电解乙酰基吡嗪废水中的硫酸铵制备过硫酸铵的研究

Study on Electrochemical Conversion of Ammonium Sulfate to Ammonium Persulfate in Acetylpyrazine Wastewater

乙酰基吡嗪是一种重要的香料,也被应用于生物、医药等领域。在生产乙酰基吡嗪的过程中会产生含过硫酸铵、Fe^(3+)、吡嗪及大量硫酸铵的废水。基于此,本研究拟利用电解法将其中的硫酸铵转化为经济效益较高的过硫酸铵。以铂电极为阳极,石墨电极为阴极,首先在无其他组分干扰的情况下对电解法生产过硫酸铵的工艺条件(如阳极液组成、电流密度、温度等)进行了探索,在阳极液(50 g)含37wt%硫酸铵、15wt%硫酸、0.06wt%硫氰酸铵,阴极液含25wt%硫酸,电流密度为8000 A·m^(-2),阳极液温度为30℃,通电量为2 A·h的优化条件下,生成过硫酸铵达到15.83wt%时,电流效率高达89.56%。然后探究了废水中Fe^(3+)和吡嗪对电解的影响,并根据乙酰基吡嗪废水的成分配制模拟废水以考察预处理效果。向模拟废水中添加氨水至pH值约为7可使Fe^(3+)浓度降至2.7 mg·L^(-1)。使用硫酸根自由基氧化法降解模拟废水中吡嗪,当过硫酸铵浓度为0.65 mol·L^(-1)时,降解率可达98.43%。最后,以预处理后的乙酰基吡嗪实际废水为阳极液进行电解,电流效率达85.21%。证明了乙酰基吡嗪废水中硫酸铵电解制备过硫酸铵的可行性。

Acetylpyrazine is an important spice and also plays important roles in biology,medicine and other fields.However,the wastewater containing ammonium persulfate,ferric ion(Fe^(3+)),pyrazine,and a large amount of ammonium sulfate was produced during the production of acetylpyrazine.In this study,ammonium sulfate in acetylpyrazine wastewater was electrolytically converted into ammonium persulfate for economic benefits.Using platinum as an anode and graphite as a cathode,the influence factors of the electrolysis process(including the composition of the anolyte,the current density,the temperature,etc.)were firstly investigated without interference from other compositions.Under the optimal condition,namely,the anolyte(50 g)composition consisted of 37wt.%ammonium sulfate,15wt.%sulfuric acid,and 0.06wt.%ammonium thiocyanate,and the catholyte composition was 25wt.%sulfuric acid,the current density was 8000 A·m^(-2),the anolyte temperature was 30 ℃,and the passed electric charge was 2 A·h,the current efficiency for the production of ammonium persulfate could be as high as 89.65%when the mass fraction of ammonium persulfate reached to 15.83wt.%.Then,the effects of Fe^(3+) and pyrazine on electrolysis were investigated.The presence of Fe^(3+) in the anolyte would affect the purity of ammonium persulfate precipitation,while the presence of pyrazine would affect the current efficiency for the production of ammonium persulfate,for example,the current efficiency would reduce by 10%when the concentration of pyrazine in the anolyte was only 0.015 mol·L^(-1).Therefore,it is necessary to remove Fe^(3+) and degrade pyrazine in the wastewater before electrolysis.And according to the composition of acetylpyrazine wastewater,the simulated wastewater was prepared to investigate the pretreatment effect.The concentration of Fe3+was dramatically reduced to 2.7 mg·L^(-1) when the pH value of the simulated wastewater was adjusted to about 7 through the addition of ammonia.Meanwhile,the sulfate radical oxidation method was adopted to degrade pyrazine in the simulated wastewater,showing 98.43%of the pyrazine degradation by activating the ammonium persulfate of 0.65 mol·L^(-1) to generate the sulfate radicals at 80℃.Finally,the current efficiency of 85.21%was achieved by using the pretreated acetylpyrazine actual wastewater as an anolyte,which proved the feasibility of electrochemical conversion of ammonium sulfate to ammonium persulfate in acetylpyrazine wastewater.