多硼酸盐的分散作用及其对碳酸钙沉淀的影响

Dispersion effect of polyborate and its influence on calcium carbonate precipitation

采用静态电导率法,研究了不同温度及硼浓度条件下,硼砂和合成的五水合五硼酸钠(SPP)对碳酸钙临界过饱和度值的影响,并利用多晶X射线衍射仪、扫描电子显微镜和能谱仪对碳酸钙沉淀进行表征。结果表明,硼砂和SPP具有分散作用,硼含量越高,分散作用越好。随着温度升高(20~70℃),硼砂和SPP的分散作用均降低,但SPP更具有耐温性。进一步研究发现,硼砂和SPP能够捕获Ca2+,导致沉淀量减少,同时能够降低碳酸钙结晶度,但是不改变碳酸钙的晶型和成分。SPP的分散作用更明显,导致沉淀中出现球状和盘状结构。这可能是由于SPP溶液中[B5O6(OH)4]-阴离子特殊的三维骨架结构更易捕获Ca2+,阻止沉淀晶粒的生成。研究结果可为高效多硼酸盐分散剂的研发提供依据。

Under different temperatures and boron concentrations,the effects of borax and synthesized sodium pentaborate pentahydrate（SPP） on critical super saturation ratio of Ca CO3 solution were studied by static conductivity method. Crystal of Ca CO3 precipitation was characterized by X-ray diffraction,scanning electron microscopy and energy dispersive spectroscopy. The results showed that borax and SPP had the dispersion effect.The dispersion performance increased with the increasing boron concentration. As the temperature increased from-20 to 70 ℃,the dispersion effects of borax and SPP were reduced. However,SPP had a better thermal tolerance ability. The further study showed that borax and SPP were able to capture Ca^2 ＋,leading to the reduction of the weight of Ca CO3 precipitation. Meanwhile,the crystallinity of Ca CO3 precipitation could be reduced by borax and SPP,but the morphism and composition of Ca CO3 precipitation were not changed. In addition,SPP had better dispersion effect,leading to the precipitation presenting spherical or plate structure. This may be due to the special three-dimensional pore structure of [B5O6（OH）4]-anion in SPP solution could capture Ca^2 ＋easier,which prevented precipitation grains growth. The results could provide a scientific basis for the development of efficient dispersant of polyborates.