Efficient Adsorption and Separation of Palladium from Industrial Wastewater by Imidazolium Cationic Polymers

doi:10.6023/A26020047

Abstract

Palladium (Pd), as a rare precious metal, is highly valued due to its unique physical and chemical properties and ubiquitous applications in important industries. However, the use of palladium has several limitations, such as high cost, high toxicity, and the extremely limited availability of natural resources, which cannot meet the increasing industrial demands. Therefore, the recovery of palladium from industrial wastewater plays a crucial role in alleviating the risk of precious metal resource depletion and reducing environmental pollution. In this study, two imidazolium-based cationic polymer networks (CPNs, CPN-1 and CPN-2) with high charge density were prepared by N-alkylation reaction, and used for the recovery of Pd(II) from industrial wastewater. The materials were systematically characterized by Fourier transform infrared (FT-IR) spectroscopy, elemental analysis (EA), Brunauer-Emmett-Teller (BET), thermogravimetric analysis (TGA), powder X-ray diffraction (PXRD), and scanning electron microscopy (SEM). Systematic adsorption experiments were carried out to investigate the adsorption performance of Pd(II). CPN-1 and CPN-2 exhibit fast adsorption kinetics (within 3 min for equilibrium) and high adsorption capacities (243 mg•g⁻¹ and 234 mg•g⁻¹, respectively). The adsorption behavior is consistent with the Langmuir adsorption isotherm model and the pseudo-second-order kinetic model, indicating that monolayer chemisorption is the predominant adsorption mechanism. In the presence of various cations and anions, CPNs still show excellent removal for Pd(II) with efficiencies over 85% (CPN-1) and 83% (CPN-2). In addition, CPN-1 and CPN-2 have good reusability, with no significant decrease in Pd(II) recovery performance after five cycles. In particular, CPN-1 also shows excellent removal efficiency (>90%) in the dynamic adsorption experiments with simulated palladium wastewater, demonstrating the application potential of CPNs materials in palladium recovery. Finally, energy dispersive spectrometer (EDS), X-ray photoelectron spectroscopy (XPS), and density functional theory (DFT) calculations reveal that the removal of Pd(II) by CPNs is mainly achieved by anion exchange. This work demonstrates great application potential of CPNs for Pd(II) recovery from industrial wastes.

Key words: cationic polymer, palladium recovery, solid-liquid adsorption, ion exchange, wastewater remediation

Cite this article

Wenxia Lin, Yidan Zhou, Fan Lin, Yimin Cai, Wen Feng. Efficient Adsorption and Separation of Palladium from Industrial Wastewater by Imidazolium Cationic Polymers[J]. Acta Chimica Sinica, 2026, 84(7): 1067-1076.

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Fig. & Tab. 6

Scheme 1. Synthetic routes of CPN-1 and CPN-2 and schematic illustration of their adsorption toward PdCl42−

Figure 1. (a) FT-IR spectra of CPN-1, DIB, TBPT; (b) CPN-2, DIBP; (c) Nitrogen adsorption/desorption isotherms; (d) SEM images and element mappings of CPN-1 and CPN-2; (e) TGA curve

材料	理论值/%			实际值/%
材料	C	H	N	C	H	N
CPN-1	59.94	5.01	14.51	54.12	5.24	13.31
CPN-2	61.00	4.98	12.34	63.32	5.39	12.99

Table 1. Element content distribution of CPN-1 and CPN-2

Figure 2. (a) The influence of pH and (b) temperature on the adsorption of Pd(II) by CPN-1 and CPN-2; (c) Adsorption kinetics curves; (d), (e) Adsorption isotherms of CPN-1 and CPN-2 fitted by the Langmuir model (insert shows the linear fitting and related parameter); The influence of competing anions (f) and cations (g) on the adsorption of Pd(II) by CPN-1 and CPN-2; (h) Comparison of performance with other palladium adsorbents

Figure 3. (a) Desorption eﬃciency of various eluents; (b) Reusability of CPN-1 and CPN-2; (c) Photo of the dynamic adsorption experimental device (right) and column after adsorption (left); (d) Dynamic elution curve for PdCl42− separation

Figure 4. SEM and EDS images of (a) CPN-1-Pd and (b) CPN-2-Pd; (c) Full XPS spectra of CPN-1 and CPN-1-Pd; (d) Pd 3d XPS survey of CPN-1-Pd; (e) N 1s XPS survey of CPN-1 and CPN-1-Pd; (f) Full XPS spectra of CPN-2 and CPN-2-Pd; (g) Pd 3d XPS survey of CPN-2-Pd; (h) N 1s XPS survey of CPN-2 and CPN-2-Pd; (i) The adsorption energies (Ea) between CPN-1, CPN-2, and PdCl42−

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