Antibiotic adsorbability and economic analysis of sodium alginate/chitosan composite-modified semi-carbonized fiber

The antibiotic adsorbability and economic performance of modified semi-carbonized fiber (SF) were investigated by using 100% chitosan (CS) to modify SF (prepared by cotton) for preparing CS-modified SF (CS-SF). Then, different ratios (0%, 10%, 20%, 50%, 100%, and 200%) of sodium alginate (SA) were used to modify 100CS-SF for preparing SA and CS-modified SF (SA/CS-SF). Batch method was used to investigate the adsorption characteristic of chlortetracycline (CTC), tetracycline (TC), and oxytetracycline (OTC) on different SA/CS-SFs. The effects of temperature, pH, and ionic strength on antibiotic adsorption were compared, and the economic performance of different SA/CS-SFs was analyzed. Results showed that (1) the Langmuir model is suitable for describing the adsorption process of antibiotics by different SA/CS-SFs. The maximum adsorption amount (q(m)) of different SA/CS-SFs for CTC, TC, and OTC were 11.17-36.36, 6.14-26.11, and 9.90-32.87 mmol/kg, respectively, ranking in the order of CTC > OTC > TC. (2) The adsorption antibiotics by different SA/CS-SFs conformed to the pseudo-first-order kinetics equation. Antibiotic adsorption on different SA/CS-SFs increased with the increase in temperature, and the adsorption was a spontaneous, endothermic, and entropy-increasing process. (3) In the pH range of 3-9 and ionic strength range of 0.01-0.2 mol/L, the adsorption amount of antibiotics on different SA/CS-SFs all 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, respectively. (4) The economy (q(m)/price) of different SA/CS-SFs for antibiotic adsorption ranged from 7.18 to 22.91 mg/(sic), and 100SA/CS-SF showed the highest economy. Compared with biochar and modified biochar, 100SA/CS-SF had higher economy in antibiotic adsorption.