مها هادي Al-Khwarizmi Engineering Journal Al-Khwarizmi Engineering Journal, Vol. 9, No. 2, P.P. 69- 76 (2013) Al-Khriet Agricultural Waste Adsorbent, for Removal Lead and Cadmium Ion from Aqueous Solutions Maha H. Al-Hassani Department of Chemical Engineering/ College of Engineering/ University of Baghdad (Received 5 November 2012; accepted 30 April 2013) Abstract The availability of low- cost adsorbent namely Al-Khriet ( a substance found in the legs of Typha Domingensis) as an agricultural waste material, for the removal of lead and cadmium from aqueous solution was investigated. In the batch tests experimental parameters were studied, including adsorbent dosage between (0.2-1) g, initial metal ions concentration between (50-200) ppm (single and binary) and contact time (1/2-6) h. The removal percentage of each ion onto Al-Khriet reached equilibrium in about 4 hours. The highest adsorption capacity was for lead (96%) while for cadmium it was (90%) with 50 ppm ions concentration, 1 g dosage of adsorbent and pH 5.5. Adsorption capacity in the binary mixture were reduce at about 8% for lead and 12 % for cadmium, which was attributed to competitive adsorption. The adsorption parameters were analyzed using both the Freundlich and Langmuir. Al-Khriet was best fitted by the Freundlich isotherm comparing with Langmuir model, and the rate constant was found to be 1.305 and 0.621 ((mg/g)(L/mg)1/n) for lead and cadmium respectively , while the kinetic of adsorption obeyed a second order rate equation and the rate constants were found to be (0.0161) for lead and ( 0.0125) mg.g-1.min-1 for cadmium. Keywords: Agricultural waste adsorbent, Biosorption, heavy metal ions, isotherm kinetic model. 1. Introduction The rapid progress in industrial technology and war remnants in Iraq causes an increase in the level of toxic ions discharged into the waste water and these metals are harmful to the human and aquatic lives. Many countries pay attention to this global issue and they devote concentrated efforts to solve this environmental problem (Abdel-Ghani et al., 2009). Lead is one of the very dangerous heavy metals, which causes many dysfunctions in all human beings. In children, excess amounts of this metal would probably lead to a decrease in their IQ score, and an impairment of learning, hearing, physical growth, the circulating system, the reproductive system, nervous system especially the brain, kidney functions and some mental disease such as dementia, depression, madness, as well as problems in metabolism system.,e.g., deficiency of vitamin D, also increasing level of this toxic metal may lead to death (Okoye et al., 2010, Okoro and Ejike, 2007). Lead as (Pb+2) has a huge efficiency to the thio (-SH) and (PO4) containing enzymes and other dangerous molecules which in turn affecting the permeability of kidney, liver and brain cells by inhibiting the synthesis of heams unit, leading to retardation or break down of these organs function (Ademoroti, 1996). Cadmium is another of heavy metals with a high toxicity. Accumulation of cadmium in the body results in, diarrhea, muscular cramps, nausea, erythritis, problem in the vision, chronic pulmonary disease (CPD), and cardio vascular disease (CVD). The world health organization (WHO) gave the recommended standards of drinking water which is 0.005mg Cd/L and 0.001 mg Pb/L (Munther I. et al.,2010). While in Iraq in the trocar of Al-Eshaki because of the effect of Al- Somood company for steel industry and power plant in the south of Baghdad, the level of toxic metals (Cd+2,Pb+2) exceeded the allowed limit for example, the concentration of cadmium ion was 8 mg/L and the concentration of lead ion was 10 Maha H. Al-Hassani Al-Khwarizmi Engineering Journal, Vol. 9, No. 2, P.P. 69- 76 (2013) 70 mg/L which was must higher than the permissible limits for drinking water. Many techniques such as ion exchange, precipitation, adsorption, flocculation, advance oxidation and membrane process have been used for the removal of toxic metal ions (Sheela et al., 2012, Mohamad et al.,2012). The reason behind our using the absorption technique is that it is a very economical process especially when using a locally available adsorbent (Saad Al-Jlil, 2010). The essential benefits of this absorption process for environmental pollution are: the low cost, simple design easy operation as well as no effect of toxic substance, when comparing to other biological treatment process (Yahia, 2006, Hameed et al., 2009). This research investigated the possibilities for using cheap wasted material, locally available in Iraq namely Al-Khriet which is found as a powder in the legs of Typha Domingesis as potential adsorbent. The Presence of this plant in industrial waste water indicates that it resists the pollutants. The effect of various parameters including the adsorbent dosage initial of metal ion concentration (single and binary) and contact time were studied onto Al-Khriet powder for removal lead and cadmium ion from aqueous solution. By reviewing other literature surveys, it is obvious that a few of them were performed on the contamination levels of different heavy metals in the waste water in Iraq. 2. Material and Methods 2.1. Material Al-Khriet was collected from marshes in the south of Iraq. First it was washed with deionized water to remove the suspended particle and then dried in the air for two days before drying in an oven at 110°C for 24 hours, Finally Al-Khriet powder was stored in discator. 2.2. Experimental Work Different concentrations of Cd+2,Pb+2 aqueous solution were prepared from the stock of 500 mg/L solution prepared by dissolving agent grade Pb(NO3)2.2H2O and Cd(NO3)2 in dionized water, the properties of these compound were shown in Table 1. Adsorption was performed in a batch experiment. The equilibrium isotherms were determined by mixing 0.5gm of Al-Khriet with 25 ml of Cd+2,Pb+2 solutions in a conical flask at different concentration (50,100,150 and 200) mg/L. Flasks were shaken in a shaker (type B,Baun Karlkob) for 4 h at room temperature. It was noticed that the adsorbed metals ions of adsorbent system reached to equilibrium after 4 h. This phenomenon was clearly seen in a series of experiments of different time intervals which showed that the adsorption process reached equilibrium after 4 h. Solution and adsorbents were separated by filtering through a filter paper. The concentration of the solute in solution was determined by using atomic absorption spectrophotomeric (type Perkin-Elmer-5000, USA) . The adsorbed amount was calculated by the following equation: w CCV q ee )( 0 −= …(1) Where eq (mg/g) is the amount adsorbed at equilibrium, V (L) is the volume of solution, 0C , eC (mg/L) is the initial and equilibrium concentration, w (g) is the amount of adsorbent. The adsorption kinetic was analyzed by adding 0.5 g of Al-Khriet to 25 ml of 50 mg/L of Cd+2, Pb+2 solutions. The samples were shaken and examined at different time intervals. The effect of adsorbent dosage and initial concentration of the feed solution were also studied by using different amount of adsorbent (0.2-1) gm for initial concentration of (50-200) mg/L (single and binary). The pH value for cadmium and lead were 5.5 before and after mixing with adsorbent. 0.1M of NaOH and HCl were used for pH adjustment to fix the pH value in all experiments. Table 1, Physical Properties of Adsorbate. 3. Results and Discussion The removal efficiency was calculated by the equation below Removal efficiency 100*)( 0 0 C CC R f − = …(2) Adsorbate Lead Nitrate Cadmium Nitrate Molecular weight (g/mol) 367.2098 236.4208 Water solubility (g/ 100ml H2O) at 20°C 52 136 Maha H. Al-Hassani Al-Khwarizmi Engineering Journal, Vol. 9, No. 2, P.P. 69- 76 (2013) 71 Where 0C and fC are the initial and final ions concentrations, respectively. 3.1. Effect of Contact Time As shown in Fig.1, the percent removal of lead ion and cadmium ion by adsorption onto Al-Khriet increases with contact time and attain equilibrium in about 4 h. Removal efficiency equal to (94.6%) and (85.9%) for lead and cadmium ion respectively at pH 5.5 and of 50 ppm ions concentration and 0.5 gm of adsorbent in 4 h. The result indicates that the rate of sorption of both ions on Al-Khriet was fast because of a largest amount of Cd+2,Pb+2 attached to the sorbents within 1 h of adsorption. Similar results were reported by Mahvi et al.,(2007), Ajmal et al.,(2003) and Madhava et al., (2008). This behavior suggests that the initial stage, sorption takes place rapidly on the external surface of the Al-khriet followed by a slower internal diffusion process, which may be the rate determine step. The reason behind our studying this part because the equilibrium time is one of the parameters for economical waste water treatment plant application. These observation agree well with the investigation by Hameed et al., (2009). Lead was found to adsorb more than cadmium, that is due to its different affinities of two ion for the reactive functional groups located on the surface of Al- Khriet powder. 0 20 40 60 80 100 0 50 100 150 200 250 300 350 tim e(m in) R em o va l p er ce n t% Lead Cadmium Fig. 1. Effect of Time on the Removal Efficiency using Al-Khriet as Adsorbent, Biomass Dosage 0.5 g, pH 5.5, 250 rpm , Cd+2 , Pd+2 Concentration 50 ppm. 3.2. The Effect of Al-Khriet Dose on Ions Adsorption The relation between Al-Khriet dose and % removal efficiency of Cd+2 and Pb+2 are shown in Figs. 2 and 3. The experiments were carried out at pH 5.5 and fixed Cd+2 and Pb+2 initial concentrations for both single and binary of 50 ppm solution on Al-Khriet. As can be depicted from these figures, when Al-Khriet dose increased, the uptake of both ion decreased and the percent removal increased for both single and binary solution due to the great possibility of exchangeable sites or surface area. It is appearance that by increasing the dosage from (0.2-1) g, the percent removal increased from (92% to 96%) for lead and from (83% to 90%) for cadmium as shown in Fig.2. Figure 3. shows that the adsorption curve for two solute together. In the binary solution adsorption percent removal of Pb+2 and Cd+2 were 88%, 79% with 1 g dosage and 50 ppm ion concentration. This indicates that the adsorption capacities of the adsorbent observed in binary mixture batch experiments were lower (about 8% for Pb and 12% for Cd) than that observed in a single solute, which was attributed to competitive adsorption. Competitive adsorption results from the available adsorption sites existing on the surface of the adsorbent when present in a multi-component metal ion aqueous solution. It was found that the removal efficiency of Al-Khriet for Pb+2 is grater than Cd+2. It can be clearly seen from table 1 that lead nitrate is less soluble than cadmium nitrate which attribute to their molecular weight, duo to the fact that the higher molecular weight, the lower solubility in a water is similar trend was reported by Riaz Qadeer (2002). This behavior might be also attributed to the molecular size. Lead ion has the smaller molecule than cadmium ion, thus it might be visible for on particular pore hold more lead ions molecules than cadmium ions molecules. The decreasing trend in adsorbed phase concentration for cadmium ion is due to the less availability of sites on the Al-Khriet because of the competitive effect of lead ions. Maha H. Al-Hassani Al-Khwarizmi Engineering Journal, Vol. 9, No. 2, P.P. 69- 76 (2013) 72 60 70 80 90 100 0 0.2 0.4 0.6 0.8 1 1.2 Adsorbrnt dosage R em o va l p er ce n t % Lead Cadmium Fig. 2. Effect of Adsorbent Dosage on the Percent Removal for Single of Cd+2, Pb+2 by Al-Khriet , Contact Time 4 h, Initial Concentration for Both Ion 50ppm. 60 70 80 90 100 0 0.2 0.4 0.6 0.8 1 1.2 Ads orbr nt dos age R em o va l p er ce nt % Lead Cadmium Fig. 3. Effect of Adsorbent Dosage on Percent Removal for Binary System of Cd+2, Pb+2, using Initial Concentration for Each Ion 50 ppm. 3.3. Effect of Initial Cd+2, Pb+2 Ions Concentration Figure 4 showed the relation between the percent removal efficiency and the initial ions concentration of Cd+2 and Pb+2, as the initial ions concentration increase the percent removal decreases. That is because at higher concentration, number of heavy metals were relatively higher in comparison with the availability of adsorbent sites. These observation agree well with the investigation reported by Sulaymon et al., (Sulaymon et al.,2010) . 0 10 20 30 40 50 60 70 80 90 100 0 50 100 150 200 250 ppm R % Lead Cadm ium Fig. 4. Removal of Cd+2, Pb+2 Ion using Different Concentration of Ions. 3.4. Adsorption Kinetic Model The pseudo first order model (PFOM) (Augustin and Emmanual,2011) is given by the following equation tkqqq ete 1ln)ln( −=− …(3) The pseudo second order model (PSOM) (Augustin and Emmanual,2011) is given by the following equation eet q t qkq t += 2 2 1 …(4) Where eq is the amount of ions adsorbed at equilibrium (mg.g-1), tq is the amount ions adsorbed at time t in ( mg.g-1 ), 1k (min -1) and 2k (g/(mg.min)) are the rate constants of PFOM and PSOM respectively. The PFOM and PSOM plots shown in Fig. 5 and 6. 1k and 2k for Cd +2, Pb+2 as well as correlation coefficient obtained are presented in table 2. It can be found out that the obtained correlation coefficient for PSOM were greater than for PFOM. These suggest that the adsorption system is the second order model based on assumption that the both sorbate (Pb,Cd) and Al-Khriet are involved in a rate determining step, which may be a chemical sorption rather than diffusion. (Ho and Mckay, 1998). Maha H. Al-Hassani Al-Khwarizmi Engineering Journal, Vol. 9, No. 2, P.P. 69- 76 (2013) 73 -3.5 -3 -2.5 -2 -1.5 -1 -0.5 0 0 50 100 150 200 250 time ln (q e- q t) Lead Cadmium Fig. 5. PFOM Plots for Cd+2, Pb+2. 0 20 40 60 80 100 120 140 0 50 100 150 200 250 300 tim e (m in) t/ q t Lead Cadmium Fig. 6. PSOM Plots for Cd+2, Pb+2. Table 2, The Rate Constant and Correlation Coefficient for Pseudo First and Second Order for Both Ions. Kinetic model Parameters Pb+2 Cd+2 PFOM k1(min-1) 0.0161 0.0099 eq (mg/g) 1.50 1.22 R12 0.9718 0.9613 PSOM k2 (mg.g-1. min-1) 0.0161 0.0125 eq (mg/g) 2.582 2.353 R1 2 0.9991 0.9866 3.5. Equilibrium Isotherms The equilibrium isotherm display a nonlinear dependence on the equilibrium concentration. The obtained adsorption data were analyzed using Freundlich and Langmuir (Ajay et al., 2010) isotherms according to the following equation: n ee kCq 1 = …(9) Freundlich e em e bC bCq q + = 1 …(10) Langmuir Equations 9 and 10 can be written in linear form as given below respectively efe Cn kq ln 1 lnln += …(11) bqq C q C mm e e e 1+= …(12) Where eq and eC are the equilibrium concentration of lead and cadmium in adsorbed and liquid phase in mg/g and mg/L , respectively , fk and n are the Freundlich constants which can be calculated from the slope and intercepted of the linear plot with eqln vs. eCln . mq and b are Langmuir constants which can be calculated from the intercept and slope of the linear plot ee qC / vs. eC . The Freundlich and Langmuir isotherms are shown graphically in Figs. 7 and 8. The fitted constant for two models are tabulated in table (3). Table (3) indicate the Freundlich model provides the best fit as judged by its correlation coefficient for Pb+2and Cd+2. The n value of Freundlich model between 1 and 10, indicates good adsorption efficiency (Treybal,1980). This demonstrate that the developed adsorbent has good adsorption efficiency for Pb+2,Cd+2 removal. 0 0.5 1 1.5 2 2.5 0 1 2 3 4 5 ln(ce) ln (q e) Lead Cadmium Fig. 7. Adsorption Isotherm of Pb,Cd at pH (5.5) by using Freundlich. Maha H. Al-Hassani Al-Khwarizmi Engineering Journal, Vol. 9, No. 2, P.P. 69- 76 (2013) 74 0 1 2 3 4 5 6 7 0 10 20 30 40 50 60 Ce C e/ q e Lead Cadmium Fig. 8. Adsorption Isotherm of Pb,Cd at pH (5.5) by using Langmuir. Table 3, Parameter of Isotherms for Cd ,Pb and Correlation Coefficient for Freundlich and Langmuir Isotherm R2. Kinetic model Parameters Pb+2 Cd+2 Langmuir mq (mg/g) 13.9 12.85 b L/mg 0.070 0.028 R2 0.9867 0.9734 Freundlich n f mg L g mg k 1 )( 1.305 0.621 n 1.636 1.529 R2 0.9983 0.9928 4. Conclusion The investigation show that Al-Khriet a local natural agent which is are abundant and low cost, therefore can be used as a bioadsorbent for removal Pb+2, Cd+2 ions from aqueous solutions. It was noted that removal process increased with contact time and attains saturation in about 4 h. The rapid kinetic of adsorption process has significant practical importance ensuring efficiency and economy. Also the adsorption of Pb+2, Cd+2 on Al-Khriet was dependent on initial concentration and dosage of adsorbent. Adsorption capacity for cadmium was less than that for lead , The highest adsorption capacity was for lead (96%) and for cadmium (90%) with 50 ppm ions concentration, 1 gram dosage of adsorbent and pH 5.5, while the mixed heavy metal were reduced at about 8% for Pb and 12% for cadmium. In this study of kinetic of adsorption, the PSOM provides better correlation of sorption data than the PFOM , while the adorption equilibrium was better described by Freunlich model than Langmuir model. Hence the material Al-Khriet under consideration would be useful economical treatment of waste water containing lead and cadmium metal. 5. References [1] Abdul-Ghani N.T. , A.K. Hegazy, G.A.El- Chaghaby,2009. Typha domingensis leaf powder for decontamination of Aluminum, iron,zinc and lead, Biosorption kinetics and equilibrium modeling, Int. J.Environ. Sci. Tech., 6(2),243-248. [2] Ademoroti,C.M.A., 1996. Environment chemistry and toxicology ,pollution by heavy metal. Foludex press, 171-172. [3] Ajay Kumar Meena, Chitra Rajagopal, Kiran and GK Mishra. 2010. Removal of heavy metal ion from aqueous solution using chemically (Na2S) treated granular activated carbon as an adsorbent, Journal of scientific and industrial research vol 69, pp 449-453. [4] Ajmal,M.,Roa,R.A., Anwar,S., Ahmad,J., Alunad,R. 2003.Adsorption studies on rice husk., removal and recovery of Cd(II) ion from waste water, Bioresour.Technol., 86(21), 147-149. [5] Augustine E. Ofomaja, Emanuel I.,2011. Adsorption kinetics of 4-nitrophenol onto a cellulosic material, mansonia wood saw dust and multi stage batch adsorption process optimization, carbohydrate polymers, 83,1192-1206. [6] Hameed B.H., J.M. Salman,A.L. Ahmad. 2009. Adsorption isotherm and kinetic modeling of 2,4-D pesticide on activated carbon derived from date stone, Journal of Hazardous materials, 163, 121-126 . [7] Ho,Y.S. Mckay,G.A., 1998. Comparision of chemisorption kinetics model applied to pollutant removal or various sorbents. Transactions of the institution of chemical engineering, 76B,332-340. [8] Madhave M. Rao,G.P.Chandra Rao, K. Seshaiah, N.V. Ghoudary, M.C.Wang. 2008. Activated carbon from Ceiba pentandra hulls, an agriculture waste as an adsorbent in the Maha H. 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Sci. vol.17 no.2, 72-100. )2013( 69- 76، صفحة 2، العدد9مجلة الخوارزمي الھندسیة المجلد مھا ھادي مصطفى 76 المائیھ المحالیل من والكادمیوم الرصاص ایونات الزالھ مازه كماده الخریط استخدام مھا ھادي مصطفى الحسني جامعة بغداد /كلیة الھندسة / قسم الھندسة الكیمیاویة الخالصة ك الخریط المائی ھ المحالی ل من والكادیمیوم كالرصاص الثقیلھ المركبات الزالة كلفھ وباقل محلیا المتوفره الزراعیھ النفایات استخدام الى البحث یھدف معا وممزجھ منفرده بصوره والكادیمیوم الرصاص أیونات تركیز ،المازه الماده تركیز تأثیر دراسة تم .مازه كماده البردي نبات سیقان في موجوده ماده وھو درجھ، التشغیلیھ الظروف عن% ٩٠ وللكادیمیوم% ٩٦ للرصاص ازالھ نسبھ عاى الحصول تم. الممتزه والكمیھ لألزالھ الموئیھ النسبھ عن األمتزاز وزمن % ٨ بح والي األمت زاز نسبة قلت األیونات مزج وعند ساعھ ٤ األمتزاز وزمن لتر لكل ملغم ٥٠ األیونات وتركیز غم ١ المازه الماده وكمیة ٥,٥ حامضیھ استخدام وكان, ناجح بشكل وفریندلج النكمایر معادلة استخدام تم. للخریط الفعالھ المراكز على والتنافس التزاحم ظاھرة بسب للكادیمیوم% ١٢و للرصاص من لكل غم \ملغم ٠,٦٢١ و ١,٣٠٥ النكمایر ثابت معدل كان حیث فریندلج معادلھ من افضل بشكل األیونات من كل امتزاز نتائج لتمثیل النكمایر معادلھ ٠,٠٦١ األمتص اص ثاب ت مع دل ك ان حی ث الثانی ھ الدرج ھ م ن بمعادل ھ تمثل ت األمتص اص عملی ة حركی ة بینم ا الت والي عل ى والك ادیمیوم الرص اص .التوالي على والكادیمیوم الرصاص من لكل دقیقھ غم\ملغم٠,٠١٢٥و