ABSTRACT
PURPOSE: Copper is a heavy metal that causes considerable deterioration to human health and ecosystems, so their elimination in water bodies is of great interest. Present investigation shows the efficiency of chicken feather as a natural adsorbent and its subsequent degradation in order to have an integral treatment and avoid the unconscious disposition. METHODS: Optimal conditions of adsorption process were determined using the Response Surface Methodology (RSM)-Box-Behnken design (BBD) with three variables (pH, temperature and adsorbent dose). After that, the optimal conditions were used to analize the adsorption isotherms by Langmuir, Freundlich and Temkin models; also thermodynamics parameters Gibbs free energy (ΔG°), enthalpy (ΔH°) and entropy (ΔS°) were obtained. Finally, the biodegradation of the residue denominated "adsorbent-adsorbate" complex was evaluated through monitoring the soluble protein production, keratinolytic activity, ninhydrin positive products, sulfhydryl groups, and gravimetrically analysis. RESULTS: The optimum conditions for the adsorption were 30°C and pH 3, the Langmuir model was better described the adsorption process at 30°C, while at 40°C was Temkin model. The chicken feather turned out a natural adsorbent competitive with respect to others used in the removal of copper in liquid systems; obtaining qmax of 7.84 and 11.48 mg/g at 30 and 40°C, respectively; it was also a favorable and spontaneous process. Finally the adsorbent used was degraded by a keratinolytic consortium. CONCLUSIONS: In this study, chicken feather was used as a low cost adsorbent for copper efficiently and with the feasibility that the adsorbent can be biodegraded and release the metal.
ABSTRACT
The aim of this work was to isolate oil-degrading bacteria that use chitin or keratin as carbon sources from oil contaminated soils; and additionally to study if oil removal by these bacteria is enhanced when a chitinous or a keratinous waste is added to the culture media. To isolate the above-mentioned bacteria, 12 soil samples were collected close to an oil-well. Such soils showed unsuitable nutrients content, but their counts of heterotrophic bacteria ranged within 10(5)-10(8) CFU g(-1) soil, of which 0.1-77% corresponded to oil hydrocarbon-degrading ones. By sampling on plates, 109 oil-degrading bacterial isolates were obtained. Their keratinase and chitinase activities were then screened by plate assays and spectrophotometric methods, resulting in 13 isolates that were used to integrate two mixed cultures, one keratinolytic and the other chitinolytic. These mixed cultures were grown in media with oil, or oil supplemented with chicken-feathers or shrimp wastes. The oil-hydrocarbon removal was measured by gas chromatography. Results showed that keratinolytic bacteria were better enzyme producers than the chitinolytic ones, and that oil removal in the presence of chicken-feathers was 3.8 times greater than with shrimp wastes, and almost twice, in comparison with oil-only added cultures. Identification of microorganisms from the mixed cultures by 16S rDNA, indicated the presence of seven different bacterial genera; Stenotrophomonas, Pseudomonas, Brevibacillus, Bacillus, Micrococcus, Lysobacter and Nocardiodes. These findings suggest that the isolated microorganisms and the chicken-feather wastes could be applied to the cleaning of oil-contaminated environments, whether in soil or water.
