Cellulose polymers with β-amino ester pendant group: design, synthesis, molecular docking and application in adsorption of toxic metals from wastewater

Abstract

Background: Cellulose polymers with multidentate chelating functionalities that have high efficiency for toxic metal ions present in water were designed, synthesized, and analyzed. The synthesis was carried out by reacting microcrystalline cellulose extracted from the solid waste of the olive industry with tert-Butyl acetoacetate (Cell-AA), produced cellulose with β-ketoester functionality was then reacted with aniline and the amino acid glycine to produce Cell-β-AN and Cell-β-GL, respectively.

Results: The adsorption efficiency of the three polymers toward Pb(II) and various toxic metal ions present in sewage was evaluated as a function of adsorbent dose, time, temperature, pH value, and initial ion concentration to determine optimum adsorption conditions. The three polymers showed excellent efficiency toward about 20 metal ions present in a sewage sample collected from the sewer. The adsorption process follows the Langmuir adsorption isotherm model with a second-order of adsorption rate, the calculated qe values (2.675, 15.252, 20.856 mg/g) were close to the experimental qe values (2.133, 13.91, 18.786 mg/g) for the three polymers Cell-AA, Cell-β-AG and Cell-β-AN, respectively. Molecular Dynamic (MD) and Monte Carlo (MC) simulations were performed on the three polymers complexed with Pb(II).

Conclusion: The waste material of the olive industry was used as a precursor for making the target cellulose polymers with β-Amino Ester Pendant Group. The polymer was characterized by SEM, proton NMR, TGA, and FT-IR spectroscopy. The efficacy of adsorption was quantitative for metal ions present in a real sample of wastewater and the efficiency didn't drop even after 7 cycles of use. The results indicate the existence of strong complexation. The thermodynamic study results showed a spontaneous bonding between of Pb(II) and the polymers pendant groups expressed by the negative value of the Gibbs free energy.

Keywords: 2-furan carbonyl chloride; Adsorption; Cellulose; Cellulose nanocrystalline; Difenoconazole; Glycine; Molecular dynamic; Monte Carlo; Persistent pesticides; Wastewater; Water treatment.

Fig. 1

Preparation of cellulose acetoacetate from Cellulose and t-BAA

Fig. 2

FT-IR spectrum for Cell-AA

Fig. 3

FT-IR spectrum for Cell-β-AN

Fig. 4

Preparation of cellulose β-aminoacetonate using glycine

Fig. 5

FT-IR spectrum for Cell-β-GL

Fig. 6

Representative structures show the interaction between Cell-β-GL and Cell-β-AN and the metal ion Pb(II)

Fig. 7

The SEM images of a Cell-β-AN and b Cell-β-GL at a magnification of 250x 500x, respectively

Fig. 8

TGA and DTG analysis results of A Cell-AA, B Cell-β-AN C Cell-β-GL polymers

Fig. 9

The effect of a: adsorbent dose, b adsorption time, c temperature, d pH, and e initial ion concentration on the metal removal by the three adsorbents

Fig. 10

Adsorption efficiency, effect of adsorbent recycling

Fig. 11

A Langmuir adsorption model and B Freundlich adsorption model of Pb(II) ions on three adsorbents

Fig. 12

A Pseudo first-order model B Pseudo-second order model and C Intra-particle diffusion model for the adsorption of Pb(II) ions onto cell-AA, cell-β-AN, and cell-β-AG at various concentrations

Fig. 13

Adsorption thermodynamics of Pb(II) ions onto cell-AA, cell-β-AN, and cell-β-AG

Fig. 14

A Different energy terms during the exploration of random MC configurations (3 000 000) and B Probability of the adsorption energy distributions during MC for the adsorbate ions onto modified cellulose surface

Fig. 15

Lowest energy configurations of Pb Pb²⁺ ions onto the corresponding modified cellulose surfaces as obtained from MD

Fig. 16

The change of the adsorption energy (and corresponding energy terms) for the Pb²⁺ions onto the modified cellulose surfaces obtained during the MD

Fig. 17

Noncovalent interaction surfaces and the plot of RDG vs sign(λ)ρ for the van der Waals interactions among the Pb²⁺ions and the modified cellulose moieties

Fig. 18

Electron localization function (ELF) analysis of the “bonding” between Pb²⁺ions and the side groups of the modified cellulose