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Comparison of separation performance of absorption column and membrane contactor system for biohydrogen upgraded from palm oil mill effluent fermentation

Treatment of palm oil mill effluent (POME) via fermentation under controlled conditions can produce a high‐value biohydrogen (H2) mixture containing carbon dioxide (CO2). This H2 can be enriched before it can be used for renewable energy, that is, in fuel cell. In this work, H2 was upgraded via two techniques, namely absorption column and membrane contactor system. Ammonium hydroxide (NH4OH), potassium hydroxide (KOH), and mixed solution of NH4OH and KOH were used as the chemical absorbents for both techniques. In the absorption column, it was found that the mixed solution provided the highest H2 purity (99%) at 1 M concentration with a gas flow rate of 0.2 L/min. Meanwhile, the mixed solution and KOH solution showed similar separation performance with H2 purity of up to 75% in the gas–liquid membrane contactor. On investigating the separation performance for each of the compared techniques, it was found that the absorption column has a superior ability to purify H2 than the membrane contactor system. However, the membrane contactor is more sustainable as it has the least drop in H2 purity at a longer separation time during the separation process. Both techniques have their own advantages in purifying H2, and thus they can be fairly considered for gas upgrading.