Abstract：
The post-harvest fumigant, sulfuryl fluoride (SO2F2), is a >1000-fold more potent greenhouse gas than carbon dioxide and methane. Pilot studies have shown that SO2F2 fumes vented from fumigation chambers can be captured and hydrolyzed by hydroxide (OH-) and hydrogen peroxide (H2O2) at pH ∼ 12 in a scrubber, producing SO42- and F- as waste salts. To reduce the costs and challenges associated with purchasing and mixing these reagents onsite, this study evaluates the electrochemical generation of OH- and H2O2 within spent scrubbing solution, taking advantage of the waste SO42- and F- as free sources of electrolyte. The study used a gas diffusion electrode constructed from carbon paper coated with carbon black as a catalyst selective for the reduction of O2 to H2O2. Under galvanostatic conditions, the study evaluated the effect of electrochemical conditions, including applied cathodic current density and electrolyte strength. Within an electrolyte containing 200 mM SO42- and 400 mM F-, comparable to the waste salts generated by a SO2F2 scrubbing event, the system produced 250 mM H2O2 at pH 12.6 within 4 h with a Faradaic efficiency of 98.8% for O2 reduction to H2O2. In a scrubbing-water sample from lab-scale fumigation, the system generated ∼200 mM H2O2 at pH 13.5 within 4 h with a Faradaic efficiency of 75.6%. A comparison of the costs to purchase NaOH and H2O2 against the electricity costs for electrochemical treatment indicated that the electrochemical approach could be 38-71% lower, depending on the local cost of electricity.
摘要：
收获后的熏蒸剂,磺酰氟（SO2F2），是比二氧化碳和甲烷强1000倍以上的温室气体。中试研究表明，从熏蒸室排出的SO2F2烟雾可以被氢氧化物（OH-）和过氧化氢（H2O2）在pH~12的洗涤器中捕获和水解，生产SO42-和F-作为废盐。为了降低与现场购买和混合这些试剂相关的成本和挑战，这项研究评估了用过的洗涤液中OH-和H2O2的电化学产生，利用废SO42-和F-作为电解质的自由来源。该研究使用由涂覆有炭黑的碳纸构成的气体扩散电极作为选择性将O2还原为H2O2的催化剂。在恒电流条件下，这项研究评估了电化学条件的影响，包括施加的阴极电流密度和电解质强度。在含有200mMSO42-和400mMF-的电解质中，与SO2F2洗涤事件产生的废盐相当，该系统在4小时内在pH12.6下产生250mMH2O2，将O2还原为H2O2的法拉第效率为98.8％。在实验室规模熏蒸的洗涤水样品中，该系统在pH13.5下在4小时内产生~200mMH2O2，法拉第效率为75.6%。购买NaOH和H2O2的成本与电化学处理的电力成本的比较表明，电化学方法可以降低38-71％，取决于当地的电力成本。
