Factors affecting the precipitation of chromium(III) in jarosite-type compounds

摘要: Jarosite precipitation is a useful means of stabilizing toxic species, and accordingly, the factors affecting chromium(III) in jarosite-type compounds was systematically investigated series laboratory experiments. Although end-member Cr(III) analogues could not be precipitated at temperatures 200 °C, analogue potassium jarosite (KCr3(SO4)2(OH)6) readily precipitated. The has R\(\bar 3\)m structure characteristic compounds, with a=7.23±0.02A c=17.02±0.02 A. well-crystallized material typically contains (wt pct): ∼7K, ∼25Cr, ∼41SO4. composition suggests partial substitution hydronium ion for some chromium vacancies structure. formation promoted by increasing temperatures, retention times, concentrations. Increasing acid concentrations reduce amount product formed but suppress undesirable amorphous phases. K2SO4 result greater mass precipitate, products from concentrated solutions are contaminated an phase. In fact, overall results suggest that phase precipitates initially forms recrystallization, or dissolution-reprecipitation,