Kinetic and modeling data on phenol removal by Iron-modified Scoria Powder (FSP) from aqueous solutions

Phenol present in industrial effluents is a toxicant matter which causes pollution of environments aqueous. In this work, scoria was modified by iron in order to increasing of adsorbent efficiency and effective removing of phenol. Effects of independent variables including pH, adsorbents dosage, contact time and adsorbate concentration on removing of phenol were studied by response surface methodology (RSM) based on the central composite designs (CCD). The characterization of raw scoria powder (RSP) and Iron-modified Scoria Powder (FSP) was determined via Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM) and Energy-dispersive X-ray spectroscopy (EDS). The obtained data showed modification by iron caused the growth of new crystalline of iron oxide on the surface of FSP. Evaluated data by RSM indicated the all variables especially pH are effective in removing of phenol (P-value < 0.001) and optimum condition was obtained at pH = 5, phenol concentration = 50 mg/l, adsorbent dosage = 1 g/l and contact time = 100 min to the value of 94.99% with desirability of 0.939. Results revealed that data were fitted by Langmuir isotherm (R2 = 0.9938) and pseudo second order kinetic (R2 = 0.9976). It was found that iron causes increasing the site active of scoria and let to significant removal of phenol.

the value of 94.99% with desirability of 0.939. Results revealed that data were fitted by Langmuir isotherm (R 2 ¼ 0.9938) and pseudo second order kinetic (R 2 ¼ 0.9976). It was found that iron causes increasing the site active of scoria and let to significant removal of phenol

Value of the data
The obtained data of this study showed that Iron modification effect on adsorbent led to increasing of equilibrium sorption capacity for removal of phenol.
Due to cheap and high availability of this type of adsorbent in Iran, the efficiency of it can be improved by making these simple modifications and so the application of it in water and wastewater treatment will be increased.
The obtained data of present study can be used for design and development of future similar studies.
Because in this study, the optimal conditions for the removal of phenol by FSP are determined. Therefore, the range of future study variables can be determined based on the optimal conditions of this study.
The raw data of this study was analyzed using the RSM method. Therefore, the results related to the optimization conditions and the determination of the effect of each parameter will be very understandable for other researchers.

Data
The maximum efficiency of for phenol removal was obtained at pH ¼ 3, phenol concentration ¼ 50 mg/l, adsorbent dosage ¼ 1 g/l and contact time ¼ 100 min (Table 1). Results demonstrated coefficient (R 2 ) and R 2 -adj value are 0.978 and 0.975 for phenol removal that suggested proper correlations between the response and variables ( Tables 2 and 3). The optimum condition was obtained for pH ¼ 5, phenol concentration ¼ 50 mg/l, adsorbent dosage ¼ 1 g/l and contact time ¼ 100 min to the value of 94.99% with desirability of 0.939 (Table 4). The percent of error between mathematical design and experimental study is 3.81% that suggested the close value of both actual and predicted data ( Table 5). Results revealed that data were fitted by Langmuir isotherm (R 2 ¼ 0.9938) and obeyed the pseudo second order kinetic (R 2 ¼ 0.9976) ( Tables 6 and 7). Fig. 1 showed the XRD patterns, Fourier transform infrared spectroscopy (FTIR), SEM images and EDS analysis of RSP and FSP. Trend of phenol removal efficiency with respect to scoria dosage, contact time, pH, and phenol concentration was showed in Fig. 2. The response surface plots for phenol removal efficiency with respect to scoria dosage, pH, phenol concentration, and contact time were showed in Fig. 3. In addition, Normal probability plot of residual, predicted vs. actual values plot, and plot of residual vs. predicted response were showed by Fig. 4.

Pumice preparation and its modification using iron
Early preparations of raw scoria powder (RSP) were performed according to Moradi et al. [15] study [2]. The raw scoria powder (RSP) was kept in Fe(NO 3 ) 3.9H 2 O (0.5 m) solution at pH ¼ 12 and

Characteristics of SP and FSP
The functional groups of adsorbents were determined by Fourier transform infrared spectroscopy (FTIR) (WQF-510 Model), X-ray diffraction (XRD) model Shimadzu XRD-6000 were used for study of chemical characteristics and surface morphology of adsorbent. Scanning electron microscope (SEM) model Philips XL30 was used to evaluation the sample's surface topography and composition. Energy Dispersive X-Ray Spectroscopy (EDS) model EM-30AX Plus was applied for determination of chemical characterization and elemental analysis of adsorbents [5,6]. Table 5 Confirmation between optimized phenol removals calculated from mathematical design and experimental study. Error ð%Þ ¼ Actual value À predicted value Actual value Â 100 3.81% Table 6 Isotherm equation parameters for phenol adsorption on FSP.

Experimental design by response surface methodology (RSM)
Design of experiments (DOE) software was used to design of experiments (the required sample size). Table 8 illustrated-the experimental range and level of the independent variables. The RSM based on central composite design (CCD) as statistical tool was used to minimization of experiments  number. On the other hand, optimum condition was determined through consideration of relationship between the measured responses (phenol removal) and number of independent variables [7-10].

The study of adsorption isotherms
Langmuir and Freundlich isotherms are the main mathematical equations for description of reaction between adsorbents adsorbate. The equilibrium adsorption capacity by adsorbent was   calculated as follows [13][14][15][16]: where, q e (mg/g) is the equilibrium adsorption capacity C 0 and C e are the initial and equilibrium concentration of phenol (mg/l) V is the volume of solution (l) M is the weight of adsorbent (g).

Langmuir isotherm
The Langmuir isotherm is used to describe the monolayer adsorption of adsorbate on the adsorbent surface. This isotherm assumed the uniform number of adsorption sites. The nonlinear equation of Langmuir was depicted (Eq. (2)). Several equations related to Langmuir isotherm were derived from nonlinear equation (Eqs. (3)-(5)) [15][16][17].
1 q e ¼ 1 bq m C e þ 1 q m ð4Þ q e C e ¼ bq m À bq e ð5Þ