Several different technologies are available for H2S removal from the gas stream of medium capacity. Among them, the most widely used is Locat with more than 120 plants worldwide. In the last decade, many new processes, such as Sulfatreat-DO, Crystasulf, Caltech, and UCSR, were proposed to overcome the drawbacks of the state-of-the-art processes (low sulfur purity, chemical degradation, thiosulfate formation). We have developed a new H2S conversion method based on acid ferric nitrate solution, co-catalyzed by a heteropolyacid. H2S was converted to pure sulfur (>99.9 %), with no traces of organic compounds. Due to the acid pH of the solution, no chelant or surfactant was needed and iron content in the solution could reach very high levels. Keggin heteropolyacid (H6PW9V3O40) catalyzed the reoxidation of reduced ferrous solution with air at mild temperature and at very high reaction rate. The undesired side reaction (NOxformation) could be avoided by simply increasing the oxygen partial pressure.