基于试验和DFT计算揭示EDTA对α-HH晶形调控的影响

Effect of EDTA on α-HH Crystal Shape Control Based on Experiment and DFT Calculations

摘要:

为探索钛石膏的高附加值利用，研究了以乙二胺四乙酸（EDTA）为转晶剂，采用钛石膏制备α-半水石膏（α-HH）的可行性，并揭示了EDTA对α-HH晶形调控的影响.结果表明：EDTA中的羧酸与Ca²⁺形成配位吸附，在不同晶面产生吸附能差异，并通过延长反应时间使各晶面的生产速率不同；由于在顶部的吸附作用较端面强，使得α-HH晶体沿着纵轴的生长能力减弱，沿横轴的生长能力增强；在EDTA掺量为0.1%时制备了出长径比为1.09∶1.00的短柱状α-HH，但随着EDTA掺量的增大，沿横轴的生长过剩，易产生板状晶形，不利于短柱状α-HH的制备.

Abstract:

To explore the high value-added utilization of titanium gypsum， ethylene diamine tetraacetic acid（EDTA） was used as crystal modifier to study the feasibility of preparing α-hehi-hydrated gypsum（α-HH） from titanium gypsum and to reveal its effect on the crystal shape control. The results show that the carboxylic acid in EDTA forms a coordination adsorption with Ca²⁺， which produces differences in adsorption energies at different crystal planes leading to different production rates at each crystal plane through prolonged reaction time. Due to the stronger adsorption at the top than at the end faces， the growth of crystals along the vertical axis is weakened and the growth along the horizontal axis is enhanced. Short columnar α-HH with an aspect ratio of 1.09∶1 is prepared at a dosage of 0.1% EDTA， but with increasing dosage the overgrowth in the horizontal axis is prone to produce a plate-like crystalline shape， which is unfavorable for the preparation of short columnar α-HH.