Science International  Volume 6 Issue 1, 2018

Research Article

Leaching Behaviour of Some Hazardous Metals from Radiated Exhausted and Metal-doping Stannic Antimonate Materials
Mamdouh Mohamed Abou-Mesalam
Atomic Energy Authority, Hot Labs. Centre, P.Code13759, Cairo, Egypt

Asmaa Bendary Ibrahim
Atomic Energy Authority, Hot Labs. Centre, P.Code13759, Cairo, Egypt

Moustafa Mohamed El-Shorbagy
Atomic Energy Authority, Hot Labs. Centre, P.Code13759, Cairo, Egypt

ABSTRACT:
Objective: The objective was to study the leaching behavior of Co2+ and Cd2+ ions from stannic antimonate, cobalt and strontium doped stannic antimonate at different conditions. Methodology: The total capacity of stannic antimonate and its dopants cobalt and strontium stannic antimonates for Co2+ and Cd2+ ions were investigated before and after irradiated at different doses. The crystallite size and lattice strain of stannic antimonate and its dopants cobalt and strontium stannic antimonates after saturation with Co2+ and Cd2+ ions were determined at different irradiation doses. The surface area values of stannic antimonates and its dopants were measured using BET-technique. Results: The leach rate values of Co2+ ion from stannic antimonate saturated with cobalt and cobalt stannic antimonate at different irradiation doses were determined and show the leach rate values of Co2+ ion from cobalt stannic antimonate lower than those obtained from stannic antimonate saturated with cobalt. Conclusion: The leach rate of ion was decreased by doping of the same ion with the ion exchanger and increasing the radiation dose that exposed to the exchange materials from 0-100 kGy.
 
    How to Cite:
Mamdouh Mohamed Abou-Mesalam, Asmaa Bendary Ibrahim and Moustafa Mohamed El-Shorbagy , 2018. Leaching Behaviour of Some Hazardous Metals from Radiated Exhausted and Metal-doping Stannic Antimonate Materials. Science International, 6: 31-38
DOI: 10.17311/sciintl.2018.31.38
 


INTRODUCTION
Powder X-ray diffraction analysis is useful for many purposes, such as structure determination, phase identification and quantification in solid mixtures, estimate of preferred orientation effects, lattice micro strain and mean crystallite size1-5. Furthermore, powder diffraction techniques do not need prior hard steps of sample preparation. For instance, sometimes only grinding procedures were enough to avoid preferred orientation of crystallites. The two main properties extracted from peak width analysis were (a) Crystallite size and (b) Lattice strain. Crystallite size is a measure of the size of a coherently diffracting domain. The crystallite size of the particles was not generally the same as the particle size due to the presence of polycrystalline aggregates6. The most common techniques used for the measurement of particle size rather than the crystallite size are BET, light scattering, scanning electron microscopy and transmission electron microscopy (TEM) analysis. Lattice strain is a measure of the distribution of lattice constants arising from crystal imperfections, such as lattice dislocation. The other sources of strain are the grain boundary triple junction, contact or sinter stresses, stacking faults, coherency stresses, etc.7. In previous publications a new category of inorganic materials was synthesized such as silico-antimonate8, uranium antimonate9 and vanadium antimonate10. The aim of this study was to estimate the crystallite size and lattice strain of stannic antimonate and its dopants cobalt stannic antimonate and strontium stannic antimonate after saturation with cobalt and strontium, also studied the leaching rates of these ion exchangers in different media.


MATERIALS AND METHODS
Chemicals and reagents: All chemicals and reagents were of analytical grade purity and used without further purification.

Synthesis of stannic-antimonate (SnSb) ion exchanger: Stannic-antimonate was synthesized by the reaction of 0.1 M stannic tetra chloride (dissolved in distilled water) with 0.1 M antimony metal (dissolved in aqua regia) with molar ratio Sn to Sb equal 1:1. During the addition process, yellow gelatinous precipitates were formed. After complete addition, few drops of diluted ammonia solution were added for complete precipitation, the precipitate left overnight standing and the mixture was hydrolyzed in distilled water and left for 2 days at room temperature. The precipitate formed was separated by centrifugation at 3000 rpm for 5 min. The precipitate was washed by 0.1 M HNO3 to be free from Cl ions and rewashed by distilled water to remove NO3. The precipitate was dried at 60 °C in a drying oven and washed with hot water (70°C) to remove the air traps in the solid and then redried at 60°C. The solid was ground, sieved to mesh size and stored at room temperature.

Synthesis of doping cobalt or strontium stannic antimonate (CoSnSb or SrSnSb) ion exchangers: Cobalt or strontium chloride solutions with concentration of 0.1 M were used for doped cobalt or strontium in-situ stannic-antimonates. Cobalt or strontium stannic-antimonate solid samples were prepared by the reaction of 0.1 M cobalt chloride or 0.1 M strontium chloride with a mixture of 0.1 M stannic tetra chloride (dissolved in distilled water) and 0.1 M antimony metal (dissolved in aqua regia) with volumetric molar ratio equal to unity (Co/or Sr:Sn:Sb equal 1:1:1). The reaction carried out in water bath at 60°C with continuous stirring for 4 h. Greenish yellow gelatinous or reddish gelatinous precipitate for CoSnSb or SrSnSb formed during the addition process of cobalt chloride or strontium chloride, respectively, to the mixture. After an overnight standing the precipitate separated by centrifugation at 3000 rpm. The solids treated by 0.1 M HNO3 to remove impurities and Cl ions. Solids rewashed with distilled water to remove NO3 ions. After drying in drying oven at 60°C, the granules solids were poured in near boiling water at 70-80°C to remove the trapped air. Dry, grand, sieve and store solids at room temperature.

Surface area measurements: The surface area values of stannic antimonate saturated with cobalt and cobalt stannic antimonate were measured using BET-technique as adsorption phenomena of nitrogen gas on the powder surface at 77 K.

X- ray diffraction patterns: Powder X-ray diffraction was performed using a Shimadzu X-ray diffractometer, model XD610, with a nickel filter and Cu-Kα radiation (1.54 A°) operating at 30 kV and 30 mA.

Capacity measurements: The capacity of synthesized stannic antimonate saturated with cobalt and cobalt stannic antimonate for Co2+ and Cd2+ ions were determined by the repeated batch technique, by equilibrating nearly 0.7 g of stannic antimonate and doping stannic antimonate with 70 mL of (30 ppm) Co2+ and Cd2+ ion solutions on a shaker thermostat adjusted at 25±1°C. After equilibrium, the solution was separated and repeated until no further sorption occurs. The capacity was calculated using the Eq. 1:

(1)

(2)
Where:
Ao and A = The initial and final concentration of ions of solution
Co = The initial concentration of solution
V = The solution volume (mL)
m = The weight of the exchanger (g)

Static leaching tests: In static leach tests, stannic antimonate saturated with cobalt and cobalt stannic antimonate samples (dried at 50°C) were used to obtain the leach rates of co2+ ion in different media. The experiments were carried out by mixing 0.1 g of stannic antimonate saturated with cobalt and cobalt stannic antimonate with 10 mL of the leachate solutions (dist. H2O, 0.1 M HNO3 and 0.5 M HNO3) at 25±1°C in absence of stirring. After an equilibrium, the solution was separated and repeated until no further desorption occurs. The liquid samples were analyzed for the leached Co2+ ion content . The leaching rates of the corresponding cations were calculated according to the following equation:

(3)
Where:
A = The amount of ions leached out from the sample in unit time (T)
Ao = The amount of ions loaded on stannic antimonate
W = The mass (g) of the sample used in the test and
S = The surface area (cm2) of the sample determined by nitrogen adsorption method


RESULTS AND DISCUSSION
X-ray diffraction analysis: The XRD patterns of synthesized stannic antimonate and doping Co2+ and Sr2+ stannic antimonate samples after saturation with Co2+ and Cd2+ ions show crystalline nature as showed in Fig. 1(a-f). The peaks intensity was sharp and narrow, confirming that the samples were of high quality with good crystallinity. Using XRD data, lattice parameters were calculated (a = 3.2491 Å and c = 5.2063 Å). The data in Fig. 1 (a-f) show different peaks at different 2θ with variable intensities indicating the crystalline nature of these materials. The brag angle 2θ and the full width at half maximum (β) were determined to evaluate the crystallite size and lattice strain of these materials.

From Debye-Scherrer’s formula:

(4)
Where:
D = The effective average crystalline size
K = The shape factor (0.89)
λ = The wavelength of CuKα radiation in nanometer
θ = The Bragg diffraction angle and
β = The measured full width at half maximum (FWHM)

The lattice strain induced in powders due to crystal imperfection and distortion was calculated using Hall equation with the formula11-13:

(5)

where, ε is the effective strain. By substitution in Eq. 5 from 4 about the value of (ε) Eq. 4 becomes:

(6)

By multiplying both sides of Eq. 6 in constant value {λ/(β.Cosθ)} and after rearranging the equation is:

(7)

From Eq. 4 and 6, it was confirmed that the peak width from crystallite size varies as 1/Cos θ strain varies as tan θ.

Figure. 1(a-f): (a)XRD of SnSb (0) after saturation by cadmium ion, (b) XRD of SnSb (0) after saturation by cobalt, (c) XRD of CoSnSb (0) after saturation by cadmium ion, (d) XRD of CoSnSb (0) after saturation by cobalt ion, (e) XRD of SrSnSb (0) after saturation by cadmium ion and (f) XRD of SrSnSb (0) after saturation by cobalt ion

Assuming that the particle size and strain contributions to line broadening are independent to each other and both have a Cauchy-like profile, the observed line breadth is simply the sum of Eq. 4 and 7:

(8)

By rearranging the above Eq. get the:

(9)

The above equations are Williamson-Hall’s (W-H) equations.

By plotting of the relation between (4 Sinθ) along the x-axis and (β.Cosθ) along the y-axis, the crystallite size and the lattice strain (ε) were estimated from the y-intercept and the slope of the fit, respectively and the results were represented in Table 1 and 2. From data in Table 1 and 2 crystallite size of cobalt stannic antimonate and strontium stannic antimonate are higher those of stannic antimonate that may be related to doping in-situ precipitation of cobalt and strontium with stannic antimonate. From the data in Table 1 and 2 the crystallite size of SnSb and doping CoSnSb and SrSnSb saturated by Cd2+ ion was found. This may be due to the higher complexbility of Co2+ ion compared to Cd2+ ion that leads to strain in the crystallite size of SnSb and CoSnSb and SrSnSb.

Table 1: Crystallite size and lattice strain for stannic antimonate and doping stannic antimonate after saturation by Cd2+ ion

Table 2: Crystallite size and lattice strain for stannic antimonate and doping stannic antimonate after saturation by Co2+ ion

Table 3: Leaching rate of Co2+ ion from unirradiated and irradiated saturated SnSb and doped Co-SnSb ion exchange materials

Also, Table 1 and 2 showed that the strain in samples saturated by Cd2+ ion was higher than those of samples saturated by Co2+ ion. Also Table 1 and 2 indicated that the strain in ion exchangers decreases as the crystallite size increased which was unusual phenomena14,15. Owing to the large number of grain boundaries and the short distance between them, the intrinsic strain associated with such interface are always present in nano-and crystallite structural materials.

Surface area measurement: The surface area values of stannic antimonate saturated with cobalt and doping cobalt stannic antimonate were found to be 36.28 and 53.51 cm2 g1, respectively, as determined by the BET adsorption of nitrogen gas. The surface area of doping cobalt stannic antimonate sample was increased from 36.28-53.51 cm2 g1. These increasing in the surface area values may be due to the bond formation of the doped Co2+ ion with tin and antimony atoms during the preparation process that leading to an increase in the structure chain of the exchanger.

Leaching rates of Co2+: Static leaching rate of Co2+ ion and doped Co-stannic antimonate were investigated in different media such as distilled water, 0.1 M HNO3 and 0.5 M HNO3. The static batch test was carried out for along 4 days and the data were represented in Table 3 and Fig. 2(a-h). Generally, from Fig. 2(a-h) the leach rate of Co2+ ion in distilled water medium was lower than that obtained in nitric acid media.

Figure. 2(a-h): (a) Leach rate of Co2+ ion from stannic antimonate saturated with cobalt as a function of time at 0 radiation, (b) Leach rate of Co2+ ion from stannic antimonate saturated with cobalt as a function of time at 10 kGy radiation, (c) Leach rate of Co2+ ion from stannic antimonate saturated with cobalt as a function of time at 50 kGy radiation, (d) Leach rate of Co2+ ion from stannic antimonate saturated with cobalt as a function of time at 100 kGy radiation, (e) Leach rate of Co2+ ion from cobalt stannic antimonate as a function of time at 0 radiation, (f) Leach rate of Co2+ ion from cobalt stannic antimonate as a function of time at 10 kGy radiation, (g) Leach rate of Co2+ ion from cobalt stannic antimonate as a function of time at 50 kGy radiation and (h) Leach rate of Co2+ ion from cobalt stannic antimonate as a function of time at 100 kGy radiation

The data in Fig. 2(a-h) indicated that the leach rate of Co2+ ion from stannic antimonate saturated by Co2+ (Fig. 2a-d) and doped Co-stannic antimonate (Fig. 2e-h) were decreased by increasing the radiation dose that exposed to the exchange materials from 0-100 kGy. This may be attributed to the collapse of the surface of stannic antimonate at high radiation dose and Co2+ ion is trapped in the cavities and channels of the exchange material16. This means that the radiation treatment led to further improvement in the leach resistance of the leaching ion from stannic antimonate. By the comparison of data from Fig. 2(a-h) found that the leaching rate of Co2+ ion from doped Co-stannic antimonate samples are very low compared to these obtained from stannic antimonate saturated by cobalt samples. This behaviour may be related to building nature of Co2+ ion in the texture of the materials. Finally Table (3) summarized the leaching rate of Co2+ ion from saturated SnSb by Co2+ ion and doped Co-SnSb after 4 days for unirradiated and irradiated materials.


CONCLUSION
The leach rate values of Co2+ ion from stannic antimonate saturated with cobalt and cobalt stannic antimonate at different irradiation doses were determined and show the leach rate values of Co2+ ion from cobalt stannic antimonate lower than those obtained from stannic antimonate saturated with cobalt. The leach rate of ion was decreased with increasing the radiation dose that exposed to the exchange materials from 0-100 kGy.


SIGNIFICANCE STATEMENT
This study for the first time conduct the effect of gamma radiation on the leaching behavior of some hazardous ions such as Co2+ ion from doped and undoped ion exchange materials in different media.


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