Efficient adsorption of trimethoprim on carboxymethyl lignin-based three-dimensional porous sponges: Qualitative and quantitative analysis of multiple interactions

Adsorption as a typical water treatment technology can effectively remove trimethoprim (TMP). However, conventional micro-nano particle adsorbents are susceptible to loss and difficult to recover, resulting in limited practical application. Here, carboxymethyl modified lignin-based polyvinyl formal sponge (PLNC) adsorbents were prepared and evaluated its adsorption performance for TMP. PLNC exhibits abundant pore structures (pore size ~10 μm) with excellent mechanical strength and compressibility. Its adsorption capacity for TMP reaches 0.147 mmol/g, which is 36.75 times higher than that of polyvinyl formal sponge. Electrostatic attraction (EA), hydrogen bonding (HB), and π-π electron donor-acceptor (π-π EDA) interactions are primary adsorption contributors, exhibiting dynamic changes with solution pH. The molecular probe combined with density functional theory calculations reveals that EA between deprotonated carboxyl group of PLNC and aromatic nitrogen of aminopyrimidine in TMP is crucial for adsorption, which was enhanced by conjugation effect of 1,2,3-trimethoxybenzene in TMP. Furthermore, PLNC exhibits superior application potential, with less than 10.0 % mass loss after five reuses and recycling by simple screening. In dynamic adsorption bed experiments, PLNC maintains TMP effluent concentrations below 50 % during stable operation at ~40 × 10 3 bed volumes. This study provides theoretical guidance and practical foundations for the development and application of novel three-dimensional porous sponge adsorbents.