Abstract
Objectives: To study the simultaneous removal of metal ions to understand the dynamics of the adsorption process for the assessment of the actual potential of an adsorbent in real-life applications. Methods: A one-step hydrothermal method was employed for the synthesis of nanomaterial. The hydrothermal treatment was performed at 110o C for 3 hours and calcined at 300o C for 2 hr to complete the nickel oxide nanoparticle synthesis. A systematic study of metal ion adsorption onto the nickel oxide nanoparticle was conducted to evaluate the maximum adsorption capacity and to understand the adsorption behaviour of the metal ions in presence of the others. The estimation of metal ion adsorption was done by measuring the residual concentrations using an atomic absorption spectrophotometer. Findings: The microscopic and spectroscopic characterizations confirmed the formation of nickel oxide nanostructures. The experimental results suggested that the adsorption process follows the Langmuir isotherm and the pseudo-secondorder model for metal ion adsorption in single and mixed solutions. A synergistic effect was observed for Pb (II) adsorption and an antagonistic effect for Cd (II) adsorption. The maximum adsorption capacity of ~650 mg/g of Pb (II) and ~475 mg/g of Cd (II) were noticed for simultaneous adsorption by the NiO nanoparticle. Novelty/improvement: The presence of more than one heavy metal ion in the wastewater is obvious, and one kind of metal ion may interface with the adsorption behaviour of the others. Further, limited studies on simultaneous adsorption of metal ions using metal-oxide nanoparticles are available in the literature. Hence, this work will provide an idea about the applicability of the NiO nanoparticle for real-life applications. Keywords: Adsorption; NiO; Heavy metal ions; Simultaneous removal
Highlights
Transition metals and metal oxides have been receiving significant attention because of their diverse applications in the field of catalysis [1,2], batteries [3], electromagnetism [4], gas sensors [5,6], and photocatalysis [7,8]
An aggregated structure of globular Nickel oxide (NiO) particles is evident in the SEM image
The pseudo-second-order model fitting provides a higher correlation coefficient (R2) compared to the pseudo-firstorder model fitting. These findings indicated that the time-dependent metal ion adsorption process could be better explained by a pseudo-second-order kinetic model equation
Summary
Transition metals and metal oxides have been receiving significant attention because of their diverse applications in the field of catalysis [1,2], batteries [3], electromagnetism [4], gas sensors [5,6], and photocatalysis [7,8] These metal/metal oxide-based nanomaterials possess a large surface-to-volume ratio, unique adsorptive properties, surface defects, Sardar / Indian Journal of Science and Technology 2021;14(28):2327–2336 and fast diffusivities [9,10]. These materials are of much interest because of their unique shape and size-dependent properties [11,12] as compared to bulk crystals with the same chemical composition. It is imperative to evaluate the adsorption performance of an adsorbent in presence of multiple metal ions to assess the potential for real-life applications
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