplied by POCh (Poland) and hydrochloric acid (37 %, TraceSelect, Fluka, Germany) were used for pH adjustment. EDTA obtained from Merck (Germany) was used as a desorption agent. Nitrates(V) of copper(II), nickel(II), manganese(II) and calcium (Fluka, Germany) were used for studies of competitive ions on chromium separation. 1,5-Diphenylcarbazide (DPC, Puriss, Fluka, Germany), methacrylic acid (MAA, Sigma-Aldrich, Germany), glycol ethylene dimethacrylate (EGDMA, 98 %, Sigma-Aldrich, Germany), lauroyl peroxide (Sigma-Aldrich, Germany) and ethanol (96 %, p.a.; POCh, Poland) were used for synthesis of the polymer. De-aeration of polymerization solutions was performed under a high-purity argon atmosphere.
Reference material of wastewater from an urban treatment plant, RES 10.2 (ielab Calidad, Spain), was used for the evaluation of accuracy of the developed procedure. Sewage samples were delivered from a municipal sewage treatment plant (Bialystok, Poland).
Reference material of wastewater from an urban treatment plant, RES 10.2 (ielab Calidad, Spain), was used for the evaluation of accuracy of the developed procedure. Sewage samples were delivered from a municipal sewage treatment plant (Bialystok, Poland).