Studies on ‘Brine mining of strategic trace metals’ for developing Secondary sources of nuclear fuel

Abstract

Thermal and membrane based desalination plants are being operated all over the world to address the demand of fresh water required by industries and large cities in water scarce coastal areas. The desalination and energy are very much interlinked, as plants are energy intensive. The energy consumption of desalination plants varies from 5 to 15 kWh m-3 of product water depending on the technology. In addition, the percentage of reject seawater/brine exiting the plants varies from 60% to 80% depending on the desalination technique. The concentrated reject brine is a source of valuable trace elements/metals, which is an untapped source that is wasted. With advances in Desalination technologies, it has been established that recovery of critical metals and elements and their selective recovery from reject brine of desalination plants gives an added advantage of energy credits to desalination plants as well as reduce cost of desalinated water [1, 2]. Research and technological developments are required for brine mining from desalination plants, i.e., by the recovery of nuclear fuel and other valuable materials (e.g. U, Li, Rb), from reject brine streams. This is being achieved by adsorption of these elements/ions onto a selective sorbent that is dipped either in reject brine/inlet seawater or in the open sea [1]. The major factor determining the practical utilization of the technology and lifetime of the adsorbent is fouling of the adsorbent by suspended particles or due to biological growth. The paper presents the status review on a recovery of important trace metals and other alkali metals from seawater and highlights the potential of Indian desalination plants for the recovery of trace metals. The adsorption studies carried out using radiation grafted polymeric adsorbents along with fouling studies are discussed in this paper. The studies involve determination fouling tendency of the adsorbents in a different environment, and recovery of uranium and vanadium from the reject brine. The paper also gives the schematic diagram and major unit operations involved in process flow scheme.