The waste sulfuric acid lake of the TiO2-plant at Armyansk, Crimea, Ukraine. Part I. Self-Sealing as an environmental protection mechanism

The TiO2-plant at Armyansk, in operation since 1969, discharges its waste sulfuric acid and other effluents into an ‘acid collector’ of 42 km2 surface area. Under the semi-arid climatic conditions, such a surface represents the equilibrium between effluent production and evaporation. In the course of its operation, the pH of the lake has slowly decreased to a value of 0.85. At the bottom of the lake a layer of natrojarosite of between 10 and 50 cm has developed, which terminates in a thin crust of Fe oxides cemented by gypsum, separating the jarosite from the underlying clay. Below this Fe crust, that acts as a perfect seal, the pH of the pore-water jumps to a value around 6.2. Heavy elements from the effluent, notably As, V and Cr, are immobilized by isomorphic substitution in the Fe crust. It is suggested that similar self-healing seals can replace conventional isolation mechanisms in disposal sites.