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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 4 of 8 <br />4.0 Results and Discussion <br />Two samples of water were received by Graver Technologies in October 2021. One sample was <br />from the Cross site and the other was from the Caribou site. Since the Cross site was contaminated <br />with water that was ionic (not filterable) only water from the Cross site was utilized in testing. <br />4.1 Removal Efficiency Testing <br />Removal efficiency testing was conducted on the Cross water to demonstrate that the Cd and the <br />Zn could be removed using the media. Removal efficiency is defined as percent removal and does <br />not provide useful data with regard to the capacity of a media. This test was conducted at a V/m <br />ratio of 100 mL of solution to 1 dry gram of media. The results of both the Cd and Zn tests showed <br />non-detected levels. <br />The calculated results are limited by the non-detect levels as reported by Eurofins Test America. <br />For this test, the Cd detection limit was 0.39 ppb, and the Zn detection limit was 6.5 ppb. The <br />percent removal was > 67.5% for Cd and > 95.3% for Zn. These values are relatively low, because <br />the EPA method contains statistical analyses that limit the detection level. Graver’s preliminary <br />data was based on raw data generated from the ICP. The limit of detection based on the Graver <br />ICP-MS was not only smaller, but the initial concentrations of the Zn and Cd in the Cross water <br />were higher. The percent removal using the Graver analysis was > 99% for Cd and Zn. <br />4.2 Total Capacity Estimation <br />Section 3.2 describes kinetic batch testing. However, when an overnight contact time is used the <br />reactions are typically considered to be “at equilibrium”. Samples of the reactions at > 18 hours <br />with different V/m ratios were combined to generate an isotherm. Isotherms can be used to show <br />the capacity of the media. These capacities do not show breakthrough (bed volumes). Instead, <br />they show what may be the maximum loading of the contaminants on the media at the tested <br />concentration of water. <br />In the Cross water, zinc was present at 169.5 ppb, on average (Eurofins TA data). It is estimated <br />that the capacity for Zn of HMRG on the Cross site will be approximately 15 mg of Zn per dry gram <br />of media (mg/g). The capacity of MetSorb® HMRG for Zn is expected to be higher than 15 mg/g <br />as a full isotherm curve could not be fully evaluated. <br />The cadmium capacities will be lower than zinc because the Cross water had a much lower <br />concentration of Cd (1.55 ppb, on average). The maximum measured capacity of MetSorb® HMRG <br />for Cd was 0.14 mg/g. Again, the capacity is expected to be higher than reported as the curve <br />could not be fully evaluated. <br />Isotherm tests typically generate nice visible curves based on the equilibrium concentration (x- <br />axis) and the calculated capacities (y-axis). In this case, the equilibrium concentrations were <br />skewed by the method detection limit reported by Eurofins Test America. The graphical analysis <br />could not be completed and used to extrapolate a maximum capacity. Instead, the capacities <br />reported are based on the very high V/m ratio of 100,000 mL/g. Since the equilibrium