膜电极电解器电解脱硫废水制备硫酸铵副产氢

Simultaneous Hydrogen and(NH_(4))_(2)SO_(4) Productions from Desulfurization Wastewater Electrolysis Using MEA Electrolyser

从废弃物中回收资源和能量是污染治理的优选途径。本文利用压滤式平板膜电极电解器电解脱硫废水,实现亚硫酸铵资源化为硫酸铵肥料并同步产氢。电解器表现出优良的SO_(3)^(2-)催化氧化性能和稳定性。在200 mA·cm^(-2)电流密度下,电压控制在2 V内,SO_(3)^(2-)转化率可达9%。每处理1 m^(3)亚硫酸铵脱硫废水,初始废水中HSO_(3)^(-)和SO_(4)^(2-)的浓度分别为392 g·L^(-1)和49 g·L^(-1),可获得0.70 t硫酸铵和2.98 kg氢气,消耗电量137.24 kWh,可创造1302.70元利润。

It is preferred to simultaneously recover resource and energy from waster.Sulfur dioxide,SO_(2),a common air pollutant,a potential energy resource,is a key link to sulfur nature circulation.SO_(2) can be conversed to NH_(4)HSO_(3) and(NH_(4))_(2)SO_(4) during the ammonia desulfurization process,which can be used to produce(NH_(4))_(2)SO_(4)fertilizer.For high quality(NH_(4))_(2)SO_(4)fertilizer and high heat transfer efficiency of the evaporative crystallization,HSO_(3)^(-) or SO_(3)^(2-) needs to be oxidized to form SO_(4)^(2-) before evaporative crystallization.Anodic oxidation of HSO_(3)^(-) or SO_(3)^(2-) coupled with hydrogen evolution can significantly reduce cost of hydrogen evolution due to a low reaction potential.This work uses a filter-press membrane electrode assembly electrochemical reactor to recover commercially valuable(NH_(4))_(2)SO_(4)fertilizer and produce hydrogen.It can simultaneously achieve waster recycle and energy storage,which is conformed to the domestic circulation and dual carbon goals.The electrooxidation mechanisms and dynamic parameters of(NH_(4))_(2)SO_(4) and NH_(4)HSO_(3) on homemade PtPd_(2.75)/C catalyst were investigated,particularly by cyclic voltammetry and rotating disk electrode system.According to Randles-Sevcik equation and Levich equation,the number of the electron transfer during the electro-oxidation of SO_(3)^(2-)or HSO_(3)^(-) is 1.86.The diffusion coefficients of SO_(3)^(2-) and HSO_(3)^(-) are 2.29×10^(-6) cm^(2)·s^(-1) and 1.18×10^(-5) cm^(2)·s^(-1),respectively.A 1 cm×1 cm electrolyser was homemade by graphite.The desulfurization wastewater was used as the anolyte,while water as the catholyte.The anolyte and catholyte were separated by a proton exchange membrane.The homemade PtPd_(2.75)/C catalyst was used as both sulfite oxidation catalyst and hydrogen evolution catalyst.The catalyst was loaded to carbon clothes firstly,and then hot-pressed to the proton exchange membrane to fabricate the membrane electrode assembly.The influences of operation conditions on the electrolyser performances have been studied by potentiodynamic scans and electrochemical impedance spectroscopy.The optimal conditions were chosen as follow:pH=7.5 of the ammonium sulfite wastewater as the anolyte,pure water as the catholyte,50 ℃.The electrolyser exhibited excellent SO_(3)^(2-) electro-oxidation performance and stability.Under the optimal experimental conditions,the electrolyser could achieve 294.63 mA·cm^(-2) at 1.5 V.At a current density of 200 mA·cm^(-2),the SO_(3)^(2-) conversion rate could reach 94%without exceeding the applied cell voltage of 2 V.It could produce 0.70 t ammonium sulfate and 2.98 kg hydrogen when 1 m3 ammonium sulfite wastewater was electrolyzed for 20 h.The electricity consumption was 137.24 kWh per m3 wastewater,which can create a profit of 1302.70 yuans.Such a strategy has shed a light on further development towards industrial application.