Crystallization-based recovery of potassium-boron rich triassic brine from sichuan basin: Modeling and experimental analysis at 348.2 K

Abstract

The Triassic marine sedimentary brines in the eastern Sichuan Basin are rich in boron and potassium. To develop and utilize these brine resources, phase diagrams for the Na⁺, K⁺//Cl⁻, B₄O₇²⁻-H₂O quaternary system and its ternary subsystems were experimentally determined. The unreported single salts parameters, mixed ion interaction parameters for the Pitzer model, and solubility product constants K of salts at 348.2 K were fitted using solubilities of ternary subsystems systematically. Subsequently, the phase equilibria of the systems listed above were predicted using the Pitzer model.Based on phase diagrams and material balance calculations, a crystallization recovery process of the brines was designed. Isothermal evaporation experiments on actual brine achieved an evaporation rate of 93.1 %, with precipitation rates of 98.8 % for sodium salts, 81.6 % for potassium salts, and 38.4 % for borates. From 5 L of brine, 1407 g of NaCl and 183 g of KCl were crystallized. The theoretical evaporation trend and salt precipitation law of brine is consistent with the crystallization pattern obtained from actual isothermal evaporation experiments. The study demonstrates the potential for industrial recovery of sodium, potassium, and boron products, while proposing a comprehensive process to extract other valuable elements from raw brine.