AUTHOR=Al-Saeedi Sameerah I. , Areej Asfa , Qamar Muhammad Tariq , Alhujaily Ahmad , Iqbal Shahid , Alotaibi Mohammed T. , Aslam Muhammad , Qayyum Muhammad Abdul , Bahadur Ali , Awwad Nasser S. , Jazaa Yosef , Elkaeed Eslam B. 

TITLE=Isotherm and kinetic studies for the adsorption of methylene blue onto a novel Mn3O4-Bi2O3 composite and their antifungal performance

JOURNAL=Frontiers in Environmental Science

VOLUME=11

YEAR=2023

URL=https://www.frontiersin.org/journals/environmental-science/articles/10.3389/fenvs.2023.1156475

DOI=10.3389/fenvs.2023.1156475

ISSN=2296-665X

ABSTRACT=<p>Metal oxide-based adsorbents are quite in for wastewater treatment because of their selectivity, stable structure and very low solubility in aqueous systems. To explore the adsorption of methylene blue (MB), Mn<sub>3</sub>O<sub>4</sub>-Bi<sub>2</sub>O<sub>3</sub> adsorbents were made using a wet-impregnation technique with various concentrations of Mn<sub>3</sub>O<sub>4</sub>. The presence of Mn<sub>3</sub>O<sub>4</sub> contents on the surface of monoclinic Bi<sub>2</sub>O<sub>3</sub> was confirmed through representative scanning electron micrographs. The diffractions pertaining to cubic Mn<sub>3</sub>O<sub>4</sub> and monoclinic Bi<sub>2</sub>O<sub>3</sub> were noticed in the XRD pattern of 5% Mn<sub>3</sub>O<sub>4</sub>-Bi<sub>2</sub>O<sub>3</sub> which confirm the composite nature of the adsorbent. XPS analysis revealed the existance of Bi 4f, Bi 4d, Bi 4p, Bi4s, and Mn 2p core levels in Mn<sub>3</sub>O<sub>4</sub>-Bi<sub>2</sub>O<sub>3</sub>. The adsorption study divulged highest efficiency (∼95% and qe = ∼1.4 mgg<sup>-1</sup>) of 5% Mn<sub>3</sub>O<sub>4</sub>-Bi<sub>2</sub>O<sub>3</sub> composite among other contestants in removing 30 ppm MB at 28 <inline-formula id="inf1"><mml:math id="m1" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mo>°</mml:mo></mml:mrow></mml:math></inline-formula> C, pH 7 and 250 rpm. In addition to the determination of adsorption ability, the effect of preliminary dye concentration (5, 10, 20, and 30 ppm) and contact time (0.5–6 h) on the removal efficiency of prepared adsorbents were also monitored. The adsorption data from the batch experiments were evaluated using the Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich-Kaganer (DRK) adsorption isotherms and pseudo 1<sup>st</sup> and 2<sup>nd</sup>-order kinetic models. The fitting of adsorption isotherms and kinetic models revealed the formation of adsorbate’s monolayer on the surface of adsorbents through the process of chemisorption. Through FTIR measurement, the MB adsorption onto the effective adsorbent (5% Mn<sub>3</sub>O<sub>4</sub>-Bi<sub>2</sub>O<sub>3</sub>) was also confirmed. Moreover, TGA analysis showed ∼1.5% weight loss by 5% Mn<sub>3</sub>O<sub>4</sub>-Bi<sub>2</sub>O<sub>3</sub> before MB adsorption whereas ∼2.6% weight loss was noticed after dye adsorption onto the adsorbent. The antifungal activity was evaluated against the fungi <italic>A. solani</italic> and <italic>M. fructicola</italic> using the agar well diffusion technique. The 5% Mn<sub>3</sub>O<sub>4</sub>-Bi<sub>2</sub>O<sub>3</sub> composites have exceptional antifungal characteristics compared to Bi<sub>2</sub>O<sub>3</sub> and Mn<sub>3</sub>O<sub>4</sub>, with zone inhibition values of 58.6 and 53.9 mm, respectively.</p>