Electrochemical remediation of sulfide in sour brine

天然气的开采总是伴随着压力水的生产，这些水被盐污染，主要是氯化钠（盐水）。通常，这些盐水也被硫化物污染；在这种情况下，它们被称为“酸盐水”，因为它们有硫化氢的气味。酸盐水除了气味难闻之外，还具有腐蚀性和剧毒，尤其是当压力被释放时，硫化氢会释放到大气中（类似于打开一罐汽水时释放出的二氧化碳）。处理含酸盐水的一种方法是在合适的地点将含酸盐水回注到地面，但这种方法成本很高，因为需要在不释放压力的情况下将含酸盐水从生产井输送到回注井。提出的研究是基于硫化物离子的电化学氧化成单质硫，这是环境友好的。我们实验室以前在水中使用硫化钠和氯化钠合成溶液的工作已经证明，氧化的发生具有优异的化学效率和优异的电流效率（这意味着电能被有效地利用，而不是浪费在诸如水的电解等塑料反应中）。然而，油田生产的酸性盐水更为复杂，主要是由于含有高浓度的环烷酸，这是一种烃基羧酸。我们的目的是利用环烷酸的表面活性剂特性，通过避免单质硫（在室温下是固体）对电极的污染来增强电化学氧化。

The extraction of natural gas is always accompanied by production of pressurized water, which is contaminated by salts, principally sodium chloride (brine). Frequently, such brines are also contaminated with sulfide; in that case they are known as "sour brines" because of their odour of hydrogen sulfide. Besides being odorous, sour brines are both corrosive and highly toxic, especially when the pressure is released, liberating hydrogen sulfide to the atmosphere (similar to releasing carbon dioxide when a can of pop is opened). One method of disposing of sour brines is reinjection to the ground at a suitable site, but this is expensive because of the need to transport the sour brine from the producer well to the reinjection well without releasing the pressure. The proposed research is based on the electrochemical oxidation of sulfide ion to elemental sulfur, which is environmentally benign. Previous work in our laboratory using synthetic solutions of sodium sulfide and sodium chloride in water has demonstrated that oxidation occurs with excellent chemical efficiency and excellent current efficiency (meaning that the electrical energy is used productively, rather than wasted in parastic reactions such as the electrolysis of water). However, sour brines produced in the field are more complex, principally due to having high concentrations of naphthenic acids, which are  ydrocarbon-based carboxylic acids. Our intention is to exploit the surfactant properties of naphthenic acids to enhance electrochemical oxidation by avoiding fouling of the electrode by the elemental sulfur, which is a solid at ambient temperatures.