Light Calcium Carbonate With Different Morphologies Was Prepared From Phosphogypsum By Phase Pransfer Method

In this dissertation,“phase transfer precipitation”,phosphogypsum（PG）as raw material,D-glucose acid sodium（SG）as phase transfer catalyst,was adopted to prepared light calcium carbonate,the process conditions of spherical,rod-shaped and cube was studied.And the influence of phase transfer agent,crystal shape control agent and process conditions for the morphology of calcium carbonate and CaCO₃ action mechanism of nucleation and growth will be discussed briefly.The main research work and conclusions are as follows:（1）Preparation of spherical calcium carbonate from phosphogypsum.CO₂ and NaOH as precipitant,STP was selected as the appropriate type crystal control agent.The suitable preparation conditions:crystal shape control agent 3%,the molar ratio of Ca²⁺to SG 2.5:1,aging temperature 45℃,aging reaction time 0.5h,precipitation reaction termination pH8,CO₂ flow rate of 400mL·min^-1.Under this condition,the samples prepared were spherical vaterite calcium carbonate with uniform particle size distribution.（2）Preparation of rod-shaped calcium carbonate from phosphogypsum.Na₂CO₃ as precipitant,acetic acid was selected as the appropriate type crystal control agent.The suitable preparation conditions:crystal shape control agent 3%,the molar ratio of Ca²⁺and PG 2.5:1,aging temperature 80℃,aged reaction time 0.5h,reaction stirring speed 300r·min^-1.Under these conditions,the samples prepared were calcite rod-shaped calcium carbonate with uniform particle size distribution.（3）Preparation of cube calcium carbonate from phosphogypsum.Na₂CO₃ as precipitant,ammonium sulfate was selected as the appropriate type crystal control agent.The suitable preparation conditions:crystal shape control agent5%,the molar ratio of Ca²⁺and PG 2.5:1,aging temperature 90℃,then aged reaction time 0h,feeding way as the phase transfer droplets into the sodium carbonate solution（ammonium sulfate）.Under this condition,the sample prepared was calcite square calcium carbonate.