Equilibrium, kinetic, and diffusion models of chromium(VI) removal using Phragmites australis and Ziziphus spina - chris
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ORIGINAL PAPER
Equilibrium, kinetic, and diffusion models of chromium(VI) removal using Phragmites australis and Ziziphus spina‑christi biomass A. E. D. Mahmoud1,2,3 · M. Fawzy1,2,3 · G. Hosny4 · A. Obaid1 Received: 3 July 2020 / Revised: 28 September 2020 / Accepted: 30 September 2020 © Islamic Azad University (IAU) 2020
Abstract In this study, we investigated the modeling of chromium (Cr(VI)) removal using globally available plant biomass: Phragmites australis and Ziziphus spina-christi. Biosorption parameters were initial Cr(VI) concentration (50–800 mg L−1), contact time (1–180 min), adsorbent dose (0.25–2.0 g L−1), and pH (2–8) at agitation speed of 100 rpm. Based on the results of batch experiments and modeling, pseudo-second-order model was fitted to the experimental data where R2 = 0.99; besides, diffusion model played a significant role in the rate-determining step. Isotherm models were fitted in the order of Langmuir > Freundlich > Temkin models. Maximum adsorption capacities were recorded 21.32 mg g−1 and 15.55 mg g−1 for Phragmites australis and Ziziphus spina-christi, respectively. Insights into biosorption behavior were determined using Fourier-transform infrared spectra (FT-IR), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDX). SEM–EDX revealed the chromium presence and its accumulation on both biosorbents after the biosorption process. Cr(VI) biosorption mechanism is illustrated and can be related to electrostatic interactions, reduction and chelation/complexation with the functional groups of both adsorbents. Keywords Water treatment · Heavy metals · Leaf biomass · Adsorption · Isotherm · Removal mechanism
Introduction
Editorial responsibility: Jing Chen. Electronic supplementary material The online version of this article (https://doi.org/10.1007/s13762-020-02968-7) contains supplementary material, which is available to authorized users. * A. E. D. Mahmoud alaa‑[email protected] 1
Environmental Sciences Department, Faculty of Science, Alexandria University, 21511 Alexandria, Egypt
2
Green Technology Group, Faculty of Science, Alexandria University, 21511 Alexandria, Egypt
3
National Biotechnology Network of Expertise (NBNE), Academy of Scientific Research and Technology (ASRT), 11334 Cairo, Egypt
4
Division of Environmental Health, Department of Environmental Studies, Institute of Graduate Studies and Research, Alexandria University, 21526 Alexandria, Egypt
Excessive use of heavy metals led their releasing into the environment through natural process and anthropogenic activities. Many industries in the worldwide such as leather, tanning, metallurgy, petrochemicals, battery, and paper manufacturing are mostly responsible of discharging various types of heavy metals into the environment. Heavy metals pose a serious threat to human health because populations can be exposed to the heavy metals through water consumption. In addition, some heavy metals can bioaccumulate in the human bodies (e.g., in lipids and the gastrointestinal syste
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