A comparative study of Zinc (II) ions removal by a locally produced Granular activated carbon

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1 Covenant University Journal A coparative study of Zinc (II) ions reoval by a locally produced Granular activated carbon Eanuel O. Aluyor & Innocent O. Oboh Abstract: Physiocheical properties of wastewater effluent fro the plants of a brewery in Lagos, Nigeria were analyzed. The adsorption capacity of Granular activated carbon fro anial horns when copared with the available coercial Granulated Activated Carbon (GAC) has been presented. Kinetics of adsorption was also investigated. The adsorption isothers could be well defined with Freundlich odel instead of Languir odel for both GAC studied. The experiental data, when applied to the first and second-order kinetic odels, followed the first-order with r² = for GAC fro anial horns while coercial GAC followed the second-order with r² = The results illustrated how anial horns, a solid waste disposal enace fro the abattoir at the Oshodi arket in Lagos etropolis, was used as an effective biosorbent for the reoval of Zn 2+ ions; offering a cheap option for priary treatent of the wastewater effluent. Keywords Biosorption, anial horns, Granulated Activated Carbon, wastewater, effluent 1. INTRODUCTION Over the past century, the advent of industrialization has increased the deand on industries to find alternative eans and cost effective ethods of waste disposal thus leading to the use of water ways by industries to dispose of waste and in the process polluting these water ways with harful and toxic substances. This pollution of our water ways has increased over 50% of water borne diseases like typhoid, cholera etc. To effectively check this trend, it has becoe iperative to ake industries subject their wastewater to proper treatent before discharge into the environent and this is undertaken by the relevant environental protection agencies with laws and regulation that are environent friendly [1]. These laws and regulations are used as pollution control easures to try and ensure that the discharge waste gets to the water ways in a for that is less harful to the environent. These pollution control easures are very necessary as virtually all industrial operations produce a certain aount of wastewater which ust be returned to the environent. Wastewater depending on it s source is a ixture of natural organic and inorganic aterials ixed up with an-ade, substances which are by products of industrial processes. It is a cobination of water borne waste reoved fro industries along with such ground and surface water that ay be present [2]. Most wastewater discharge by industries apart fro being serious pollutants contain a lot of toxic aterial which can be very deadly when exposed or allowed to coe in contact with the huan body. Toxic substances are poisonous and harful to the huan body. For instance, hepatic toxic substances attack and destroy the liver when this organ is exposed to the. Most water borne diseases are also caused as a result of indiscriinate discharge of poorly treated wastewater into the environent. Diseases like cholera, typhoid fever, dysentery etc can all be related to polluted water ways. Also ost industrial wastewater effluents contain heavy etals like lead (Pb), Mercury (Hg), Arsenic (As) etc. These etals have a neuro-toxic effect when absorbed into the body. Most heavy etals are classified as priority pollutants. Excessive quantities of these etals due to their toxic nature ay interfere with proper use of water. Also soe heavy etals are necessary for the growth of biological life. It is therefore desirable to easure and control the concentration of these substances. The adsorption process using activated carbon and ion exchange resin as adsorbents is widely applied in the advanced treatent of wastewater [3]. However, the high costs of adsorption restrict the extensive application of activated carbon and ion exchange resin. The ain factors affecting the adsorption costs include adsorption rate and the capacity of the adsorbent. Therefore, iproving the rate and capacity is an effective way to reduce the adsorption operating costs [4]. Granular activated carbon is irregular shaped particles with sizes ranging fro 0.2 to 0.5. It is used in both liquid and gas phase applications. It is used in wastewater treatent to iprove settle ability of activated sludge and reove toxic aterials such as heavy etals. The quality and quantity of brewery waste depends on the processes which the brewery undertakes e.g. raw aterials 14

2 handling, horst preparation, ferentation, filtration etc. The aount of wastewater produced is thus related to the specific water consuption (expressed as Hector litre (hl) for beer brewed). A portion is lost to evaporation thus usually the wastewater to the beer ratio is about 1.2 2hl less than the water to beer ratio. The ai of this study is to show that the granular activated carbon obtained fro anial horn can be an alternative for coercial activated carbon in the treatent of industrial wastewater. 2. METHODOLOGY 2.1 Saple Collection The anial horns (fro cattle) were collected fro the Abattoir at the Oshodi arket in Lagos etropolis. The wastewater saples were collected fro the reservoir of effluent fro the plants of a brewery in Lagos, Nigeria and physiocheical analysis was carried out using AOAC ethod of analysis [5]. Atoic adsorption spectroeter (AAS) was used to deterine the concentration of Zn 2+ ions present in the brewery wastewater studied. 2.2 Preparation of Granular activated carbon The anial horns were cut to sizes of about 5 to l0, washed to reove dirt and then sorted. It was then dried in an oven at about 100 C. The saple was then charred by carbonizing in a furnace at a teperature of about 560 C for three (3) hours then cooled at abient teperatures in a desiccator. 2 kg of the saple was ixed with 250 l of 5.5M HCl solution and refluxed by boiling for 3 hours. After slight cooling, the slurry is filtered and washed using distilled water with ph near neutrality. The product is later dried at 120 C for an hour. 2.3 Deterination of best adsorbent dose The studies were conducted by varying the aount of adsorbent. A known volue of the wastewater saple was treated with different doses of activated carbon ranging fro 30g/L to 240g/L. The saples were agitated for 60 inutes, filtered then analyzed for residual paraeters. 2.4 Deterination of contact tie The study for the contact tie was carried out by agitating the best adsorbent Concentrations, 90 g /L for anial horn and 30g/L for coercial activated carbon for the ranges of 30 to 300 inutes. 2.5 Deterination of etal (Zinc) concentrations The etal concentrations were deterined using the spectroetric ethod of atoic adsorption spectrophotoeter (AAS). 3. RESULTS AND DISCUSSION Languir and Freundlich are general atheatical relationships that were developed to describe the equilibriu distribution of a solute between the dissolved (liquid) and adsorbed (solid) phases. 3.1 Languir isother The Languir adsorption isother equation (6) was derived and is defined as x Q0 bce (1) 1 bce And the linearized Languir odel is given by; ce 1 c b e. (2) x Q Q 0 0 where; x q is the aount adsorbed per unit weight/ass of adsorbent Q o, b are the Languir constants related to axiu adsorption capacity and energy of adsorption respectively. C e is the equilibriu concentration of adsorbate in solution after adsorption. The constants in the Languir isother can be deterined by plotting q c e versus C e adsorption. 3.2 Freundlich isother The epirically derived equation proposed by Freundlich is given as follows [7]. x 1 n k f C. (3) where; k f and n are the Freundlich constants that incorporate all factors affecting the adsorption process such as adsorption capacity and intensity. x = Cs is the aount of adsorbate/weight adsorbed (solute) per unit weight of adsorbent C is the concentration in fluid (adsorbate in solution after adsorption is coplete at equilibriu) g/l Taking logs on both sides of equation 3 and rearranging; 1 * log Cs' log k f log c. (4) n The coefficient k f and n can be estiated fro slopes and by substituting values fro a line fitted to a graph of log Cs ' versus log C*; log k f is the intercept; the sorption capacity and the slope n 1 is the function of the strength of adsorption. It agrees with Languir equation over a oderate range of concentrations. 15

3 TABLE 1 PHYSICOCHEMICAL ANALYSIS OF WASTEWATER EFFLUENT Paraeters Concentration Maxiu Perissible liit ph EC(.h.c.g/c 40.2 Not Applicable Teperature ( o C) Turbidity (NTU) Total solids (TS) T.S.S T.D.S COD TOC BOD Zn 2+ ions Fig. 3: 1st order adsorption kinetics of Zinc (Zn) ions using 30g/L of coercial GAC Fig. 1: 1st order adsorption kinetics of Zinc (Zn) ions using 90g/L of anial horn GAC Fig. 4: 2nd order adsorption kinetics of Zinc (Zn) ions using 30g/L of coercial GAC Fig. 2: 2nd order adsorption kinetics of Zinc (Zn) ions using 90g/L of anial horn GAC Fig. 5a: Languir isother for Zinc ions using anial horns GAC 16

4 Fig. 5b: Freundlich adsorption for Zinc ions using anial horns GAC Fig. 6a: Languir isother for Lead ions using coercial GAC Fig. 6b: Freundlich adsorption for Zinc ions using coercial GAC Table 1 showed the physicocheical paraeters on analysis before the biosorption studies were carried out. The results obtained also indicated that the wastewater effluent obtained fro the brewery was alkaline with ph 8.7. Kinetics studies carried out showed that the adsorption reaction was first order. This was shown in figures 1 to 4. It was observed that for GAC obtained fro anial horns, the regression value (R 2 ) for first order was 0.931(figure 1) which was higher than that for the second order which was (figure 2) and as such the reaction was first order and followed Freundlich isother. The kinetics studies for coercial GAC did not follow the pattern of GAC produced fro anial horns. The coefficient of deterination (R 2 ) for first order was (figure 3) which was lower than that for the second order which was (figure 4) and as such the reaction was second order and followed Freundlich isother. Two different adsorption isothers - Languir and Freundlich were studied. The data obtained for both odels were represented graphically. When Figure 5a was copared to Figure 5b for GAC prepared fro anial horns it was observed that the adsorption adhered to the Freundlich isother with the coefficient of deterination of being greater than that of Languir with a coefficient of deterination of The sae pattern was also observed with that for coercial GAC. The squared regression of Freundlich isother was when copared to that of Languir of squared regression of as shown in both figures 6a and 6b. Thus it can be concluded that adsorption using any of the two fors of activated carbon followed the Freundlich adsorption isother. 4. CONCLUSIONS Analysis carried out on the GAC produced fro anial horns gave results which suggested that it could be used in the biosorption of Zn 2+ ions fro industrial wastewater effluent and also as a viable substitute for coercial grade activated carbon in wastewater treatent processes. The experiental results obtained showed that of the two adsorption isothers studied, the Freundlich adsorption isother a higher coefficient of deterination than that of Languir for the two types of activated carbon considered. For the kinetics in the adsorption of Zinc (II) ions for GAC fro anial horns, it followed the first order while that for the coercial GAC followed that of the second order reaction. 17

5 References [1] Perry R. H. and Greene D. W., 1997.Perry s Cheical Engineer s Handbook, 7 th edition McGraw Hill Copany Singapore pp. [2] Gray, N. F Water technology. An introduction for Environental scientists and Engineers. Co published in North, Central and South Aerica by John Wiley and sons Inc., 287pp. [3] Oboh, I. O. (2011). Evaluation of Luffa cylindrica as a biosorbent in heavy etal sorption fro aqueous solutions. Ph.D. thesis, University of Benin, Benin City, Nigeria. [4] Luqan, C. A., Muhaad, Saidatul S. J. and Thoas S. Y. C. (2010). Modelling of Single and Binary Adsorptions of Heavy etals onto Activated carbon- Equilibriu studies. Pertanika Journal of Science and Technology 18(1): [5] Mohan, D., Singh, K.P. and Singh,V.K. (2005). Reoval of hexavalent chroiu fro aqueous solution using low-cost activated carbons derived fro agricultural waste aterials and activated carbon fabric cloth, Ind. Eng. Che. Res. 44, [6] Okieien, C.O. (2008). Process developent for the utilisation of activated carbon fro pal kernel shell in waste water treatent. Ph.D. thesis, University of Benin, Benin City, Nigeria. [7] Cao L L, Zhang X J, Wang Z S, Liu W J, Li S, Zhang S X, Jiang Y, Wu W G, Jin W R., Adsorption characteristics of haloacetic acids by activated carbon in drinking water treatent. Environental Science, 20(5): (in Chinese). [8] Wang K. P., Qi R., Zhang Y., Yang M., Deng R. S. Adsorption perforance of haloacetic acids onto 5 GACs fro water environental science. Environental Science, 2005, 26(3): (in Chinese). [9] Liu R X, Wang Y X, Tang H X., Reoval of arsenate by a new type of ion exchange fiber. Environental Science, 23(5): (in Chinese). [10] Han Yanhe, Quan Xie, Zhao Huiin, Chen Shuo, Zhao Yazhi, Kinetics of enhanced adsorption by polarization for organic pollutants on activated carbon fiber. Front. Environ. Sci. Engin. China, 1(1): [11] Aerican Public Health Association (APHA), Standard ethods for the exaination of water and wastewater. 17th APHA, AWWA, Washington D.C.:1325. About the Authors: Eanuel O. Aluyor 1 and Innocent O. Oboh 2 : 1 Departent of Cheical Engineering, University of Benin, Benin City, Nigeria. 2 Departent of Cheical and Petroleu Engineering, University of Uyo, Uyo, Nigeria. Eail: eoaluyor@yahoo.co, innoboh@yahoo.co.uk 18