Atrazine adsorption removal with nylon6/polypyrrole core-shell nanofibers mat: possible mechanism and characteristics

Abstract

A functionalized nylon6/polypyrrole core-shell nanofibers mat (PA6/PPy NFM) was prepared via situ polymerization on nylon6 electrospun nanofibers mat (PA6 NFM) template and used as an adsorbent to remove atrazine from aqueous solutions. The core-shell structure of PA6/PPy NFM can be clearly proved under scanning electron microscope (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). The effects of initial solution pH and ionic strength, as well as the comparison of the adsorption capacity of functionalized (PA6/PPy NFM) and non-functionalized (PA6 NFM) adsorbent, were examined to reveal the possible adsorption mechanism. The results indicated that π-π interaction and electrostatic interaction should play a key role in the adsorption process. The kinetics and thermodynamics studies also further elucidated the detailed adsorption characteristics of atrazine removal by PA6/PPy NFM. The adsorption of atrazine could be well described by the pseudo-second-order equation. The adsorption equilibrium data was well fitted with the Freundlich isotherm model with a maximum adsorption capacity value of 14.8 mg/g. In addition, the increase of adsorption rate caused by a temperature increase could be felicitously explained by the endothermic reaction. The desorption results showed that the adsorption capacity remained almost unchanged after six adsorption/desorption cycles. These results suggest that PA6/PPy NFM could be employed as an efficient adsorbent for removing atrazine from contaminated water sources.

Nanofiber-Based Materials for Persistent Organic Pollutants in Water Remediation by Adsorption

“…Nylon-Poly(pyrrole) core-shell nanofibers showed an adsorption capacity of 2.77 mg/g, corresponding to an efficiency of 27% (Table 4, N3). The aromatic ring of Poly(pyrrole) enables π-π interaction with the Atrazine triazine ring, while nylon does not have unsaturated bonds [41]. Experiments here were reported for a neutral solution pH.…”

“…However, the Poly(pyrrole) isoelectric point has been reported around 10, meaning that at neutral pH both adsorbent and atrazine exhibited a positive surface charge [41]. It was concluded that a pH slightly above 10 would favour adsorption with a negative Poly(pyrrole) surface and still slightly protonated atrazine [41].…”

“…Ionic strength also has an impact on the adsorption process. Indeed, electrical double layers can form on the adsorbent surface [41]. In a case of a neutral pH, when falling below the adsorbent isoelectric point the adsorbent surface would carry a positive charge, and would therefore attract the anions present in the solution to the interface to form what is called a stern layer.…”

“…The thickness of the electrical double layers can prevent the adsorption reaction. However, when the ionic strength increases, the electrolyte will compress the electrical double layer and thus influence electrostatic interactions between adsorbate and adsorbent [41]. Figure 7 shows the variation in adsorption performance in function of the solution pH.…”

“…Nylon 6-Poly(pyrrole) core-shell nanofibers have been investigated for atrazine desorption and adsorbent regenerability [41]. The desorption procedure consisted of successive washing in methanol and deionized water for 5 min each to elute atrazine, followed by air-drying of nanofibers at room temperature.…”