Effects of ultrasound and process parameters on the precipitation of CaCO3 polymorphs from synthetic soda ash industry liquid waste

Abstract

In this study, calcium carbonate has been produced continuously using synthetic soda ash industry liquid waste with different process variables. The effect of process variables such as gas flow rate (1000 to 4000 ml/min), waste liquid flow rate (80 to 280 ml/min), CO2 concentration (20% to 40%), ultrasonic probe area (2.83 to 4.90 cm2), ultrasonic probe immersion depth (2/3 h to 1/2 h), ultrasonic power (0% to 70%), and reaction temperature (30°C to 50°C) on product quality was investigated by using D-optimal design. According to the experimental results, precipitated calcium carbonate (PCC) having different particle sizes (D (4:3)) ranging from 2.9 µm to 8.7 µm was obtained. It was observed that crystal structure of product is highly dependent on the pH of reaction medium. While vaterite and aragonite crystal structure were formed at low pH values, calcite crystal structure was formed at higher pH values. Particle size decreases when ultrasound power applied at 35% when compared to silent reactions. Overall, precipitated CaCO3 with desired particle size and crystal type can be produced by controlling the process variables. The CaCO3 was produced in amounts ranging from 3.4 g to 11 g depending on the experimental conditions.