Preparing Of Ultrafine Zinc Phosphate In The Submerged Circulating Impinging Stream Reactor(SCISR)

Zinc phosphate is a kind of environment-friendly anti-rust pigment,which is low toxic and harmless,and is usually used to replace traditional chrome series,lead series and other metal pigments.However,zinc phosphate in the industrial production process also affects its anti-corrosion performance due to its large particle size and low conversion rate,which seriously affects its anti-rust effect.In order to reduce its particle size,complex processes such as hydrothermal method,solution gel method,hydrolysis precipitation method and so on are often used,and even ball milling,air grinding and other processes need to be added.These methods have high energy consumption,long production preparation cycle,and low production efficiency,which limit its industrial large-scale production.At the same time,high temperature and high pressure process conditions are required,resulting in increased production costs.Therefore,in the research of zinc phosphate production process,a method of preparing ultra-fine zinc phosphate with short process flow,stable and reliable products and low cost was explored.Impinging stream reaction-precipitation method is usually used to prepare ultra-fine powder,which can solve the problem of product particle size distribution.Under normal pressure,ultra-fine zinc phosphate with high purity and small particle size can be prepared in one step without processing such as crushing.The method is simple and low cost,which is suitable for industrial large-scale production.In this paper,using zinc oxide and phosphoric acid as raw materials,ultrafine zinc phosphate was prepared by impinging stream reaction-precipitation method and the effect of different process conditions on particle size distribution was investigated.By adjusting the control parameters such as reaction temperature,concentration,reaction time and rotational speed,the optimum process conditions for preparing zinc phosphate were explored.On this basis,the solution system of the precipitation reaction process in the impinging stream reactor was changed by replacing part of the aqueous solution with ethanol solution and adding dispersant,further reducing the particle size of the product,and the rule of particle size distribution of the product prepared under different conditions was explored.（1）Zinc phosphate was prepared in a submerged circulating impinging stream reactor with water as the reaction solvent.The effects of reactant concentration,reaction temperature,reaction time,and the stirring speed of the reactor on the particle size distribution of zinc phosphate products were investigated by designing orthogonal experiments.The results showed that the effects of reaction temperature,reaction time,and reactor stirring rotation speed on the particle size distribution of zinc phosphate products are significant.According to the single-factor experimental analysis,the optimum reaction conditions are:reactant concentration of 0.86 mol/L,reaction temperature of 70℃,reaction time of 1 h,the stirring speed of the reactor of 2400 r/min,and the average particle size of the product prepared under this condition is 8.616μm.The percentage content of Zn²⁺is 51.00%,the percentage content of PO₄^3-is 48.52%,and the product yield is 99.32%（2）The original process was improved by using ethanol solution as the reaction solvent and adding dispersant cetyltrimethylamine bromide to prepare zinc phosphate in the submerged circulating impinging stream reactor.According to the orthogonal experiment and single factor experiment analysis,the optimum reaction conditions after the process optimization are:the volume fraction of ethanol is 50%,the dosage of dispersant is 1.0%（mass fraction relative to the theoretical product yield）,the molar ratio of phosphoric acid to zinc oxide is 0.74,the concentration of reactant is 0.86 mol/L,the reaction temperature is 70℃,the reaction time is 1 h,the stirring speed of the reactor is 2400 r/min,and the average particle size of the prepared product is from 8.616μm decreases to 7.094μm,the percentage content of Zn²⁺ⁱs 50.83%,the percentage content of PO₄^3-is 49.16%,and the product yield is 99.90%.（3）The product was tested and characterized by laser particle size meter,scanning electron microscope（SEM）and X-ray diffraction.According to the analysis of the results,compared with the products prepared in the stirred reactor,the zinc phosphate products prepared in the impinging stream reactor have smaller particle size and more uniform particle size distribution,and the morphology show a regular sheets.The particle size of the product prepared by the improved process is smaller and more uniform than that before,and its morphology is more regular and very thin.The particle size is smaller,and the minimum thickness is close to nanometer.