^{1}

^{*}

^{2}

The adsorption behavior of eosin yellow (EY) from aqueous solution onto
γ-Al
_{2}O
_{3} nanoparticles in batch technique was studied.
γ-Al
_{2}O
_{3} NPs was prepared and characterized by SEM, TEM, XRD and FTIR analysis. The effect of pH, dosage of adsorbent, contact time, temperature, and the initial concentration of dye was investigated. The maximum amount of dye removal found about 99.36% at pH4, the adsorption dose 1g/L, with the initial dye concentration of 100 mg/L, and the temperature of 25°C,
with contact time 120
min. The adsorption behavior of the eosin yellow dye is applicable to Langmuir isotherm model, with the maximum sorption capacity of 47.78 mg/g of
γ-Al
_{2}O
_{3}. The kinetic data also described by the pseudo-second-order model with a correlation coefficient (0.9999), and the mechanism of the process showed a multi-linear steps and the intra-particle diffusion was not only rate controlling step. The adsorption process was endothermic with positive enthalpy of 121.8 kJ/mol, and showed spontaneous process with a mean free energy -5.19 kJ/mol, and increase randomness, 369.77 J/mol. k, at the adsorbent solution interface. The adsorption process was chemisorption in nature The activation energy estimated from Arrhenius and modified Arrhenius is 40.9 kJ/mol, 106.37 kJ/mol respectively. The sticking probability of EY onto Al
_{2}O
_{3} NPs very high estimated from the value of S* < 1, (4.82E-19).

The dyes appear in the environment in the form of wastewater colored of many manu- facturing industries, such as paper, textile, leather, cosmetic, and printing [

The most efficiency in recent years to removal of dyes pollutants is adsorption technique [

The most active area of research in recent year is the nanotechnology materials, the scale of nonmaterial from 1 to 100 nm, increased in application of nanoparticles due to large surface area, high thermal stability, and wide applicability in many areas, such as, chemistry energy, electronics, catalysis, and photochemistry [_{2}O_{3}) powder, First, γ-Al_{2}O_{3} is more stable after calcination at high temperature caused growth the powder, and make it difficult to get nano scale particles, second, during the dehydration process in the wet chemistry method the particles tend to aggregate. To solve this problem, it is needed to prepare the nano size of γ-Al2O3 by sol-gel technique. The advantage of this method is produced the ultrafine powder and size distribution of particles in a relatively short time at a very low temperature. The Eosin yellow dye is widely used in the detection of bacterial species as grame staining type due to the red color and strong absorption by red blood cells. The EY is highly toxic and affects on eye and skin irritation, damage to kidneys, liver and lung by ingestion and inhalation, thus very important to remove dye from wastewater to avoid the different damage.

In this study the efficiency of aluminum oxide NPs prepared by the sol-gel method for removal of eosin yellow was investigated by several parameters such as pH, time removal, dose adsorbent effects, Langmuir, Freundlich, Tempkin, Elovich and Dubinin-Radushkevich modelling isotherm, kinetic equations pseudo-first-order, pseudo- second-order, Elovich, and Bangham’s models and Thermodynamic parameters was investigated by Arrhenius, modified Arrhenius and Van’t Hoff equations. The experiment was carried out in batch mode at different temperatures.

Generic names of adsorbent are Eosin yellow, also known as Acid red 87, C.I. 45,380, Bromofluorescein; Sodium eosine, with Molecular Formula C_{20}H_{6}Br_{4}Na_{2}O_{5}, and molecular weight equal 691.58 g/mol

The concentration of dye in solution was measured by a Shimadzu spectrophotometer (UV-1800, ENG 240 V, soft Japan) at maximum wavelength 516 nm.

Aluminum oxide NPs was synthesized through a sol-gel method at lower temperature with a simple equipment setup. The Aluminum oxide and Urea were dissolved in a certain amount of distilled water then Formaldehyde was added to the mixture stirred for 30 min at 200 RPM to complete dissolve at room temperature, then add ethylene glycol and NH_{4}OH drop-wise to the mixture the pH about 8 - 9. Allow the mixture under vigorous stirring (500 RPM) for 2 h at 70˚C to obtain a gel form, dried the sample overnight and calcination at 500˚C for 3 hrs. The pH was adjusted by 0.1 NHCl and NaOH.

The X-ray diffractogram of the sample was measured by using Shimadzu X-ray diffractometer (XRD-6000)-Japan with a scanning speed of 2θ = 2.5˚ min^{−1}. FTIR spectroscopy was taken to confirm surface of γ-Al_{2}O_{3} nanoparticles and examine the structure of adsorbed EY. The FT-IR spectra were recorded by (FT-IR-6300 model), the absorption spectra at resolution 4 cm^{−1} over the range (400 - 4000 cm^{−1}). The scanning electron microscope (SEM) micrographs were measured using a model of JEOL-JSM-5500 LV (Japan). Transmission Electron Microscope (TEM) Measured technique using by a JEM-100 CX electron microscope at an accelerating voltage of 200 KV. The sample was put on the carbon foil with a micro grid and observed with minimum electron irradiation to prevent damage to sample structure.

Using the batch process in order to evaluate the effect of parameters affects on the amount of dye adsorbed at equilibrium, q_{e} (mg/g), such as the effect of initial concentration of dye, contact time, pH and temperature. To determine the residual concentration of the dye sample solution was withdrawn at certain time by using UV-V is spectrophotometer at λ_{max} of 516 nm. Adsorption equilibrium calculated by equation:

The percentage of adsorption was calculated by the following equation.

where C_{o}, C_{e}, and C_{t} (mg/L) are the concentration of adsorbate at initial, equilibrium and at interval time respectively.

Adsorption isotherms, used for presentation of the amount of solute adsorbed per unit of adsorbent, as a function of equilibrium concentration in bulk solution at constant temperature five isotherm models have been tested, namely, Langmuir [^{2} values.

Kinetics is important for adsorption studies because it can predict the rate of pollutant removal from aqueous solutions and understanding the mechanism of sorption reactions for the data. In order to investigate the mechanism of dye sorption onto Al_{2}O_{3} nanoparticles, pseudo-first-order [_{2}O_{3} NPs. Withdrawn of dye samples from the flask at regular time intervals, centrifuged and the concentration of dye in the supernatant solution was analyzed. A majority of adsorption from aqueous solutions was completed within 120 min.

In order to investigate the type of adsorption process onto Al_{2}O_{3} nanoparticles, Arrhenius and Van’t Hoff equations was adopted, and the probability sticking S^{*} is a function of the adsorbate/adsorbent system under investigation. The value of activation energy confirmed that the chemisorption or physicsorption process, and the experimental was carried out in batch mode like procedure in above section.

FTIR is one of the powerful technique to explore the solid-liquid interface. The spectra of γ-Al_{2}O_{3} before and after adsorption of EY can be shown in ^{−1}. The bands appeared in the range between 500 and 1000 cm^{−1}, corresponding to the vibrational frequencies of co-ordinate O-Al-O characterized to nano amorphous γ-Al_{2}O_{3} [^{−1} contributed to octahedral and tetrahedral environments. The peak between 1070 and 612 cm^{−1} correspond to the Al-O vibration [^{−1}, Furthermore, bands at 1338, 1250, 1066 cm^{−1} due to changes in the surface structure of Al particles when adsorbent attached to it. A small band is observed at 2900 cm^{−1} for the water molecule, the bands appearing at 1352, and 1407 cm^{−1} are typical for gamma-alumina. The Al-O vibration is observed at 1371 and 1363 cm^{−1}. Bonded hydroxyl groups, isolated OH groups, and stretching vibrations of adsorbed water molecules appeared bands at 3471, and 3423 cm^{−1}. After adsorbing eosin Y, obvious changes are observed at the frequency level of 1550 - 1650 cm^{−1} and 3415 cm^{−1} from spectrum, which indicates that the carboxylic group of the EY participate in the adsorption process. The additional peaks appeared in the region of 1100 - 1700 cm^{−1} represent the presence of physisorbed water [_{2}O_{3} irregular shapes with a less agglomeration, high dispersion was

observed and the particles mostly in nano size. The produced nano-sized confirmed by TEM.

The X-ray diffraction pattern of sample calcined at 500˚C is shown in

c

The pH of the dye solution (100 mL of 100 mg/L initial concentration) was adjusted to the range of 2 - 6, using either sodium hydroxide or hydrochloride acid. The adsorption of eosin Y for γ-Al_{2}O_{3} NPs depends on pH. _{2}O_{3} NPs increases drastically when pH increased from 2 to 4 and then fluctuated after pH 5, change in the nature and structure of both substances which subsequently control the type and strength of attractive or repulsive forces. In the acidic solution, the adsorption of anionic dye eosin Y process by γ-Al_{2}O_{3} NPs is an electrostatic interaction, where the two species of aluminum hydroxide two species of positive charge

pH are highly present in this medium and reaches the positive charge which interacts with the anionic groups of the dye [^{−} ions present and compete with the anionic bromide groups of EY for the adsorption sites of γ-Al_{2}O_{3} NPs, thus the available adsorption sites for anionic EY decrease [

The Langmuir isotherm, which given by a non-linear form and the linear form Equation (4) and Equation (5).

Equilibrium parameter R_{L} can be calculated from below equation by Webber and Chakkravorti [

where, C_{o} donated to the adsorbate initial concentration (mg/L), Langmuir constant K_{L} A plot of C_{e}/q_{e} against C_{e} gives a straight line with slope of 1/Q_{o} and intercepts 1/Q_{o}K_{L} and with highest correlation coefficient R^{2} = 0.9999 as shown in _{max} value is (47.78 mg∙g^{−1}) and K_{L} equal (0.1293 L∙mg^{−1}). The lower R_{L} values for all different concentrations (75 - 200 mg/l) of EY between (0.093 - 0.037) reflects that adsorption is more favorable and deduce that a monolayer formation is taking place during the adsorption of EY over the surface of Al_{2}O_{3} NPs.

The Dubinin-Radushkevich isotherm used to evaluate the porosity properties of the adsorbent and the energy of adsorption process. _{e} versus

where R, is the gas constant (8.314 J/mol∙K), T absolute temperature (K) and C_{e} repre- sent to adsorbate equilibrium concentration (mg/L).

The value of E_{D}_{-R}, _{D} equal 13.7 kJ/mol suggested that ion exchange is the major mechanism responsible for the adsorption process or chemical adsorption of dye molecule.

The Freundlich isotherm applicable for adsorption process, the value n, K_{F} and R^{2} constants shown in ^{2} value is lower than the Langmuir value.

To determine the heat of adsorption of adsorbate molecules with the extent of coverage over the surface of NPs applied Tempkin isotherm model at room temperature repre- sented by the Equation (7). From

of adsorption B (J/mol) Equation (8) can be evaluated from the slope and intercept of linear line when plotting q_{e} versus lnC_{e}.

where,

R the gas constant (8.314 J/mol∙K), and T is the temperature, the positive value of constant B is 25.45 J/mol indicates an endothermic process. The fit to experimental data (R^{2} = 0.9868) and A = 565.13. The values of the Tempkin constants (A and B) and the correlation coefﬁcient are listed in ^{2} value is higher than the Elovich value, but lower than the Freundlich Langmuir value.

The adsorption sites increased with time and form multilayer, Elovich model describes the adsorption process by the equation:

where K_{E} is the Elovich equilibrium constant (Lmg^{−1}) and q_{m} is the Elovich maximum adsorption capacity (mgm^{−1}) can be calculated from the slopes and the intercepts of the linear plot between ln(q_{e}/C_{e}) versus q_{e} give a straight line with the correlation coefficient 0.9834 and K_{E} 1700 (L/mg). By comparison of the experimental points with the present isotherms, results show that isotherms gave good agreement with the experimental data ^{2}) for Langmuir isotherm close to unity (0.9999). The correlation coefficient of different adsorption models is lower than other applicable models and the order is Langmuir 0.9999 > D-R model 0.9925 > Freundlich 0.9871 > Tempkin 0.9868 > Elovich 0.9834.

The pseudo-first-order kinetic model (the Lagergren kinetic equation) is given by:

Model | Parameter | |
---|---|---|

Langmuir | q_{m} (mg/g) | 47.78 |

K_{L} (L∙mg^{−1}) | 0.1294 | |

R_{L} | 0.06283 | |

R^{2} | 0.9999 | |

D-R | q_{D} (mg/g) | 47.31 |

B | 0.0026 | |

E (KJ/mol^{2}) | 13.47 | |

R^{2} | 0.9925 | |

Freundlich | n | 10.10 |

KF [(mg/g) (mg/L)^{n}] | 27.939 | |

R^{2} | 0.9871 | |

Elovich | q_{m} | 4.5 |

KE (L/mg) | 1700.8 | |

R^{2} | 0.9834 | |

Timpkin | A | 565.5 |

B | 4.0178 | |

R^{2} | 0.9868 |

where q_{e} the amounts of dye adsorbed (mg/g) at equilibrium and q_{t} at time t (min) and k_{1} (min^{−1}) is the pseudo first-order rate constant. Calculated the values of k_{1} from the plots of _{1}/2.303) and intercept of logq_{e}. The obtained data were evaluated to check its validity for pseudo-first order or Lagergren equation. The experimental data of q_{e} as shown in ^{2} of pseudo first order model are lower than second order model indicating that the EY adsorption does not obey pseudo first order kinetics with two different parameters of concentration and temperatures.

The rate equation for pseudo-second-order model is given by: [

where, k_{2} (gmol^{−1}∙min^{−1}) is the equilibrium rate constant of pseudo-second-order model, q_{t} and q_{e} are the amount of dye adsorbed at equilibrium and at time t. The value of k_{2} and q_{e} can be obtained from the slope and intercept of plots of t/q_{t} versus t. The plot of t/q_{t} versus t is linear, showing that chemisorption is the main rate controlling step of the adsorption process. The calculated values of maximum adsorption capacities q_{e} and the values of R^{2} obtained for the pseudo second order model are in accordance with the experimental values and suggested the applicability of the pseudo-second order kinetic model to describe the adsorption process of eosin Y uptake on the Al_{2}O_{3} NPs adsorbents. This refers to that the overall rate of the adsorption process was controlled by the exchange of electrons between the sorbent and the sorbate or chemisorption which involved valence forces through sharing, and its agreement with the rate controlling step when the mechanism is chemisorption. Thus the adsorption obeys a pseudo second order model at different temperatures or concentration (

This equation used when the adsorbing surface is heterogeneous. The Elovich equation used to describe the second order kinetic but the equation does not prove any definite mechanism for adsorbate-adsorbent, and the linear form is given as

The constant α (mg/g∙min) is the initial adsorption rate and β (g/mg) related to the extent of surface coverage and activation energy for chemisorption which can be evaluated from the slope and intercept of and the data fitted (^{2} > 0.95 at lower concentrations this indicate that the diffusion rate-limiting is the rate limiting step. The initial rate (α) not regular with increasing the initial dye concentration from 75 to 200 mg/l.

Model | Parameter | Initial concentration of dye mg/l | ||||
---|---|---|---|---|---|---|

75 | 100 | 150 | 200 | |||

Pseudo-first-order | qe_{(exp)} mg/g | 39.50 | 43.35 | 44.19 | 39.89 | |

qe_{(cal)} mg/g | 78.46 | 106.68 | 77.08 | 21.08 | ||

K_{1} (min^{−1}) | 0.02268 | 0.02429 | 0.02151 | 0.01762 | ||

R^{2} | 0.7253 | 0.6815 | 0.6562 | 0.9587 | ||

Pseudo-second-order | qe_{(exp)} mg/g | 39.50 | 43.35 | 44.19 | 39.89 | |

qe_{(cal)} mg/g | 49.16 | 57.95 | 47.70 | 43.03 | ||

K_{2} (g/mg/min) | 0.0203 | 0.017 | 0.021 | 0.0232 | ||

R^{2} | 0.9792 | 0.9686 | 0.9764 | 0.9917 | ||

Elovich kinetic | α (mg/g∙min) | 3.57 | 3.33 | 5.97 | 55.60 | |

Β (g/mg) | 0.0965 | 0.0844 | 0.1055 | 0.1579 | ||

R^{2} | 0.9587 | 0.9555 | 0.9612 | 0.9088 | ||

Bangham | K_{b} | 0.00106 | 0.00062 | 0.0008 | 0.0018 | |

R^{2} | 0.9823 | 0.9829 | 0.914 | 0.9055 | ||

α (mg/g∙min) | 0.4867 | 0.5635 | 0.4014 | 0.1694 | ||

Intra-diffusion particle | K_{id} | 4.2422 | 3.3166 | 0.1318 | 0.0004 | |

C | 1.38 | 1.24 | 7.342 | 22.9 | ||

R^{2} | 0.9826 | 0.9826 | 0.9132 | 0.9056 | ||

Model | Parameter | Different Temperature | ||||

25 | 35 | 45 | 55 | 65 | ||

Pseudo-first-order | qe_{(exp)} mg/g | 43.35 | 59.97 | 73.10 | 97.20 | 98.59 |

qe_{(cal)} mg/g | 46.20 | 50.53 | 63.91 | 113.31 | 121.64 | |

K_{1} (min^{−1}) | 0.030169 | 0.02418 | 0.02625 | 0.03062 | 0.03984 | |

R^{2} | 0.9488 | 0.9597 | 0.9612 | 0.9715 | 0.9774 | |

Pseudo-second-order | qe_{(exp)} mg/g | 43.35 | 59.97 | 73.10 | 97.20 | 98.59 |

qe_{(cal)} mg/g | 57.80 | 66.66 | 85.47 | 128.20 | 129.87 | |

K_{2} (g/mg/min) | 4.19 × 10^{−4} | 7.69 × 10^{−4} | 5.31 × 10^{−4} | 1.97 × 10^{−4} | 2.26 × 10^{−4} | |

R^{2} | 0.9686 | 0.9739 | 0.9736 | 0.972 | 0.9805 | |

Elovich kinetic | α (mg/g∙min) | 3.30 | 12.88 | 10.60 | 7.78 | 8.77 |

Β (g/mg) | 0.083202 | 0.086311 | 0.060132 | 0.037991 | 0.036759 | |

R^{2} | 0.9552 | 0.9207 | 0.9442 | 0.9627 | 0.9563 | |

Bangham | K_{b} | 2.613 | 2.482 | 2.352 | 2.011 | 1.011 |

R^{2} | 0.9829 | 0.9584 | 0.9683 | 0.9746 | 0.9594 | |

α (mg/g∙min) | 0.5635 | 0.2487 | 0.3593 | 0.5156 | 0.5053 | |

Intra-diffusion particle | K_{id} | 4.27 | 4.81 | 6.48 | 9.40 | 9.87 |

C | 0.76 | 10.20 | 8.88 | 0.38 | 2.18 | |

R^{2} | 0.9842 | 0.9403 | 0.9519 | 0.9876 | 0.9627 |

The Bangham’s equation used to check the adsorption process follow only to rate controlling step or not by using an equation.

where C_{s} is the weight of adsorbent per liter of solution (g/L), and α (<1) and k_{b} are con-

stants estimated from the slope and intercept when plot

against logt, (

The adsorption mechanism was investigated using the intra-particle diffusion model, Bangham’s and Boyd kinetics model at different initial concentration and Temperatures.

Both of the Pseudo-first and second order does not provide the mechanism of mass transport on the surface of adsorbent. A comprehensive model was also tested to assign the rate controlling step during adsorption of dyes on the surface of adsorbent [

where k_{id} is the intraparticle rate constant (g∙mol^{−1}∙min^{−1/2}) and C is the intercept. The intraparticle diffusion model implies that the plot of q_{t} versus t^{1/2} should be linear straight line when the adsorption mechanism follows the sole intraparticle diffusion process. From the ^{2} (

Three models can be interpreted the mechanism of resulting data and can be compared with each other with the correlation coefficient value The effects of temperature on the adsorption mechanism were shown in (

_{b} decreases with increasing the temperature and good correlation coefficients in Bangham model than an Elovich kinetic model. The values of K constant of all stages showed an increase as temperature increases. This may be due to increase in boundary layer thickness would decrease the external mass transfer, thus increasing the chance of internal mass transfer. The third phase that does not pass through the original, so confirmed it as shown in previous figure.

Different parameters for adsorption was studied at different temperature. The Gibbs free energy ∆G°, enthalpy ΔH° and entropy ΔS° were calculated from van’t Hoff equation

Parameters | 25 | 35 | 45 | 55 | 65 |
---|---|---|---|---|---|

K1 | 4.42893 | 7.412492 | 9.390919 | 10.28414 | 9.900485 |

K2 | 3.229261 | 5.560741 | 6.792148 | 10.09048 | 15.09227 |

K3 | 1.598397 | 2.788087 | 2.040957 | 3.34753 | 1.681642 |

C1 | −1.07101 | 3.690991 | 3.690991 | −1.89739 | −0.84643 |

C2 | 2.130307 | 5.759513 | 6.70831 | −10.3435 | −10.8517 |

C2 | 25.80634 | 28.55244 | 50.6309 | 59.69479 | 79.33432 |

(R_{1})^{2} | 0.983934 | 0.946259 | 0.994491 | 0.946259 | 0.99372 |

(R_{2})^{2} | 0.997492 | 0.933392 | 0.928288 | 0.987404 | 0.985234 |

(R_{3})^{2} | 0.998452 | 0.98131 | 0.978387 | 0.959304 | 0.963484 |

shown below

where K is the equilibrium constant, and equal q_{e}/C_{e} the data listed in _{e}/C_{e} given in Equation (19), respectively.

The positive values of the enthalpy change (ΔH°) indicate that the adsorption process is endothermic. The value of ∆H° (121.8 kJ/mol) is greater than 40 kJ/mol indicates that the adsorption is chemisorption in nature and involves strong attraction between dye and surface of adsorbent. The positive value of ΔS° increasing randomness at the solid/solution interface and some structural changes in the adsorbate and adsorbents

Van’t Hoff | ||||
---|---|---|---|---|

Temperatures, K | ∆G, kJ/mol | ∆H, kJ/mol | ∆S, J/mol∙K | |

298 | −0.67994 | 121.83 | 396.77 | |

308 | −1.03559 | |||

318 | −2.64388 | |||

328 | −9.69541 | |||

338 | −11.9433 | |||

Modified Arrhenius | Arrhenius | |||

E_{a} | 106.39 | E_{a} | 40.97 | |

S^{*} | 4.82 × 10^{−19} | A | 8.45 × 10^{−11} |

during the adsorption process of EY on the NPs [

The rate of reaction increase with an increase the temperature, the type of adsorption process can be obtained from Arrhenius equation when used to calculate the activation energy the linear form represented as

where A is the pre-exponential factor and E_{a} is the activation energy, and R is the gas constant. The E_{a} can be evaluated from the slope of the curve between lnk vs. 1/T (

From _{a}) and the propability sticking (S^{*}), from the surface coverage (θ) as follows according to modified Arrhenius type equation [

The S^{*} is a function of the adsorbate/adsorbent system under investigation, its value lies in the range 0 < S^{*} < 1 and is dependent on the temperature of the system. The value of θ can be calculated from the following equation

The E_{a} was calculated from the slope of the plot of _{a} 106.39 kJ/mol this indicated that the adsorption process is chemisorption and favors at higher temperature and the process is endothermic in nature, the value of S^{*} is <1, (4.82E−19) thus the sticking probability of EY onto Al_{2}O_{3} NPs are very high.

This study presents the information about the effects of different parameters on the adsorption of EY as a model of anionic dye from water using γ-Al_{2}O_{3} nanoparticles prepared by the sol-gel method, the main conclusions are:

・ Acidic pH is highly affect on the adsorption processes and the maximum removal about 99.36% was achieved at pH 4. These behaviors due to positive charge are highly present on the surface of γ-Al_{2}O_{3}.

・ The adsorption parameters are investigated using four adsorption models, Langmuir, Freundlich, Tempkin and Dubinin-Radushkevich, and the Langmuir isotherm have a high correlation coefficient.

・ The kinetics adsorption of EY on γ-Al_{2}O_{3} NPs is fitted to pseudo-second-order model at different temperatures and the rate controlling step is chemisorption in nature and a strong attraction occurs between the dye and the surface of Al_{2}O_{3} NPs.

・ The intra-particle diffusion model not only rate controlling step, the Elovich and Bangham’s kinetic models revealed that the adsorption kinetics is limited by the pore diffusion. This result confirmed that the pore diffusion is the rate-controlling step.

・ The negative value of free energy ∆G° and increasing with increasing the temperature indicates that the adsorption process is spontaneous, and more favorable at high temperature. This data is confirmed by the positive value of ΔH° (endothermic) and the positive value of ∆S°.

・ The chemisorption process is confirmed by Arrhenius, Vant’s Hoff, and modified Arrhenius activation models where the obtained values are 40.9 kJ/mol. 106.39 kJ/mol and the value of S^{*} is <1, (4.82E−19) thus the sticking probability of EY onto Al_{2}O_{3} NPs is very high.

Thabet, M.S. and Ismaiel, A.M. (2016) Sol-Gel γ-Al_{2}O_{3} Nanoparticles Assessment of the Removal of Eo- sin Yellow Using: Adsorption, Kinetic and Thermodynamic Parameters. Journal of En- capsulation and Adsorption Sciences, 6, 70- 90. http://dx.doi.org/10.4236/jeas.2016.63007