Method for preparing melamine polyphosphate by recycling phosphoric acid waste liquid

Abstract

The invention provides a method for preparing melamine pyrophosphate. The method mainly comprises the following steps: firstly, evaporating a phosphorus-containing acid waste liquid to obtain a phosphorus-containing acid waste liquid concentrated solution; secondly, adding urea into the phosphorus-containing acid waste liquid concentrated solution to obtain a first reaction solution; thirdly, carrying out cooling and crystallizing on the reacted first reaction solution to obtain a crystal containing urea phosphate and a mother solution; fourthly, diluting the filtrated mother solution and then adding melamine to obtain a second reaction solution; filtering the reacted second reaction solution to obtain a reaction intermediate; fifthly, carrying out washing, drying and calcining treatment on the reaction intermediate to obtain the melamine polyphosphate. The invention also provides a recycling method for the phosphorus-containing acidic waste liquid. The method provided by the invention is simple and feasible and large-scale production can be easily realized; in addition, an obtained product has higher added value and higher economic and environmental benefits.

Description

technical field [0001] The invention relates to a method for recycling industrial wastewater, in particular to a method for recycling phosphorus-containing acidic waste liquid. Background technique [0002] In recent years, my country has become the world's largest display production base. The etching process is widely used in the processing of liquid crystal display devices and organic light emitting display devices used as flat panel displays. The etching solution used in the etching process usually contains more than 50% by weight of phosphoric acid, and also includes a certain amount of nitric acid and acetic acid as stabilizers. When the etching solution is consumed or its purity decreases during the etching process, it needs to be replaced, thereby generating a large amount of phosphoric acid-containing etching waste. In 2012, the output of industrial etching waste liquid in my country was about 2 million tons, with an annual growth rate of more than 5%. Since the d...

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Problems solved by technology

Zhang Licai disclosed a method for preparing feed-grade calcium hydrogen phosphate using waste etching acid containing phosphoric acid as a raw material in "The Process of Preparing Feed-Grade Calcium Hydrogen Phosphate from Phosphoric Acid-Containing Etching Waste Acid". The added value of hydrogen calcium is relatively low

Bi Yafan disclosed in "Preparation of Waste Etching Solution and Low-grade Phosphate Rock as Raw Material Phosphate Compound Fertilizer" a method for preparing phosphorus compound fertilizer using aluminum etching waste liquid and low-grade phosphate rock as raw material, but the method used The concentration of various harmful metal cations except aluminum and copper in the aluminum etching waste liquid must meet the standard of acid for fertilizer production, which limits the scope of application of this method