Research on biohydrogen production via fermentation process has shown a tremendous progress for the past few years. As biohydrogen production is being established, the purification of biohydrogen should consider the process flow for future application. This paper presents an experimental study of biohydrogen purification using two-stage chemical absorption. The research work focuses on carbon dioxide (CO2) removal, which is a major unwanted fermentation gas product via activated methyldiethanolamine (MDEA) and caustic (NaOH) in two-stage chemical absorption. The experiment was conducted at low pressure of 1 bar and normal room temperature of 29 °C using a ratio of 1:1 of CO2:H2 standard gas mixture as the feed. In the first stage, 40 wt. % MDEA was activated by using piperazine (PZ) with the concentration between 2 and 10 wt. %, whereas 20 wt. % NaOH was used in the second stage. It was found that 6 wt. % of PZ was required to fully activate 40 wt. % MDEA, which resulted in 79% CO2 removal. To improve CO2 removal, a gas distributor and wire mesh packed were used to create gas bubbles at higher geometrical surface. The experimental study successfully removed 99.59% of the total CO2, producing >99 mol% hydrogen gas purity from the second stage that used 20 wt. % NaOH.

The industry is challenged to replace toxic chemical-based surfactants with environmentally friendly and biodegradable surfactants. In this study, binary mixtures of sodium lauryl sulfoacetate (SLSA) and an alkyl polyglucoside (APG10) in various proportions were investigated for their effectiveness as degreasing agents. Efficacy was characterised using surface tension measurements, oil dispersion tests, emulsification, pH and cleaning efficacy in removing engine oil from a metal plate. The surface tension results for all solutions showed a critical micelle concentration of 1500 ppm. The dispersion tests (with oil:surfactant ratios of 1:2 and 1:3) showed that the oil was fully dispersed at an oil:surfactant ratio of 1:2 i.e., at a concentration of 2500 ppm SLSA and 2000 ppm of a binary solution with a volume ratio of SLSA:APG10 of 75:25. At a ratio of 1:3, the oil was fully dispersed with 2500 ppm of a binary solution with a ratio of SLSA:APG10 of 75:25. Overall, the solution with a volume ratio of SLSA:APG10 of 75:25 was the most favourable. The results also showed that a solution containing only SLSA had good potential as a degreaser, as it achieved a cleaning performance of 90% in removing oil from the metal plate despite low emulsification levels (E24) for both surfactants. In summary, a combination of these two green surfactants can be used effectively as a degreasing agent.