Enhanced Defluoridation Capacity From Aqueous Media via Hydroxyapatite Decorated With Carbon Nanotube

Abstract

In this work, the potential of a novel hydroxyapatite decorated with carbon nanotube composite (CNT-HAP) for fluoride removal was investigated. The synthesized CNT-HAP composite was systematically characterized by X-ray diffraction(XRD), Fourier Transform infrared spectroscopy(FTIR), scanning electron microscope (SEM) and Brunauer–Emmett–Teller(BET). Batch adsorption experiments were conducted to investigate the defluorination capacity of CNT-HAP. The CNT-HAP composite has a maximum adsorption capacity of 11.05 mg·g−1 for fluoride, and the isothermal adsorption data were fitted by the Freundlich model to calculate the thermodynamic parameters. Thermodynamic analysis implies that the adsorption of fluoride on CNT-HAP is a spontaneous process. Furthermore, the adsorption of fluoride follows pseudo-second-order model. The effects of solution pH, co-existing anions and reaction temperature on defluorination efficiency were examined to optimize the operation conditions for fluoride adsorption. It is found that the optimized pH-value for fluoride removal by CNT-HAP composite is 6. In addition, among five common anions studied in this work, the presence of HCO3- and PO43- could considerably affect the fluoride removal by CNT-HPA in aqueous media. Finally, the underlying mechanism for the fluoride removal by CNT-HAP is analyzed, and an anion exchange process is proposed.

Eggshell-Derived Nanohydroxyapatite Adsorbent for Defluoridation of Drinking Water from Bofo of Ethiopia

“…Therefore, this parameter determines the rate of mass transfer from the solution to the surface of the adsorbent, and the data were used to study the kinetic study of batch adsorption. This trend was also reported by other studies on defluoridation processes [11,18]. This is due to the faster saturation of the active sites with time.…”

“…The experimental equilibrium adsorption capacity and the calculated capacity are close to the R 2 value of 0.999 [34]. This indicated that it is unity and the adequate linear fitting of the plots confirmed that the adsorption of fluoride ions using the synthesized hydroxyapatite followed pseudo-second-order kinetics [15,18].…”

“…Recently, several researchers have investigated a range of calciumbased adsorbent materials, of which synthetic hydroxyapatite has been the promising candidate due to its identical chemical composition with bone, nontoxicity, and specifically high fluoride removal capability [11][12][13][14][15][16][17]. Recently, researches indicate that HA has better defluoridation capability and the defluoridation efficiency is greatly size dependent on synthetic hydroxyapatite [13,18,19]. Traditionally, the preparation of synthetic HA uses any of the following methods such as wet precipitation methods, sol-gel technique, hydrothermal technique, or low-temperature synthesis.…”

Carbon-Based Materials for De-Fluoridation of Water: Current Status and Challenges

“…Tang et al investigated the defluoridation of water by using novel hydroxyapatite decorated with carbon nanotube composite (CNT-HAP) [56]. Maximum adsorption capacity using CNT-HAP composite for removal of fluoride was found to be 11.05 mg/g at pH 6.…”

Efficient Colorimetric Fluoride Anion Chemosensors With Varied Colors Based on Simple Aminobenzodifuranone Organic Π-Conjugated Dyes

“…With the rapid development of the chemical industry, F − has come to exist not only in the aqueous environment but also in organic media such as fluoride anion-containing pesticides and waste organic liquor (Clark, 1980). Recognition and detection of fluoride in organic solvent with a simple sensor and minimal instrumental assistance are imperative for practical applications (Yang et al, 2013;Kaur and Choi, 2015;Curnow et al, 2018;Tang et al, 2018;Murfin et al, 2020). Among various F − sensors, fluorescence sensors have been widely investigated due to their multiple advantages .…”