Facile synthesis of Poly(epichlorohydrin-diethylenetriamine) hydrogel for highly selective diclofenac sodium removal

Diclofenac sodium (DS), which remains in natural aqueous environments, is eco-toxic. To remove DS in aqueous solutions, a new adsorbent, poly(epichlorohydrin-diethylenetriamine) [P(ECH-DETA)] hydrogel, was simply synthesized by crosslinking copolymerization. In this work, the newly prepared P(ECH-DETA) hydrogel has the advantages of the simple synthesis method, certain anti-interference ability for DS adsorption, the relatively high adsorption capacity, and the obvious selective adsorption performance for DS in mixed-pharmaceuticals solutions. The adsorption inhibitory effects were acceptable within a range of wide pH (pH = 3–10), interfering ions concentration (0.1–10 mmol/L) and coexisting humic acid (1–15 mg/L). Besides, the adsorption capacity can reach 540.3 mg/g according to the Langmuir fitting model, much higher than that of DS adsorbents reported in most studies. After 5 times of recycle, the adsorption capacity still maintained 80.32%, indicating high sustainability. In addition, the selective adsorption capacity was evaluated by testing the adsorption performance on 6 different pharmaceuticals besides DS. The results indicated that P(ECH-DETA) hydrogel could selectively adsorb DS from DS/quinolones and DS/tetracyclines. The adsorption mechanisms of DS were studied by Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS), indicating that the adsorption mechanisms are mainly amine groups (electrostatic attraction) and hydroxyl groups (hydrogen bonding). P(ECH-DETA) hydrogel prepared in this study is a hopeful adsorbent for DS removal.