In-vitro synthesis of marble apatite as a novel adsorbent for removal of fluoride ions from ground water: An ultrasonic approach

Abstract

Marble waste powder consisting of calcium and magnesium compounds was used to synthesize a novel biocompatible product, marble apatite (MA) primarily hydroxyapatite (Hap) for applications in defluoridation of drinking water. Synthesis of marble apatite was carried out by using calcium compounds (mixture of hydroxide and nitrate) extracted from marble waste powder which was treated with potassium dihydrogen phosphate at 80°C under alkaline conditions using conventional precipitation method (CM) and ultrasonication method (USM). Qualitative analysis of synthesized marble apatite from both the methods was carried out using FTIR, phase analysis by XRD and microstructure analysis by SEM and TEM. When ultrasonication (USM) method was used, the yield of marble apatite was improved from 67.5% to 78.4%, with reduction in crystallite size (58.46nm), lesser agglomeration and comparatively well-defined spherical morphology compared to the CM method. Studies also include estimation of the defluoridation capacity of MA as an adsorbent for drinking water treatment and effects of process parameters such as pH, contact time, initial fluoride concentration, dosage and presence of other co-ions on fluoride removal capacity. The results showed that the experimental adsorption capacity of the marble apatite synthesized using USM method was significantly higher (1.826mg/g) than marble apatite synthesized using conventional method (0.96mg/g) at pH 7 with a contact time of 90min. The mechanism of adsorption was studied, and it was observed that Langmuir isotherm model fitted best to the experimental data, while the kinetic studies revealed that the process followed pseudo-second order model. This novel compound, marble apatite synthesized from marble waste powder is found to be promising for defluoridation of drinking water and will help in alleviating the problems of fluorosis as well as reduce the problems of disposal of marble waste.

Synthesis and Characterization of Mg–Hydroxyapatite and Its β-Cyclodextrin Composite as Enhanced Bio-Carrier of 5-Fluorouracil Drug; Equilibrium and Release Kinetics

“…The essential functional groups of hydroxyapatite were identified clearly from the spectrum of Mg·HPA. This involved the essential phosphorus-bearing chemical groups such as asymmetric P–O bonds of the PO 4 3– group (1039.4 cm –1 ), HPO 4 2– groups (871.2 cm –1 ), symmetric (570.8 cm –1 ) and asymmetric (603.3 cm –1 ) O–P–O bonds of the PO 4 3– groups, in addition to the hydroxyl groups (O–H) (3434.4 cm –1 ) (Figure A). ,,, The corresponding bands of N–H bonds (1390.6 cm –1 ) and CO 3 2– groups (2376.19 cm –1 ) were assigned to the trapped ions during the dissolution of the precursor by nitric acid and the evolved CO 2 gas from the dissolved carbonate impurities, respectively (Figure A). ,, For the free β-cyclodextrin, its spectrum reflects notably the characteristic groups of the polymeric polysaccharide structures such as O–H stretching vibration (3376 cm –1 ), −CH/CH 2 asymmetrical stretching (2926 cm –1 ), stretching mode of C–C and/or H–O–H deformation within the β-CD cavity (1666.2 cm –1 ), CO stretching and/or OH bending (1636 cm –1 ), C–OH bending vibration (1482 cm –1 ), symmetrical C–O–C (1200 cm –1 ), asymmetrical C–O–C stretching (1158 cm –1 ), and symmetrical C–O stretching (1000 cm –1 ) (Figure B). , …”

“…3− group (1039.4 cm −1 ), HPO 4 2− groups (871.2 cm −1 ), symmetric (570.8 cm −1 ) and asymmetric (603.3 cm −1 ) O−P− O bonds of the PO 4 3− groups, in addition to the hydroxyl groups (O−H) (3434.4 cm −1 ) (Figure 3A). 26,32,43,44 The corresponding bands of N−H bonds (1390.6 cm −1 ) and CO 3 2− groups (2376.19 cm −1 ) were assigned to the trapped ions during the dissolution of the precursor by nitric acid and the evolved CO 2 gas from the dissolved carbonate impurities, respectively (Figure 3A). 41,45,46 For the free β-cyclodextrin, its spectrum reflects notably the characteristic groups of the polymeric polysaccharide structures such as O−H stretching vibration (3376 cm 3B).…”

Optimization of defluoridation using Ficus benghalensis leaf biosorbent through Taguchi's method

“…In the above‐mentioned Equation , q c (mg/g) is the equilibrium capacity calculated from the model, q e (mg/g) is the experimental equilibrium capacity, and N is the number of measurements. Lower chi‐square (χ 2 ) value indicates better isotherm fitting (Mehta, Mondal, Saharan, & George, ). It is clear that Langmuir adsorption isotherm has given a better fit with lower χ 2 value and higher R 2 value.…”

“…Higher values of correlation coefficient and lower values of SSE imply to best‐fitting kinetic model (Mehta et al., ). It has been noticed that, among the various kinetic models, a pseudo‐second‐order kinetic model with the highest correlation coefficient ( R 2 = 0.998) and lowest SSE of 0.121 suggests that the adsorption of fluoride onto Ficus benghalensis leaves developed biosorbent follows pseudo‐second‐order sorption kinetics (Figure ).…”

“…Before AŌer Research Article isotherm fitting (Mehta, Mondal, Saharan, & George, 2018). It is clear that Langmuir adsorption isotherm has given a better fit with lower χ 2 value and higher R 2 value.…”