No abstract

The concentrations of iron, zinc, manganese, copper, chromium, nickel, lead, arsenic, and cadmium were determined using flame (FAAS) and graphite furnace atomic absorption spectrometry (GFAAS) in nine herbal tea samples. Hawthorn, yarrow, elderflower, and bearberry are herbal teas for which the metal content has been rarely determined. The concentration of cadmium in St John's wort exceeded the maximum permissible limit of 0.3 mg/kg. The metals were also determined in aqueous extracts following 5, 10, and 20 min of boiling and using different preparation, including acidification with lemon juice. The influence of these factors on metal release was demonstrated using multivariate analyses by redundancy analysis (RDA) and principal component analysis (PCA). The metal release was not considerably affected by the boiling time, while the acidity of the medium was generally positively correlated. For the infusions, arsenic was detected only in acidified mint tea. The extraction efficiencies of metals were determined and classified as highly, moderately and poorly extractable, with chromium showing largest variations.

The sepiolite/ZrO2 composites were prepared by sepiolite (Sep) modification with zirconium propoxide in toluene at room temperature for 24 h (Sep–ZrI) or 95 °C for 4 h (sample Sep–ZrII). The efficiency of the obtained composites for the removal of phosphate from aqueous solutions at initial pH = 4 and pH = 8 was investigated. Characterization of the samples shows that synthesis at a higher temperature for a shorter time provides a slightly higher content of amorphous Zr phase, which is deposited on the sepiolite fibers as a thin layer and agglomerated nanoparticles. Compared to Sep, the composites have a lower point of zero charge and higher specific surface area and pore volume. The adsorption kinetics follow the pseudo second-order model. The adsorption capacities of the composites are approximately the same at both initial pH and higher at initial pH = 4 than at pH = 8. The XPS and ATR-FTIR of Sep–ZrI before and after adsorption identifies the formation of inner-sphere complexes as the mechanism of phosphate adsorption. The slow release during desorption with NaOH solution confirms the strong bonds of the phosphates with the surface of the composites.

The sepiolite/ZrO2 composites were prepared by sepiolite (Sep) modification with zirconium propoxide in toluene, at room temperature for 24 h (Sep –ZrI) or 95 °C for 4h (sample Sep –ZrII). The efficiency of the obtained adsorbents for the removal of phosphate from aqueous solutions at initial pH = 4 and pH = 8, was investigated. Characterization of the samples showed that higher temperature of synthesis for shorter time provided slightly higher content of amorphous Zr-phase, which was deposited on sepiolite fibers as a thin layer and agglomerated nanoparticles. Compared to Sep, the composites had lower point of zero charge and higher specific surface area and pore volume. The adsorption kinetics follows the pseudo second-order model. The adsorption capacities of the composites were approximately the same at both initial pH and higher at initial pH = 4 than at pH = 8. The XPS and ATR-FTIR of Sep-ZrI before and after adsorption identified the formation of inner-sphere complexes as the mechanism of phosphate adsorption. The slow release during desorption with NaOH solution confirmed strong bonds of phosphates with the surface of the composites.