Optimized biosorbent for ethanol sorption refrigeration: Adsorption kinetics, thermodynamic performance, and entransy evaluation.

Commercial adsorbents like silica gel, zeolite, and Maxsorb III have been widely studied for adsorption cooling. Recent focus has shifted towards biomass-based activated carbons, though hard lignocellulosic sources remain underexplored. This first-of-its-kind study introduces pistachio shell-derived activated carbon for cooling applications. The eco-friendly biosorbent is produced through a two-step process, slow pyrolysis and thermochemical activation, with optimized parameters: 562.5 ◦C and a 1:4 biochar-to-KOH ratio. The ethanol uptake measurements are performed using a customized adsorption setup at temperatures ranging from 20 ◦C to 80 ◦C, for evaporator temperatures of 5 ◦C, 10 ◦C, and 15 ◦C. The experimental adsorption performance has been modelled using the Dubinin-Astakhov isotherm, while a third-order polynomial equation is proposed to describe the temperature-dependent specific heat capacity of the prepared biosorbent. The performance analysis reveals that the optimum values of ethanol uptake, volumetric cooling energy, and COP are estimated as 42.71 kg m-3, 144.12 MJ m-3, and 0.7924, respectively, at a desorption temperature of 78.46 ◦C and evaporator pressure of 2.22 kPa. The proposed biosorbent–ethanol pair demonstrates strong potential compared to commercial adsorbents, based on a comprehensive assessment of porous properties, cooling performance, and costeffectiveness. The novel entransy and destruction analysis further highlights that the desorber possesses the highest entransy, which decreases from 37.5 % to 30.1 % as evaporator pressure increases from 1.09 kPa to 4.28 kPa, indicating enhanced system efficiency with lower thermal input demand. With promising scalability, this sustainable biosorbent aligns with SDG 12 and SDG 13 by reducing environmental impact and supporting ecofriendly cooling solutions.