Different Adsorption Behaviors and Mechanisms of Anionic Azo Dyes on Polydopamine–Polyethyleneimine Modified Thermoplastic Polyurethane Nanofiber Membranes

Abstract

Considering the notable mechanical properties of thermoplastic polyurethane (TPU), polydopamine–polyethyleneimine (PEI) -modified TPU nanofiber membranes (PDA/PEI-TPU NFMs) have been developed successfully for removal of anionic azo dyes. The adsorption capacity of PDA/PEI-TPU NFMs was evaluated using three anionic dyes: congo red (CR), sunset yellow (SY), and methyl orange (MO). Interestingly, it exhibited different adsorption behaviors and mechanisms of CR on PDA/PEI-TPU NFMs compared with SY and MO. With the decrease in pH, leading to more positive charges on the PDA/PEI-TPU NFMs, the adsorption capacity of SY and MO increased, indicating electrostatic interaction as a main mechanism for SY and MO adsorption. However, wide pH range adaptability and superior adsorption have been observed during the CR adsorption process compared to SY and MO, suggesting a synergistic effect of hydrogen bonding and electrostatic interaction, likely as a critical factor. The adsorption kinetics revealed that chemical interactions predominate in the CR adsorption process, and multiple stages control the adsorption process at the same time. According to the Langmuir model, the maximum adsorption capacity of CR, SY and MO were reached 263, 17 and 23 mg/g, respectively. After six iterations of adsorption–desorption, the adsorption performance of the PDA/PEI-TPU NFMs did not decrease significantly, which indicated that the PDA/PEI-TPU NFMs have a potential application for the removal of CR molecules by adsorption from wastewater.

Electrocatalytic Determination of Uric Acid with the Poly(Tartrazine)-Modified Pencil Graphite Electrode in Human Serum and Artificial Urine

“… 47 , 48 N 1S spectra show the presence of −N–C structures at 399.7 eV and imine (−C=N) structures at 402.5 eV ( Figure 3 B III ). 49 The BEs of S 2p 1/2 and S 2p 3/2 at 169.5 and 168.2 eV correspond to the SO 3 structures ( Figure 3 B IV ). 50 …”

“…The formal oxidation state at 1071.6 eV may be attributed to the diffused sodium ions into the pTRT from the salt of TRT (Figure B II ) . The two most important pieces of evidence of electro-polymerization are the emergence of N 1S and S 2p chemical environments in XPS measurements. , N 1S spectra show the presence of −N–C structures at 399.7 eV and imine (−CN) structures at 402.5 eV (Figure B III ) . The BEs of S 2p 1/2 and S 2p 3/2 at 169.5 and 168.2 eV correspond to the SO 3 structures (Figure B IV ) …”

Adsorption and Removal of Composite Contaminants in Water Using Thermoplastic Polyurethane Nanofiber Membranes with Polydopamine–Polyethyleneimine Coatings

“…The material preparation processes have been reported in previous research publications from our group [18,19]. The ratio of the reaction monomers (DA and PEI) and the co-deposition time affect the amount of PDA/PEI co-deposited layers that can be grafted onto the surface of a TPU NFM, which, in turn, affects the adsorption performance of the membrane.…”

“…We found remarkable differences in the adsorption capacities of the PDA/PEI-TPU NFMs for CR, SY, and EY in the monomeric system [18,19]. In order to more quantitatively analyze the adsorption patterns of the PDA/PEI-TPU NFMs for the dye-BPA binary composite wastewater system, a gradient setting was applied to the dye and BPA concentrations.…”

“…Our group previously reported the successful synthesis of TPU NFMs and PDA/PEI-TPU NFMs [18,19]. In this study, the zeta potentials of both the TPU support membrane and PDA/PEI-modified membrane were measured to determine the type of charge carried by the materials under different pH levels, as this parameter is pertinent to the electrostatic adsorption between the materials and the contaminants.…”