Abstract:

Based on the huge pressure of CO₂ emission reduction and resource utilization of phosphogypsum in China, the academic idea of coupling CO₂ mineralization and phosphogypsum resource utilization process of auxiliary recycling was put forward. In this paper, phosphogypsum was used as the raw material explore the reaction of ammonia-strengthened phosphogypsum leaching solution to mineralize CO₂ and produce high-purity CaCO₃ in a CH₃COONa-H₂O system. The effects of different process conditions on the leaching of Ca²⁺ from phosphogypsum and the reaction efficiency of the leaching solution to mineralize CO₂ were systematically discussed. The effects of process parameters on grain size, structure and morphology of mineralization product were analyzed systematically. According to the results, 1t of phosphogypsum could sequestrate 208kg of CO₂ at low temperature and atmospheric pressure, producing 472kg of spherical vaterite with a purity of 99.63%. The grain size of the product was controlled by adjusting reaction conditions. A rise in reaction temperature and a prolonged reaction time were conducive to transforming vaterite with metastable state to aragonite and calcite, two more thermodynamically stable phases. The experiment realized the successful recycling and recovery of CH₃COONa. This paper provided a new idea for the creative recycling of phosphogypsum and preparation of high-purity CaCO₃.

Key words: phosphogypsum, CO₂ mineralization, CaCO₃, cyclic utilization, product control

摘要：

基于我国面临CO₂减排与磷石膏资源化利用的巨大压力，本文提出助剂循环使用的CO₂矿化与磷石膏资源化利用过程耦合的学术思想，立题以磷石膏为原料，研究醋酸钠体系下氨水强化磷石膏浸出液矿化CO₂联产高纯CaCO₃的反应过程。实验过程中系统讨论了不同工艺条件对磷石膏中Ca²⁺的浸出及浸出液矿化CO₂反应效能的影响，并系统表征了反应条件对矿化产物晶粒尺寸、结构与形貌的影响。结果表明：低温常压条件下1t磷石膏可以矿化吸收208kg的CO₂，同时联产472kg纯度为99.63%的球形球霰石。通过调节矿化反应条件可有效调控矿化产物的晶粒尺寸；提高反应温度和延长反应时间有利于亚稳态的球霰石向热力学更稳定的文石和方解石转化。实验过程中实现了醋酸钠的循环利用与回收。本文为磷石膏的资源化利用与高纯CaCO₃的制备提供了新的思路。

关键词: 磷石膏, CO₂矿化, 碳酸钙, 循环利用, 产物调控