Supplementary material

Performance of novel hydroxyapatite nanowires in treatment of fluoride

contaminated water

Junyong He a, b, Kaisheng Zhang a, b, Shibiao Wu a, Xingguo Cai a, b, Kai Chen a, b,

Yulian Li a, b, Bai Sun a, Yong Jia a, Fanli Meng a, Zhen Jin a, Lingtao Kong a, *, and

Jinhuai Liu a

a Nano-Materials and Environmental Detection Laboratory, Institute of Intelligent

Machines, Chinese Academy of Sciences, Hefei 230031, People's Republic of China.

b Department of Chemistry, University of Science and Technology of China, Hefei,

Anhui 230026, People's Republic of China.

Corresponding Author

*E-mail address: ltkong@iim.ac.cn (L. Kong); Fax: +86-551-65592420; Tel: +86-551-

65591142.

S1. Membrane filtration system

The injector with HAP membrane in it was fixed on the syringe pump, the flow rate

can be set by the syringe pump. With the pump working, the solution was pushed out

through the membrane dropwise.

S1

Fig. S1. The real filtration system for removal of fluoride.

S2. The pseudo-first-order kinetic plots for the adsorption of fluoride

Fig. S2. The pseudo-first-order kinetic plots for the adsorption of fluoride on the

surface of the HAP nanowires. (adsorbent dose: 0.5 g/L, pH: 7.0)

S3. Langmuir isotherm models for fitting of fluoride adsorption on HAP

nanowires

S2

Fig S3. (a) fluoride adsorption isotherms on HAP nanowires at three different

temperatures (adsorbent dose: 0.5 g/L, pH: 7.0). (b) Freundlich isotherm models for

fitting of fluoride adsorption on HAP nanowires.

S4. Calculation of thermodynamic data

The ln Kd as function of Ce at T = 298 K, 308 K and 318 K was given in Fig. S4.

The adsorption equilibrium constants (K0) at different temperature were obtained by

linear extrapolating Ce to zero, ln K0 = 7.56 at T = 298 K, ln K0 = 7.85 at T = 308 K,

and ln K0 = 8.05 at T = 318 K, and △G0 = −18.73 kJ/mol at 298 K, −20.10 kJ/mol at

308 K, and −21.28 kJ/mol at 318 K, respectively. The values of △H0 and △S0 can be

obtained from the plot of ln K0 vs. 1/T (Fig. S5). The value of △H0 and △S0 was

calculated to be 1.851 kJ/mol and 125.21 J/mol K, respectively.

S3

Fig. S4. Linear plots of lnKd vs Ce for the adsorption of fluoride on HAP nanowires at

298, 308 and 318 K.

Fig. S5. Linear plot of lnK0 vs 1/T for the adsorption of fluoride on HAP nanowires at

298, 308 and 318 K.

S5 Desorption and regeneration

S4

Fig. S6. The fluoride removal using regenerated HAP nanowires. (C0: 5 mg/L,

temperature :25 °C, pH: 7.0, adsorbent dose: 1.5 g/L)

S6 Practical underground water samples

Table S1. Characteristics of the underground water sample from Xingwang Village,

Inner Mongolia of China.

Items Value

pH 7.6

Fluoride (mg/L) 2.820

Chloride (mg/L) 119.6

Nitrate (mg/L) 1.42

Sulfate (mg/L) 4.740

Na (mg/L) 123.4

Mg (mg/L) 12.2

As (mg/L) 0.103

Hg (mg/L) 0.006

Pb (mg/L) 0.003

S5

TOC 31.39

S6