Precipitation of jarosite-type double salts from spent acid solutions from a chemical coal cleaning process

Technical Report · Fri Sep 21 04:00:00 EDT 1990

DOI:https://doi.org/10.2172/6568266· OSTI ID:6568266

Norton, G

The precipitation of jarosite compounds to remove Na, K, Fe, and SO{sub 4}{sup 2{minus}} impurities from spent acid solutions from a chemical coal cleaning process was studied. Simple heating of model solutions containing Fe{sub 2}(SO{sub 4}){sub 3}, Na{sub 2}SO{sub 4}, and K{sub 2}SO{sub 4} caused jarosite (KFe{sub 3}(SO{sub 4}){sub 2}(OH){sub 6}) to form preferentially to natrojarosite (NaFe{sub 3}(SO{sub 4}){sub 2}(OH){sub 6}). Virtually all of the K, about 90% of the Fe, and about 30% of the SO{sub 4}{sup 2{minus}} could be precipitated from those solutions at 95{degree}C, while little or no Na was removed. However, simple heating of model solutions containing only Fe{sub 2}(SO{sub 4}){sub 3} and Na{sub 2}SO{sub 4} up to 95{degree}C for {le}12 hours produced low yields of jarosite compounds, and the Fe concentration in the solution had to be increased to avoid the formation of undesirable Fe compounds. Precipitate yields could be increased dramatically in model solutions of Na{sub 2}SO{sub 4}/Fe{sub 2}(SO{sub 4}){sub 3} containing excess Fe by using either CaCO{sub 3}, Ca(OH){sub 2}, or ZnO to neutralize H{sub 2}SO{sub 4} released during hydrolysis of the Fe{sub 2}(SO{sub 4}){sub 3} and during the precipitation reactions. Results obtained from the studies with model solutions were applied to spent acids produced during laboratory countercurrent washing of coal which had been leached with a molten NaOH/KOH mixture. Results indicated that jarosite compounds can be precipitated effectively from spent acid solutions by heating for 6 hours at 80{degree}C while maintaining a pH of about 1.5 using CaCO{sub 3}.

• Research Organization: Ames Lab., IA (USA)
• Sponsoring Organization: DOE/FE; DOI
• DOE Contract Number: W-7405-ENG-82
• OSTI ID: 6568266
• Report Number(s): IS-T-1455; ON: DE91000744; CNN: G1194119
• Country of Publication: United States
• Language: English

Related Subjects

01 COAL, LIGNITE, AND PEAT
010402* -- Coal
Lignite
& Peat-- Purification & Upgrading
010800 -- Coal
Lignite
& Peat-- Waste Management
ALKALI METAL COMPOUNDS
ALKALI METALS
ALKALINE EARTH METAL COMPOUNDS
CALCIUM CARBONATES
CALCIUM COMPOUNDS
CALCIUM SULFATES
CARBON COMPOUNDS
CARBONACEOUS MATERIALS
CARBONATES
CLEANING
COAL
DISPERSIONS
ELEMENTS
ENERGY SOURCES
FOSSIL FUELS
FUELS
GYPSUM
IRON
IRON COMPOUNDS
IRON SULFATES
MATERIALS
METALS
MINERALS
MIXTURES
OXYGEN COMPOUNDS
PH VALUE
POTASSIUM
POTASSIUM COMPOUNDS
POTASSIUM SULFATES
PRECIPITATION
SALTS
SEPARATION PROCESSES
SODIUM
SODIUM COMPOUNDS
SODIUM SULFATES
SOLUTIONS
SULFATE MINERALS
SULFATES
SULFUR COMPOUNDS
TEMPERATURE EFFECTS
TRANSITION ELEMENT COMPOUNDS
TRANSITION ELEMENTS