Comparison of oxytetracycline adsorption on semi-carbonized acrylic fibers under different orthogonal modifications

In this study, sodium alginate (SA), dimethyl dodecyl betaine (BS), and chitosan (CS) were used for single, binary, and ternary modifications on the surface of semi-carbonized fibers (Sf) prepared using acrylic fiber. Batch method was used to investigate the adsorption characteristic of oxytetracycline (OTC) on the tested materials, and the effects of pH, temperature, and ionic strength on oxytetracycline adsorption were compared. The structural particularities of the tested materials was studied using scanning electron microscopy (SEM) and Fourier-transform infrared spectroscopy (FTIR). Results showed that: (1) Langmuir model can better fitted the adsorption isotherms of OTC than Henry and Freundlich models, with the maximum adsorption capacity (qm) maintained at 16.11–65.25 mmol/kg. The qmof oxytetracycline presented the trend of ternary > binary > single modification. (2) In the pH range of 1–9 and ionic strength range of 0.01–0.5 mol/L, the adsorption amount of OTC on different modified Sfs increased first and then decreased with increasing pH and ionic strength, reaching the maximum value at pH 5 and ionic strength of 0.1 mol/L. (3) OTC adsorption on different modified Sfs increased with the increase in temperature, and the adsorption was a spontaneous, endothermic, and entropy-increasing process, which conformed to the pseudo-second-order kinetic equation. (4) SEM and FTIR results proved that the modifiers were modified on the surface and that they changed the surface properties of Sf. The adsorption amount of OTC on 100SA/BS/CS-Sf still reached about 50% of the original material after three times of regeneration.