Lignin-Based Magnetic Nanoparticle Adsorbent for Diclofenac Sodium Removal: Adsorption Behavior and Mechanisms

Abstract

Diclofenac sodium, as a typical deputation of non-steroidal anti-inflammatory drugs, is widely used in clinical treatment. Due to the heavy use, diclofenac sodium is commonly detected in water environment, and the removal of diclofenac sodium from wastewater is important for environmental protection. Notably, magnetic separation technology has become a novel performance in the removal of organic pollutants from wastewater in recent years. Herein, we engineered a lignin-based magnetic nanoparticle adsorbent (LMNA) by loading a magnetic core (Fe3O4) onto alkali lignin. This novel adsorbent has the advantage of green synthesis and low cost, making it an ideal material for wastewater treatment. Remarkably, the BET surface area of LMNA (739.2 m2 g−1) was higher than that of alkali lignin (2.2 m2 g−1). Adsorption batch experiments confirmed that the LMNA exhibited good adsorption performance to diclofenac sodium with a higher adsorption capacity of 106.4 mg g−1. The adsorption kinetic data and isothermal were well fitted by the pseudo-second-order rate equation (R2 = 0.980) and the Langmuir equation (R2 = 0.991), respectively. Moreover, the reaction mechanisms between the diclofenac sodium and LMNA mainly related to the synergism of electrostatic attractions, π–π stacking interactions and hydrogen bonding interactions. Especially, the LMNA exhibited high magnetic saturation strength (10.5 emu g−1) which made it easy to recycle, showing excellent reusability (4 cycles). Our work might introduce significant theoretical and experimental basis for realizing excellent adsorption of emerging organic pollutants from wastewater by the magnetic nanoparticle adsorbent.