Ultrasonic cavitation-driven hierarchical pore engineering of activated carbon for enhanced bilirubin adsorption: Quantitative structure-function relationships.

Hemoperfusion (HP) is a clinically important therapeutic strategy for the management of hyperbilirubinemia, particularly in situations where liver transplantation is limited by donor availability or where surgical intervention presents substantial risk. However, the performance of current HP adsorbents remains constrained by insufficient adsorption capacity. Moreover, the relative contributions of physical confinement and surface chemical interactions to bilirubin adsorption remain incompletely elucidated, hindering the rational design of high-efficiency adsorbent materials. In this study, the pore size distribution of activated carbon (AC) was systematically tailored via ultrasonic treatment across a wide power range (10-100 %), leveraging cavitation-induced microjets and shear forces to restructure the pore architecture while preserving surface chemical functionality. Quantitative correlation analysis revealed that bilirubin adsorption is highly pore-size-dependent, with the strongest contributions arising from pores in the 2-3 nm and 10-20 nm ranges, both exhibiting high coefficients of determination (R2 = 0.807 and 0.808, respectively). The optimised sample (AC50) exhibited a high specific surface area of 986.13 m2 g-1 and an adsorption capacity of 84.23 mg g-1, corresponding to increases of 53.5 % and 16.1 %, respectively, relative to untreated AC. These enhancements indicate a synergistic improvement in textural properties and adsorption performance induced by ultrasonic treatment. Notably, the resulting hierarchical pore architecture, comprising 2-3 nm size-matched confinement zones and 10-20 nm adsorption chambers, facilitates efficient molecular transport and confinement within the pore network. For albumin-bound bilirubin, pores larger than 30 nm primarily serve as transport pathways, facilitating the diffusion of the bilirubin-albumin complex, whereas internal surface interactions predominantly govern adsorption. Building on these insights, this study establishes a quantitative framework that links pore size to adsorption functionality, enabling the rational optimisation of chemically active sites within targeted pore domains. Furthermore, the results demonstrate that ultrasonication represents a green and efficient strategy for engineering next-generation HP adsorbents with precisely tailored hierarchical porosity.