Charged Membrane Ultrafiltration of Multisalt Systems: Application to Acid Mine Waters

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Abstract
Ultrafiltration of dissolved and precipitated inorganic salts from synthetic and actual acid mine waters is investigated experimentally in a bench-scale, continuous-flow unit, utilizing negatively charged, noncellulosic membranes. The process is evaluated in terms of the simultaneous achievement of good water flux without membrane fouling and of adequate ultrafiltrate quality at high water recovery for water reuse operation. At a transmembrane pressure of 5.6 X 105 N/m2 and a channel Reynolds number of 6,000, the flux drop is less than 30%, even with a concentrated acid mine water containing 16,000 mg/1 total solids and a high CaSO4 concentration. At 90% ultrafiltrate recovery, depending on the type of noncellulosic membrane utilized, 98% iron removal, 85% aluminum removal, and 50 to 73% calcium and manganese removals can be obtained at an average water flux from 6.4X10−4 to 13.2X10−4 cm/sec. The overall ultrafiltrate quality is considerably better than that observed with a lime precipitation process.