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Title
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Histidine‑Functionalised Polypyrrole Hybrid
Nanocomposite for Adsorption of Toxic Hexavalent
Chromium from Water
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Creator
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Chigondo, Marko
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Nyamunda, Benias
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Maposa, Munashe
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Nyenyayi, Knowledge
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Nyadenga, Delroy
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Chigondo, Fidelis
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Abstract
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Abstract
Chromium(VI) is one of the most toxic metal ions as it can bioaccumulate and its excessive assimilation may result in anaemia, nervous system failure, kidney damage, cancers of the digestive tract and lungs. In this study a polypyrrole (PPy) modified with histidine (His) by in situ polymerisation tech nique was investigated for the removal of Cr(VI) from aqueous and characterised by means of Fourier trans form infrared (FTIR) spectroscopy, X-ray diffraction (XRD), field emission scanning electron microscopy/ energy dispersive X-ray spectroscopy (FE-SEM/ EDS), high resolution-transmission electron micros copy (HR-TEM) and X-ray photoelectron spectros copy (XPS).The influence of solution pH, adsorption time, initial adsorption concentration, temperature and coexisting ions on its adsorption were investi gated. The results showed that the optimum adsorp tion pH was 2.0 with the adsorption being endo thermic and chemisorption in nature. Mono-layer adsorption was witnessed as the Langmuir isotherm best described the process with a maximum adsorp tion capacity 274.73 mg g−1 at 25 °C. Although the removal of Cr(VI) was the primary drive, the reduc tion of Cr(VI) to Cr(III) during treatment turned out to be very significant to avoid secondary pollu tion. The adsorption mechanisms were mainly ion exchange, electrostatic attractions, complexation, chelation reactions with protonated histidine sites and reduction. Remarkably, the His-PPy nanocomposite exhibited an exceptional removal for Cr(VI) ions after three cycles of adsorption–desorption (over 99%) suggesting the adsorbent’s exceptional recyclability. The adsorption equilibrium was attained from 60 to 150 min and best described by pseudo-second-order kinetics. The high adsorption efficiency, stability and selectivity makes the His-PPy nanocomposite adsor bent potentially suitable for large-scale Cr(VI) ions removal from water.
Keywords: Histidine · Polypyrrole · Nanocomposite · Adsorption · Chromium (VI
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Date
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05 August 2024
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Source
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Water Air Soil Pollut
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pages
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235:572
