Cow bones char as a green sorbent for fluorides removal from aqueous solutions: batch and fixed-bed studies.
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, N2-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/C0→ 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; msorbent= 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.
Mining Engineering Department, Universidade Federal de Minas Gerais, Av. Antônio Carlos, 7727, Pampulha, Belo Horizonte, Brazil.
Elbert M
EM
Nigri
Laboratório de Transferência de Massa e Simulação Numérica de Sistemas Químicos, Federal University of Santa Catarina, PO Box 476, Florianópolis, SC, CEP 88040-900, Brazil.
Maria Alice P
MA
Cechinel
Laboratório de Transferência de Massa e Simulação Numérica de Sistemas Químicos, Federal University of Santa Catarina, PO Box 476, Florianópolis, SC, CEP 88040-900, Brazil.
Diego A
DA
Mayer
Laboratory of Separation and Reaction Engineering - Laboratory of Catalysis and Materials (LSRE-LCM), Chemical Engineering Department, Faculty of Engineering, University of Porto, Rua Dr. Roberto Frias, 4200-465, Porto, Portugal.
Luciana P
LP
Mazur
Laboratory of Separation and Reaction Engineering - Laboratory of Catalysis and Materials (LSRE-LCM), Chemical Engineering Department, Faculty of Engineering, University of Porto, Rua Dr. Roberto Frias, 4200-465, Porto, Portugal.
José M
JM
Loureiro
Mining Engineering Department, Universidade Federal de Minas Gerais, Av. Antônio Carlos, 7727, Pampulha, Belo Horizonte, Brazil. sdrocha@demin.ufmg.br.
Sônia D F
SD
Rocha
Laboratory of Separation and Reaction Engineering - Laboratory of Catalysis and Materials (LSRE-LCM), Chemical Engineering Department, Faculty of Engineering, University of Porto, Rua Dr. Roberto Frias, 4200-465, Porto, Portugal. vilar@fe.up.pt.
Vítor J P
VJ
Vilar
D000327:Adsorption; D000818:Animals; D001842:Bone and Bones; D002417:Cattle; D004058:Diffusion; D005260:Female; D005459:Fluorides; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D010710:Phosphates; D012996:Solutions; D018508:Water Purification / Q000379:methods*
D010710:Phosphates; D012996:Solutions; C012980:fluorophosphate; D005459:Fluorides
Bone char; Fixed bed; Fluoride removal; Pore diffusion model; Sorption