High-permeability selective acid-resistant nanofiltration membrane material as well as preparation method and application thereof

Abstract

The invention discloses a high-permeability selective acid-resistant nanofiltration membrane material as well as a preparation method and application thereof. The nanofiltration membrane material comprises a dense separation layer which is formed by assembling an amine and a quaternary ammonium salt polycation electrolyte and a polyanion electrolyte material with sulfonic acid groups or sulfuric acid groups layer by layer; the concentration of the polycation is 0.1-20 g / L, and the polycation is dissolved in a salt solution of 0.05-5 mol / L; the used polyanion electrolyte polymer material is a polymer material with sulfonic acid groups or sulfuric acid groups, the concentration of polyanion is 0.1-20g / L, and the polyanion is dissolved in a 0.05-5mol / L salt solution; the dense separation layer of the nanofiltration membrane is formed by layer-by-layer assembly, and has better permeation selectivity and excellent acid-resistant stability than a commercial nanofiltration membrane. The retention rate of the membrane to multivalent cations is greater than 90%, the permeability of the membrane to phosphoric acid is greater than 80%, and the permeability of phosphoric acid is one order of magnitude layer than that of that of a commercial membrane. The high-permeability selective acid-resistant nanofiltration membrane material is used in phosphoric acid refining and recycling processes, inorganic compounds in phosphoric acid-containing feed liquid are removed through pretreatment, then substances such as large particles and colloids are removed through ultrafiltration, stable operation of a nanofiltration membrane process is achieved, high-purity phosphoric acid of different grades is obtained, and the high-permeability selective acid-resistant nanofiltration membrane material has wide application in the aspects of phosphoric acid refining and phosphoric acid recycling.

Description

technical field [0001] The invention relates to the field of refining and recovering phosphoric acid by membrane separation technology, in particular to a process for refining and recovering a phosphoric acid-containing material liquid by a highly permeable and selective acid-resistant nanofiltration membrane. Background technique [0002] Phosphate rock in nature is mainly used to produce phosphoric acid, and then phosphoric acid is used as raw material to further produce phosphate fertilizer and various phosphorus chemical products. Phosphoric acid production process is mainly divided into thermal phosphoric acid process and wet phosphoric acid process, among which the energy consumption and cost of wet process are lower than that of thermal phosphoric acid. The output of wet-process phosphoric acid in the world has accounted for 85%-90% of the total output of phosphoric acid. However, wet-process phosphoric acid products have low purity and contain various impurity ions ...

AI Technical Summary

Problems solved by technology

Therefore, the phosphorus content in the sludge leachate is very high, if not effectively recycled, it will lead to the loss of phosphorus resources and pollute the environment

[0008] At present, nanofiltration technology uses commercial acid-resistant nanofiltration membranes for phosphoric acid purification and phosphorus resource recovery. They are interfacial polymeric membranes with low permeation selectivity, operating pressures above 50 bar, and phosphoric acid permeability coefficient <1.0LMHbar, so energy consumption is high. The operating cost is high. At the same time, because the performance of the nanofiltration membrane is not up to standard, many combined processes are added before and after, and the overall process chain is greatly extended.

Moreover, commercial films are mostly prepared by interfacial polymerization, which requires the participation of organic solvents, and the preparation process is not environmentally friendly.

Moreover, the composition of phosphoric acid-containing feed liquid is often very complex, especially waste liquid from phosphoric acid plant, sludge leachate, etc., which contain a variety of impurity ions. If nanofiltration is performed directly, serious fouling will occur, which will greatly reduce the service life of the membrane.

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