Designing degradable lignin-grafted magnetic nano-composite materials for cost-effectively sustainable removal of fluoroquinolone antibiotics from environmental water

Developing a novel green adsorbent to meet the requirements of low-cost, high quality of enrichment for analytes, and environmental sustainability is significant but remains a challenge. Herein, an eco-friendly dealkaline lignin-grafted magnetic iron oxide nanoparticle (Fe3O4@DAL) used as a dispersion solid adsorbent for the removal of fluoroquinolone antibiotics (FQs) from environmental water was developed based on the amide reactions between cost-effective plant-derived dealkaline lignin (DAL) and amino-functionalized Fe3O4 nanoparticles at room temperature. Fe3O4@DAL combined with the advantages of lignin and magnetic nanoparticles, which had abundant functional groups (phenols and aliphatic hydroxyl, carboxyl, phenyl) and high separation efficiency, so typical FQs including pefloxacin (PEF), lomefloxacin (LOM), enrofloxacin (ENR) and difluoxacin (DIF) could be easily removed by multiple interactions. The Langmuir isotherm model and pseudo-second-order model could be more suitable to describe the adsorption process of FQs on Fe3O4@DAL. The maximum adsorption capacities of Fe3O4@DAL for PEF, LOM, ENR, DIF were 25.2 mg g−1, 19.2 mg g−1, 30.0 mg g−1, 33.7 mg g−1, respectively. And the total maximum adsorption capacities of four FQs could reach 108.2 mg g−1. The whole adsorption process was spontaneous and endothermic based on thermodynamic data. Moreover, Fe3O4@DAL was of great reusability and could be used at least 5 cycles. In particular, the recycled adsorbent can be degraded as slow-release fertilizer under the action of soil microorganisms, which helps the growth of plants and further expands application range of lignin. As an effective, environmental-friendly, low-cost adsorbent for alleviating FQs contamination not only increased the added value of natural raw materials, but also had a great potential in the field of water treatment.