Lignin xanthate resin-bentonite clay composite as a highly effective and low-cost adsorbent for the removal of doxycycline hydrochloride antibiotic and mercury ions in water

Natural-occurring polymer intercalated inorganic clay composites have received increasing interests in water cleanup for the features of eco-friendliness, cost-effectiveness, and availability. Herein, a new lignin xanthate resin (LXR) intercalated bentonite clay composite (LXR-BT) for the adsorption of representative organic doxycycline hydrochloride (DCH) antibiotic and inorganic Hg(II) in water was created through a feasible process. Structural characterizations by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, Thermo gravimetric analysis (TG), and scanning electron microscopy (SEM) confirmed LXR was successfully intercalated between the layers of bentonite clay. The adsorption performance of DCH/Hg(II) by LXR-BT was studied in detail with varied dosage, solution pH, contact time, and initial DCH/Hg(II) concentration. The results indicated that the adsorption capacities of DCH/Hg(II) on LXR-BT were much higher than that on bentonite, and the adsorption kinetics and isotherms followed the pseudo-second-order model and Langmuir model, respectively. X-ray photoelectron spectroscopy (XPS) analysis confirmed the adsorption mechanisms of DCH (or Hg(II)) was mainly due to 7G-n interaction and hydrogen bonding interaction of DCH (or the complexation of Hg(II)) with the functional groups in the LXR-BT. This study suggested the possibility of LXR-BT as a new cost-effective adsorbent for both organic and inorganic pollutants removal in water.