Environmentally Friendly Cellulose/Lignin Aerogel as Adsorbent for Efficiently Adsorptive Removal of Trimethoprim from Water

An environmentally friendly aerogel (CE/LN), composed of cellulose (CE) and lignin (LN) was synthesized via one-pot cross-linking method at room temperature, followed by freeze-drying. The CE/LN aerogel exhibited good mechanical properties and abundant functional groups, making it an effective adsorbent for the adsorption and removal of the antibiotic trimethoprim (TMP) from water. This study systematically investigated the effects of solution pH, aerogel dose, contact time, initial TMP concentration, temperature, ionic strength, and various water sources on TMP adsorption. The CE/LN aerogel demonstrated a higher TMP adsorption capacity of TMP than the CE aerogel across the entire pH range of 2.0–10.0. The adsorption process was well described by the Langmuir isotherm model and pseudo-second-order kinetic model. The CE/LN 6% aerogel achieved the highest adsorption capacity, with a theoretically maximal TMP uptake of 0.402 mmol/g at pH 6.0. However, high concentration of NaCl significantly reduced TMP uptake on the CE/LN 6% aerogel due to the electrostatic shielding effect. After five cycles of adsorption, the CE/LN 6% aerogel maintained a high adsorption capacity, retaining 80% of its initial uptake. Combined with the adsorption performance, the Fourier transform infrared spectrometry and X-ray photoelectron spectroscopy analyses spectroscopy analysis before and after TMP adsorption, it can be concluded that the adsorption mechanism involved hydrogen bonding, electrostatic interactions, and π–π electron donor–acceptor interactions. Thus, the CE/LN aerogel, with its simple preparation method, good adsorption capacity, and reusability, shows great potential for widespread application in the removal of antibiotics from water.