Research Journal of Chemical Sciences ___ ______________________________ ______ ____ ___ ISSN 22 31 - 606X Vol. 3 ( 2 ), 44 - 53 , February (201 3 ) Res. J. Chem. Sci. International Science Congress Association 44 A Comparative Study of Modified Lignite Fly Ash for the Adsorption of Nickel from Aqueous Solution by Column and Batch Mode Study Malarvizhi T.S. 1 * , Santhi T. 1 and Manonmani S. 2 1 Department of Chemistry, Karpagam University, Coimbatore - 641021, INDIA 2 Depa rtment of Chemistry, P.S.G. College of Arts and Science, Coimbatore, INDIA Available online at: www.isca.in Received 24 th November 201 2 , revised 2 nd December 201 2 , accepted 16 th December 2012 Abstract The removal of N i 2+ from an aqueous solution using fly ash was modified by alkali (FAN), alkali and dye modified fly ash (FAN - MO) were compared. The influence of the four parameters (solution pH, contact time, initial metal ion concentration and dose of the adsorbent) on the removal of Ni 2+ at 27 5C was studied by batch mode and column study. The adsorption of Ni 2+ was higher at pH 3 for FAN (95.45%) in batch mode study and 57.4% in column study. For FAN - MO at pH 5, the adsorption was 89.2% in batch mode study and 7 4.69% in column study. The maximum adsorption of Ni 2+ onto FAN and FAN - MO was achieved at 50 minutes. The linear forms of Langmuir, Freundlich, Tempkin, D - R, Harkin - Jura and Frenkel Halsey isotherms were utilised for experiments with varying metal concent rations. The adsorption of Ni 2+ ions satisfies only Langmuir isotherm model. Influence of Cu 2+ ions and Zn 2+ ions on adsorption of Ni 2+ ions on FAN and FAN - MO in binary and tertiary systems showed certain decrease of adsorption ability. Keywords : Alkali - a ctivation, b atch mode studies, c olumn studies . Introduction Coal/Lignite based Thermal Power Generation has been the backbone of capacity addition in the country. Indian coal is of low grade having high ash content up to 40% in comparison to imported co als which have ash content of the order of 10 - 15%. Large quantity of ash is being generated at coal/lignite based Thermal Power Stations in the country, which has been one of the sources of pollution of both air and water. The demand for industrial and dom estic energy results in the production of a large volume of fly ash from solid coal fuel, which will increase in the world on an unprecedented scale during the next years. Therefore, fly ash should not only be disposed of safely to prevent environment poll ution, but should be treated a valuable resource 1 . Traditionally, fly ash has been used as pozzolanic material to enhance physical, chemical and mechanical properties of cements and concretes. However, only amounts of 20 - 30% of fly ash have been currentl y used for this purpose while remaining 70 - 80% is land filled or surface - impounded. For the remaining material, disposal practices involve holding ponds lagoons, landfills and slag heaps, all of which can be regarded as unsightly, environmentally undesir able and / or a non - productive use of land resources, as well as posing an on - going financial burden through their long - term maintenance. Furthermore, for those coal power plants located in urban areas, finding disposal sites must be well managed, so that local surface and ground water supplies are protected. This can cause significant economic burden to achieve the necessary water and land management. These factors have prompted researchers to look for alternative usages for fly ash, other than the cemen t and construction industry 2 . Most of the fly ashes from the combustion of coal are made up of aluminosilicate and silica glasses with small amounts of crystalline materials, including mullite, quartz, haematite, and magnetite 3 . The reactivity of a fly as h depends upon many parameters, most important of which are chemical and mineralogical composition of fly ash, curing temperature and the use of chemical activators 4 - 9 . The use of fly ash for the heavy metals removal, from wastewaters resulted in the dye f inishing industry, faces a supplementary problem, related to the dyes affinity for oxide surfaces. Previous studies proved that further conditioning by alkali treatment can be needed for enhancing the adsorption efficiency of heavy metals 10 , or multi compo nent systems of heavy metals and dyes, on fly ash. Good efficiencies of heavy metals removal were obtained on fly ash treated with 2N NaOH solutions 11 . Some dyes fixed on the fly ash surface can act as complexion agents, increasing the adsorption efficien cy of the heavy metals. Every development in science and technology brings in new problems. Now, it's for us to decide, how we intend to use the power of technology placed in our hands. The presence of heavy metals in the aquatic ecosystem has been of in creasing concern because of their toxic properties and other adverse effects on natural waters quality, such as Ni, Cu, Zn, Cr, Cd and Pb find its way to water bodies through waste water from metal plating industries, cadmium – nickel batteries and alloys . Exposure to nickel causes decrease in body weight, heart and liver damage and skin irritation. Nickel powder (T; R48 - 23) has been classified in chronic toxicity classification as per environmental risk assessment report on nickel. NiSO 4 , NiCl 2 , NiCO 3 and NiNO 3 are classified as carcinogen class I (by inhalation), reproductive toxicants class II (may cause harm to unborn Research Journal of Chemical Sci ences ___ _ _ _______________________________ ______________ _ ________ ISSN 22 31 - 606X Vol. 3 ( 2 ), 44 - 53 , February (201 3 ) Res. J. Chem. Sci. International Science Congress Association 45 children) and chronic toxicants (T; R48 23). If particle size of nickel powder found to be less that 0.1 mm, it is classified as T; R52 - 5 3 (harmful to the aquatic environment) 12,13 . The higher concentration of Ni(II) in ingested water may cause severe damage to lungs, kidneys, gastrointestinal distress, e.g., nausea, vomiting, diarrhoeas, pulmonary fibrosis, renal oedema, and skin dermatiti s. It is also a known carcinogen 14 . The average concentration in the effluent from the plating plants ranges between 10 and 80 mg/l. Due to toxicity of metals, the Ministry of Environment and Forests (MOEF), Government of India, has set Minimal National St andards (MINAS) of 2.0 mg/l for Ni(II) for safe discharge of the effluents containing these metal ions into surface water 15 - 18 . The presence of heavy metal in wastewaters is due to the discharge of many industrial units. This paper presents a comparati ve study of the efficiency of the Ni(II) uptake onto modified fly ash by alkali treatment 4N NaOH (FAN) and by Methyl orange (FAN - MO). The adsorption kinetics were studied and the substrate capacities are discussed and correlated with the surface structure (SEM and EDX) by batch and column study. Material and Methods Preparation of adsorbents: The fly ash used for this study was collected from the NLC Power Plant, Neyveli, Tamil Nadu, India. One part of the fly ash was treated with 4N NaOH and then kept i n magnetic stir at 90C for 1 h. After that the solution was allowed to settle for 24 hrs. and washed with distilled water again and again till the conductivity of the filtrate was below 300 s. It was then filtered and dried in hot air oven at the temper ature of 105 o C. The dried alkali treated fly ash (FAN) was then powdered, ground and used for further studies 19 . It was divided into two parts and one part was used as such and the other part of the FAN was further treated with Methyl orange dyes for 48 h ours at room temperature followed by filtration and flush with distilled water, dried (FAN - MO) and used for adsorption of Ni(II) ions. The yield for FAN was found to be 95.3% and for FAN - MO it was found to be 96%. Preparation of Adsorbate: Nickel sulphate hexahydrate (NiSO 4 .6H 2 O), Zinc sulphate heptahydrate (ZnSO 4 .7H 2 O), were purchased from Spectrum reagents and chemicals Pvt. Ltd., Adayar, Aluva. Copper sulphate pentahydrate (CuSO 4 .5H 2 O), NaOH, HCl, HNO 3, were obtained in S D fine – Chem. Limited, Mumba i and used without further purification. Stock solutions were prepared by dissolving 1g/L d ouble distilled water was used through out the study. Characterization of adsorbent: Acidity and basicity of adsorbent (Boehm titration): Acidity and basicity were estimated by mixing 0.2 g of adsorbent (FAN and FAN - MO separately) with 20 mL of 0.1 M NaOH, 20 ml of 0.1 M Na 2 CO 3 , 20 ml of 0.1 M NaHCO 3 in a closed flask separately, and agitating for 48 h at room temperature. Filtered and from that filtrate 5 mL was pip etted out and titrated with 0.1 M HCl 20,21 . Fourier transform infrared analysis: Functional groups in FAN and FAN - MO were examined by using the FTIR method of analysis. The FTIR spectrophotometer was based on changes in dipole moment resulting from bond v ibration upon absorption of IR radiation. It was carried out at room temperature using Spectrum RX1 "Pelmer" version 5.3 Spectrophotometer in the spectral range of 4000 to 400 cm - 1 with a resolution of 4 cm - 1 . Adsorption and kinetic studies: A stock solut ion of NiSO 4 .6H 2 O (1000mg/L) was prepared and suitably diluted accordingly to the various initial concentrations. Adsorption studies were carried out at room temperature (27 5 o C). Batch adsorption studies were carried out using 0.2g of adsorbent for eac h bottle, the adsorption experiments were carried out with 50 mL of solution of required concentration and pH of the solutions varied from 2 to 10 in a bench shaker at a fixed shaking speed of 120 rpm. The resulting mixture was filtered (Whatmann filter pa per No.41) and the initial and final concentrations of the metal ions were determined by UV - 2450 vis spectrophotometer. The pH of the solution was adjusted using 0.1M HCl and 0.1M NaOH. The experiments were carried out for various adsorbent dosages, differ ent initial Ni(II) ions concentration, for various contact time and different initial pH of the solution. The stock solution of NiSO 4 .6H 2 O was prepared for the concentration of 1000 ppm and it was diluted to various required concentrations. From the initia l and final concentration, percentage removal can be calculated by (1) where, C o - initial concentration of nickel in mg/L, C f - final concentration of nickel in mg/L. The data obtained in batch mode kinetics were used to calculate the equilibrium metal uptake capacity. It was also calculated for adsorptive quantity of nickel by using the following expression: (2) Where q e is the equilibrium metal ion uptake c apacity in mg/g, is the sample volume in litre, C o the initial metal ion concentration in mg/L, C e the equilibrium metal ion concentration in mg/L and w is the dry weight of adsorbent in grams. Adsorption isotherms: Equilibrium studies were undertaken to understand the behaviour of the adsorbent at an equilibrium condition. Equilibrium data are basic requirements for the design of adsorption systems and adsorption models, which are used for the mathematical description of the adsorption equi librium of the metal ion on to the adsorbent. The results obtained on the adsorption of nickel were analysed by the well - known models given by Langmuir, Freundlich, Tempkin, Dubinin - Radushkevich, Harkin - Jura and Frenkel - Halsey - Hill isotherms. For the sorpt ion isotherms, initial metal ion concentration was varied while the pH of the solution and adsorbent weight in each sample held constant. The sorption Research Journal of Chemical Sci ences ___ _ _ _______________________________ ______________ _ ________ ISSN 22 31 - 606X Vol. 3 ( 2 ), 44 - 53 , February (201 3 ) Res. J. Chem. Sci. International Science Congress Association 46 isotherms were realized with FAN at solution pH 3 and FAN - MO for nickel at solution pH 5 for nickel ion a dsorption. The experimental results were used for the calibration of parameters of the six adsorption isotherm are presented in table - 1. Langmuir isotherm: Langmuir model is the simplest theoretical model related to monolayer adsorption on the surface w ith finite number of available identical sites 22,23 . The linear form of Langmuir equation is derived as: (3) Where Q e (mg/g) and K L (dm 3 /g) are Langmuir constants related to adsorption capacity and rate of a dsorption. Freundlich isotherm: Freundlich isotherm expression is an empirical equation assumes heterogeneous surface energies, in which the energy term in Langmuir equation varies as a function of the surface coverage 24 . The well - known logarithmic form of the Freundlich isotherm is given by: (4) where K F (mg/g) (l/mg) and 1/n are the Freundlich adsorption constant and a measure of adsorption intensity. Tempkin isotherm: Tempkin assumes that heat of adsorption (function of temperature) of all molecules in the layer would decrease linearly rather than logarithmic with coverage. Its derivation is characterized by a uniform distribution of binding energies (up to some maximum binding energy) 25 . The Tempkin isothe rm has been used in the form of: (5) where B=RT/b, b and A, R and T are the Tempkin constant related to heat of sorption (J/mol), equilibrium binding constant (l/g), gas constant (8.314 J/mol K) and absolut e temperature (K).Dubinin - Radushkevich isotherm. The D - R model was applied to estimate the porosity, apparent free energy and the characteristics of adsorption 26 - 28 . The D - R isotherm does not assume a homogeneous surface or constant adsorption potential. The D - R model has commonly been applied in the following equation (6) and its linear form can be shown in equation (7) (6) (7) whe re K is a constant related to the adsorption energy, Q m the thorticalaturationcapacity,ɛthPolanyipotntial, calculated from equation (8) (8) The slope of the plot of ln q e vruɛ²givmol 2 /(kJ 2 )) and the intercept yields the adsorption capacity, Q m (mg/g). The mean free energy of adsorption (E), defined as the free energy change when one mole of ion is transferred from infinity in solution to the surface of the sol id, was calculated from the K value using the following relation 29 . From the value of E, the adsorption mechanism was predicted. (9) Harkin – Jura adsorption: The Harkin - Jura adsorptio n isotherm can be expressed as (10) where B 2 is the isotherm constant. 1/q e 2 was plotted vs. log C e . This isotherm explains the multilayer adsorption by the existence of a heterogeneous pore distribution 30 . Fren kel - Halsey - Hill isotherm: The Frenkel - Halsey - Hill isotherm can be expressed as (11) In q e was plotted vs. ln C e . This isotherm explains the multilayer adsorption b y the existence of a heterogeneous pore distribution of the adsorbent 31 . Results and Discussion Characterization of adsorbents: Scanning electron microscopic studies (SEM): The f igure - 1.a., 1.b and f igure - 2 clearly shows that the SEM was employed to obser ve the physical morphology of the FAN and FAN - MO at 1000 X magnification. The SEM images shown in f igure - 1 , a clearly show that finer fly ash particles are primarily spherical, whereas the alkali treated fly ash particles shown in f igure - 1.b are mainly composed of irregular and porous particles in FAN and the FAN - MO, f igure - 2 shows the i ncreased roughness of surface compared to fly ash and FAN. Figure - 1 a SEM image of fly ash Figure - 1b SEM image of FAN Research Journal of Chemical Sci ences ___ _ _ _______________________________ ______________ _ ________ ISSN 22 31 - 606X Vol. 3 ( 2 ), 44 - 53 , February (201 3 ) Res. J. Chem. Sci. International Science Congress Association 47 Figure - 2 SEM image of FAN - MO Energy dispersive X - ray spectrosco pic analysis (EDX) : The components of fly ash was SiO 2 38.1%, Al 2 O 3 36.36%, CaO 17.39%, MgO 3.28%, TiO 3 2.55% and FeO 2.31%. The major components of FAN was SiO 2 36.89%, Al 2 O 3 33.04%, CaO 16.37%, MgO 4.77%, TiO 3 1.38%, FeO 1.85 Na 2 O 5.71% and for FAN - MO wa s SiO 2 33.76 %, Al 2 O 3 38.36%, CaO 17.40%, MgO 4.99%, TiO 3 1.73% and FeO 3.76% respectively. The presence of the above mentioned oxides in fly ash, FAN, FAN - MO are clearly shown in figure - 3.a, 3.b and 4 SiO 2 and Al 2 O 3 contents make up about 70% of the f ly ash. FeO and CaO contents compose about 19%. Figure - 3a EDX analysis of fly ash Figure - 3b EDX analysis of FAN Figure - 4 EDX analysis of FAN - MO FTIR spectroscopic studies: Surface functional groups were detected by Fourier t ransform infrared (FTIR) spectroscopy from the scanning range (4000 cm - 1 - 400cm - 1 ) and elemental analysis was performed using an elemental analysis. FTIR spectra for FAN and FAN - MO shows broadband between 3454.1 and 3448.7 cm - 1 in figure - 5a and figure 5b. respectively. This indicates the presence of hydrogen bonded OH groups such as water either OH groups either of clay minerals or phenolic groups. This stretching is due to both the silanol groups (Si - OH) and adsorbed water (peak at 3400 cm - 1 ) 32 . The FTIR spectra of FAN indicated peak in the region of 1614 due to C=C or C=O aromatic ring stretching bands (aromatic carbon peaks) aldehydes and ketones. The band at 1428 cm - 1 may be due to aliphatic C - H stretching vibrations in FAN - MO. The FTIR of FAN - MO showe d a transmittance at 1113.5 cm - 1 due to the vibration of the C=O group in lactones 33 . Additionally intense vibration at 558.2 cm - 1 for FAN - MO is attributed to clay and silicate minerals 34 . The strong presence of peaks associated with bounded water, 3799.6, 3854.6 and 3840.5 cm - 1 , indicates that exposure of hydrolysed silica to compressive stress increased water dissolution into the silica structure as hydroxyl, for FAN and FAN - MO as expected by theory respectively 35 . Although some interference can be drawn about the surface functional groups from FTIR spectra, the weak and broad bands do not provide any authentic information about the nature of the surface oxides. The presence of polar groups on the surface are likely to give considerable cation exchange cap acity to the adsorbents. Figure - 5a FTIR spectrum of FAN Figure - 5b FTIR spectrum of FAN - MO Research Journal of Chemical Sci ences ___ _ _ _______________________________ ______________ _ ________ ISSN 22 31 - 606X Vol. 3 ( 2 ), 44 - 53 , February (201 3 ) Res. J. Chem. Sci. International Science Congress Association 48 Acidity and basicity: (Boehm titration): This titration shows the number of acidic, basic, phenolic, carboxyl and lactones sites. For FAN, the numbers of basic sites present were found to be 1.7 m.Eq/g. L, the numbers of phenolic, carboxyl and lactones groups were found to be 4.5mEq/g .L and the numbers of carboxyl groups present were found to be 2.44mEq/g.L. For FAN - MO, the numbers of basic sites present were found to be 1.8 m.Eq/g. L, the numbers of phenolic, carboxyl and lactones groups were 3.44mEq/g.L and the numbers of carboxyl groups present were 1.83 mEq/g. L. The above values for FAN and FAN - MO were also favourable for the possibilit y of ion exchange mechanism during the adsorption of Ni(II)process because the number of phenolic, carboxyl and lactones groups in FAN was higher compared to FAN - MO 36 - 39 . Effect of pH on adsorption, desorption and recycling ability : The pH of the solution has a significant impact on the uptake of heavy metals. The pHzpc of FAN was 2 and for FAN - MO, it was 4. The solution pH is above than the pH zpc of adsorbent, the surface of the adsorbent is highly loaded with negatively charged ion. It favours the ads orption of metal cation onto the negative surface of the adsorbent due to the electrostatic attraction. Therefore, it can be expected that positively charged metal ions are likely to adsorb onto the negatively charged adsorbents at a pH above ZPC for FAN a nd FAN - MO 40 . Metal cations in aqueous solutions hydrolyse according to the generalized expression for divalent metals. M 2 + (aq . ) + n H 2 O˂ ˃ M(OH) 2 − n + n H + The silica in FAN and FAN - MO could adsorb either positive or negative contaminants depending on the pH of the solution. The central ion of silicates has an electron affinity, giving the oxygen atoms bound to it low basicity. This allows the silica surface to act as a weak acid, which can react with water, forming silanol (SiOH) groups. As a result, at low pH the silica surface is positively charged and at high pH values it is negatively charge. The pHzpc of silica is generally in the neighbourhood of 2.0. Other solid material, such as iron and alumina, also shows the same phenomenon of developing positive or negative charges depending on pH. Iron as Fe 2 O 3 has a zero point charge 6.7, while that of alumina pHzpc equal to 8 41 - 43 . This indicates that the maximum Ni(II) ions adsorption capacity of FAN and FAN - MO can be attributed to the electrostatic interacti on of the adsorbate with surface silica and iron sites of the adsorbents 44 - 46 . Figure - 6 indicates that the pH of the solution (2.0 - 10.0) had a significant effect on the adsorption of Ni(II)onto FAN and FAN - MO. At pH 3, the adsorptions of Ni 2+ on FAN and a t pH 5, the adsorption of Ni 2+ on FAN - MO were found to be 95.41% and 89.2% respectively. Ni 2+ ions were removed by precipitation not in adsorption if the solution pH is above pH 8 for FAN as well as FAN - MO 47 . Thus, we fixed the pH 3 for FAN and pH 5.0 fo r FAN - MO in this study. As shown, the precipitation of the heavy metal ions except copper was less than 20% at pH below 8, indicating that the removal of the metals except copper was mainly accomplished by adsorption below pH 8. Since the FAN has a low ZP C, the surface of the fly ash was negatively charged under the pH investigated. As pH increased from 3 to 8, it can be expected that the fly ash surface becomes more negatively charged. Thus, more favourable electrostatic attractive forces enhanced cationi c metal ion adsorption as pH increased. However, the dependence of heavy metal adsorption on pH was different for each metal. The effect of pH on adsorption desorption and recycling capacities of FAN and FAN - MO for Ni 2+ removal in aqueous solution was give n in the figure - 6. Figure - 6 Effect of pH on adsorption and desorption of Ni(II) ions onto FAN and FAN - MO For FAN, the adsorption capacity increases initially to 95.41% until the pH reaches 3 and after pH 3, it decreases slightly, then increased and rem ained constant. But for FAN - MO, the adsorption capacity increased to 89.21% at pH 5 and decreased slightly, then increased to certain extent and remained constant. In the wastewater treatment systems using adsorption process, the regeneration of the ad sorbent and /or disposal of the loaded adsorbent are very important. Desorption studies were carried out for both the adsorbents FAN and FAN - MO by employing batch methods shown in figure - 6. The maximum desorption of 48.29% took place in acidic medium at th e pH 2 for FAN and 37.46% for FAN - MO at pH 2. The results indicate that nickel (II) ions adsorbed onto both FAN and FAN - MO can be recovered by distilled water which was higher for FAN compared to FAN - MO. After desorption the adsorbent were further used for adsorption process for the removal of Ni(II) ions. The percentage of removal of Ni(II) ions were found to be 81.89 % for FAN at pH 3 and 80.32% for FAN - MO at pH 5 given in f igure - 6. The increase in the removal of Ni(II) ions took place after pH 7 may be d ue to precipitation of metal ions in alkaline medium and not by adsorption. Effect of contact time: Aqueous nickel metal ion solutions with initial ion concentration of 100mg/L were kept in contact with FAN and FAN - MO from 5 minutes to 60 minutes. The rat e of removal was rapid for first 25 minutes for both the adsorbents Research Journal of Chemical Sci ences ___ _ _ _______________________________ ______________ _ ________ ISSN 22 31 - 606X Vol. 3 ( 2 ), 44 - 53 , February (201 3 ) Res. J. Chem. Sci. International Science Congress Association 49 and thereafter the rate of metal removal attains equilibrium. No significant change in metal ion removal after 45 minutes for both FAN and FAN - MO. During the initial stage of adsorption, a large number of vacant surface sites are available for adsorption. After a lapse of some time, the remaining vacant surface sites are difficult to occupy due to repulsive forces between the adsorbate molecules on the solid surface. The maximum uptake of nickel metal ions at pH 3 for FAN were 95.41% and at pH 5, the maximum uptake of nickel metal ions were 89.21% at the equilibrium time of 50 minutes. Adsorption Kinetics: The adsorption process of Ni 2+ can be fitted well using the pseudo second order ra te for both FAN and FAN - MO. The kinetic parameters were given in the table - 1. The q e value (25.44) obtained from second order kinetic equation for FAN was close to the experimental q e value (21.1) and the linear regression coefficient value R 2 value (0.997 8) obtained for pseudo second order kinetics was close to unity compared to the R 2 value (0.7694) obtained from first order kinetics. The values on initial sorption (h) that represents the rate of initial adsorption, is 4.6 mg(gmin) - 1 for FAN. This indicate s the adsorption of Ni(II) ions onto FAN follows pseudo second order kinetics. The q e value (23.42) obtained from second order kinetic equation for FAN - MO was close to the experimental q e value (19.33) and the linear regression coefficient value (R 2 value 0.9947) obtained for pseudo second order kinetics was close to unity compared to the R 2 value (0.5998) obtained from first order kinetics. The values on initial sorption (h) that represents the rate of initial adsorption, is 5 mg(g min) - 1 for FAN - MO. This i ndicates the adsorption of Ni(II) ions onto FAN - MO follows pseudo second order kinetics. The Elovich equation, the linear coefficient value for FAN was found to be 0.9547, where as it was 0.9032 for FAN - MO. Elovich constants A E (desorption constant, g m g - 1 ) and B E (Initial adsorption rate, mg(g min) - 1)for FAN were 0.2647 mg/g min and 772.57 g/min respectively. Elovich constants A E and B E for FAN - MO were 0.3476 mg/g min and 7823.5 g/min respectively. This value also best for FAN - MO compared to FAN, proves the applicability of Elovich equation for FAN - MO than FAN. In intraparticle diffusion model, the values of q t were found to be linearly correlated with values of t 1/2 . The K d values were calculated by using correlation analysis. K d =1.59 mg g - 1 min - 1/2 , R 2 =0.9005, C=12.445 for FAN and K d =1.27 mg g - 1 min - 1/2 , R 2 =0.9453, C=12.36) for FAN - MO were obtained using intraparticle diffusion model. The R 2 values were found to be close to unity for FAN - MO compared to FAN, indicating the application of this model is best fitted to FAN - MO compared to FAN. This reveals the presence of intra particle diffusion process in FAN - MO than for FAN. The values of intercept C given inTable - 1 provide information about the thickness of the boundary layer, the resistance to the external mass transfer increase as the intercept increase. The value of C for FAN was 12.445 and the value for C was 12.36 for FAN - MO. Effect of adsorbent dose: T he maximum adsorption capacities of FAN at pH 3 recorded as 95.41 % and 89.2% for FAN - MO at pH 5 for the dosage of 0.2 g/50 mL. This was increased to98.55% for FAN and 96.88% for FAN - MO. This was due to the increase in the adsorption sites as increase the dose from 0.2g to 1g in 50 mL. Effect of Ni(II) ion concentration on adsorption: The init ial metal concentration provides an important driving force; hence a higher initial concentration of metal ions will increase the sorption rate. As the concentration of Ni(II) ions increased from 25 mg/L to 200 mg/L, the percentage of adsorption decreased. The percentage of adsorption for FAN was found be decreased to 85.32% and for the percentage of adsorption for FAN - MO was decreased to 80.49%. This was due to the increase in concentration of Ni(II) ions for lesser number of adsorption sites. Adsorptio n isotherm: To optimize the design of an adsorption system for the adsorption of Adsorbate, it is important to establish the most appropriate isotherm model. Various isotherm equations like those of Langmuir, Freundlich, Tempkin, Dubinin - Radushkevich, Har kin Jura and Frenkel Halsey isotherm have been used to describe the mono - component equilibrium characteristics of adsorption of Ni(II) ions onto FAN and FAN - MO. The experimental equilibrium adsorption data were obtained by varying the concentration of Ni( II) ions with fixed dosage of FAN and FAN - MO. The adsorption parameters for each metal ion obtained from the fitting of different isotherm models with the experimental data are listed in Table - 2 along with the linear regression coefficients, R 2 . FAN and F AN - MO have a homogeneous surface for the adsorption of metal ions. Therefore, it is expected that the Langmuir isotherm equation can be better represent the equilibrium adsorption data. The R 2 value is closer to unity for Langmuir model than that for the other isotherm models for both FAN (R 2 =0.9995) and FAN - MO (R 2 =0.999). Therefore, the equilibrium adsorption data of Ni(II) ion adsorption on FAN and FAN - MO was represented appropriately by the Langmuir model in the studied concentration range. The cal culated value of D - R parameters is given in Table - 2. The saturation adsorption capacity Q m obtained using D - R isotherm model for adsorption of Ni(II) ions onto FAN and FAN - MO is 22.32 and 21.28 mg g - 1 at 0.2g 50mL - 1 adsorbent dose, which is close to that o btained (21.23 and 20.04) from Langmuir isotherm model given in Table - 2 respectively. The values of E calculated using Eq. 8 is 5KJ mole - 1 and 4.083 KJ mole - 1 for FAN and FAN - MO respectively, which indicating that the ion exchange mechanism was favourabl y taking place in the adsorption of Ni 2+ ion adsorption onto FAN and FAN - MO (for Ion exchange mechanism the value of E was found to be within 1.3 to 9.6 KJ mole - 1 ) 48 . Column studies: Breakthrough capacity curves are important in process design because the y are directly related to the feasibility Research Journal of Chemical Sci ences ___ _ _ _______________________________ ______________ _ ________ ISSN 22 31 - 606X Vol. 3 ( 2 ), 44 - 53 , February (201 3 ) Res. J. Chem. Sci. International Science Congress Association 50 and economics of a given process 49 . The time taken for elution is very less compared to batch mode studies where it took 50 minutes to attain equilibrium. Figure - 7 shows that 50 mL of Ni 2+ ion solution(100 mg/L) o f pH 3 for FAN and 50 ml of Ni 2+ ion solution(100mg/L) of pH 5 for FAN - MO could be passed through a column without any Ni 2+ ions being detected in the effluent when 0.2 g adsorbent used. The results obtained at 5 mL/min were calculated from the breakthro ugh curve. The retention time of the analyte (V R ) determined as 41.5 ml for FAN and 31.7 ml for FAN - MO corresponding to the volume respect to the half the initial concentration 50 . Figure - 7 Break through capacity of FAN and FAN - MO (12) The breakthrough volume (V B ) is usually defined (13) whrσᵥithtandarddviationwhichcanbdtrmind graphicallyfromthbrakthroughcurvσᵥiindirctrlation to the efficiency of the solid phase extraction column, the number of theoretical plates (N) which can be calculated from the break through curve shown in figure - 7 using the equation: (14) The capacity factor of the solute (k), can be calculated from the fundamental equation of chromatography: (15) Thrcovryfactor‘r’canalodirctlyrlatdtoth breakthrough curve. The recovery factor can be calculated by using the equation: (16) where V M represents the hold up volume of the solid phase extraction cartridge. The parameters calculated by using the above relationships for both FAN and FAN - MO were given in the table - 3. For the desorption experiments, several solvents (acids, bases and water) have been used. Desorption with water was found to be 24.1%which was higher than for other desorbing agent used for FAN. Desorption with 0.1M HCl was found to be 62.22% higher than other desorbing agent for FAN - MO. Influence of other metals on adsorption of Ni(II) ions : Influence of Zinc (II) ions and Cu(II) ions on adsorption of Ni(II) ions . The concentration of Ni(II) ion solution was kept as 100 ppm. The concentration of Cu(II) ions were varied as 10, 20, 30 and 40 mg/L. Each solution was taken in the bottles and the pH was adjusted to 3 for FAN and after shaking 50 minutes, the percentage of adsorption was calculated. The percentage of adsorption decreased from 95.41 % to 83% as the concentration of Cu(II) solution increased in both the cases. This showed that there was a competitive adsorption taking place to certain extends between the Ni(II) ions and the Cu(II) ions. The same procedure was repeated for Ni(II) ions in presence of Zn(II) ions. The adsorption percentage of Ni(II) ions was decreased to 95.41% to 81.2 5% in presence of Zn(II) ions. The same procedure was repeated for FAN - MO at solution pH 5 and the adsorption was decreased to 89.25% to 79.06% in presence of Cu(II) ions. The adsorption percentage of Ni(II) ions was decreased to 89.25% to 80.86% in presen ce of Zn(II) ions. Influence of Zn(II) ions and Cu(II) ions on adsorption of Ni(II) ions : The concentration of Ni(II) ion solution was kept as 100 mg/L. The concentration of Zn(II) ion solutions and Cu(II) ion solutions were varied as 10, 20, 30 and 40 m g/L. Each solution was taken in the bottles, which were added to Ni(II) solution, and the pH was adjusted to 3 for FAN and after shaking 50 minutes, the percentage of adsorption was calculated. The percentage of adsorption decreased from 95.45% to 82.44% as the concentration of Ni(II) ions and Cu(II) ions increased. This showed that there was a competitive adsorption taking place to certain extends between the Ni(II) ions, the Zn(II) ions and Cu(II) ions. The percentage of adsorption of Ni(II) in presence of other metals was decreased. The same procedure was repeated for the adsorbent FAN - MO at pH 5 and the percentage of adsorption was decreased from 89.25% to 75.83%. Table - 1 Comparison of kinetic parameters of Ni(II) adsorption on FAN and FAN - MO Pseudo - first - order equation Pseudo - second - order equation Elovich equation Intraparticle diffusion Adsorbent q e, cal (mg/g) k 1sec - 1 q e, exp (mg/g) R 2 k 2 (Lmole - 1 sec - 1 ) h q e, cal (mg/g) R 2 A E (mg/g min) B E (g/min) R 2 kd (mg/g min) R 2 C FAN 13.49 0.082 21.1 0.76 94 0.0072 4.6 25.44 0.9978 0.2647 772.57 0.9547 1.58 0.9005 12.45 FAN - MO 10.34 0.062 19.33 0.5998 0.0092 5 23.42 0.9947 0.3476 7823.5 0.9032 1.27 0.9453 12.36 Research Journal of Chemical Sci ences ___ _ _ _______________________________ ______________ _ ________ ISSN 22 31 - 606X Vol. 3 ( 2 ), 44 - 53 , February (201 3 ) Res. J. Chem. Sci. International Science Congress Association 51 Table - 2 Isotherm constants and coefficients of determinations for FAN and FAN - MO Isotherm mode l FAN FAN - MO Isotherm model FAN FAN - MO Langmuir Q m ( mg/g) K a (l/ mg) R 2 21.23 3.16 0.9995 20.04 1.686 0.999 Dubinin - Radushkevich Q m mg/g K (x10 - 8 mol 2 /KJ 2 ) E (kJ mol - 1 ) R 2 2.32 2 5 0.1083 21.28 3 4.083 0.349 Freundlich 1/n K F ( mg /g) R 2 0.0259 23.65 0.5363 0.0384 23.56 0.8087 Harkin - Jura R 2 A B q e 0.9252 2500 4.5 26.83 0.792 2500 4.5 27.52 Tempkin α (l/g) βmgl b R 2 36.76 0.5761 4372.8 0.5292 23.35 0.8276 3043.9 0.8162 Frenkel - Halsey R 2 1/n K 0.5363 0.0259 1.1x10 53 0.8087 0.0383 6.69x10 35 Table - 3 The parameters calculated for FAN and FAN - MO for adsorption of Ni(II)ions Conclusion Treating the fly ash with alkaline NaOH ( 4N) solutions, the surface is modified by dissolution and reprecipitation reactions. By dissolution of acid oxides, the specific surface area is enhanced and activated and the efficiency of heavy metal removal increases. Adding dye to the fly ash surface r esults in a new surface, which is one more homogeneous but less negatively charged. The overall effect is a decrease in the affinity for heavy metals. The adsorption of Ni(II) ions is pH - dependent with maximum adsorption of 95.45% occurring at pH 3 for FA N and 89.25% for FAN - MO at pH 5. The adsorption data was well fitted by the Langmuir isotherm model which shows monolayer adsorption capacity of FAN and FAN - MO. Adsorption of Ni(II) ions onto FAN and FAN obeyed pseudo second order kinetics. The adsorption of Ni(II) ions can be desorbed from both the adsorbents using water was 48.29% of adsorbed Ni(II) ions from FAN and 37.46 % of adsorbed Ni(II) ions were recovered from FAN - MO by batch mode studies at pH 3. The percentage of adsorption of Ni(II) ions on FA N and FAN - MO was slightly higher in single system than binary and tertiary system which shows the competitive adsorption between the metal ions. Compared to FAN - MO, FAN had higher adsorption ability for the removal of Ni(II) ions from aqueous solution. In column studies, the removal efficiency of Ni(II) ions were less compared to batch mode studies for both FAN and FAN - MO, but the time taken for adsorption was only 10 minutes. With these conditions, we found the column study was not much suitable compared to batch mode studies for removal of Ni(II) ions onto FAN and FAN - MO. The experimental results show that this can be an up - scalable solution and represent a step in investigating the process of complex treatment of wastewater containing dyes and heavy meta ls. References 1. Guerrero A., Goni S., Macias A. and Luxn M.P., Hydraulic activity and microstructral characterization of new fly ash - belite cement synthesized at different temperatures, J. Mater. Res. , 14(6) , 2680 (1999) % of desorpt ion Parameters % of adsorption VB (ml) VR (ml) VM (ml) N r% HCl Water NaOH K FAN 57.4 0.1 41.5 2.4 2.01 84.8 9.5 24.1 24.8 16.3 FAN - MO 96.56 0.7 31.7 4 2.14 55.4 62.22 32.1 8.26 16.93 Research Journal of Chemical Sci ences ___ _ _ _______________________________ ______________ _ ________ ISSN 22 31 - 606X Vol. 3 ( 2 ), 44 - 53 , February (201 3 ) Res. J. Chem. Sci. International Science Congress Association 52 2. Iyer R.S. J. A. Scott/ Resources, Conservation and Recycling, 31 , 217 - 228 (2001) 3. Luxan M.P. , Scnchez de Rohas M.I. and Frias M., Investigations on the fly ash - calcium hydroxide reactions , Cement and concrete Res., 19 , 69 (1989) 4. Arjun P., Silsbee M.R. and Roy D.M., Chemical activation of lo w calcium fly ash: part: identification of the most appropriate activators and their dosage, Proceedings of the Intl. Ash Utilization Symposium, Kentucky, (2001) 5. Bakharev T., Sanjayan J.G. and Cheng Y.B., Effect of elevated temperature curing on propertie s of alkali - activated slag concrete, Cement and Concrete Res ., 29 , 1629 (1994) 6. Ma W., Liu C., Brown P.W. and Komameni S., Pore structure of fly ashes activated by Ca(OH) 2 and CaSO 4 .H 2 O, Cement amd concrete Res ., 19 , 69 (1995) 7. Pietersen H.S., Fraay L.A . an d Bijen J.M. , Reactivity of fly ash at high pH, Mater. Res. Soc. Symp. Proc. , 178, 139 (1990) 8. Fernndez - Jimnez A . , Puertas F. and Palomo J.G., Alkali - activated slag mortars: Mechanical strength behaviour, Cement and concrete Res. , 29 , 1313 (1999) 9. Shi C. and Day R.L., Pozzolanic reaction in the presence of chemical activators: I. Reaction kinetics, Cement and Concrete Res. , 30 , 1625 (2000) 10. Visa M., Isaac L. And Duta A., Fly ash - activated carbon powder for dyes and heavy metals removal, Adv. Mater. Res. , 7 9(82) 243 - 243 (2009) 11. Visa M., Luminit A. A . and Duta A . , Advanced treatment of waste water with methyl orange and heavy metals on TiO2, fly ash and their mixtures, J. Catal. Today , (2008) 12. http: \ \ www.enia.org/index.cfm/ci_id/3741.htm , accessed on February 2, (2008) 13. Kinhikar V.R., Removal of Nickel (II) from Aqueous Solutions by Adsorption with Granular Activated Carbon (GAC), Res.J.chem.sci ., 2(6), 6 - 11 (2012) 14. Axtell N.R., Sternberg S.P.K. and Claussen K. , Lead and Ni(II) removal using Microspore and Lemna minor , Bioresour Technol ., 89 , 41 - 48 (2003) 15. MINAS pollution control acts, rules, notification issued there under Central Pollution Control Board, Ministry of Environment and Forests, Government of India, New Delhi, September (2001) 16. Deshpande S.M. and Aher K.R., Evaluation of Groundwater Quality and its Suitability for Drinking and Agriculture use in Parts of Vaijapur, District Aurangabad, MS, India, Res.J.chem.sci ., 2(1), 25 - 31 (2012) 17. Vaishnav M.M. and Dewangan S., Assessment of Water Quality Status in Ref erence to Statistical Parameters in Different Aquifers of Balco Industrial Area, Korba, C.G. INDIA, Res.J.chem.sci ., 1(9), 67 - 72 (2011) 18. Sharma Shraddha, Vishwakarma Rakesh, Dixit Savita and Jain Pravee n, Evaluation of Water Quality of Narmada river with r eference to Physco - chemical Parameters at Hoshangabad city, M.P., India, Res.J.chem.sci. , 1(3) , 40 - 48 (2011) 19. Aziz H.A., Adlan M.N., Ariffin K.S . , Heavy metals (Cd, Pb, Zn, Ni, Cu and Cr(III) removal from water in Malaysia: post treatment by high quality limenstone, Bioresour. Technol. , 99 , 1578 – 1583 (2008) 20. Enemose Edith A. and Osakwe S.A., Studies on the effect of pH on the sorption of Al 3+ and Cr 6+ Ions from aqueous solutions by Almond Tree (Terminalia catappa L.) Biomass , Res.J.chem.sci., 2(4) , 13 - 17 (2 012) 21. Suantak Kamsonlian, Chandrajit Balomajumder and Shri Chand, Removal of As (III) from Aqueous Solution by Biosorption onto Maize (Zea mays) Leaves Surface: Parameters Optimization Sorption Isotherm, Kinetic and Thermodynamics Studies, Res.J.chem.sci., 1(5), 73 - 79 (2011) 22. Cho H., Oh D. and Kim K., A study on removal characteristics of heavy metals from aqueous solution by fly ash, J. Hazard Mater . , 127 , 187 – 195 (2005) 23. Langmuir I . , The constitution and fundamental properties of solids and liquids , J. Am. C hem. Soc. , 38 , 2221 - 2295 (1916) 24. Freundlich H . , ber die, Adsorption in lsungen (adsorption in solution) , Z. Phys.Chem. , 57 , 384 - 470 (1906) 25. Tempkin M.I . and Pyzhev V . , Kinetics of ammonia synthesis on promoted iron catalyst , Acta Phys.Chim. USSR , 12, 327 - 3 56 (1940) 26. Dubinin M.M., The potential theory of adsorption of gases and vapors for adsorbents with energetically non - uniform surface, chem.Rev. , 60 , 235 - 266 (1960) 27. Dubinin M.M . , Modern state of the theory of volume filling of micropore adsorbents during a dsorption of gases and steams on carbon adsorbents, Zh. Fiz. Khim , 39 , 1305 - 1317 (1965) 28. Radushkevich L.V . , Potential theory of sorption and structure of carbons, Zh. Fiz. Khim. , 23 , 1410 - 1420 (1949) 29. Kundu S. , Gupta A.K . , Investigation on the adsorption eff iciency of iron oxide coated cement (IOCC) towards As (V) - kinetics, equilibrium and thermodynamic studies, Colloid Surf. A: Physicochem. Eng. Aspects, 273 , 121 - 128 (2006) 30. Basker C.A., Applicability of the various adsorption models of three dyes adsorption onto activated carbon Research Journal of Chemical Sci ences ___ _ _ _______________________________ ______________ _ ________ ISSN 22 31 - 606X Vol. 3 ( 2 ), 44 - 53 , February (201 3 ) Res. J. Chem. Sci. International Science Congress Association 53 prepared waste apricot, J. Hazard. Mater., 135B , 232 - 241 (2006) 31. Halsey , J .Chem. Phys. 16 , 931, (1948) 32. Hsieh Y.M., Tsai M.S., Yen F. S., Pore size and adsorption capacity of unburned carbon affected by gasification with carbon dioxi de, J. Environ. Sci. Health A,Toxic Hazard. Subst. Environ. Eng . 39, 2143 - 2155, (2000) 33. Nogami M. and Tomozawa M. , J. Am. Ceram. Soc. , 67 , 151 (1984) 34. Bayat B . , Combined removal of zinc(II) and cadmium(II) from aqueous solutions by adsorption onto high - calc ium Turkish fly ash, Water Air Soil Pollut. , 136 , 69 – 92 (2002) 35. Bayat B., Comparative study of adsorption properties of Turkish fly ashes.I. The case of nickel (II), copper (II) and zinc(II), J. Hazard. Mater. , 3897 , 1 – 2 (2002) 36. Pehlivan E . and Arslan G . , R emoval of metal ions using lignite in aqueous solution low cost biosorbent, Fuel Processing Technology , 88 , 99 – 106 (2007) 37. Qi Y., Hoadley A.F.A, Chaffee A.E., Garnier G., Characterization of lignite as an industrial adsorbent , Fuel , 90 , 1567 – 1574 (2011) 38. La fferty C . , Hobday M . , The use of low rank brown coal as an ion exchange material:1. Basic parameters and the ion exchange mehanism, Fuel , 69 , 78 – 83 (1990) 39. Santhi T . , Manonmani S . and Smitha T., Removal of malachite green from aqueous solution by activat ed carbon prepared from the epicarp of Ricinus communis by adsorption, J. Hazard. Mater. , 179 , 178 – 186 (2010) 40. Panday K.K., Prasad G . , Singh V.N . , Copper (II) removal from aqueous solutions by fly ash, Water Res. , 19 , 869 – 873 (1985) 41. Bayat B., Comparative study of adsorption properties of Turkish fly ashes. II. The case of Chromium (VI) and cadmium(II), J. Hazard. Mater . , 3898 , 1 – 16, (2002) 42. GuptaV.K., Jain C.K ., I. Ali, Sharma M., Saini V.K., Removal of cadmium and nickel from wastewater using bagasse fly ash — a sugar industry waste, Water Res. , 37 , 4038 – 4044 (2003) 43. Gupta V.K., Mohan D., Sharma S . , Park K.T., Removal of chromium (VI) from electroplating industry wastewater using bagasse fly ash — a sugar industry waste material, Environmenta list , 19 , 129 – 136 (1999) 44. Rao. M , Parwate. A.V, Bhole. A.G , Removal of Cr (VI) and Ni(II) from aqueous solution using bagasse and fly ash, Waste Manage . 22, 821 – 830, (2002) 45. HAˆqutV,RicouP,LcuyrI,LCloircP,Rmoval of Cu(II) and Zn(II) in aqueous solutions by sorption onto mixed fly ash, Fuel, 80 , 851 – 856, (2001) 46. Gupta V.K., Ali, I., Removal of lead and chromium from wastewater using bagasse fly ash - a sugar industry waste, J. Colloid Interface Sci., 271 , 321 – 328, (2004) 47. Bailey S.E . , Olin T.J. Mark Bricka R . , Dean Adrian D . , A review of potentially low - cost sorbents for heavy metals, Water Res ., 33 (11) , 2469 – 2479 (1999) 48. Helfferich F., Ion exchange, New Yark, Mc Grow Hill, 166 , (1962) 49. Rifaqat Ali Khan RaO, Moonis Ali Khan and Fouzia Rehman, Batch and column Studies for the Removal of Lead (II) Ions from Aqueous Solution onto Lignite, Adsorption Science & Technology , 291, (2011) 50. Gelencser A . , Kiss G . , Krivacsy Z . , Varga - Puchony Z . , J. Chromatogr. A , 693 , 217 (1995)