Study On Preparation Of Hydroiodic Acid And Sodium Hydroxide With Bipolar Membrane Electrodialysis

Hydroiodic acid is an aqueous solution of hydrogen iodide,which is a strong acid with a strong pungent acidity.Hydroiodic acid is mainly used for the preparation of analytical reagents,reducing agents,pharmaceutical intermediates,bactericide raw materials,and organic iodides.Hydrogen iodate is added as a co-catalyst in the production of acetic acid from SOPO's acetic acid plant to ensure the catalytic efficiency of the main catalyst triiodide.Traditional techniques for hydroiodic acid preparation include direct synthesis method,synthesis method from iodine and red phosphorus,and a hydrogen sulfide reduction method.However,these techniques have some shortcomings such as explosion hazard,environmental pollution and high investment cost.The whole synthetic process of hydroiodic acid by bipolar membrane electrodialysis mainly consumes sodium iodide and electricity without industrial waste produced.In theory,this process is relatively environmentally friendly.In this thesis,sodium iodide was used as raw material to produce hydroiodic acid and sodium hydroxide by bipolar membrane electrodialysis method.The process conditions,including sodium iodide concentration and operating current density,were investigated based on the yield of products,current efficiency and energy consumption.The results were obtained as below:the concentration of NaOH increased,the current efficiency decreased,and energy consumption raised at the same concentration of sodium iodide with operating current density increasing;the concentration of NaOH decreased,the current efficiency increased,and energy consumption reduced at the same current density with the concentration of sodium iodide increasing.Based on the comprehensive consideration of various factors,the concentration of sodium iodide was set to 1 mol·L^-1,and operating current density was set to 40 mA·cm^-22 finally.Hydroiodic acid could be purified from the mixed solution by distilling the electrodialysis mother liquor at about 126.5?.The concentration of distilled hydroiodic acid ranged from 30%to 50%with the highest of 52.58%.According to economic benefit analysis,the bipolar membrane electrodialysis method could not be utilized to produce hydroiodic acid,although it was theoretically feasible,because the purity and concentration of prepared hydroiodic acid could not meet the production requirements of the company due to the lack of a suitable anion membrane.Therefore,this method could be reserved at present and the further study of this project could be continued after the appropriate anionic membrane found.