Trace contaminant removal from mining process and waste waters with selective media.

The particular functional groups of different ion exchange resins can make them highly selective for specific elements. A Type 1 strong-base anion exchange resin will load U(CO3)3 even when it is present only at ppb levels in the presence of ppm levels of sulphates and chlorides. The amine functional groups of anion exchange resins can be modified for selective removal of perchlorate over nitrate. Nitrate itself may be removed either by non-selective trimethylamine (Type 1) or dimethyl ethanolamine (Type 2) strong-base anion exchangers or by selective exchangers with more exotic trimethylamine functional groups. Unusual functional groups developed to be very selective for Cu, Ni, Zn and Co under acidic conditions are hydroxypropyl picolylamine (HPPA) and bispicolylamine (BPA), BPA resins being particularly useful to separate Co and Ni in refineries or mine circuits. The thiouronium group can achieve almost complete removal of Pt, Pd and Rh from strongly acidic solutions with negligible loading of other metals, despite the presence of significant Cu and Zn concentrations; cost-effective recovery by ashing is practical. Ions with low solubility, such as Ra, can be precipitated within ion exchange beads while As can be removed by complexing with Fe- or Ti-based media. Hg, challenging because of its redox nature and existence in multiple forms as metal, cation or organic complex, is best tackled by a family of different media with varying functional groups and properties, that together can reduce Hg levels to less than 5 parts per trillion.
The particular functional groups of different ion exchange resins can make them highly selective for specific elements. A Type 1 strong-base anion exchange resin will load U(CO3)3 even when it is present only at ppb levels in the presence of ppm levels of sulphates and chlorides. The amine functional groups of anion exchange resins can be modified for selective removal of perchlorate over nitrate. Nitrate itself may be removed either by non-selective trimethylamine (Type 1) or dimethyl ethanolamine (Type 2) strong-base anion exchangers or by selective exchangers with more exotic trimethylamine functional groups. Unusual functional groups developed to be very selective for Cu, Ni, Zn and Co under acidic conditions are hydroxypropyl picolylamine (HPPA) and bispicolylamine (BPA), BPA resins being particularly useful to separate Co and Ni in refineries or mine circuits. The thiouronium group can achieve almost complete removal of Pt, Pd and Rh from strongly acidic solutions with negligible loading of other metals, despite the presence of significant Cu and Zn concentrations; cost-effective recovery by ashing is practical. Ions with low solubility, such as Ra, can be precipitated within ion exchange beads while As can be removed by complexing with Fe- or Ti-based media. Hg, challenging because of its redox nature and existence in multiple forms as metal, cation or organic complex, is best tackled by a family of different media with varying functional groups and properties, that together can reduce Hg levels to less than 5 parts per trillion.