Aqueous phase reforming of wastewaters from the hydrothermal carbonization of microalgae: tackling the catalyst deactivation challenge via upstream pretreatment

Aqueous phase reforming (APR) is a promising route to produce hydrogen, but implementation with real feedstocks is limited by rapid deactivation. Here, we report for the first time the APR of wastewater from microalgae hydrothermal carbonization. The effects of carbon concentration and temperature were investigated, with the highest hydrogen productivity obtained at 1.7 gC/L and 270 ◦C, yielding 13 mmol H2/gC. Catalyst deactivation was elucidated through an integrated approach: carbon deposition was demonstrated by N2 physisorption analysis and TGA, while inorganic accumulation by XPS and FE-SEM/EDX, pointing to a combined mechanism. Therefore, mitigation strategies were proposed, including thermal pretreatment to avoid solid formation and adsorption of phosphate. Among the options, the latter markedly improved APR up to 30 mmol H2/ gC. Overall, by correlating wastewater characterization with a dual deactivation route, and demonstrating a viable upstream mitigation approach, this study provides a practical basis for improving APR robustness when processing real streams.