Preparation and assessment of ionic liquid and few-layered graphene composites to enhance heat and mass transfer in adsorption cooling and desalination systems

Abstract

Adsorption systems can utilise low-temperature renewable and waste heat sources, which have emerged as a feasible alternative to conventional water desalination and cooling systems. However, the material of poor heat and mass transfer performance stall their widespread utilisation. This article presents the development and investigation of new composites employing few-layered graphene platelets and ionic liquids, namely ethyl-methylimidazolium methane sulfonate ([EMIM][CH3SO3]) and Ethyl-methylimidazolium-chloride ([EMIM][Cl]) to address such challenges. The impact of the few-layered graphene platelets, thermal properties, water adsorption properties of the developed composites and their thermal diffusivity were experimentally investigated. Besides, the overall cyclic performance was studied experimentally at the material level and computationally at the component level by employing a previously validated 2D dynamic heat and mass transfer model. The experimental investigation indicated that pristine few-layered graphene has a surface area of 56.8978 m2/g and a relatively high thermal diffusivity of 22.23 mm2/s. The developed composites showed higher thermal diffusivity than the baseline adsorbent silica gel. The highest thermal diffusivity was 11.84 mm2/s for GP-CH3SO3-10, 394 times higher than silica gel. Water adsorption characteristics of the composites were carried out, and the Dubinin–Astakhov (D-A) model was employed to model the experimental isotherms with good accuracy. The cumulative advanced adsorption and thermal characteristics of the developed composites resulted in higher cyclic performance by up to 82 % and 85 % than that of the baseline silica gel.