Arsenic-removing filtering method for high-concentration polyphosphoric acid

Abstract

The invention provides an arsenic-removing filtering method for high-concentration polyphosphoric acid, which includes: using industrial polyphosphoric acid as the raw material, adding water-soluble phosphorus pentasulfide emulsion used as arsenic-removing agent to enable arsenic contained in the polyphosphoric acid to form sulfide precipitate under the acidic condition, and purifying and refining the polyphosphoric acid by means of filtering, aerating and the like to produce low-arsenic polyphosphoric acid. By the low-arsenic polyphosphoric acid production method that filter cakes are formed on filter media from the dilute polyphosphoric acid containing arsenic residue first, and then the polyphosphoric acid with added arsenic-removing agent is filtered, the technical problem of filtering in the low-arsenic polyphosphoric acid preparation process is solved, and low-arsenic polyphosphoric acid production can be industrialized. Further, the arsenic-removing filtering method for high-concentration polyphosphoric acid is low in operating cost and simple in operating process, and low-arsenic polyphosphoric acid products, which cannot be obtained by conventional methods and are 105%-118% in concentration, namely percentage composition of P2O5 ranges from 76.1% to 85.5%, and arsenic content is no more than 10ppm, can be obtained by the arsenic-removing filtering method.

Description

technical field [0001] The invention relates to a method for producing low-arsenic polyphosphoric acid by removing arsenic from polyphosphoric acid and filtering. The method can effectively reduce the content of arsenic and heavy metals in polyphosphoric acid, and thus obtain relatively pure low-arsenic polyphosphoric acid, which is expected to be used in textiles, food , medicine and other fields have been widely used. Background technique [0002] There are two methods commonly used in the industry to produce polyphosphoric acid. One method is similar to the production of thermal phosphoric acid, that is, phosphorus pentoxide is produced by burning yellow phosphorus, and absorbed by water circulation until the acid concentration of the product reaches 100%, that is, P 2 o 5 The percentage content is more than 72.45%, directly producing polyphosphoric acid products with a high degree of polymerization. Another method is to use finished phosphoric acid (concentration lower ...

AI Technical Summary

Problems solved by technology

This method is currently the main method for producing low-arsenic polyphosphoric acid products in China. It has the advantages of simple production process and good production flexibility. The limit of arsenic content in phosphorus oxide, under current conditions, the highest concentration can only produce polyphosphoric acid with a concentration of 105%, and its arsenic content is lower than 10PPm; Phosphoric acid should be low; thirdly, the low-arsenic phosphorus pentoxide raw material used in this process is difficult to purchase in the market. At present, there is no industrial device for large-scale production of low-arsenic phosphorus pentoxide, and the production cost is relatively high, so the production is limited. Many, do not have the economy and practicability to realize the industrialized production of low-arsenic polyphosphoric acid