Abstract
In this work, cellulose nanocrystals (CNCs) obtained by the acid hydrolysis of waste bamboo powder were used to synthesize cellulose nanocrystal-g-poly(acrylic acid-co-acrylamide) (CNC-g-P(AA/AM)) aerogels via graft copolymerization followed by freeze-drying. The structure and morphology of the resulting aerogels were characterized by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM), and the CNC-g-P(AA/AM) aerogels exhibited excellent absorbent properties and adsorption capacities. Subsequent Pb(II) adsorption studies showed that the kinetic data followed the pseudo-second-order equation, while the adsorption isotherms were best described using the Langmuir model. The maximum Pb(II) adsorption capacity calculated by the Langmuir model reached up to 366.3 mg/g, which is a capacity that outperformed that of the pure CNC aerogel. The CNC-g-P (AA/AM) aerogels become structurally stable through chemical cross-linking, which enabled them to be easily regenerated in HCl solution and retain the adsorption capacity after repeated use. The aerogels were found to maintain 81.3% removal efficiency after five consecutive adsorption–desorption cycles. Therefore, this study demonstrated an effective method for the fabrication of an aerogel adsorbent with an excellent reusability in the effective removal of Pb(II) from aqueous solutions.
Highlights
Over the past few decades, contamination from lead has caused major public health issues due to the widespread usage of this element in many important industries, such as battery manufacturing, electroplating, pigments, and finishing [1,2]
The cellulose nanocrystals (CNCs)-g-P(AA/AM) aerogels were prepared by free radical graft polymerization
With the introduction of monomer molecules (AA and AM) into the system, the active radical sites on CNC would initiate chain propagation in the monomer vinyl groups, thereby resulting in cross-linking reactions taking place simultaneously, and the MBA becoming connected to the polymer chains by covalent bonds to form a three-dimensional network
Summary
Over the past few decades, contamination from lead has caused major public health issues due to the widespread usage of this element in many important industries, such as battery manufacturing, electroplating, pigments, and finishing [1,2]. Activated carbon is not well suited for the treatment of industrial effluents containing low concentrations of Pb(II), and as such, the development of new high-efficiency adsorbents as an alternative to activated carbon is necessary [16]. Recovery of the nanocellulose is challenging after its use in water treatment processes due to its tendency to agglomerate and due to its nano-sized dimensions, thereby rendering it unsuitable for direct use as an adsorbent [24] To address this issue, nanocellulose is often converted into an aerogel or film by appropriate cross-linking [25]. We report the preparation of CNC-based aerogels exhibiting high adsorption capacities and excellent reusability properties, in which poly(acrylic acid-co-acrylamide) (P(AA/AM)). The reusability of each CNC-g-P(AA/AM) aerogel is investigated as an important performance parameter
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