Controllable preparation of aragonite calcium carbonate according to PG mineralization and its mechanism Investigation

This is the authors' abstract. We don't add key points for this paper.

Phosphogypsum (PG) is a massive solid waste byproduct during the wet-process phosphoric acid production, with a global stockpile exceeding 6 billion tons and a comprehensive utilization rate of less than 25%. Existing PG-based CO 2 mineralization technologies primarily produce low-value calcite-phase CaCO 3 , limiting the economic viability of this approach. To achieve the controllable preparation of aragonite, which is of greater economic value, this work systematically investigated the influences of various processing parameters on the crystal structure of the obtained CaCO 3 . According to the comparative experiments of one-step and two-step direct mineralization processes, it was found that, under optimized conditions (70 °C, Mg 2+ concentration of 5.00 × 10 −3 mol/L, CO 2 flow rate of 400 mL/min, and stirring speed of 250 rpm), the one-step mineralization process enables the direct synthesis of aragonite whiskers with an aspect ratio of up to 10:1, a product purity exceeding 95% and a PG conversion ratio over 99%. In contrast, the two-step mineralization method failed to produce aragonite due to the excessively high supersaturation. Furthermore, the study revealed that the aragonite formation follows a four-stage mechanism: CO 2 absorption − dominant nucleation − multiphase coexistence − crystal phase transformation. This work not only achieved the controllable synthesis of aragonite, but also elucidated its formation mechanism, providing an efficient and feasible pathway for PG resource utilization and CO 2 reduction.