水溶液的pH值对铀沉淀的影响

形成酸性或碱性含铀溶液,而后又发生中和作用,这是形成铀矿床的一对极有利的条件。接近中性的水介质有利于铀的沉淀。中和作用是各种铀沉淀作用的触发钮。由中和作用引起的铀的还原沉淀作用称为中和还原作用。铀的还原沉淀是在水-铀比电位值△Eh_水~U<0的条件下发生的(△Eh_水~U=Eh_水-Eh_0~U)。铀的还原沉淀不仅是依靠Eh_水的降低,同时与Eh_水~U的回升或下降速率有关。花岗岩铀矿床中往往不存在强烈的还原剂,热液上升过程中,一般很难提高它的还原能力,这时中和还原作用就显得格外重要。这是研究铀矿成矿机制和富矿条件的一条新线索。

THE INFLUENCE OF NATURAL WATERS pH VALUE ON THE 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 neutralization is favourable for the precipitation 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 neutrali zing reduction. The reduction-precipitation of uranium occurs under the condition of (E_W~U=Eh_W-Eh_0~U). Not only the reduction-precipitation of uranium depends on the decrease of Eh_W, but also is related to the increasing or decreasing rate of Eh_0~U. By means of thermodynamic calculations and diagrams this paper shows that though the reducer has not increased, the Eh_W~U 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.