Adsorption of ethanol onto novel and indigenous green adsorbents: Synthesis, characterization, and applications

Adsorption refrigeration is considered the most promising cooling option, yet its commercialization is hindered by bulkiness and low performance due to the lack of suitable adsorbents. In India, crop residue management is a challenge because of the open-field burning of waste biomass that leads to global warming and health problems. Therefore, the present article focuses on developing and sustainable application of novel porous activated carbons (ACs) from abundantly available crop residues to address these issues. The ACs synthesized through KOH activation of optimized biochar, exhibited significant specific surface area of 2002 m(2)/g and 1241 m(2)/g with distinctive micro- and meso-pores for sugarcane bagasse (SBAC), and rice straw (RSAC), respectively compared to other. The surface morphology study provides the honeycomb structure as evidence of micropores developed during activation processes. The experimental data of ethanol uptake is best fitted to calculate the structural constants of the Dubinin-Astakhov (D-A) model. A new performance index known as the mass of adsorbent to combustion fuel ratio (m(ad)/m(cf)) is proposed for the performance analysis of newly synthesized ACs as adsorbent with ethanol refrigerant in a renewable energy-powered adsorption cooling system (ACS). The SBAC-ethanol pair shows the highest effective uptake, and energy density of 0.535 kg/kg, and 612.24 kJ/kg, respectively at 80 degrees C and 4.28 kPa. Further, energy reduction potential evaluation for the newly prepared working pairs reveals a substantial decrease in energy input compared to composite-ethanol pairs from existing literature, indicating process improvements toward cleaner and more sustainable production. Thus, the present research underscores the proposed ACs as prime candidates for efficient and sustainable cooling and heat-pumping applications.