Experimental and computational data set on adsorption of Cr (VI) from water using an activated carbon

Chromium (Cr) is a widely used metal in metallurgical and chemical industries, whose waste contaminates the surface and groundwater. Cr (VI) is toxic and produces carcinogenic effects owing to its high mobility in water and soil. In this work, computational and experimental studies from the adsorption of Cr(VI) from aqueous solutions on teak wood residues activated with ZnCl2 (AT) are presented. Full interpretation of data can be found in DOI:10.1016/j.jece.2020.103702 [1]. Experimental data were adjusted to Langmuir, Freundlich and Temkin isothermal models and the nonlinear and linear forms of the Pseudo-first and Pseudo-second order kinetic models. Computational data allow to understand the adsorption process of Cr(VI) on carbonaceous materials.


Data description
Data present in this work correspond to the kinetics adsorption process of Cr(VI) on activated carbon obtained from chemical activation (ZnCl 2 ) of teakwood sawdust [1]. Fig. 1 shows the experimental setup where all adsorption experiments were carried out. Fig. 2 shows a comparison between the removal percentage of Cr(VI) using activated and no-activated teakwood sawdust. Fig. 3 presents the data adjustment for the Langmuir [2], Freundlich [3] and Temkin [4] isothermal models. Table 1 and Fig. 4 show the parameters found by nonlinear and linear forms from the Pseudo-first [5] and Pseudosecond order kinetic models [6]. Finally, Table 2 shows the Cartesian coordinates for the most stable configurations during the adsorption process of Cr 3þ and HCrO 4 À on carbonaceous structures obtaining by Gaussian 09 program. The raw data of all Figures are shared as supplementary material.
Specifications Table   Subject Environmental Value of the Data Computational data is useful to describe the interaction between Cr 3þ and HCrO 4 À on carbonaceous surfaces, and thus are essential to predict the better properties of the adsorbents (functional groups on surfaces) during experimental design of materials. Data of isotherms and kinetics is informative to predict and model the adsorption of Cr (VI) from water. They are also useful for the academic community to complete research on anion adsorption. Adsorption isotherms, kinetics and computational data allow to predict several important issues (adsorption capacity, surface properties and adsorption mechanism) which can advance elaboration of renewable, efficient, novel and low cost adsorbent materials for removal of Cr (VI) from water; with good potential application in the water treatment industry. Data in this study have significance for improving water quality with the removal of Cr (VI) and others heavy metal cations using a low-cost and selective adsorbent

Table 1
Parameters of pseudo-first order and pseudo second-order models.
Pseudo First-Order Pseudo Second-Order k 1 (min À1 ) x 10 À2 q e (mg g À1 ) R 2 k 2 (g mg À1 min À1 ) x 10 À2 q e (mg g À1 ) R 2     Fig. 1 shows the reaction systems used during the adsorption experiments of Cr (VI) on activated teak (AT). 500 mL of each solution, at pH 2 and 0.5 g of AT, was brought in contact with a three-layer glass reactor placed in a constant-temperature bath at 25 C. The reactor was stirred at 200 rpm with a turbine propeller operated by a rotor. Samples were taken at 30, 60, 120, 180, 300, 420, 1380, 1740, 2640, 3120, 4080, and 4320 min, until reaching equilibrium. The Cr (VI) concentration of each sample was measured using a Shimadzu UV 1900 UV/VIS spectrophotometer at 542-nm wavelength. Fig. 2 shows that the activation process of teakwood sawdust with ZnCl 2 improves the adsorption of Cr (VI). The removal rate increased for AT 8 times respect to T. Fig. 3 shows the linear fit of the experimental data to the Langmuir, Freundlich and Temkin isotherm models. Equilibrium experiments were carried out using Cr (VI) solutions at different initial concentrations (35, 50, 100, 170, 250 and 290 mg L À1 ), adsorbent dose of 0.5 g, temperature of 25 C, stirring speed of 200 rpm and adjusted the solution pH at 2 with an optimal contact time of 4500 min. The experimental data were treated mathematically using the Excel 2013 software to calculate the isotherm parameters, as follows: when plotting C e /q e based on C e , K L and q, two parameters (K L and q max ) can be obtained by using the slope and the intercept (Langmuir constants). When plotting Log q e against Log C e , K F and 1/n (Freundlich constants) are estimated. By plotting q e against Ln C e , K T and b (Temkin constants) are calculated. Table 1 y Fig. 4 present the obtained parameters from the experimental data adjusted to nolineal and lineal kinetics models (Pseudo-first and Pseudo second order). The experimental data were treated mathematically using the Excel 2013 software. Constants from lineal form were calculated as follows: for the PFO model, a Log (q e -q t ) graph was developed as a function of time (t), from which the values of q e and k 1 were calculated. In addition, for the PSO model, q e and k 2 were calculated by plotting t/q t against t. To calculate nonlinear shape constants of the kinetic models, the least squares model derived from the RosenbrockeNewton optimization algorithm was applied through the Statistical software.

Experimental adsorption
C A0 (mg L À1 ) is the initial Cr (VI) concentration of the solution; k 1 (min À1 ) is the pseudo first-order rate constant; q e is the amounts of Cr (VI) adsorbed in the equilibrium (mg g À1 ); k 2 (g mg À1 min À1 ) is the pseudo second-order rate constant; R 2 is the correlation coefficient. Table 2 shows the Cartesian coordinates for the most stable configurations during the adsorption process of Cr 3þ and HCrO 4 À on carbonaceous structures.