Influence of natural water's pH value on precipitation of uranium

The formation of acid or alkali uranium-bearing solutions and the subsequent neutralization are a pair of favourable conditions to the formation of uranium deposits. The water media close to neutrality is favourable for the percipitation of uranium. Neutralization is a key factor setting off all reactions leading to the precipitation of uranium. The process of reduction precipitation of uranium caused by the neutralization is called neutralizing reduction. The reduction-precipitation of uranium occurs under the condition of (EWU = EhW - EhoU). Not only the reduction-precipitation of uranium depends on the decrease of EhW, but also is related to the increasing or decreasing rate of EhoU. By means of thermodynamic calculations and diagrams this paper shows that though the reducer has not increased, the EhWU will also be realized, when acid and alkali uranium-bearing solutions are neutralized. The strong reducer is not found in the granite uranium deposits, and during the process of rising thermal water upward from the depth, the increase of the reducing capacity of thermal water is difficult. In this case, the neutralizing reduction will be very important. This is a new clue to the study of uranium metallogenetic mechanism and formation conditions of rich uranium ores