Characterization, kinetic, and isotherm data for Cr (VI) removal from aqueous solution by Populus alba biochar modified by a cationic surfactant

Populus alba is fast and auto- growing tree which profoundly accessible in around the world. The usage of the wastes of this tree would be admirable from environmental and solid waste management point of view. Thus, herein, this data set presents a facile method for providing an adsorbent from wastes of P. alba tree. The prepared adsorbent was modified by the cationic surfactant of (C16H33)N(CH3)3Br and applied to remove Cr (VI) from aqueous solution. The characterization data of the modified adsorbent were analyzed using FTIR and SEM methods. The information regarding kinetics, isotherms, and thermodynamics of chromium ions adsorption were listed. The data implied that the maximum adsorption capacity of adsorbent to uptake Cr (VI) from aqueous solution was obtained 52.63 mg/g. The acquired data indicated that the adsorption of Cr (VI) by the adsorbent prepared from P. alba is an promising technique for treating Cr-bearing wastewaters.


Subject area
Environmental Engineering More specific subject area

Adsorption
Type of data Table, image, figure How data was acquired -The uptake of Cr (VI) by the adsorbent (q e ) was determined based on the subtraction of the initial and final concentration of adsorbate.  The isotherm, kinetic, and thermodynamic data will be informative and useful for predicting and modeling the adsorption capacity and mechanism of chromium removal by the adsorbent from P. alba.
The acquired data will be advantageous for the scientific community wanting to scale up and design an adsorption column with P. alba biochar as medium for the removal of Cr (VI)-containing waters or wastewaters.

Data
The FTIR of the fresh MPAB at wave numbers from 400 to 4000 cm À 1 are given in Fig. 1. The SEM image of prepared adsorbent from Populus alba is also illustrated in Fig. 1. The kinetics, isotherms, and thermodynamic parameters were estimated using models listed in Table 1. The data of isotherms and kinetics for adsorption of chromium ions onto MPAB is presented in Tables 2 and 3. Fig. 2 is depicted the comparison data for Cr (VI) adsorption by the MPAB and PAB.

Materials
All chemical used in this data article such as K 2 Cr 2 O 7 , (C 16 H 33 )N(CH 3 ) 3 Br, HNO 3 , and NaOH was purchased from Merck Co. Ltd. The double distilled water was used for preparing working solutions.

Preparation of Populus alba biochar
The wastes branches of Populus alba tree was gathered from the auto-grown tree beside Symareh River, Iran. Preparation of P. alba biochar was done according to method explained in the literature [4,5]. The sampled wastes branches were first debarked and washed with Symareh River water for Table 1 Isotherm and kinetic and thermodynamic models/equations used in this data article [1][2][3].

Model
Functional form Plotting ln K t vs 1/T q max ¼ maximum adsorption capacity, k L ¼ Langmuir constant, k f and n ¼ Freundlich constants; and k T and b ¼ Temkin constants, k 1 ¼ rate constant of pseudo first order model, k 2 ¼ rate constant of pseudo second order model, q t ¼ adsorbed amount at any time, q e ¼ adsorbed amount at equilibrium, R ¼ universal gas constant, T ¼ absolute temperature (K), ΔG°¼ Gibbs free energy change (kJ/mol), ΔH°¼ enthalpy change (kJ/mol), ΔS°¼ entropy change (kJ/mol K), and K T ¼ thermodynamic constant (mL/g). removing debris and sand and then shipped to a carpentry workshop. In the carpentry workshop the branches of P. alba was cut to achieve 1 cm pieces. After that, by using a Muffle Furnace (350°C) and a residence time of 6 h, the P. alba biochar was provided. The biochar was milled and passed through 25-mesh ASTM-sieve to obtain uniform particles with diameter of 0.707 mm. The uniformed particles i.e., P. alba biochar (PAB) were applied in chromium adsorption experiments.

Modification of PAB by [(C 16 H 33 )N(CH 3 ) 3 Br] surfactant
The PAB modification was performed following the method described in our previous study [6] with a little change. Briefly, about 20 g of PAB was poured into 180 mL contain 0.06 M (C 16 H 33 )N (CH 3 ) 3 Br (surfactant) solution and agitated at 130 rpm for around 10 h. The mixture of PAB-surfactant was then filtered by 0.42-filter papers, and the separated mass was rinsed several times with distilled water to remove unreacted surfactant monomers. The achieved material (adsorbent) was finally fully

. General conditions
All tests were done in a batch mode in a 100-mL flask and stirred at 150 rpm in a shaker-incubator instrument (Fan Azma Co., Iran). The initial pH of the solution was regulated to 6 by addition desired amount of 0.1 M HNO 3 . The initial adsorbent dose and solution temperature for all tests was regulated to 7 g/L and 25°C, respectively. After the sample reached to equilibrium point, the sample was passed through a 0.42 mm-Whatman filter, and the concentration of the residual chromium was determined. The amounts of Cr (VI) adsorbed per gram of MPAB, q e (mg/g), and the adsorption efficiency of MPAB were obtained as follows [7,8]: where Cr in and Cr out (mg/L) are initial and equilibrium concentration of Cr (VI), respectively. M ads (g/L) denote the dry mass of PAB or MPAB in the solution. Duplicate tests were done to ensure the reproducibility of data, and the average measurements are reported herein. Blank tests containing no PAB or MPAB were also prepared.

Isotherms tests
Isotherms analyses were done with Cr (VI) concentrations of 5, 10, 30, 50, 70, and 100 mg/L and contact time of 8 h. The isotherm models of Freundlich, Langmuir, and Temkin was used for isotherm evaluation (see Table 1).

Kinetic tests
Kinetic tests were done using a given initial concentration (50 mg/L) for contact times of 0, 5, 10, 20, 40, 60, and 80 min. The kinetic models of pseudo firstand pseudo second-order were used for kinetic evaluation.

Thermodynamics tests
The thermodynamics of Cr (VI) adsorption by MPAB was performed at solution temperature of 25°C (298 K) and thermodynamics parameters was acquired using an estimated change in ΔG°, ΔH°, and ΔS°as defined in Table 1.

Effect of MPAB and PAB dose on Cr (VI) removal
The adsorption efficiency of MPAB and PAB was compared at conditions of solution temperature of 25°C, initial concentration of 50 mg/L, contact time of 60 min, and pH of 6.

Analytical methods
The fresh MPAB samples were pressed into tablets with KBr powder and then were detected by Fourier transform infrared spectrometer apparatus (Shimadzu 4300, Japan) with the scanning range from 400 to 4000 cm À 1 . The morphological characterization of the fresh MPAB was done by scanning electron microscopy (SEM, Hitachi, SU 70). The measurement of residual Cr (VI) concentration in solutions was carried out by using an atomic absorption spectroscopy (AAnalyst 200 Perkin-Elmer). The solutions pH analyses were performed using a pH meter (METLER TOLEDO FE20).
The correlation coefficients (R 2 ) and standard deviation (SD) of the two measurements was applied to assess the suitability of the kinetic and isotherm models. SD was obtained as follow: where M 1 , M 2 , …, M n are the acquired values of measurements, M is the mean value of measurements, and n is the sample size.