1. Marine Science Centre, College of Education for Pure Science, University of Basrah, Basrah-Iraq
2. College of Education for Pure Science, University of Basrah, Basrah-Iraq
Author
Correspondence author
International Journal of Marine Science, 2015, Vol. 5, No. 29 doi: 10.5376/ijms.2015.05.0029
Received: 22 Apr., 2015 Accepted: 03 May, 2015 Published: 06 May, 2015
Porcellanite; Batch adsorption; Copper and lead; Langmuir and Frendlich; Thermodynamics
Pollution is the addition of undesirable foreign matter to the environment as a result of enormous industrial development and modernization (Zietz et al., 2003). Heavy metal ions existing in aqueous waste streams of various industries such as metal plating, mining operations, battery manufacturing and tannery Fabrication are posing serious risk to the environment. Leaking of the toxic heavy metals to the soil contaminates ground and surface water leading to serious impacts on the health of human and animals. Treatment of high volumes of waste water containing low concentrations of heavy metals pollutants is becoming increasingly important as the discharge regulations become more stringent (Zhu et al., 2008). The harmful heavy metals ions associated with such industrial activities include Ni(II), Cr(II), Cu(II), Cd(II), Pb(II), Fe(III), Mn(II), Zn(II) and Hg(II) (Amdur et al., 1991).
Copper contamination of the environment is primarily due to man made (anthropogenic) activities, making it the most everywhere toxic metal in the environment. Copper is one of the most common toxic metals that find its way to water sources from various industries, includes electroplating, mining, electrical and electronics ion and steal production,printing and photographic industries. Copper concentration in humans have increased to toxic levels causing various diseases and disorders such as liver damage )Zhu et al., 2008).
Lead pollution includes the use of tetra methyl and tetra ethyl lead as gasoline additives, the main facture of storage batteries, the formation of alloys with antimony and tin to be use in power and telephone cables, the manufacture of soldering materials and lead paints (Newland and Dawn, 1982). In addition lead is also generated in the effluents from the production of television picture tubes, pigments, petroleum, fuels, photographic materials, explosives, printing, glass industrial operations and inorganic chemical manufacturing industries are also main sources of lead pollution. The toxicity and deleterious of lead are well documented, as it has been recognized for centuries as accumulative poison (WHO, 1977; ltorrison and laven, 1981). Acute lead poisoning in humans causes sever destruction in kidney, reproductive system, liver, brain and central nervous system. Mild lead poisoning causes anemia, the victim may have headache and sore muscles and may generally feel fatigue and irritable. Lead is also toxic to aquatic organisms. The concentration of lead in water below the world health organization standard (50 mg/l) cannot be considered as a serious of lead intake (Fugas and Saric, 1981). The accumulation of relatively small amounts of lead over along period of time in human body can lead to the malfunctioning of the organs and chronic toxicity (Stoker and Seager, 1976). According to the WHO, the maximum permissible limit (MPL) of lead in drinking water is (0.05 mg/l) (WHO, 1984). For these reasons, copper and lead must be removed as much as possible from industrial effluents. Several methods has been reported such as cementation of Pb(II) on spheres, on affixed bed contractor, adsorption on inert material treated with chelating reagent having selective affinity for Pb(II), non aqueous solvent extraction using organo-phosphorous compounds and chemical treatment followed by removal as precipitated carbonated (Taher et al., 2011), precipitation, ion exchange, electro chemical reduction, exploration, reverse osmosis, etc. Most of these methods are very costly and economically unfavorable. Adsorption is effective, cheap method among the chemical treatments (Hawari et al., 2009). A number of materials have been used to remove heavy toxic metals from water such as sawdust (Bulut and Tez, 2007), magnetic egg shell Fe3O4 powder (Jianwe et al., 2011), nation 117 membrane (Nasef and Yahaya, 2009), activated carbon from pesia populnea bark (Prabakaran et al., 2011), Conocarpus erectus leaves (Al-tameemi et al., 2012), activated carbon synthesized from water melon shell and walnut shell (Moreno-Barbosa et al., 2013).The present study is to investigate the possible use of locally porcellanite as an adsorbent material for removal of Cu(II) and Pb(II) ions from aqueous solution. The effect of adsorbent dose, contact time, initial metal ion concentration, temperature of solution and pH of the medium were calculated and discussed.
1 Materials and Methods
1.1 Preparation of adsorbent
Porcellanite rock was obtained from the General Company for GeologicalSurvey and Mining, Baghdad, Iraq, washed with deionized water to be completely free from dirt, dried in an oven at 120°C for a period of 3h, then ground and sieved in, to different particle sizes ranges between 75 to 300 µm, the powder was preserved in glass bottles for use as adsorbent.
1.2Chemical reagents
Metal salts used was of analytical reagent grade (Merk). Deionized water was used for the preparation of solution. Stock solutions of different concentrations (0.02-4 mg/l) of Cu(II) and (0.5-12 mg/l) of Pb(II) were prepared by dissolving exactly the amount of metal salt in deionized water.
1.3 Adsorption studies
Batch adsorption method was employed for the study of adsorption of Cu(II) and Pb(II) onto adsorbent. Adsorption of ions was carried out in 50ml stopper conical flask by adding 0.5g of porcellanite of particle size of 75 µm to 50 ml of 50 mg/l of Cu(II) and Pb(II) ions. All experiments were done at room temperature, often gentle shaking for desired time at 120rpm. The contents were filtered through filter paper (Qualitative filter paper). Concentrations of ions in the filtrate were then determined by using flame atomic absorption spectrophotometer (Pg instruments AA500). The amount of ions adsorbed were calculated based on the difference between the ions concentration in aqueous solution before and after adsorption from relation (Chu and Hashim, 2001).
Qe = V(C0 – Ce)/m ........... (1)
Where; Qe is the equilibrium adsorption capacity (mg/g), V is the volume of solution (l), m is the weight of the adsorbent (g), Co= Initial concentration of solution, Ce= Concentration of the solution after adsorption.
2 Results and Discussion
2.1Characterization of the adsorbent
FT-IR apparatus type Shimadzu (400-4000 cm-1) was used in order to identify the functional groups in the powder of porcellanite. The FTIR spectra as show in Figure 1 indicate the appearance of strong band in the region (3460-3621 cm-1) attributed to stretching vibration of hydroxyl group, the band at 1138 cm-1 belong to the stretching vibration of the (Si = O) group, the band at 476.42 cm-1 related to the stretching vibration Fe-O group and the band at 792 cm-1 related to the stretching vibration Al-O group (Silverstein et al., 2005).
2.2 Effect of contact time
The effect of contact time on the amount of metal ions adsorbed was investigated at different period (5-180 min) at 25°C. Figure 2 shows that the metal ions removal percentages increased with an increase in contact time before attaining equilibrium. The rate of metal removal is higher at the beginning due to the large surface area of the adsorbent being available for the adsorption of the metal (El-Ashtoukhy et al., 2008). Equilibrium time was attained at 90 min for Cu(II) and 30min for Pb(II). The removal percentage of metal ions in porcellanite powder for Cu(II) and Pb(II) were found to be 68.96% and 97.43% respectively.
Figure 2 Effect of contact time on adsorption of Cu, Pb ions onto porcelanite
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2.3 Effect of pH on the adsorption
pH is an important parameter for adsorption of metal ions from aqueous solution, because it affects the solubility of the metal ions, concentration of the counter ions on the functional groups of the adsorbent and degree of ionization of the adsorbate during reaction (Adamson and Gast, 2001).The effect of pH on the adsorption of Cu(II) and Pb(II) ions on the porcellanitein different media (pH=2, 4, 6, 8 and 10) was studied by using a fixed concentration 50 mg/l and time contact of 30, 90min for Cu(II) and Pb(II) at 25°C respectively. Figure 3 demonstrate the influence of pH on the adsorption.
Figure 3 Effect of pH on Cu(II) and Pb(II) adsorption on porcellanite
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The results showed an increase in the removal percentage of Cu(II) and Pb(II) with increasing pH values of the solution. At low pH value, binding sites are generally protanated or positively charged by the hydronium ions, this repulsion occurs between the metal cation and the adsorbent. At a higher pH value, binding sites start deprotonation, and make different functional groups available for metal binding. In general, cation binding increase as pH increases (Esposito et al., 2012). In addition, the solubility of Cu(II) and Pb(II) ions are greatly decreased as the pH increased causing an increase in the adsosption affinity towards the porcellanite surface (Lund, 1994). Accordingly, the subsequent experiments were done at pH 6.5 to avoid uncertainly in results as additional mechanism such as precipitation might play a role in metal removal from solution.
2.4 Effect of initial concentration of Cu(II) and Pb(II) ions
The effect of initial concentration of metal ions on the adsorption was carried out for different initial concentrations of metal ions in the range of (10-100mg/l), (50-400mg/l) to Cu(II) and Pb(II), respectively. The dependence of percent of metal ion removal on initial concentration of metal ions is represented in Figure 4. Percent removal was found to be maximum at low initial concentrations of metal ions. It is 89.25 %, 97.43 % for 10 mg/l, 50 mg/l of Cu(II) and Pb(II), respectively. At low initial concentrations of metal ions nearly all the metal ions adsorbed due to availability of active adsorption sites. As the metal concentration increases active sites become occupied and hence the less adsorption (Meena et al., 2005).
Figure 4 Effect of initial concentration on adsorption of Cu(II), Pb(II)
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2.5 Adsorption isotherm
The adsorption of Cu(II), Pb(II) from aqueous solution on porcelanite has been studied at different temperatures (10, 25, 37.5 and 50°C). The general shapes of Cu(II), Pb(II) adsorption isotherm are shown in Figure 5 where the quantities adsorbed on porcelanite (Qe) are plotted as a function of equilibrium concentration (Ce) at (10, 25, 37.5 and 50°C).
Figure 5 Adsorption isotherm of Cu(II), Pb(II) on porcellanite surface at different temperatures
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The shape of the adsorption isotherm of Cu(II), Pb(II) on porcellanite is consistent with H-type on the Giles classification. H-type adsorption isotherm indicated high affinity between Cu(II), Pb(II) and porcellanite surface in very diluted solution (Giles et al., 1960). The experimental adsorption data were applied to both the theoretical Langmuir isotherm equation and empirical Freundlich equation. The results of applying Freundlich (eq.2) and Langmuir (eq. 3) (Veena and Robert, 2002), isotherm on the adsorption data are listed in Table 1.
Table 1 Results of the application of Freundlich and Langmuir isotherms on the system studied
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log Qe = log Kf + 1/n log Ce……… (2)
Where Kf is a fanction of the adsorption capacity and n is the intensity of adsorption.
Ce/Qe = 1/Qmb + Ce/Qm ………(3)
Where Qm is the maximum adsorption capacities (mg/g) and b is related to the adsorption energy.
The Freundlich and Langmuir isotherms are applied on the experimental data of the adsorption of Cu(II) and Pb(II) ions on porcellanite by plotting log Qe versus log Ce and Ce /Qe versus Ce, respectively (Figure 6 and 7). The results of Table 1 show that the Langmuir isotherms is better fitted on this system than the Freundlich as shown by the linear relationship of (Ce/Qe) versus (Ce) (Figure 7).
Figure 6 Linear form of Freundlich isotherms of Cu(II), Pb(II) on porcellanite at different temperatures
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Figure 7 Linear form of Langmuir isotherms of Cu(II), Pb(II) on porcellanite at different temperatures
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2.6 Thermodynamic studies
The effect of temperature on the adsorption of Cu(II) and Pb(II) was studied in the range of 10-50°C using different initial concentrations .The feasibitility of the adsorption process can be estimated by the Thermodynamic parameters of Gibbs energy change (DG), enthalpy change (DH) and entropy change (DS) by the following equations.
ΔG = -RT lnk………………..…(4)
K = Csolid / Cliquid……….……..(5)
lnK = ΔS / R – ΔH / RT……(6)
Where DG is the Gibbs energy change (KJ.mol-1), K is the equilibrium constant, Csolid is the solid phase concentration at equilibrium (mg/l), Cliquid is the liquid phase concentration at equilibrium (mg/l), T is the temperature in Kelvin and R is the gas constant (0.0083 KJ.mol-1 K-1).
ΔH (KJ.mol-1) and ΔS (KJ.mol-1.k-1) can be calculated from the slope and intercept of Eq.(6), respectively. The Thermodynamic parameters at the studied temperature ranges are listed in Table 2.
Table 2 Thermodynamic functions for adsorption of Cu(II), Pb(II) ions
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The plots of lnK versus. 1/T were found to be linear with a correlation coefficient (R2 = 0.871-0.977) and (0.948-0.990) for adsorption of Cu(II) and Pb(II), respectively (Figure 8).
Figure 8 Plot of van, t Hoff relationship between LnK versus 1/T
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Table 2 indicate, ΔG at all temperatures were negative and increrased with an increase in temperature, indicating the spontaneity of the adsorption of Cu(II) and Pb(II) onto porcellanite powder (Hefne et al., 2008). The positive value of ΔH indicates endothermic nature of the adsorption process, while the positive value of ΔS revealed the increase in randomness at the solid/solution interface during the adsorption process (Al-Saadie and Jassim, 2010).
3 Conclusion
The present study emphasize that porcellanite powder was employed as an adsorbent for the removal of Cu(II) and Pb(II) from aqueous solutions. The material showed enhanced Cu(II) and Pb(II) adsorption capacities compared with most materials reported in literature. the equilibrium data followed Langmuir isotherm model. The maximum percentage removal of 68.96% and 97.43% for Cu(II) and Pb(II) occurred at pH 6.5 and 25°C. It can be concluded that porcellanite powder is a promising low lost and high efficiency adsorbent for Cu(II) and Pb(II) removal from waste water and can be applied in a magnetically assisted water treatment technology.
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