| CLT acid(2-amino-4-methyl-5-chlorobenzenesulfonic acid)is a red organic pigment intermediate,which is widely used in the textile and dyeing industry.At present,the most commonly used method for the production of CLT acid is toluene sulfonation.During the preparation process,a large amount of magnesium sulfate and sodium sulfate acid wastewater will be produced.Direct discharge will not only waste the sulfate in the wastewater,but also damage the environment.For this reason,this paper uses crystallization thermodynamics and kinetics as basic research methods,and applies the obtained metastable zone characteristics and particle size distribution characteristics to the process of crystallization and separation of magnesium sulfate and sodium sulfate from CLT acid high-salt wastewater,and finally explores and optimizes the separation Process,the research conclusions are as follows:(1)Experimental study on thermodynamics of crystallization of CLT acid and high-salt wastewater: In order to study the influence of different operating parameters on the width of the metastable zone of magnesium sulfate and sodium sulfate in the CLT acid-water solution system,the cooling rate,stirring rate,etc.are commonly used in evaporation and concentration.The operating parameters are taken as the influencing factors,and its influence law is studied.The results show that the precipitation of magnesium sulfate and sodium sulfate crystals lags behind when the cooling rate is increasing,which is not conducive to crystallization;under acidic and alkaline conditions,the precipitation of crystals is inhibited,but the effect of alkaline inhibition is not obvious;In the process of enlargement,the metastable zone is reduced,which promotes the precipitation of crystals;the presence of iron ions helps the precipitation of crystals,but the purity after precipitation is not high and contains impurities,which can be replaced by seed crystals.(2)Experimental study on crystallization kinetics of CLT acid and high-salt wastewater: So as to revise the influence of unequal operating conditions on the distribution of magnesium sulfate crystals.The results show that: after the residence time reaches 40 min,the crystal growth is completed and resources are maximized;adding 3g/L crystals The average particle size of the species is reduced to 146μm,and the dispersion degree is 1.42.Excessive seed crystals will inhibit the formation of new nuclei in the solution,and the crystal size will be larger;the presence of organic matter can reduce the particle size and average degree of magnesium sulfate crystals to a certain extent,but the crystals contain impurities.The chroma is high and does not meet the requirements.(3)Research on the desalination process of CLT acid high-salt wastewater: In order to determine the crystallization separation process of magnesium sulfate in CLT acid high-salt wastewater,compare the configuration solution with the original wastewater solution and confirm that the concentration ratio is 1.4 and the crystallization separation effect is the best,and The purity can reach more than 96%.The final process conditions are: first carry out the process of removing impurities and organic matter;then carry out evaporation and concentration,the evaporation temperature is 60℃,the cooling rate is 0.2℃/min,the PH value is 3,and the rotation speed is 200 r/min;after evaporation and concentration,the crystal slurry Recrystallization is carried out,and the crystallization conditions are as follows: concentration ratio of 1.5,residence time of 40 min,and seed content of 3 g/L;the purity of the final separated magnesium sulfate crystals can reach more than 96%,which meets the national standard. |
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