Highly Efficient Adsorption of Cd(II) onto Carboxylated Camelthorn Biomass: Applicability of Three-Parameter Isotherm Mo
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ORIGINAL PAPER
Highly Efficient Adsorption of Cd(II) onto Carboxylated Camelthorn Biomass: Applicability of Three‑Parameter Isotherm Models, Kinetics, and Mechanism A. Hashem1 · G. M. Taha1 · A. J. Fletcher2 · L. A. Mohamed3 · S. H. Samaha4 Accepted: 26 November 2020 © The Author(s) 2020
Abstract A series of malonic acid treated camelthorn (MATC) sorbents were produced via the reaction of camelthorn biomass with malonic acid, and factors affecting the extent of modification were investigated, including malonic acid concentration, dehydration time and temperature. The optimum sorbent, by carboxylic acid content, was subsequently characterised for surface charge behaviour (pHPZC), surface chemical functionalities (FTIR), morphological structure (SEM), and available surface area. The sorbent was subsequently utilised for adsorption of Cd(II) ions from aqueous media, and parameters influencing adsorption at 30 °C, such as sorbent dose, initial solution pH, exposure time, metal concentration, were investigated. Isothermal analyses were performed using eight models, including two and three parameter equations, with appropriateness of fit assessed via non-linear regression analysis. The adsorption data indicated that the Langmuir model gives the most appropriate fit to experimental curves, with the models ordered as Langmuir > Hill > Toth > Sips > Jossens > Khan > RedlichPeterson > Freundlich. The highest uptake ( qmax) of 582.6 mg g−1 was determined at pH 6. The Freundlich constants, K F and n, at 30 °C were found to be 24.94 mg g−1 and 2.33, respectively. The value of n (2.33), being in the range 0–10, indicates that adsorption of Cd(II) ions onto malonic acid treated camelthorn biomass is favourable. Evaluation of a series of kinetic models, allowed elucidation of the adsorption mechanism, as a pseudo-second order model gave the most appropriate fit, indicating that chemisorption processes are involved. Cd(II) ions adsorption onto MATC is enhanced by a higher level of active surface sites but was show to be independent of surface area. The work presented here indicates that this sorbent offers effective adsorption potential for Cd(II) ions from water, with potential in wastewater processing. Keywords Camelthorn · Chemical modification · Isotherm models · Kinetic models
Introduction Remediation of heavy metal species from industrial and mine wastewaters is a key challenge in reducing related water and flora contamination. Cadmium has attracted * A. J. Fletcher [email protected] 1
National Research Centre, Textile Research Division, National Research Centre, Dokki, Cairo, Egypt
2
Department of Chemical and Process Engineering, University of Strathclyde, Glasgow G1 1XJ, UK
3
Microbial Chemistry Department, National Research Centre, Dokki, Cairo, Egypt
4
Textile Metrology Department, National Institute of Standards, El-Haram, Giza, Egypt
significant attention from those working in environmental remediation as a result of its high toxicity in the ionic form, which enters the environme
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