Cow bones char as a green sorbent for fluorides removal from aqueous solutions: batch and fixed-bed studies

• Published in: Environmental science and pollution research international Vol. 24; no. 3; pp. 2364 - 2380
• Main Authors: Nigri, Elbert M., Cechinel, Maria Alice. P., Mayer, Diego A., Mazur, Luciana. P., Loureiro, José M., Rocha, Sônia D. F., Vilar, Vítor J. P.
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 2017; Springer Nature B.V
• Subjects: Adsorption; Animals; Aquatic Pollution; Aqueous solutions; Atmospheric Protection/Air Quality Control/Air Pollution; Bicarbonates; Bone and Bones; Bone composition; Bone growth; Bones; Carbonates; Cattle; Diffusion; Diffusion rate; Drinking water; Earth and Environmental Science; Ecotoxicology; Environment; Environmental Chemistry; Environmental Health; Environmental science; Equilibrium; Female; Flow rates; Flow velocity; Fluorides; Functional groups; Hydrogen-Ion Concentration; Kinetics; Mass transfer; Mathematical models; Mechanical loading; Phosphates; Regeneration; Research Article; Sodium hydroxide; Solutions; Sorption; Waste Water Technology; Water Management; Water Pollution Control; Water Purification - methods; Sorption; Pore diffusion model; Bone char; Fixed bed; Fluoride removal
• ISSN: 0944-1344; 1614-7499
• DOI: 10.1007/s11356-016-7816-5

Cow bone char was investigated as sorbent for the defluoridation of aqueous solutions. The cow bone char was characterized in terms of its morphology, chemical composition, and functional groups present on the bone char surface using different analytical techniques: SEM, EDS, N 2 -BET method, and FTIR. Batch equilibrium studies were performed for the bone chars prepared using different procedures. The highest sorption capacities for fluoride were obtained for the acid washed ( q  = 6.2 ± 0.5 mg/g) and Al-doped ( q  = 6.4 ± 0.3 mg/g) bone chars. Langmuir and Freundlich models fitted well the equilibrium sorption data. Fluoride removal rate in batch system is fast in the first 5 h, decreasing after this time until achieving equilibrium due to pore diffusion. The presence of carbonate and bicarbonate ions in the aqueous solution contributes to a decrease of the fluoride sorption capacity of the bone char by 79 and 31 %, respectively. Regeneration of the F-loaded bone char using 0.5 M NaOH solution leads to a sorption capacity for fluoride of 3.1 mg/g in the second loading cycle. Fluoride breakthrough curve obtained in a fixed-bed column presents an asymmetrical S -shaped form, with a slow approach of C / C 0  → 1.0 due to pore diffusion phenomena. Considering the guideline value for drinking water of 1.5 mg F − /L, as recommended by World Health Organization, the service cycle for fluoride removal was of 71.0 h ([F − ] feed  ∼ 9 mg/L; flow rate = 1 mL/min; m sorbent  = 12.6 g). A mass transfer model considering the pore diffusion was able to satisfactorily describe the experimental data obtained in batch and continuous systems.