Optimization of thermally activated persulfate pretreatment of corn straw and its effect on anaerobic digestion performance and stability.

The effect of thermally activated persulfate on anaerobic digestion is incompletely understood. An orthogonal test was used to optimize the pretreatment process of corn straw using thermally activated persulfate, a lab-scale batch anaerobic digester was used for exploring the effect of pretreatment on anaerobic digestion. The optimal pretreatment conditions were 50 °C, 16 h, 0.5% Na 2 S 2 O 8 , pH = 5, and solid–liquid mass ratio (S:L) = 1:10, which was the most crucial factor. Lignin pretreatment with thermally activated sodium persulfate (SPS) considerably decreased. The yield of reducing sugar (RS) and VFAs were observably higher than the untreated group. This trend occurred because the thermal activation of persulfate primarily destroys the benzene ring in lignin by generating and releasing active sulfate radical (SO 4 ·−); moreover, hydroxyl radical (·OH) and SO 4 − work together during thermal activation. Furthermore, the daily biogas production of the groups pretreated for 16 and 48 h without elution were 22.78% and 26.80% higher than that of the group untreated, respectively. The degradation rates of total and volatile solids increased to 60% and 70% after the pretreatment. Therefore, thermally activated SPS could improve the performance and stability of anaerobic digestion, and the impact of dissolved organic matter loss exceeded that of residual Na+ and SO 4 2−. [Display omitted] • The optimum condition was 50 °C, 48 h, 0.5% Na 2 S 2 O 8 , pH 5, S: L = 1:10. • The lignin of straw was degraded by 77.18% after thermal activated SPS pretreatment. • The yields of RS and VFA were 2.38 and 0.67 times higher than control group. • Cumulative methane production pretreated by SPS reached 271.6 mL·g−1 VS [ABSTRACT FROM AUTHOR]