Study of a Novel Thermo-Responsive Polymer for Atmospheric Water Collection System

Abstract

A growing global concern is water scarcity, with 783 million people reportedly experiencing acute water scarcity year-round. Due to the limited natural water resources in the United Arab Emirates, groundwater and desalinated water—which account for 44% and 42% of total water—are more commonly used. The depletion of groundwater and the high energy input required for the desalination process underscores the need for developing more sustainable water resources. Therefore, the objective of the project is to design and build a water collection system that uses a novel desiccant material to harvest atmospheric water. A good water supply in dry places may be made possible using sorbent-based atmospheric water harvesting technology that uses a desiccant-coated heat exchanger (DCHE). Sorbents may absorb moisture from arid environments and release water when heated to the right temperature. This work explores the possible use of a composite material of NIPAM with laponite that is a thermo-responsive super porous hydrogels (SPH) for the adsorption of water vapor from moist air. X-ray diffraction (XRD), TGA, and SEM were used to characterize the synthesized materials to study the production of SPHs and the inclusion of laponite inside the polymer matrix. Additionally, water vapor from wet air has been absorbed using P(NIPAM-co-AA)SPH and COMP30%. When water vapor was adsorbed on these two materials, type III isotherms were seen. At 25°C, the maximal adsorption capacities for P(NIPAM-co-AA)-SPH and COMP30%were 0.83 and 1.32 gw/gads, respectively. The higher adsorption capacity of COMP30% can be attributed to the presence of hydrophilic laponite particles in the composite material. The adsorption kinetics were well explained by the liquid film diffusion model, and in P(NIPAM-co-AA)-SPH, water molecule diffusion was non-Fickian, whereas in COMP30%, it followed Fickian type diffusion. The materials that were produced also showed strong reusability and worked well for ten adsorption cycles. A heat exchanger that uses the sorption property of the desiccant to absorb water vapor was coated with COMP30% using a dip coating technique. Thus, tests were run on the system setup to examine how air mass flow and relative humidity changes affected the water collected and the system's ability to remove moisture. It was concluded that as relative humidity and air mass flow increased, moisture removal capacity (MRC) and moisture removal rate (MRR) also increased. Lastly, a simulation was conducted to examine the impact of air flow velocity, inlet temperature, and humidity on the operation of the water collection system. The findings imply that when air temperature decreases and humidity increases, moisture removal capacity (MRC), moisture removal rate (MRR) and water production rate also increased. It emerged that increasing airflow increases water intake and gained output ratio (GOR) due to the improved mass transfer through the system. The findings obtained demonstrate the feasibility of water collection utilizing the suggested method.

Date of Award	7 May 2024
Original language	American English
Supervisor	MD FAZLULKARIM (Supervisor)