Application of adsorption on activated carbons and natural zeolite for the removal of lincomycin from wastewater of swine production industry

Abstract

The occurrence of antibiotics in natural water bodies have concerned the scientific community because of the potential development of antibiotic resistance in bacteria. Lincomycin is a lincosamide antibiotic used in the Saskatchewan swine industry for infection treatment, prevention, and possibly weight gain. The dose recommended for swine contains 22 g of lincomycin per metric ton of feed. Due to partial metabolization, part of the lincomycin is excreted through manure. It has been reported that after 5 weeks of storage, 74 % of this compound is degraded by natural processes in the manure. Therefore, it is important to remove the remaining lincomycin from manure before its application to land. Adsorption on activated carbons and zeolites was used for removing lincomycin from water and synthetic manure. For activated carbons, lincomycin adsorption was greater at solution initial pH 10, above the lincomycin’s pKa (7.8), than at initial neutral pH of 6.5. On the other hand, increasing the pH value reduced the adsorption capacity in the natural zeolite. The presence of NaCl did not affect the adsorption capacity of activated carbons because non-electrostatic interactions controlled the process. Conversely, for natural zeolite, increasing ionic strength decreased the adsorption capacity, probably, because the cationic exchange process was affected. From the thermodynamic characterization, it was determined that the adsorption, on both activated carbons and zeolites, was endothermic and spontaneous. The better performance adsorbents were evaluated in the removal of lincomycin from synthetic and real manure. In synthetic manure, the adsorption capacities were similar to the ones found at pH 10 in deionized water. The lack of solids and compounds competing for active sites, in the synthetic manure formulation, contributed to the unaltered adsorption capacities. On the other hand, in the real manure, due to competition and the presence of solids, the concentration of activated carbon used in the experiments with deionized water (50 mg/L) was insufficient for separating lincomycin. Different doses of activated carbon were tested and the simplified background equivalent compound model was used for predicting the lincomycin removal efficiency based on the used adsorbent dose. Activated carbon 1240 showed higher lincomycin adsorption capacity than F400 in real manure. As a comparison, for 60% lincomycin removal, doses of 900 mg/L and 1300 mg/L of 1240 and F400 can be used, respectively.