Abstract
Adsorption is a surface process. By evolution, nature has created design principles such as scaffolds that allow to carrying surface bound agents at high density. We used a nanofibrous pullulan/poly(vinyl alcohol)/poly(acrylic acid) (Pul/PVA/PAA) support to carry surface active PAMAM dendrimer similar to spores attached to mushroom gills. A monolayer of ceria (CeO2) nanoparticles served as the linker between PAMAM and the nanofiber. The nanocomposite was a highly effective Cr(VI) adsorbent and the maximum adsorption capacity qmax = 847 mg g−1 is the highest reported value for the same kind of materials so far. The materials was characterized by scanning electron microscopy (SEM), thermogravimetric analysis (TGA), Fourier transform-infrared spectroscopy (FTIR), zeta potential and multipoint BET method to measure the specific surface area. Removal of Cr(VI) from aqueous media was tested under different batch and fixed bed column operation conditions such as pH, temperature and competing ions. Thermodynamic properties were determined based on a modified Langmuir adsorption isotherm and the adsorption kinetic was investigated. Positive entropy of adsorption and an endothermic adsorption process was found, while the rate-limiting step was pseudo second order which is associated with a chemisorption process. The nanocomposite was reusable and up to 95% of the adsorbed Cr(IV) ions were recovered by alkyne washing.
Highlights
Nowadays, detoxification of various pollutants from wastewaters is a challenging issue in water treatment and environmental protection processes
Thermodynamic and kinetic parameters are given with a 95% confidence interval and the fit quality is expressed in terms of the coefficient of determination (R2), the root mean square deviation (RMSD), and the relative root mean square deviation (RRMSD), see Supporting information and Tables S1–S3
During the dendrimer treatment process partial adhesion between the nanofibers took place (Fig. 1c) which can be related to the high cross-linking that happened during the silanization and dendrimer treatment process due to different active methyl groups of GPTMS as well as to the huge amount of active amine groups of the PAMAM dendrimer that can attach to more than one CeO2-NP surfaces at the same time
Summary
Detoxification of various pollutants from wastewaters is a challenging issue in water treatment and environmental protection processes. Electrospun nanofibers are promising and widely used materials in a vast variety of fields such as water treatment - in particular the heavy metal removal processes - due to a high surface area and their porous structure [4,13,14,15,16,17,18,19,20,21,22,23]. Journal of Environmental Chemical Engineering 7 (2019) 102817 nanoparticles [4,24,25] Such combined materials do provide an efficient adsorbent for the heavy metal removal process, but the separation of the adsorbent from the filtrate is easy and convenient without the necessity of using any further method. The nanocomposite provided a high amount of amine groups and it was a super active adsorbent for Cr(VI) removal
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