Synthesis of hydroxyapatite nanorods for application in water defluoridation and optimization of process variables: Advantage of ultrasonication with precipitation method over conventional method

Abstract

This research work presents the synthesis of hydroxyapatite (Hap) nanorods for defluoridation of drinking water by using both conventional (CM) and ultrasonication with precipitation (USPM) methods. Calcium nitrate was reacted with potassium phosphate in presence of ammonia for controlled pH to synthesize Hap nanorods, which was characterized using FTIR, XRD, SEM, TG-DTA, and TEM/EDS for determining its phase composition, structural and thermal decomposition behavior. When USPM method was used for synthesis, the yield of the Hap nanorods was improved from 83.24±1.0% to 90.2±1.0%, and complete phase transformation occurred with formation of elongated Hap nanorods. Effects of process parameters such as solution pH, contact time and adsorbent dose were studied through response surface methodology (RSM). A simple quadratic model was developed using Central Composite Design (CCD) and optimum parameters for fluoride adsorption process were determined to be pH 7, contact time 3h and adsorbent dose 7g/L for maximum removal capacity. Fluoride removal efficiency was predicted to be 93.64% which was very close to the experimental value obtained at 92.86% using ultrasonically prepared Hap. Fluoride adsorption isotherms fitted the Freundlich isotherm with an adsorption capacity of 1.49mg/g, while the kinetic studies revealed that the process followed pseudo-second order model. The treated water quality parameters such as residual fluoride, calcium leached, total hardness and alkalinity was investigated, and it was observed that all these parameters were within the permissible limits as per WHO and BIS standards.

Hydrothermal synthesis of hydroxyapatite powders using Response Surface Methodology (RSM)

“…Y is the number of experiments, x is the number of variables, and Cx is the number of center points repetitions [15]. In this study, the number of variables is 3, and the number of center…”

Development and characterisation of a novel krill oil nanostructured lipid carrier based on 1,3‐glycerol distearate

“…Ultrasonication is a very efficient technology for preparing nanoparticles. Ultrasound induces cavitation which can generate excess energy that breaks the large oil droplets into nano‐droplets (Mehta et al ., 2017). Ultrasonication is simple to operate and environmentally friendly, does not require organic solvents and is very effective in breaking up aggregates and reducing particle size and polydispersity of nanoparticles (Tang et al ., 2003; Yu et al ., 2020).…”

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

“…However, challenges on obtaining high-quality bone char materials and hygiene-related issues limited their usage on a large scale worldwide. 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].…”

“…Among them, the wet chemical precipitation method has shown to be advantageous over other methods due to its costeffective simple procedure [12]. In addition, the main advantage of this method is that it is eco-friendly and water is the only by-product.…”

“…In addition, the main advantage of this method is that it is eco-friendly and water is the only by-product. In general, HA can be synthesized either from biowastes like coral and seashell or from calcium and phosphate source precursors [12,20,21]. Eggshells are a naturally occurring calcium source.…”