Ceftriaxone Removal with Sulfonic-phosphoric Acid Resin Based on Cation Adsorption Characteristic

To study an effective removal method of residual cephalosporin antibiotics in water, taking the ceftriaxone sodium (CFS) as a research object, the adsorption effects of the resins with different characteristic parameters for CFS were investigated in the pH range of 2.0–5.0. MTS9570, a sorbent containing sulfonic-phosphoric acid bi-functional group, was optimally selected and further to study the adsorption removal behavior to CFS in depth for the first time. Owning to the highest fitness of the pseudo-second-order and intra-particle diffusion (R² > 0.99), two models can better describe the process of CFS onto MTS9570, indicating that the process is controlled by the chemi-sorption and intra-particle diffusion together. Compared with Freundlich and Temkin isotherm, Langmuir isotherm is the best fitness with highest R² and lowest AIC values, indicating that there exists a monolayer adsorption on the surface of MTS9570 sorbent to CFS. ∆H < 0, ∆S > 0 and ∆G < 0, imply that the adsorption is an exothermic spontaneous process with increased randomness at the solid–liquid interface. The adsorption ability of MTS9570 after six adsorption–desorption cycles can still reach 90.13% of the initial adsorption capacity, indicating that the adsorbent has good reusability. Combining the above results with the bi-functional group of the adsorbent as well as the molecular structure of CFS, we speculate that the potential adsorption mechanism of MTS9570 to CFS may be mainly controlled by electrostatic interaction and supplemented by hydrogen bonding.