Structural, Sorption, and Regeneration Properties of Poly(methacrylic acid): Poly(4-vinylpyridine) Interpolymer...

The sorption, structural, and thermal properties of the interpolymer system based on polymethacrylic acid (PMAA) and poly-4-vinylpyridine (P4VP) were studied at different component ratios for the extraction of rhenium (ReO₄^-) and molybdenum (MoO42-) ions from model solutions. The results showed that sorption efficiency depends on both composition and contact time. Systems with molar ratios of 3:3 and 2:4 exhibited the highest activity, reaching more than 90% extraction for rhenium and up to 94% for molybdenum after 48 h. FTIR spectra indicated the involvement of carboxyl and pyridine groups in complex formation with the metal ions, as evidenced by band shifts and the appearance of new absorption features. Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) demonstrated that modification of PMAA with P4VP enhances the thermal stability of the system, which is maintained even after desorption. The system with the optimal composition showed structural stability and the ability to regenerate without a notable decrease in sorption capacity. Sorption performance was preserved across a wide pH interval, with maximum values at pH 2-4, which makes the system suitable for hydrometallurgical applications. Comparison with literature data indicates agreement with current approaches to rare-metal recovery, while the PMAA-P4VP system is distinguished by improved stability and potential for further development. These findings provide a basis for the design of selective and environmentally safe processes for rhenium and molybdenum recovery, relevant to the conditions of the Republic of Kazakhstan, where technogenic solutions rich in these metals are available.