Preparation of calcium carbonate microrods from the gypsum scale layer of evaporation equipment

Abstract

The difficult-to-remove CaSO₄ scale layer attached to an evaporator wall is a major problem in related industries. How to efficiently remove the CaSO₄ scale layer and convert it into fine chemicals with high added value, so as to turn waste into treasure, is a current research hotspot. In this study, a CaSO₄ scale layer was removed by 15 min rotary washing via a phase transfer route. Further, using the eluted calcium gluconate solution as a raw material and polyethylene glycol as the crystal control agent, CaCO₃ was prepared by a CO₂ carbonization method. The preparation conditions of CaCO₃ were optimized by single factor experiments, and the phase and morphology of the prepared samples were characterized by XRD and FESEM. The results show that the optimized conditions are as follows: reaction temperature 80 °C, reaction time 1 h, polyethylene glycol addition 3%, and a stirring rate of 400 rpm. The samples prepared under these conditions are pure-phase calcite-type CaCO₃ microrods with lengths of 1–2 μm and diameters of 300–500 nm.