Temperature robustness of sulfur and hydrogen autotrophic reduction systems for antimonate detoxification: Experiment...

This study, for the first time, revealed the temperature robustness of elemental sulfur (S⁰) (SAR) and hydrogen (H₂) (HAR), and a combination of S⁰ and H₂ autotrophic reduction (SHAR) systems for Sb(V) removal from water. SHAR system demonstrated superior temperature stability, with only a 4.4-fold decline in the maximum specific removal rate (q_max) for Sb(V) from 30°C to 10°C compared to 9.1-fold for SAR and 5.0-fold for HAR. Furthermore, SHAR systems showed a 70% lower sulfate generation rate than SAR systems, and the generation rate decreased by around half when the temperature decreased from 30°C to 10°C for both systems. In addition, the sulfide generation rate in the SHAR was only 0.14 times that in the SAR system at 30°C, and low temperatures significantly inhibited sulfide production in both systems. Arrhenius and thermodynamic analyses showed that the energy barrier in the SHAR system was reduced by 51.2% due to the synergy of S⁰ and H₂ compared to the SAR system, and that spontaneous Sb(V) removal occurred at 20°C-30°C but was non-spontaneous at 10°C. Machine learning revealed that categorical boosting (CatBoost) achieved high accuracy in predicting Sb removal and byproduct generation, and Shapley additive explanations (SHAP) analysis confirmed that the SHAR system exhibited superior temperature robustness compared to SAR and HAR systems. SHAR system enriched a relatively independent genus, Cloacibacterium, and the temperature-tolerant Sb(V)-reducing genera Ralstonia and Defluviimonas, enabling them to withstand temperature changes, further stabilizing expression of key functional genes.