六偏磷酸钠对制备超细生石膏粉体的助磨作用及其机理研究

采用胶体磨以六偏磷酸钠为助磨剂制备超细生石膏粉体，通过激光粒度仪和XRD等方法对超细磨产品进行表征。结果表明，当生石膏料浆质量浓度为20%、排矿口宽度为12 mm、超细磨时间为15 min、六偏磷酸钠用量为0.20%时，可制备出d₅₀为11.12 μm的超细生石膏粉体。六偏磷酸钠的加入引起生石膏颗粒晶粒尺寸与显微应变的变化，使晶格受到破坏，导致生石膏超细磨矿产品结晶度减小并且趋于无定形化。同时磷酸氢根离子可吸附在生石膏颗粒表面并使生石膏表面ζ电位由-8.83 mV负移至-13.39 mV，生石膏料浆的浊度由13 NTU增大至17 NTU，其黏度则由72.49 mPa·s减小至48.91 mPa·s，促进了生石膏颗粒的分散。在上述因素共同作用下，超细生石膏粉体粒度降低，生石膏的超细磨矿效率提高。研究对超细生石膏粉体的制备和提高超细生石膏粉体质量有一定参考意义。 

Effect of Sodium Hexametaphosphate on Preparation of Ultrafine Gypsum Powder and Its Mechanism

Ultrafine gypsum powder was prepared with sodium hexametaphosphate as a grinding agent by colloid mill, and ultra-fine grinding products were characterized through methods such as laser particle size analysis and XRD. The results showed that when the slurry concentration was 20%, and the discharge width was 12 mm, and the dosage of sodium hexametaphosphate was 0.20%, and the ultrafine grinding time was 15 min, the superfine gypsum powder with d₅₀ of 11.12 μm could be obtained. Moreover, the change of grain size and micro-strain of gypsum particles caused by ultra-fine grinding damage the lattice, resulting in the decrease of crystallinity ultrafine grinding products and the tendency of amorphous. In addition, hydrogen phosphate ions could be adsorbed on the surface of gypsum particles to make the ζ potential of gypsum surface shifted from -8.83 mV to -13.39 mV, and the turbidity of gypsum slurry increased from 13 NTU to 17 NTU while its viscosity decreased from 72.49 mPa·s to 48.91 mPa·s, which promotes the dispersion of gypsum particles. Under the combined action of the above factors, the particle size of superfine gypsum powder was reduced and the superfine grinding efficiency of gypsum was improved. The research has certain reference significance for preparing ultrafine gypsum powder and improving the quality of ultrafine gypsum powder.