循环分解磷石膏制备高纯硫酸钙工艺Ⅱ:磷石膏分解液双极膜电渗析研究
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摘要
循环利用化学试剂从磷石膏中提取SO_4~(2-)和Ca~(2+)制备高纯硫酸钙的关键步骤是从双极膜电解除杂后的磷石膏分解液中提取SO_4~(2-)和Na~+,得到NaOH溶液和H_2SO_4溶液,用于循环制备高纯度硫酸钙。本研究对此过程中的电流密度和分解液浓度进行了单因素试验分析,在不同电流密度和磷石膏分解液浓度下,考察了磷石膏分解液的电解率、电解能耗以及电流效率的差异。试验结果表明:在电流密度为47.6mA/cm2,磷石膏分解液浓度为1.143mol/L时,电解率达到99.04%,能耗1.529kW·h/kg,电流效率为62.23%,此时能耗最低且效率最高,电解效果最佳。经分析可知,酸溶液中主要含H+和SO_4~(2-),硫酸浓度达到0.924 9mol/L;碱溶液中主要含Na+和OH-,也含有少量的K+,氢氧化钠(氢氧化钾)浓度达到2.125 7mol/L。酸碱溶液中几乎不含有其他杂质,可直接返回用于循环分解磷石膏。
SO_4~(2-)and Ca2+were extracted from phosphogypsum by recycling chemical reagents to prepare high-purity calcium sulfate.The key step of this recycling process is to extract SO_4~(2-)and Na+from the phosphogypsum decomposition solution after impurities removal by bipolar membrane electrolysis,and then obtain NaOH solution and H_2SO_4 solution,which are used for recycling to prepare high-purity calcium sulfate.In this study,single-factor test analysis was made on the current density and the concentration of the decomposition solution in this process.Under different current density and concentration of phosphogypsum decomposition solution,the differences in electrolysis rate,energy consumption of electrolysis and current efficiency of phosphogypsum decomposition solution were investigated.The test results show that with the current density being 47.6 mA/cm2 and the concentration of phosphogypsum decomposition solution1.143 mol/L,the electrolysis rate reaching 99.04%,the energy consumption 1.529 kW · h/kg,and the current efficiency62.23%,the energy consumption is the lowest and the efficiency is the highest,and the electrolysis effect is the best.According to the analysis,the acid solution is mainly H+and sulfate,the concentration of sulfuric acid is 0.9249 mol/L;the alkali solution is mainly Na+and OH-,and also contains a small amount of K+,and the concentration of sodium hydroxide(potassium hydroxide)reaches 2.1257 mol/L.The acid-base solution contains almost no other impurities and can be directly returned for recycling to decompose phosphogypsum.
SO_4~(2-)and Ca2+were extracted from phosphogypsum by recycling chemical reagents to prepare high-purity calcium sulfate.The key step of this recycling process is to extract SO_4~(2-)and Na+from the phosphogypsum decomposition solution after impurities removal by bipolar membrane electrolysis,and then obtain NaOH solution and H_2SO_4 solution,which are used for recycling to prepare high-purity calcium sulfate.In this study,single-factor test analysis was made on the current density and the concentration of the decomposition solution in this process.Under different current density and concentration of phosphogypsum decomposition solution,the differences in electrolysis rate,energy consumption of electrolysis and current efficiency of phosphogypsum decomposition solution were investigated.The test results show that with the current density being 47.6 mA/cm2 and the concentration of phosphogypsum decomposition solution1.143 mol/L,the electrolysis rate reaching 99.04%,the energy consumption 1.529 kW · h/kg,and the current efficiency62.23%,the energy consumption is the lowest and the efficiency is the highest,and the electrolysis effect is the best.According to the analysis,the acid solution is mainly H+and sulfate,the concentration of sulfuric acid is 0.9249 mol/L;the alkali solution is mainly Na+and OH-,and also contains a small amount of K+,and the concentration of sodium hydroxide(potassium hydroxide)reaches 2.1257 mol/L.The acid-base solution contains almost no other impurities and can be directly returned for recycling to decompose phosphogypsum.
引文
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[5]杨林,柏光山,曹建新,等.磷石膏水热合成硫酸钙晶须的研究[J].化工矿物与加工,2011,40(3):16-19.
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