氯盐体系下阳离子对脱硫石膏晶须水热结晶的影响及其机理

Effect of cation on hydrothermal crystallization of desulfurized gypsum whiskers in chloride system and its mechanism

为探索阳离子对水热制备脱硫石膏晶须结晶调控的影响,本文以预处理后的脱硫石膏为原料,NaCl、CuCl_(2)、AlCl_(3)为添加剂采用水热法制备脱硫石膏晶须,重点研究Cl^(-)存在条件下阳离子对脱硫石膏晶须结晶的影响及其作用机理。结果表明,Na^(+)、Cu^(2+)、Al^(3+)对脱硫石膏晶须的显微结构、长径比和品质均有一定的影响,其中Cu^(2+)影响最为显著。Cu^(2+)可在晶须的(200)、(400)和(020)晶面发生化学吸附形成CuSO_(4)膜层,使其径向生长受阻;同时,少量Cu^(2+)可取代Ca^(2+),促进Ca^(2+)的去溶剂化,使晶须长径比增大至200。Na^(+)和Al^(3+)均通过物理吸附作用于脱硫石膏晶须(200)、(400)和(020)晶面而阻碍其径向生长。此外,Al^(3+)与溶液中的OH-通过羟基化反应生成Al(OH)^(2+)和Al(OH)^(2+),吸附在带负电的(200)、(400)和(020)晶面,降低这些晶面的表面能,从而促进脱硫石膏晶须沿c轴生长。

Using pretreated desulfurized gypsum as raw material,and NaCl,CuCl_(2)and AlCl_(3)as additives,desulfurized gypsum whiskers were prepared by hydrothermal method in order to explore the effect of cations on their crystallization regulation.The study focused on the effect of cations on the crystal of desulfurized gypsum whiskers in the presence of Cl^(-)and their mechanism.The results showed that Na^(+),Cu^(2+),Al^(3+)could affect the microstructure,aspect ratio and quality of desulfurized gypsum whiskers,but the effect of Cu^(2+)was more significant.Cu^(2+)could chemically adsorb on(200),(400)and(020)crystal faces of the crystal of whisker to form a CuSO_(4) film,which hindered its radial growth.At the same time,a little of Cu^(2+)could replace Ca^(2+),thereby promoting the desolvation of Ca^(2+),which caused an increase of the whisker aspect ratio to 200.However,both Na^(+)and Al^(3+)acted on(200),(400)and(020)crystal faces through physical adsorption and hindered the radial growth of desulfurized gypsum whiskers.In addition,Al^(3+)reacted with OH-in the solution to generate Al(OH)^(2+)and Al(OH)^(2+),and they were adsorbed on the(200),(400)and(020)planes with negative charges,which reduced surface energy of the above planes and also promoted the growth of desulfurized gypsum whiskers along the c-axis.