Enhanced H2S removal from diverse fuels by a coupled absorption and biological process uses CO2 as carbon resource for microbial ecosystem

Abstract

Physico-chemical methods for H2S removal are costly due to their complex recovery. However, biological processes require carbon source and benign operation for safe H2S removal. Herein, absorption and biological processes were coupled to convert H2S/CO2 into sulfur fertilizer rapidly. Metallic-doped zeolitic imidazolate framework-8 (ZIF-8) was used to absorb H2S & CO2 in the adsorption column, and microbial nutrients solution to desorb/carry H2S/CO2 and feed it into the biological process, with the core aim to the develop rapid H2S/CO2 utilizing microbial ecosystem. The system consisted of adsorption, biological and separation processes. The adsorption system comprised (i) Cu-Zn-ZIF-8@FPUF responsible for H2S absorption and (ii) a specially designed microbial-media solution to desorb/carry absorbed H2S/CO2 stream into the biological process. The biological process was composed of aerobic, anaerobic, and facultative microbial groups, sequentially developing a high-performance microbial ecosystem due to the efficient recycling of metabolites/by-products. Process converted energetic H2S into S0 and SO42- while utilizing CO2 to boost metabolism. During stable operation, H2S bio removal was very competitive with adsorption rates as H2S bioremoval of 3.8 kg/m3/day (100%) was accomplished with maximum CO2 consumption of 60 kg/m3/day (100%). Interestingly, H2S bioremoval was highly correlated with CO2 fixation, as the H2S uptake rate reached 600 mol/h/g dry weight while assimilating 510 mol/h/g protein of CO2. Simultaneous utilization of H2S and CO2 was possible because of the highly efficient microbial ecosystem developed by ten sulfur assimilating microbial groups. OD600 drastically increased from 0.2 to 4.0, due to the efficient channeling of H2S to each microbial cell within the engineered microbial ecosystem. We believe our developed system could be highly useful for cleaning a variety of fuels highly polluted with H2S and CO2.