Adsorptive and Coagulative Removal of Trace Metals from Water Using Surface Modified Sawdust-Based Cellulose Nanocrystals

Opeyemi A. Oyewo, Sam Ramaila, Lydia Mavuru, Taile Leswifi and Maurice S. Onyango
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Opeyemi A. Oyewo: Department of Science and Technology Education, University of Johannesburg, Johannesburg 2092, South Africa
Sam Ramaila: Department of Science and Technology Education, University of Johannesburg, Johannesburg 2092, South Africa
Lydia Mavuru: Department of Science and Technology Education, University of Johannesburg, Johannesburg 2092, South Africa
Taile Leswifi: Department of Chemical and Civil Engineering, University of South Africa, Florida Campus, Roodepoort 1709, South Africa
Maurice S. Onyango: Department of Chemical, Metallurgical and Materials Engineering, Tshwane University of Technology, Pretoria 0001, South Africa

J, 2021, vol. 4, issue 2, 1-13

Abstract: The presence of toxic metals in surface and natural waters, even at trace levels, poses a great danger to humans and the ecosystem. Although the combination of adsorption and coagulation techniques has the potential to eradicate this problem, the use of inappropriate media remains a major drawback. This study reports on the application of NaNO 2 /NaHCO 3 modified sawdust-based cellulose nanocrystals (MCNC) as both coagulant and adsorbent for the removal of Cu, Fe and Pb from aqueous solution. The surface modified coagulants, prepared by electrostatic interactions, were characterized using Fourier transform infrared, X-ray diffraction (XRD), and scanning electron microscopy/energy-dispersive spectrometry (SEM/EDS). The amount of coagulated/adsorbed trace metals was then analysed using inductively coupled plasma atomic emission spectroscopy (ICP-AES). SEM analysis revealed the patchy and distributed floccules on Fe-flocs, which was an indication of multiple mechanisms responsible for Fe removal onto MCNC. A shift in the peak position attributed to C 2 H 192 N 64 O 16 from 2? = 30 to 24.5° occurred in the XRD pattern of both Pb- and Cu-flocs. Different process variables, including initial metal ions concentration (10–200 mg/L), solution pH (2–10), and temperature (25–45 °C) were studied in order to investigate how they affect the reaction process. Both Cu and Pb adsorption followed the Langmuir isotherm with a maximum adsorption capacity of 111.1 and 2.82 mg/g, respectively, whereas the adsorption of Fe was suggestive of a multilayer adsorption process; however, Fe Langmuir maximum adsorption capacity was found to be 81.96 mg/g. The sequence of trace metals removal followed the order: Cu > Fe > Pb. The utilization of this product in different water matrices is an effective way to establish their robustness.

Keywords: adsorption; coagulation; cellulose nanocrystals; sawdust; trace metals (search for similar items in EconPapers)
JEL-codes: I1 I10 I12 I13 I14 I18 I19 (search for similar items in EconPapers)
Date: 2021
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