Fluoride ion adsorption onto palm stone: Optimization through response surface methodology, isotherm, and adsorbent characteristics data

In some part of the world, groundwater source can become unsafe for drinking due to the high concentration of fluoride ions [1]. The low cost and facile-produced adsorbent like palm stone could effectively removed fluoride ions through adsorption process. In this dataset, the influence of fluoride ion concentration, solution pH, adsorbent dosage, and contact time on fluoride ion adsorption by palm stones was tested by central composite design (CCD) under response surface methodology (RSM). The data stone carbonized adsorbent was prepared by a simple and facile method at relatively low temperature of 250 °C during 3 h. The adsorbent had the main functional groups of O–H, –OH, Si–H, C=O, N=O, C–C, C–OR, C–H, and C–Br on its surface. At the optimized conditions obtained by RSM, about 84.78% of fluoride ion was removed using the adsorbent. The Langmuir isotherm was suitable for correlation of equilibrium data (maximum adsorption capacity= 3.95 mg/g). Overall, the data offer a facile adsorbent to water and wastewater works which face to high level of fluoride water/ wastewater content.


a b s t r a c t
In some part of the world, groundwater source can become unsafe for drinking due to the high concentration of fluoride ions [1]. The low cost and facile-produced adsorbent like palm stone could effectively removed fluoride ions through adsorption process. In this dataset, the influence of fluoride ion concentration, solution pH, adsorbent dosage, and contact time on fluoride ion adsorption by palm stones was tested by central composite design (CCD) under response surface methodology (RSM). The data stone carbonized adsorbent was prepared by a simple and facile method at relatively low temperature of 250°C during 3 h. The adsorbent had the main functional groups of O-H, -OH, Si-H, C¼ O, N ¼ O, C-C, C-OR, C-H, and C-Br on its surface. At the optimized conditions obtained by RSM, about 84.78% of fluoride ion was removed using the adsorbent. The Langmuir isotherm was suitable for correlation of equilibrium data (maximum adsorption capacity ¼ 3.95 mg/g). Overall, the data offer a facile adsorbent to water and wastewater works which face to high level of fluoride water/ wastewater content. &

Subject area
Chemical engineering More specific subject area

Environmental engineering
Type of data

Value of the data
This data offer a simple method for preparation of adsorbent from palm stones. This data article presents a user friendly-statistical method (RSM) to optimize fluoride ion removal from aqueous solution using adsorption process.
The dataset will be useful for fluoride ion removal from waters and wastewaters. Table 1 in this data article contains data for independent variables and their coded levels to central composite design. Normal probability plot and residual versus fit plot for fluoride adsorption efficiency are depicted in Fig. 1. Central composite design 3-D surface plots which showing effect of various parameters on fluoride removal efficiency with the adsorbent are presented in Fig. 2. The data for model summary statistics and ANOVA for central composite design are listed in Tables 2 and 3. The FTIR spectra for fresh and used adsorbent in the F adsorption are also depicted in Fig. 3. The surface morphology (SEM) of the adsorbent was presented in Fig. 4. The XRD analysis was used to explore fresh and used adsorbent structure; the results of this analysis are shown in Fig. 5. The pHzpc factor which is important for explanation the pH effect on the removal of pollutant [1,2] is seen in Fig. 6. Table 4 shows isotherm models data used in this article.

Adsorbent preparation
The palm stones used in this study were prepared from a local agricultural palm field in Bushehr province, Iran. All palm trees were belonged to Phoenix dactylifera species. After separating the stones from dates, they were washed three times by distilled water and dried at 105°C for 3 h. Dried stones were milled, grinded and sieved in the size ranged from 1 to 2 mm [5,6]. These sieved stones were carbonized in the oven in 250°C for 3 h, and then cooled and stored in a plastic bag under the desiccators and used for the adsorption tests. Thus, this adsorbent could easily provide with a simple method, however, the production of palm date wastes (the base material for the adsorbent) is time depended.

Adsorption tests
Response surface methodology may be summarized as a collection of statistical tools and techniques for constructing and exploring an approximate functional relationship between a response variable and a set of design variables. This experimental method has high finding efficiency for the operating conditions at least of cost, while give good knowledge about variable interaction [7][8][9]. The effect of four parameters was evaluated by using Central Composite Design (CCD). Each factor in the experimental design was studied at five different levels as shown in Table 1. Experiments were planned in 2 4 trials plus 4 centre points, and 8 axial points. Thus, twenty eight experiments were conducted at the room temperature (25 71°C). The Design Expert software (version 7.0, Stat-Ease) was used for data analyzing.
The working fluoride solutions were prepared via diluting the stock solution 1000 mg/L of sodium fluoride (Germany, Merck Co.), in Erlenmeyer flasks to obtain concentrations (2,5,8,11, and 14 mg/L). The flasks were agitated at 120 rpm in different contact times, adsorbent dosages and pH in order to reach the adsorption equilibrium conditions. After the completion the contact time, the solution was  The experiments were carried out in batch mode. The following equation was used for calculation of the adsorption percentage [10][11][12]: Where: C i and C are the initial and final fluoride concentration (mg/L), respectively. We noted that the optimized F removal value by the Design Expert software and confirmation test were achieved 84.78 and 81.55%, respectively. Further, by using regression analysis on the data, the    6. Variation of pH (pH initial -pH final ) versus initial pH for determining the adsorbent pH zpc .

Measurements
The residual fluoride concentration was measured by using a UV-Vis spectrophotometer (HACH, USA, model CAM Spec M501) with a standard SPADNS reagent (Germany, Merck Co.) at 570 nm according to the Standard Methods of Examination of Water and Wastewater [13]. The solution pH was also adjusted using 0.1 N HCl or NaOH solutions and measured by a digital pH meter (827 pH labs Metrohm AG, Herisau, Switzerland). Fourier transform infrared spectroscopy (FTIR) spectrum of the fresh and used adsorbent samples was obtained using VERTEX 70/70 v FT-IR spectrometers. The FTIR data showed that the functional groups of O-H, -OH, Si-H, C¼ O, N¼O, C-C, C-OR, C-H, and C-Br are probably played role in the adsorption process [14][15][16]. The morphology of the adsorbent particles was performed by scanning electron microscopy ( JSM-5510, Jeol Ltd., Tokyo, Japan) under an acceleration voltage of 30 kV. The XRD pattern of the fresh and used adsorbent was recorded by an automated X-ray diffracto-meter (Philips X'Pert, Netherlands) at the condition explained in the literature [17,18]. The pHzpc factor was obtained using method specified by published studies [19][20][21], briefly; in the batch equilibrium method we used the ratio of 1:250 adsorbent to distilled water in 0.01 M NaCl solution, as an inert electrolyte. Table 4 Isotherm models used in this dataset [3,4]. Langmuir (q e ¼ Q m KL Ce 1 þ KL Ce ): q e ¼ the amount of adsorbed fluoride per gram of adsorbent at equilibrium (mg/g), Ce ¼ equilibrium fluoride concentration (mg/L), Q m ¼ maximum adsorption capacity (mg/g), K L ¼ Langmuir constant (L/mg) Freundlich (q e ¼ K f Ce 1=n ): K f ¼ Freundlich constant, n ¼ Freundlich constant (mg/g(L/mg) 1/n )