The chemical composition analysis was carried out by using visible-light spectrophotometry (DR 3900, Hach Lange, Germany). The analysis of the content of Zn2+ ions was carried out by using the Zincon method No. 8009 (Hach Lange). The analysis of the content of Mn2+ ions was carried out by using the 1-(2-pyridylazo)-2-naphthol (PAN) method No. 8149 (Hach Lange). The chemical composition analysis was carried out by using inductively coupled argon plasma optical emission spectrometry (ICP-OES) (Thermo Scientific, iCAP model 6000, Great Britain).
Samples for the quantitative analysis were prepared as follows: 5 mg of powder was weighed in a 110 mL Teflon vessel and 15 mL of deionised water (HLP 20UV, Hydrolab, Poland) was added; then 6 mL of HNO3 was added and the solution subjected to one microwave heating cycle in a Magnum II reactor (600 W, 2.45 GHz, ERTEC, Poland). After cooling the sample volume was filled up to 50 mL with deionized water [66 (link)]. The pH of samples before the colorimetric analysis was adjusted in accordance with the recommendations of procedures No. 8009 and No. 8149.
Quantitative microanalysis was carried out through energy-dispersive X-ray spectroscopy (EDS) by using an EDS analyser (Quantax 400, Bruker, USA). Samples for EDS tests were pressed to pellets with a diameter of 5 mm.
Samples for the quantitative analysis were prepared as follows: 5 mg of powder was weighed in a 110 mL Teflon vessel and 15 mL of deionised water (HLP 20UV, Hydrolab, Poland) was added; then 6 mL of HNO3 was added and the solution subjected to one microwave heating cycle in a Magnum II reactor (600 W, 2.45 GHz, ERTEC, Poland). After cooling the sample volume was filled up to 50 mL with deionized water [66 (link)]. The pH of samples before the colorimetric analysis was adjusted in accordance with the recommendations of procedures No. 8009 and No. 8149.
Quantitative microanalysis was carried out through energy-dispersive X-ray spectroscopy (EDS) by using an EDS analyser (Quantax 400, Bruker, USA). Samples for EDS tests were pressed to pellets with a diameter of 5 mm.
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