Preparation Of Precipitated Calcium Carbonate From By-Product Phosphogypsum And Its Morphology Control

In recent years,the demand for high-grade calcium carbonate in various industries has remained high,the industrialized production of high-grade calcium carbonate is carbonization process namely feeding CO₂ gas into lime water.This paper aims to prepare high-grade activated calcium carbonate products with solid waste phosphogypsum.Controlling the technological conditions and ensuring the conversion rate of the reaction,Selecting the excellent crystal controlled agent control the preparation of calcium carbonate for different morphologies and sizes.The prepared samples were modified and optimized,then the performance index of activated calcium carbonate was determined,which indicated calcium carbonate products met the national standard of calcium carbonate industry.The economic value of phosphogypsum in the preparation of high value-added products was realized ultimately.The paper studied the effect of phosphogypsum conversion by metathesis process molar ratio,liquid-solid ratio,reaction temperature,reaction time,and the conclusion through the single factor experiment and orthogonal experiment was obtained:in the material ratio of 1.2:1,5:1,the ratio of liquid to solid temperature of 55?,300 r/min and 75 min reaction time,the conversion rate can reach more than 96%.On the basis of high conversion rate,the impacts of material ratio,the ratio of liquid to solid,temperature,time and speed on the morphologies of calcium carbonate crystals were explored;the sucrose,citric acid,pentaerythritol,sodium tripolyphosphate and SDBS were chosen as crystal control agent for the specific morphology and structure characterization,the samples were tested by SEM,XRD and DLS,and results showed that sucrose regulated spherical calcium carbonate about 100 nm,citric acid regulated generation aspect ratio as high as 20:1,pentaerythritol regulated cubic crystal at 1?m,sodium tripolyphosphate generate short rod crystals like coral plexus,SDBS regulated hollow spherical crystal structure of regulation.In the condition of adding sodium stearate at 3.5%mass fraction of calcium carbonate,the temperature of 80?and 30min reaction time,the active degree of modified calcium carbonate close to 100%,the oil absorption of products was low to21.3 mL/100g,the settlement volume was up to 2.18 mL/g,and the whiteness reached96.Compared with ordinary precipitated calcium carbonate,the performance of active calcium carbonate is better,meeting the national first grade standard and suiting for the application of rubber,coating and other industries.FT-IR,TG and SEM characterization of the modified calcium carbonate with sodium stearate were tested,showing the chemical and physical adsorption on calcium carbonate surface coating by sodium stearate,the amount of coat was consistent with the dosage,and fine calcium stearate enwrapped in the surface of calcium carbonate,achieving the effect of performance optimization.