Discussion Arsenic Removal Process Of Polyphosphoric Acid

Developing of the fine phosphorus chemical industry, the purity of polyphosphoric acid as a new , basis, raw material has been concerned widly, because the end use depends on its degree of purification . The element arsenic is not only one of important indicators on studying the degree of purification of phosphoric acid, but also one of the impurities that remove difficultly, thus how to reduce the content of arsenic of polyphosphoric acid to achieve the requirement of low arsenic (≤10ppm) phosphoric acid is a hot and difficult research currently . This paper is related to arsenic removal process of polyphosohoric acid , which is based on mentioned demand earlier, and in the light of no reports in this regard at present .In this paper, compared with various kinds of arsenic removal process of phosphoric acid, considered the characteristic of polyphosphoric acid, and the form of arsenic removal possible, at last define the arsenic removal process of polyphosphoric acid-halide process, this is a new process without filtration and treatment method; Inspect some factors, which contained how to choice arsenic removal substance, reaction temperature, reaction time, stirring rate as well as the amount of arsenic removal substance and so on, they effect arsenic removal simultaneously; Obtain the best conditions by orthogonal experiment.When hydrogen-halogenated is arsenic removal substance, the optimum conditions are reaction temperature: 150℃, reaction time: 60min, stirring rate: 250rpm and the amount of arsenic removal substance: 0.8%(w%).When Hydrohalogenic acid is arsenic removal substance, the optimum conditions are reaction temperature: 135℃, reaction time: 5min, stirring rate: 250rpm and the amount of arsenic removal substance: 1.5%(w%).The content of arsenic in polyphosphoric acid are 3.9ppm and 2.8ppm by the front arsenic removal process respectively, which have been reached a low arsenic trioxide requirements, the recovery rate is more than 98%. On the basis of this, study the process of how to broaden the scope of the application.Furthermore , discuss the reaction mechanism of arsenic removal of polyphosphoric acid from the perspective of thermodynamics preliminarily . This paper will have certain guiding sense to the future work.