Electrochemical remediation of sulfide in sour brine

天然气的开采总是伴随着压水的生产，压水受到盐类的污染，主要是氯化钠(盐水)。通常，这种卤水也被硫化物污染；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。除了气味，酸性盐水还具有腐蚀性和剧毒，特别是当压力释放时，会向大气中释放硫化氢(类似于打开汽水罐头时释放二氧化碳)。处理含硫卤水的一种方法是在合适的地点将含硫盐水重新注入地面，但这是昂贵的，因为需要在不释放压力的情况下将含硫盐水从生产井输送到回注井。建议的研究是基于硫化物离子的电化学氧化生成元素硫，这对环境是无害的。我们实验室以前使用硫化钠和氯化钠在水中的合成溶液进行的工作已经证明，氧化发生时具有极高的化学效率和极高的电流效率(这意味着电能被有效地利用，而不是浪费在辅助反应中，如电解水)。然而，油田生产的酸性卤水更加复杂，主要是因为环烷酸的浓度很高，环烷酸是一种以氢碳为基础的羧酸。我们的目的是利用环烷酸的表面活性特性，通过避免元素硫对电极的污染来加强电化学氧化，元素硫在常温下是固体。

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.