Issue 9, 2024, Issue in Progress

Exploring moisture adsorption on cobalt-doped ZnFe2O4 for applications in atmospheric water harvesting

Abstract

Sorption-based atmospheric water harvesting (SBAWH) is a highly promising approach for extracting water from the atmosphere thanks to its sustainability, exceptional energy efficiency, and affordability. In this work, ZnFe2O4 and Zn0.4Co0.6Fe2O4 were evaluated for moisture adsorption. The desired materials were synthesized by a surfactant-assisted sol–gel method. Synthesized samples were characterized using X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM), energy dispersive X-ray (EDX) spectroscopy, Fourier transform infrared (FTIR) spectroscopy, vibrating sample magnetometry (VSM), and point of zero charge (PZC). Crystallinity and phase composition were evaluated by XRD analysis. Several parameters were determined using XRD analysis: lattice parameter, unit cell volume, crystallite size, and bulk density. The morphology of synthesized materials was assessed via SEM, and unveiled the acquisition of consistent, homogeneous, and uniform crystals. Elemental composition was determined through EDX spectroscopy. Water adsorption on the surface was evaluated by FTIR spectroscopy. The magnetic properties of synthesized ZnFe2O4 and cobalt-doped ZnFe2O4 ferrites were investigated using VSM. The negative charge on the Zn0.4Co0.6Fe2O4 surface was explored using PZC. Adsorption studies on synthesized materials were conducted with the help of an atmospheric water harvesting (AWH) plant created by our team. Moisture adsorption isotherms of synthesized materials were determined using a gravimetric method under varying temperature and relative humidity (45–95%) conditions. The moisture content (Mc) of Zn0.4Co0.6Fe2O4 and ZnFe2O4 was 597 mg g−1 and 104 mg g−1, respectively. Key thermodynamic properties, including isosteric heat of adsorption (Qst), change in Gibbs free energy (ΔG), and change in sorption entropy (ΔS), were evaluated. Qst was negative, which confirmed the sorption of water vapors on the material surface. ΔG and ΔS indicated that water-vapor adsorption was spontaneous and exothermic. A second-order kinetics study was carried out on synthesized materials, demonstrating their chemisorption behavior. The latter was due to the oxygen defects created by replacement of Co2+ and Fe3+ at tetrahedral and octahedral sites. Water vapors in the atmosphere became attached to the surface and deprotonation occurred, and the hydroxyl ions were formed. Water vapor attached to these hydroxyl ions. A second-order kinetics study was carried out to confirm the chemisorption behavior of synthesized materials.

Graphical abstract: Exploring moisture adsorption on cobalt-doped ZnFe2O4 for applications in atmospheric water harvesting

Supplementary files

Transparent peer review

To support increased transparency, we offer authors the option to publish the peer review history alongside their article.

View this article’s peer review history

Article information

Article type
Paper
Submitted
28 Nov 2023
Accepted
18 Jan 2024
First published
19 Feb 2024
This article is Open Access
Creative Commons BY license

RSC Adv., 2024,14, 6165-6177

Exploring moisture adsorption on cobalt-doped ZnFe2O4 for applications in atmospheric water harvesting

M. Ehtisham, A. K. Badawi, A. M. Khan, R. A. Khan and B. Ismail, RSC Adv., 2024, 14, 6165 DOI: 10.1039/D3RA08152D

This article is licensed under a Creative Commons Attribution 3.0 Unported Licence. You can use material from this article in other publications without requesting further permissions from the RSC, provided that the correct acknowledgement is given.

Read more about how to correctly acknowledge RSC content.

Social activity

Spotlight

Advertisements