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ADS-RPT-2021-14 <br />ESS-Nederland Mine _ 60 <br />November 4, 2021 <br />200 Lake Drive, Glasgow, DE 19702 302.731.1700 Fax 302.731.1701 <br />www.gravertech.com <br />Proprietary and Confidential <br />Page 1 of 8 <br />Preliminary Investigation in Nederland Mine (Cross) Water Treatment by <br />MetSorb® HMRG <br />1.0 Summary <br />Environmental Site Solutions is working with Nederland to remove zinc (Zn) and cadmium (Cd) <br />from their mining sites to meet regulatory limits. MetSorb® HMRG, an adsorbent by Graver <br />Technologies, has historically been able to treat water for both Cd and Zn. Contaminated water <br />from the Cross mine was sent to Graver’s facility in Glasgow, DE, USA for testing. A series of batch <br />tests (kinetic and equilibrium) were conducted to evaluate the capacity and kinetics of MetSorb® <br />HMRG for removing Cd and Zn present in the Cross water. In the Cross water MetSorb® HMRG <br />was found to have a capacity of over 15 mg/g for Zn and over 0.14 mg/g for Cd. Typical contact <br />time for HMRG is usually between 1.5 – 3 minutes. The low concentration of Cd in the Cross water <br />makes the HMRG kinetically hindered; a contact time of 10 minutes is not only practical but should <br />be sufficient to remove the Cd. The kinetic data on Zn removal shows that 40% of the Zn can be <br />removed within 10 minutes. In a vessel configuration (lead-lag), this should be sufficient to <br />remove a significant portion of the Zn from the Cross water. The major recommendation of this <br />report is that a pilot test be conducted. A pilot test with a lead-lag configuration and appropriate <br />sampling would provide a more complete evaluation of the media’s ability to remove both Cd and <br />Zn to the necessary requirements for the Cross site. <br />2.0 Introduction: <br />Environmental Site Solutions and Nederland contacted Graver Technologies to determine if mine <br />water containing cadmium, zinc, and other contaminants could be treated by MetSorb® products. <br />There are two sites that can be compared based on the data presented to Graver. Site 1 is the <br />Caribou Tunnel Site. Site 2 is the Cross Tunnel Site (Cross). <br />Both water chemistries have been analyzed by Nederland. Both water samples were treated by <br />filtration: a 5 um, 0.45 um and a 0.1 um filter. The samples for Caribou show that filtration <br />removes all of the contaminants including cadmium, zinc, copper, lead, and silver. This indicates <br />that contamination in the Caribou water is mostly solid. Filtration alone should clean the water <br />from the site. The same filtration was carried out on the Cross water. The Cross water, however, <br />did not filter as well. The cadmium was mostly soluble with ~ 93% of the concentration passing <br />through the filters. The zinc was also mostly soluble with 92% of the concentration passing <br />through the filters. Lead and silver were removed completely. <br />MetSorb® products have been known and used to treat many ions. Cadmium, one of the <br />contaminants of concern, should be mostly Cd2+ in a pH of 0-7. Above 7, the Cd may convert to