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Pore Engineering and Competitive Kinetics for Selective Dye Adsorption on γ-Fe 2 O 3 Nanoparticles

Year: 2026

Type: article

Abstract: High Resolution Image Download MS PowerPoint Slide Adsorption process can be utilized to selectively separate the dyes from the medium based on the nature of charge and size of dye molecules. The separation of dyes having similar charges and sizes is still an intricate problem. Here, we present the competitive adsorption studies of cationic and similarly sized methylene blue (MB) and safranin O (SO) systems on porous γ-Fe 2 O 3 nanoparticles. To demonstrate the relation between pore size and selectivity, γ-Fe 2 O 3 nanoparticles were lixiviated using a citrate buffer and the lixiviated samples were subjected to further pretreatment methods before dye adsorption studies. The pretreated samples exhibit enhanced pore size, which results in higher adsorption capacity for both MB and SO dyes. The selectivities for MB exhibited by pretreated samples with average pore sizes of 3.4 and 2.2 nm are 10% and 22%, respectively. On the other hand, MB, despite being less preferred than SO from a thermodynamic point of view and possessing a relatively larger size, has a higher pseudo-second-order adsorption kinetic constant. Provided an accommodating pore size in γ-Fe 2 O 3 nanoparticles, by virtue of greater mass transfer of MB to accessible sites in the pore region, the selectivity of MB is enhanced. While a larger pore is equitable to the dye molecules resulting in the loss of selectivity, we hypothesize that combined factors of pore size requisite in adsorbent, thermodynamics and kinetics of adsorption, and dye molecular size need to be harnessed for a better selectivity in dye adsorption.

Source: ACS Omega

DOI: 10.1021/acsomega.5c04371

Authors: Ankita Singh, Balaji Gopalan

Institutions: Birla Institute of Technology and Science - Hyderabad Campus, Birla Institute of Technology and Science, Pilani

Language: English

Topic: Adsorption and biosorption for pollutant removal

Subfield: Water Science and Technology

Field: Environmental Science

Domain: Physical Sciences

Open Access status: gold

Estimated APC paid: $1,935

Funders: Department of Science and Technology, Ministry of Science and Technology, India, Birla Institute of Technology and Science, Pilani, Science and Engineering Research Board