Abstract
A new and inexpensive lignocellulose/montmorillonite (LNC/MMT) nanocomposite was prepared by a chemical intercalation of LNC into MMT and was subsequently investigated as an adsorbent in batch systems for the adsorption-desorption of Ni(II) ions in an aqueous solution. The optimum conditions for the Ni(II) ion adsorption capacity of the LNC/MMT nanocomposite were studied in detail by varying parameters such as the initial Ni(II) concentration, the solution pH value, the adsorption temperature and time. The results indicated that the maximum adsorption capacity of Ni(II) reached 94.86 mg/g at an initial Ni(II) concentration of 0.0032 mol/L, a solution pH of 6.8, an adsorption temperature of 70°C, and adsorption time of 40 min. The represented adsorption kinetics model exhibited good agreement between the experimental data and the pseudo-second-order kinetic model. The Langmuir isotherm equation best fit the experimental data. The structure of the LNC/MMT nanocomposite was characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM), whereas the adsorption mechanism was discussed in combination with the results obtained from scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and Fourier-transform infrared spectroscopy analyses (FTIR). The desorption capacity of the LNC/MMT nanocomposite depended on parameters such as HNO3 concentration, desorption temperature, and desorption time. The satisfactory desorption capacity of 81.34 mg/g was obtained at a HNO3 concentration, desorption temperature, and desorption time of 0.2 mol/L, 60 ºC, and 30 min, respectively. The regeneration studies showed that the adsorption capacity of the LNC/MMT nanocomposite was consistent for five cycles without any appreciable loss in the batch process and confirmed that the LNC/MMT nanocomposite was reusable. The overall study revealed that the LNC/MMT nanocomposite functioned as an effective adsorbent in the detoxification of Ni(II)-contaminated wastewater.
Highlights
Water contamination caused by heavy-metal ions generated from alloys, pigments, electroplating, mining, metallurgical activities, nuclear power plant operations, aerospace industries, electrical contacts, printing, and the manufacture of paper, rubber, plastics, and batteries [1, 2] is a global problem receiving worldwide attention
The adsorption capacity of the LNC/ MMT nanocomposite toward Ni(II) first increased and remained constant with increasing initial Ni(II) concentration. This result was observed because higher Ni(II) concentrations result in an increased concentration gradient, which, leads to a higher probability of collision among Ni(II) ions and the active adsorption sites on the LNC/MMT nanocomposite, thereby increasing adsorption capacity
With further increases in Ni(II) concentration, the adsorption capacity remained constant because the active adsorption sites became saturated [25]
Summary
Water contamination caused by heavy-metal ions generated from alloys, pigments, electroplating, mining, metallurgical activities, nuclear power plant operations, aerospace industries, electrical contacts, printing, and the manufacture of paper, rubber, plastics, and batteries [1, 2] is a global problem receiving worldwide attention. Increased awareness of heavy metal toxicity has led to a dramatic increase in research on various technologies to clean targeted water environments. Different methods, such as ion exchange, reduction, flocculation, reverse osmosis, membrane filtration, and precipitation, have been investigated for the removal of Ni(II) ions from aqueous solutions; most of these methods are expensive or generate harmful waste products [10,11,12,13,14]. Natural polymeric materials [15] are a promising alternative as adsorbents for wastewater treatment
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