Controlled Synthesis and Selective Adsorption Properties of Pr₂CuO₄ Nanosheets: a Discussion of Mechanism

Tetragonal-phase Pr₂CuO₄ nanosheets with a thickness of about 60 nm were synthesized using the coordination compound methods (CCMs), then used as highly efficient selective adsorbent towards malachite green (MG) in aqueous solutions. The Pr₂CuO₄ samples were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), UV-Vis diffuse reflectance spectrum (DRS), and standard Brunauer-Emmett-Teller (BET) methods. The maximum adsorption capacity (Q_m) of as-prepared samples was determined by adsorption isotherms with different adsorbent doses (m) of 0.03-0.07 g at 298, 318, and 338 K based on the Langmuir model. When m < 0.03 g or > 0.07 g, effects of systemic mass loss and particle aggregation were discussed on the data deviation from the Langmuir model at 298 K. Based on the hydrogen bond and coordination bond, a possible mechanism of selective adsorption of MG by Pr₂CuO₄ is proposed, which was further verified by the adsorption experiments of CuO and Pr₂O₃ towards MG and competing-ion experiments. Finally, the theoretic studies were performed at DFT level to reveal the possible adsorption process.