Phase Developments during Natural Evaporation Simulation of Lake Katwe Brine Based on Pitzer’s Model

Lake Katwe is the largest of the eight saline crater lakes in the pleistocene Katwe-Kikorongo volcanic field situated in the western arm of the great East African Rift system in southwestern Uganda. The salt lake is hydro-chemically of a carbonate type with its brines representing an important source of mineral salts of high economic value. In the present work, the geochemical simulation of the crystallization route of the natural evaporation of the lake brine in PHREEQC based on Pitzer’s thermodynamic model was done. The precipitation sequence of the different mineral salts that crystallized step by step from the brine during natural evaporation at 30ºC was obtained. The results show that the mineral salt precipitation sequence following the saturation data is: Sulfates, chlorides and carbonates. During the evaporative concentration process, the brines become enriched in Na+, K+, HCO3- + CO32-, and depleted in Cl- and SO42- with massive halite precipitation. The study provides the basis for the future comprehensive utilization of the natural brine resource in Lake Katwe.