Adsorption of pyridine from aqueous solutions by polymeric adsorbents MN 200 and MN 500. Part 1: Adsorption performance and PFG-NMR studies

• Published in: Chemical engineering journal (Lausanne, Switzerland : 1996) Switzerland : 1996), 2016-12, Vol.306, p.67-76
• Main Authors: Zhu, Qingyu, Moggridge, Geoff D., Ainte, Mohamed, Mantle, Mick D., Gladden, Lynn F., D’Agostino, Carmine
• Format: Article
• Language: English
• Subjects: Adsorption isotherms; Kinetics; Macronet adsorbents; PFG-NMR; Pyridine removal; Thermodynamics
• ISSN: 1385-8947; 1873-3212
• DOI: 10.1016/j.cej.2016.07.039

[Display omitted] •Pyridine adsorption from aqueous solutions was performed using MN200 and MN500.•Better performance on MN500 is observed due to the presence of sulfonic acid groups.•Structural and surface properties of porous adsorbents were probed with PFG-NMR.•The link between diffusion, pore structure and adsorption performance is discussed.•MN200 and particularly MN500 are attractive adsorbents for pyridine removal. The removal of pyridine from aqueous solutions was carried out using Macronet polymeric adsorbents MN 200 and MN 500. The optimal pyridine uptakes were in approximately neutral solutions as a result of optimal effect of π-π hydrophobic and attractive electrostatic interactions between pyridine and the adsorbents. These adsorbents showed superior pyridine uptake capacities than some apatite and activated carbons in isotherm studies. Thermodynamic analysis showed that pyridine adsorption is exothermic on MN 200 and endothermic on MN 500, implying that the adsorption on MN 500 is an activated process, which is attributed to the presence of sulfonic acid groups. Pseudo-first and second order rate models were used to fit the adsorption kinetics for the adsorbents. Translational dynamics of guest molecules within the porous polymers was analysed by PFG-NMR diffusion technique and the diffusion behaviour was characterised by two distinctive diffusion regions. PFG-NMR derived self-diffusion coefficients of pyridine in MN 500 were much slower than the expected diffusion coefficients based on a purely geometrical confinement effect, which suggests the interaction of pyridine with the sulfonic acid groups on MN 500 and their stronger effect on diffusivity also enhances the adsorption performance of this adsorbent. These studies reveal new insights into adsorption properties of pyridine in porous polymers in relation to the structural and surface properties probed by PFG-NMR and account for the effectiveness of these adsorbents in the treatment of waste water containing the aromatic N-heterocyclic compound.