Natural clays with an inherent uranium component that nevertheless sequester uranium from contaminated water

Abstract

Clays present a cost effective and sustainable method for removing uranium and heavy metals from drinking water because of their cation exchange capabilities. However, managing muddy suspensions is problematic; therefore, clay pellets as presented in this article are a promising alternative. Three standard clays and two regional clays were evaluated for sorption, both in powder form and in pellet structure for comparison. The objective was to evaluate individual sorption processes and assess the effect on uranium sorption due to the process of altering the clay powder to produce pellets. The sorption capacity of the pellets is sufficiently large to not only sorb the intrinsic non-bonded uranium but to continue to sorb uranium from contaminated water. Furthermore, the uranyl cation was also removed preferentially in the presence of Pb²⁺ and Cd²⁺ heavy metal cations, hydronium ions, and more importantly the naturally occurring cations, Na¹⁺, Ca²⁺, and Mg²⁺ that occur in abundant concentrations. Clay pellets as well as powders reduced uranium concentrations, and in extreme cases from 450 ppb, 15 times the Environmental Protection Agency maximum contaminant level to non-detectable limits. Clay pellets are excellent candidates for the safe and manageable removal of uranium and heavy metals to produce potable water

Keywords:

• clay ceramics
• sorption
• uranium
• intrinsic geologic uranium
• water

Additional information

Funding

This research was supported by New Mexico State Legislature NMWRRI2017-18, administered by the New Mexico Water Resources Research Institute; McCune Charitable Foundation; New Mexico Dept. of Agriculture, State Chemist; Center for Animal Health and Food Safety (NMSU). This work was also supported in part by the U.S. Department of Agriculture (USDA) (Grant # 2014-38422-22078); National Institutes of General Medical Health MBRS R25GM061222.