Metabolism and kinetic study of bioH 2 production by anaerobic sludge under different acid pretreatments

Abstract

Abstract This study presents results pertaining to bioH 2 production carried out in batch experiments under different inorganic acid pretreatments of sludge. The sludge was collected from an anaerobic digester and was subjected to different acid (H 2 SO 4 , H 3 PO 4 , HNO 3 , and HCl) pretreatments at pH 3 for 24 h. The results showed that electron equivalent balance closure was within −12 to +10% for all experiments; the portion of electrons as bioH 2 fluctuated from 16% to 25%. H 2 SO 4 pretreatments significantly increased H 2 yields to 3.3 mol H 2 /mol glucose followed by HNO 3 , HCl, and H 3 PO 4 pretreatments which averaged 2.5 ± 0.5. Enthalpy (ΔH°) and Gibb’s free energies (ΔG°) fluctuated from 120.5 to 192.7 (kJ/mol) and from −2.2 to −5.9 (kJ/mol). The modified Gompertz was assessed and determined that the maximum bioH 2 production potential, 1551 mL and maximum rate of bioH 2 production, 303 mL/h occurred using the H 2 SO 4 pretreatment.