Atomic Absorption and Vibrational Spectral Magnetic Studies on the Removal of Cu ( II ) and Co ( II ) Ions Using Synthetic Nano Adsorbent Fe 3 O 4

Adsorption of Cu(II) and Co(II) from aqueous solutions on synthetic nano Fe3O4 has been studied. The effect of experimental parameters such as initial concentration of the metal ions, adsorbent dosage, contact time and pH has been investigated. Optimum removal efficiency of Cu(II) ion was found to be 97.8% with the dose rate of 1.07 g/L in 60 minutes at pH = 5.5 and for Co(II) ion, it was found to be 99.2% with the dose rate of 2.57 g/L in 10 minutes at pH = 5.4. The removal of Co(II) ions require only 10 minutes with the efficient removal of 99.2%, whereas Cu(II) ions require 60 minutes with the maximum removal of 97.8%. In order to understand the effective removal of Cu(II) and Co(II) ions on Fe3O4, room temperature magnetic measurement was carried out using Vibrational Spectrum Magnetometer (VSM), before and after adsorption with a maximum applied magnetic field of 20,000 G.


Introduction
The daily requirement of copper is about 2.0 mg for an adult [1].Even though copper is needed for all human beings, problems arise when it is deficient or in excess.The Environmental Protection Agency's (EPA) lead and copper rule promulgated, in 1991, that the maximum contaminant level goal (MCLG) for copper [2] is 13 mg•L −1 .The presence of excess of copper causes Wilson's disease [3] due to which the bio-synthesis of ceruloplasmin is suppressed.The ingestion of acute toxic levels of copper may result in nausea, vomiting, diarrhea, liver damage, hemoglobinuria and hematuria.Higher doses of cobalt can adversely affect the hemoglobin content of the patient's blood and produce polycythemia and hyperlipemia [4].Cobalt poisoning leads to gastrointestinal distress and heart failure.The hazardous nature of heavy metals (like copper and cobalt), even in trace quantities due to their tendency for chelation and accumulation with the organic and biomolecules, makes it necessary to develop suitable cost-effective methods for the removal of heavy metals from waste water systems and industrial effluents fed into water stream.

Experimental Procedure
Preparation of Nano Fe 3 O 4 6.48 g of Ferrous Chloride and 4.78 g of Ferric Chloride dissolved in 200 mL of distilled water and 10% Polyethylene glycol together and dispersed by ultra sonic stirring for 10 min.The mixture was heated to 75˚C followed by the drop wise addition of 2 mol/L sodium hydroxide until the pH value of the mixture reached about 11.5.The mixing tested for 2 hrs at 60˚C and then aged at 80˚C for 30 min, purified and washed several times with distilled water at 80˚C [5,6].

SEM Analysis
Figure 2 shows the high resolution scanning electron microscope (HRSEM) image of Fe 3 O 4 and shows the formation of mild agllomeration with particles in the range of 18 -23 nms.A X-ray energy dispersion analysis (EDAX) of the copper and cobalt solution treated Fe 3 O 4 is depicted in Figures 3(a) and (b).From the EDAX spectrum, it is observed that there is major component of Fe and O due to Fe 3 O 4 and presence of copper and cobalt adsorbed on it.

Effect of Initial Concentration
The   served that the percentage removal of Cu(II) and Co(II) ions by nano Fe 3 O 4 is low at higher concentration and gradually increases as the concentration decreases.This is due to the fact that after the formation of mono-ionic layer at lower concentration over the adsorbent surface, further formation of layer is highly hindered at higher concentration due to interaction between Cu(II) and Co(II) surface and in the solution.In addition to that at low concentration of the Cu(II) and Co(II) ions, the ratio of the initial number of moles of the Cu(II) and Co(II) ions to the available surface area of the adsorbent is large and subsequently, the fraction of the adsorption becomes independent of the initial concentration of the metal ion.But at higher concentration, the adsorption sites available for adsorption become lesser, and hence, the percentage removal of the metal ions at higher concentration decreases [5,7].The optimum concentration was found as 50 ppm for both Cu(II) and Co(II) ion with the effective removal of 97.8% for Cu(II) and 99.2% for Co(II) ions.

Effect of Dose Rate
The removal of the Cu(II) and Co(II) ions was studied with different dose of synthetic nano Fe 3 O 4 from (0.82 to 2.07 g/L) at the optimum concentration of 50 ppm for both the metal ions with fixed contact time (60 min), pH (5 -6) and temperature of 28˚C ± 1˚C.The effect of the dose rate of synthetic nano Fe 3 O 4 on the removal of Cu(II) and Co(II) is pictured in Figure 5.It was noted that the percentage removal of the Cu(II) and Co(II) ion increases as the concentration of nano Fe 3 O 4 increases owing to the enhanced total surface area of the adsorbent.This means that the toxic ions can be removed effectively from the contaminated water with the proper amount of the adsorbent, which would possess more adsorption sites available for the metal ion uptake from the solution [5,7].The optimum dose rate was found to be 1.07 g/L for Cu(II) ion and 2.57 g/L for Co(II) ion with the effective removal of 97.8% for Cu(II) and 99.2% for Co(II) ions.

Effect of Contact Time
In order to study the effect of contact time on the removal of Cu(II) and Co(II) ions, experiment were conducted at different contact times (from 10 to 60 min) keeping the following conditions: optimum concentration (50 ppm for Cu(II) and Co(II) ions), fixed dose of synthetic nano Fe 3 O 4 (1.07 g/L for Cu(II) ions, 2.57 g/L for Co(II) ions), pH (5 -6) and temperature of 28˚C ± 1˚C.The variation of the percentage removal of Cu(II) and Co(II) ions by synthetic nano Fe 3 O 4 with contact time was shown in Figure 6.The extent removal of Cu(II) and Co(II) ion increases sharply initially and found to be constant after the optimum contact time.The optimum contact time was found to be 60 minutes for Cu(II) ions and 10 minutes for Co(II) ions with the effective adsorption of 97.8% for Cu(II) and 99.2% for Co(II) ions.

Effect of pH
The pH is one of the important parameter controlling the uptake of Cu(II) and Co(II) ions from aqueous solution by the adsorbent.The adsorption potential of the synthetic nano Fe 3 O 4 was found out at various pH values (1.8 -6) keeping the system at the following conditions: optimum concentration (50 ppm for both Cu(II) and Co(II) ions), fixed dose of synthetic nano Fe 3 O 4 (1.07 g/L for Cu(II) and 2.57 g/L for Co(II) ions), optimum contact time (60 min for Cu(II) ion and 10 min for Co(II) ions) and temperature 28˚C ± 1˚C.The removal of the Cu(II) and Co(II) ions by synthetic nano Fe 3 O 4 was effective in acidic medium only and the effective pH range was found to be 5.5 for Cu(II) ions and 5.4 for Co(II) ions.This observation reveals that the adsorption process is pH dependent [5,7].At low pH, because of the higher concentration of the H + ion and its higher mobility due to smaller size, the H + ions are preferentially adsorbed compared to the Cu(II) and Co(II) ions, thus lowering the extent of the removal of the metal ions.At optimum pH, the concentration of the H + ions is lowered which leads to the preferential adsorption of the Cu(II) and Co(II) ions.At higher pH the hydroxide ion concentration is increased and preferentially adsorbed on the adsorbent.Moreover, at higher pH, the Cu(II) and Co (II) ion forms various complex anion, hydroxide complexes, etc., which are retarded by the negatively charged surface of the adsorbent.The plots of the percentage removal of Cu(II) and Co(II) ions with respect to pH change were shown in

Conclusion
In the present study, the efficiency of the synthetic nano Fe 3 O 4 towards the removal of the Cu(II) and Co(II) ions was examined.Optimum conditions for the removal of Cu(II) and Co(II) ions by using synthetic nano Fe 3 O 4 were given in Table 2. Cobalt is Ferro magnetic in nature, hence it shows optimum contact time of 10 minutes only whereas copper is diamagnetic in nature so it requires the optimum contact time of 60 minutes.The results indicated that the synthetic nano Fe 3 O 4 was found to be more suitable for the removal of Co(II) ions than Cu(II) ions with the minimum contact time of 10min only.

Figure 1 (
Figure 1 (a and b) shows the X-Ray diffraction pattern

Figure 4 .
Figure 4. Effect of initial concentration of Cu(II) and Co(II) ions on synthetic nano Fe 3 O 4 .

Figure 5 .
Figure 5.Effect of the dose rate in the percentage removal of the Cu(II) and Co(II) ions by adsorption on synthetic nano Fe 3 O 4 .

Figure 6 .
Figure 6.Effect of Contact错误！未定义书签。 time in percentage removal of the Cu(II) and Co(II) ions by adsorption on synthetic nano Fe 3 O 4 .
It was observed that for the removal of Co(II) ions by synthetic nano Fe 3 O 4 require only 10 minutes for the maximum removal, whereas for Cu(II) ions it requires 60 minutes for the maximum removal.The less time required for Co(II) ion is because Cobalt is Ferro magnetic in nature, hence it was easily attracted by synthetic nano Fe 3 O 4 .In the case of Cu(II) ions, which are Dia magnetic in nature, it does not experience magnetic force so it require 60 minutes for the maximum removal.It was further confirmed by Vibrational Spectral Studies and given in Table1and the results are shown in Figures8(a) and (b).

Figure 7 .Figure 8 .
Figure 7. Variation in the percentage removal of the Cu(II) and Co(II) ions by adsorption on synthetic nano Fe 3 O 4 .