Examination of the Desorption of Iron From Zeolites Used to Treat Acid Rock Drainage
Additional Funding Sources
The project described was supported by a student grant from the UI Office of Undergraduate Research.
Abstract
Passive treatment of acid rock drainage relies on chemical interactions to reduce solubility of metals such as iron. Sorption has been a primary process for treatment of mine drainage and currently is being tested for use with acid rock drainage. Substrates considered for sorption of metals from acidic drainage include natural silicates, such as zeolite minerals. The weak bonding of sorption raises questions about retention of metals in a zeolite passive treatment system because of the flux of environmental conditions, such as changes in pH and temperature. Static batch sorption experiments were designed to assess the ability of zeolite to retain iron sorbed from an acidic, iron- and sulfate-rich solution. Zeolite saturated with sorbed iron was exposed to various water types—including ultrapure water, nickel-rich water, and natural creek water—under different pH and temperature conditions. Results indicate that low pH solutions 2.0 +/-0.1 for all water types greatly decreased the ability of zeolite to retain sorbed iron, with a maximum of 6.88 milligrams desorbing per liter, while pH above 4.0 +/- 0.1 and temperature variance between 5° and 20° only induced desorption of iron at a maximum of 1.02 milligrams per liter for all water types. With the knowledge gained from these experiments, protocols can be developed that maximize the effectiveness of future passive treatment systems for acid rock drainage that utilize zeolite as a substrate.
Examination of the Desorption of Iron From Zeolites Used to Treat Acid Rock Drainage
Passive treatment of acid rock drainage relies on chemical interactions to reduce solubility of metals such as iron. Sorption has been a primary process for treatment of mine drainage and currently is being tested for use with acid rock drainage. Substrates considered for sorption of metals from acidic drainage include natural silicates, such as zeolite minerals. The weak bonding of sorption raises questions about retention of metals in a zeolite passive treatment system because of the flux of environmental conditions, such as changes in pH and temperature. Static batch sorption experiments were designed to assess the ability of zeolite to retain iron sorbed from an acidic, iron- and sulfate-rich solution. Zeolite saturated with sorbed iron was exposed to various water types—including ultrapure water, nickel-rich water, and natural creek water—under different pH and temperature conditions. Results indicate that low pH solutions 2.0 +/-0.1 for all water types greatly decreased the ability of zeolite to retain sorbed iron, with a maximum of 6.88 milligrams desorbing per liter, while pH above 4.0 +/- 0.1 and temperature variance between 5° and 20° only induced desorption of iron at a maximum of 1.02 milligrams per liter for all water types. With the knowledge gained from these experiments, protocols can be developed that maximize the effectiveness of future passive treatment systems for acid rock drainage that utilize zeolite as a substrate.
Comments
W76