Process for resource-based preparation of soda ash from waste sodium sulfate based on double displacement reaction: Optimization using response surface methodology

With the growing emphasis on green chemistry and sustainable development, the resource utilization of waste salt has garnered significant attention. The production of soda ash from waste sodium sulfate presents a viable and sustainable pathway for the green transformation of the chemical industry. Current studies on this production method primarily focuses on single-factor effects on product purity, often overlooking the critical synergistic or antagonistic interactions between key process parameters. To address the aforementioned issues, this study systematically investigated the key factors and their interactions using response surface methodology. The process began with a pretreatment stage that effectively removed total organic carbon and color, while also adsorbing organic impurities such as heterocycles, anilines, ketones, phenols, and long-chain alkanes. For the soda ash synthesis via the double decomposition reaction of the pretreated waste sodium sulfate, single-factor experiments and response surface methodology optimization established the following optimal conditions: a reaction time of 1.96 h, a reaction temperature of 39 °C, and a material mass ratio of 1.284 (m (ammonium bicarbonate): m (sodium sulfate)). Under these conditions, the maximum soda ash purity of 99.35% was achieved. Furthermore, a binary regression model was developed for the process, with predictions showing excellent agreement with experimental data, confirming its reliability and practical utility. Additionally, the kinetics of the double decomposition reaction were determined by fitting a pseudo-second-order kinetic model in combination with the Arrhenius equation, and the resulting expression is as follows. 1 / t ln β 0 − X β 0 1 − X − β X / t = exp − 69475 / R T + 4.3637 × 10 − 16 . Through this waste-salt valorization pathway, not only can the accumulation of industrial waste sodium sulfate and associated environmental pollution risks be effectively reduced, the production cost per ton of sodium carbonate can be reduced by approximately 600 RMB, yielding significant sustainable economic benefits and providing strong support for advancing a green and low-carbon economy.