Tuning hydrochar properties for enhanced mesopore development in activated carbon by hydrothermal carbonization

• Use of optimized hydrothermal conditions for enhanced mesopore area.
• Up to 80% increase in mesopore area by tuning hydrothermal conditions.
• Higher hydrothermal temperature increases ZnCl2 diffusion and biomass dehydration.
• Higher hydrothermal temperature leads to reduced solubility of ZnCl2.
• Working ranges for hydrothermal temperature and ZnCl2 content are found.

Simple tuning of hydrothermal pre-treatment parameters is shown to result in significant enhancement in the mesopore area of activated carbon obtained from biomass (coconut shell). ZnCl2 content and temperature were used as parameters to improve the effectiveness of hydrothermal pre-treatment. With progressive increase in the treatment temperature, the enhancement of ZnCl2 diffusion was tempered by its reduced solubility. By identifying favorable working ranges for ZnCl2 content and temperature to promote mesopore formation, up to 80% increase in mesopore area is achieved in comparison to the conventional soaking process for formation of mesoporous activated carbon. The enhancement in mesopore area was substantiated by high adsorption capacities for a mixture of phenol red and phenol up to 351 and 264 mg/g, respectively.

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