EDTA对加压水热法制备α-半水磷石膏的影响

Effect of Ethylenediaminetetraacetic Acid on the Preparation ofα-Hemihydrate Gypsum from Phosphogypsum with Hydrothermal Autoclave Method

磷石膏因含磷、氟、有机物等杂质导致其特性与天然石膏及脱硫石膏有很大差异,使其利用成为技术难题。为探索磷石膏资源化途径,本实验采用加压水热法制备α-半水磷石膏,研究了乙二胺四乙酸（EDTA）对磷石膏脱水反应、α-半水磷石膏晶体形貌的影响及其机理。结果表明：掺加EDTA可降低磷石膏脱水速率,且速率降低程度与EDTA掺量密切相关,掺量为0.4-1.0%时脱水速率降低显著;掺加EDTA影响α-半水磷石膏晶体形貌,使其由针状转变为短柱状,但对其晶型没有影响;控制EDTA掺量为0.40%和pH=7可制备长径比为1.5∶1的短柱状α-半水磷石膏晶体。

Phosphogypsum shows different properties with natural gypsum and flue gas desulfurization gypsum due to the existence of a variety of impurities, including phosphorus, fluorine, organic compounds and other ingredients.It has been a barrier for the application of phosphgypsum.In order to explore the ways for its application,the effect and related mechanism of ethylenediaminetetraacetic acid（ EDTA） on the dehydration rate of phosphogypsum and crystal morphology of α-hemihydrate gypsum in hydrothermal autoclave method was investigated in present study.Results show that,the dehydration rate of phosphogypsum decreased with the addition and increasing of EDTA.It was significantly decreased when the dosage of EDTA changed from 0.4% to 1.0%.With the addition of EDTA,the morphology ofα-hemihydrate gypsum was modulated from acicular or need-like to short columnar crystals,but the type of crystals was not affected.Short columnar α-hemihydrate gypsum crystals with a length-diameter ratio of 1.5∶ 1 was obtained at the EDTA dosage of 0.40% and pH value of 7.