Comparative Study of Rates of Biosorption for Selected Single and Mixed Metal Ions using Natural Products

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Comparaive Sudy of Raes of Biosorpion for Seleced Single and Mixed Meal Ions using Naural Producs Kiplaga Ayabei * Luswei Kiuyi Deparmen of Chemisry & Biochemisry, School of Science, Chepkoilel Universiy
Comparaive Sudy of Raes of Biosorpion for Seleced Single and Mixed Meal Ions using Naural Producs Kiplaga Ayabei * Luswei Kiuyi Deparmen of Chemisry & Biochemisry, School of Science, Chepkoilel Universiy College, P.O BOX 1125, Eldore, Kenya * Auhor o whom correspondence should be addressed; Absrac Heavy meals are usually found in low concenraions in naural auaic ecosysem. In recen imes, however, he occurrence of meal conaminans especially heavy meals in excess of naural loads has become a problem of increasing concern. The conribuing facors are rapid growh of populaion, increased urbanizaion and expansion of indusrial aciviies, exploraion and exploiaion of naural resources, exension of irrigaion and oher modern agriculural pracices as well as lack of environmenal regulaions. This herefore, calls for efficien, cheap, available and non polluing mehod of conrolling presence of heavy meals in waer bodies. Use of naural biosorbens such as algae has demonsraed grea poenial o remove heavy meals from wasewaer. An invesigaion of he effec of conac ime, reacion kineics, influence of ionic sizes and influence of presence of oher meal ions in biosorpion of heavy meals Cu, Zn and Pb using Ascophyllum nodosum has been done. Model wasewaer soluion conaining a known concenraion of he given heavy meal ions was prepared for boh single and mixed a a fixed ph of 5. A 0.25g mass of dry algae was inroduced for every 100 ml soluion. Change in level of concenraion was moniored a inervals of 10 minues using AAS unil he rae of biosorpion was almos consan. The sorpion process occurred in wo sages; firs being rapid adsorpion and hen gradual adsorpion ha was almos consan. Pb was mos biosorbed while Zn was leas for boh sysems, adoping he order Pb Cu Zn. The daa obained fied boh Langmuir isoherm and experimenal parameers were deermined. The order of reacion was found o follow pseudo second order afer comparison of R 2 values ha were deduced from firs and second order linearized plos. Key words: Biosorpion, heavy meals, algae, wasewaer, polluion 1. Inroducion Worldwide human populaion is increasing leading o promp growh of indusries wih he sole purpose of saisfying heir needs. Conseuenly, wase producs are generaed; some are renewable while ohers are unrenewable of which hey are disposed o he environmen via adjacen sreams or public sewers. There is need herefore o monior he levels of harmful conaminans prior o heir discharge. Indusries have applied several convenional echniues in order o comply wih accepable levels ha are specified by governmens and local auhoriies. The convenional echniues include chemical precipiaion, chemical oxidaion and reducion, ionexchange, filraion, elecrochemical reamen, reverse osmosis (membrane echnologies), evaporaive recovery and solven exracion. These echniues give rise o several problems such as unpredicable meal ions removal and generaion of oxic sludge which are ofen difficul o dewaer and reuire exreme cauion in heir disposal. Besides ha, mos of hese mehods also presen some limiaions whereby hey are only economically viable a high or moderae concenraions of meals bu no a low concenraions from 1 o 100 mg/l of dissolved meal ions (Cossich e al., 2001). Heavy meal removal by classical echniues involves expensive mehodologies. These are due o high energy and reagen reuiremens (Xia and Liyuan, 2002). The curren sudy aimed a evaluaing he efficiency of Ascophyllum nodosum in removal of Cu, Zn and Pb from wasewaer and invesigaing he effec of mixed meal ions in comparison o single meal ions. 2. Maerials and Mehods 2.1 Biomass preparaion The brown algae Ascophyllum nodosum was used as biosorben for he biosorpion of he meal ions. Samples of marine alga were colleced from he coasal region, Kenya. The algae were washed several imes wih ap waer hen disilled waer o remove impuriies and sals. The biomass was sun-dried and hen dried in an oven a 60 C for 48 hours (Mohamad, 2008). The dried alga biomass was cu ino small pieces, ground in a morar and subseuenly sieved and he paricles wih an average size of 0.5mm were used for biosorpion. 1.2 Meal ion Soluion Preparaion Model soluion conaining Cu, Pb and Zn were prepared a approximaely 50 mg/l and ph adjused o 5 using niric acid or sodium hydroxide, 0.25g of dry algae was inroduced for every 100 ml soluion, sirred for seven minues and he soluion allowed o sele, afer en minues 1 ml of soluion was wihdrawn ready for he concenraion deerminaion using AAS (Model A A-6200, Shimadzu, Corp., Kyoo, Japan). The same was 1 repeaed a he inervals of en minues unil change in concenraion was almos consan. The preliminaries showed ha afer 80 minues he was no furher change in concenraion hence for uniformiy reasons, he biosorpion process for all cases were carried ou for eighy minues. 3. Resuls and Discussion 3.1 Reacion Kineics The dependence of a chemical reacion on iniial reacan concenraion can be shown by a rae euaion. The rae euaion gives an expression of he variaion in concenraion wih ime. The order of reacion was deduced from he inegraed rae euaion by appropriae plo of variables o give a linearized plo. A reacion can eiher be pseudo firs order or pseudo second order. The firs order rae euaion for meal adsorpion on algae is; = k1 ( e ) where and e are he masses of meal adsorbed by he algae in (mg/g) a any ime and a euilibrium respecively, k 1 is he rae consan for he adsorpion. On inegraion, euaion (i) gives he soluion; k = ln ln ( ) 1 e e (ii) Plo of ime agains ln( e ) gave a sraigh line. The following figures (a - d) shows he plos 1 s and 2 nd order kineics for Cu when single and when in mix wih Zn and Pb. Figure 1: Graphs (a-d) comparing 1 s and 2 nd order for single and mixed meal ions The second order rae euaion can be represened as; = k ( ) 2 2 e... (iii) Where k 2 is he second order rae consan, e and have same meanings as before. Upon inegraion, euaion (iii) gives he soluion; e + k 2 1 = (iv) 2 e The plo of / agains gave a sraigh line as shown in figure 1 (a) and (b) from which he rae consan k 2 and e were calculaed. 2 The lineariy of he graphs reveals ha he reacion kineics is bes described by 2 nd order kineics hence deduced consans can be summarized in he able below; Table 1: Summary of consans for pseudo second order for he mixed and single meal ions Meal Pseudo second order Singles Mixed K 2 e R 2 K 2 e R 2 Cu Pb Zn The uaniy of meal upake a euilibrium ( e ) was paramoun in predicion of order of preference on biosorpion of meal ions o he surface especially when he meal ions were mixed. The analysis revealed ha he order of preference o he acive sies presen in he algae was Pb Cu Zn, he order was he same even for single meal upake. I should be noiced also ha when he meals were mixed e for Pb was high due o is large ionic size hence occupying large number of acive sies conseuenly e for Cu and Zn were small compared o when hey were single. 1.2 Effec of Conac Time Among my research uesions was for how long should he biosorben be in conac wih he meal ions? herefore, esimaion of he ime reuired for uaniaive amoun of upake of he meal ions from he soluion was essenial. As oulined in he mehodology, he iniial concenraion of any given meal ion was predeermined prior o inroducion of he biosorben and change in concenraion moniored unil change in concenraion was almos consan. To deermine he average ime reuired for maximum biosorpion ono he surface, a graph of ime in minues agains uaniy of he meal upake was ploed has shown below. Figure 2: Graphs showing effec of conac ime on he amoun of meal upake I was deduced from he plos ha he adorpion process ocurred in wo sages; he firs sage being rapid and he laer being gradual. The firs sage occurred wihin he firs minues and his was due o infinie number of acive sies, he second sage occurred when mos of he acive sies had been occupied and hence involved diffusion of he meal ions ino he cells of he algae. 3.3 Influence of Ionic Sizes Biosorpion raes for differen meal ions were compared o esablish wheher he algae biosorbed Cu 2+, Pb 2+, and Zn 2+ in he same manner or differenly. Invesigaion was done for boh single and meal ions. One way ANOVA a 95% confidence level was used o es wheher here was significan difference or no. The resuls of he es are summarized in figures 3 and 4 below. 3 ANOVA singles (Cu, Pb and Zn) Source of Variaion SS df MS F P-value F cri Beween Groups Wihin Groups Toal Figure 3: One way ANOVA resuls for comparison of biosorpion raes Cu, Pb and Zn for single meal ions. ANOVA Mix (Cu, Pb and Zn) Source of Variaion SS df MS F P-value F cri Beween Groups E Wihin Groups Toal Figure 4: One way ANOVA resuls for comparison of biosorpion raes Cu, Pb and Zn for single meal ions. From he ANOVA resuls i can be seen ha p- value for boh mixed and single meal ions is less ha 0.05 implying ha he biosorpion of he hree meal ions wheher hey appear in he wasewaer alone or in mix wih ohers hey are biosorbed differenly, his is aribued o differences in ionic radiuses. 3.4 Influence of Presence of oher Meal ions Indusrial effluens can be conaminaed by one or more meal ions; in his research i was considered imporan o compare he biosorpion raes in each meal ion wheher i occupied he wasewaer alone or in company of oher meal ions. The ANOVA resuls are summarized in he able 2 below. Table 2: Summary of one way ANOVA resuls comparing influence of mixing meal ions on biosorpion raes Parameer P-value F calculaed F criical Cu Pb Zn The es revealed ha wheher he meal ions are mixed or in presence of ohers hey were biosorbed in he same way since he p-value was greaer han Mos probably ionic size plays a greaer role han presence of oher meal ions. 3.5 Adsorpion isoherms Langmuir and Freundlich isoherms were used o describe he adsorpion process and o reveal he naure of biosorben surface. The Langmuir isoherm model assumes ha he sorpion process forms a monolayer a he surface and ha he surface has a finie number of idenical sies. This isoherm can be defined according o he following euaion: = max bce 1+ bc e where is he amoun of adsorbed meal per uni weigh biomass a euilibrium (mg/g), C e is he residual meal concenraion in soluion a euilibrium (mg/l), max is he maximum amoun of meal per uni of biomass (mg/g) and b is a consan relaed o he affiniy of he binding sies (l/mg). A graph of Langmuir isoherm for Cu when single and in mix wih oher meal ions is shown below: 4 Figure 5: Graphs of Langmuir isoherms model for Cu in single and when in mix wih oher meal ions. On he oher hand, Freundlich isoherm is used for modeling he adsorpion on heerogeneous surfaces. This isoherm can be described as follows: e = K f (C e )1/n where K f and n are he Freundlich consans relaed o he adsorpion capaciy and inensiy of he sorben, respecively. For he linearized forms of euaion were used o draw he linearized plos as shown in he figure below for Cu. Figure 6: Graph of Freundlich isoherm model for Cu in single and when in mix wih oher meal ions. The linearized graphs aided calculaion of he conans max and b for langmuir ha used predic he amoun of meal upake o he surface and he affiniy of meal ions o he acive sies presen a he surface of he biosorben, respecively. The consans of Freundlich isoherm were ignored since he daa did no fi he model and hence could no be used o predic amoun biosorbed nor affiniy of he meal ions o he surface. The consans for Langmuir model are summarized in he able below; Table 3: Summary of Langmuir consans Meal Single Mixed max B R 2 max b R 2 Cu Pb Zn The daa fied Langmuir for boh Pb and Zn jus like Cu as demonsraed in figure 5 and 6. This, herefore, means ha he surface of brown algae has homogenious a surface wih finie number of idenical sies. max prediced ha he order of decreasing uaniy of meal ion biosorbed was Pb Cu Zn, b also prediced ha he order of decreasing affiniy o he acive sies presen in he algae were Pb Cu Zn. This was in agreemen wih he order prediced by e of pseudo second order. I also agrees wih finding of oher researches (Maa el al., 2008, Volesky and Chong, 1995, Volesky e al., 1995). 4. Conclusion The affiniy o funcional groups presen in he algae depends on he ype of he meal ion. When meal ions appear singly or when mixed wih oher meal ions i does no affec he rae of biosorpion. The daa obained fied Langmuir more han Freundlich isoherm suggesing ha he surface of biosorben in homogeneous and 5 characerized wih finie number of idenical acive sies based on assumpions of Langmuir isoherm. The order of he reacion was deduced o follow pseudo second order meaning ha he biosorpion process is dependen on boh concenraion of meal ion and biosorben. The order of reacion was obained by appropriae plos for firs and second order; he correlaion coefficien (R 2 ) from he linearized graphs showed ha he linearized graphs of second order had higher values. The Ascophyllum nodosum proved o be efficien reaching over 50% for Cu, Pb, and Zn. 5. Recommendaion Indusries whose effluens are conaminaed wih heavy meals especially Cu, Pb and Zn wheher singly or mixed can employ brown algae as he biosorben. A 0.25g of he brown algae should be used for every 100 ml of wasewaer a ph of 5 and a room emperaure (20-24 o C). The indusry should monior he concenraion of he individual heavy meals and apply he algae seuenially unil all he meal ions are removed compleely or o accepable level. 6. Acknowledgemens The auhors are indebed o Chepkoilel Universiy College and JKUAT for echnical suppor. Reference Cossich, E.S., Tavares, C.R.G., Ravagnani, T.M.K. (2001), Biosorpion of Chromium (III) by Sargassum sp. Biomass. Journal of Bioechnology, 5( 2): Mohamad, H. (2008), Biosorpion of Cadmium from Aueous Soluion using Dead Biomass of Brown Alga Sargassum Sp. Maser of Science in Chemical Engineering, Amirkabir Universiy of Technology(Tehran Polyechnic), Tehran, Iran. Msc. Thesis. Maa, Y.N., Bl azuez, M.L., Balleser, A., Gonz alez, F.,Mu noz, J.A. (2008), Characerizaion of he biosorpion of cadmium, lead and copper wih he brown alga Fucus vesiculosus. Journal of Hazardous Maerials 158: Volesky, B., de Carvalho, R. P., Chong, K.H. (1995), Evaluaion of he Cd, Cu, and Zn Biosorpion in Two- Meal Sysems Using an Algal Biosorben. Bioechnol. Prog. 11(1): Volesky, B., Chong, K. H.(1995), Meal Biosorpion Euilibria in a Ternary Sysem. Bioechnology and Bioengineering 49: This academic aricle was published by The Inernaional Insiue for Science, Technology and Educaion (IISTE). The IISTE is a pioneer in he Open Access Publishing service based in he U.S. and Europe. The aim of he insiue is Acceleraing Global Knowledge Sharing. More informaion abou he publisher can be found in he IISTE s homepage: hp:// CALL FOR PAPERS The IISTE is currenly hosing more han 30 peer-reviewed academic journals and collaboraing wih academic insiuions around he world. There s no deadline for submission. Prospecive auhors of IISTE journals can find he submission insrucion on he following page: hp:///journals/ The IISTE ediorial eam promises o he review and publish all he ualified submissions in a fas manner. All he journals aricles are available online o he readers all over he world wihou financial, legal, or echnical barriers oher han hose inseparable from gaining access o he inerne iself. Prined version of he journals is also available upon reues of readers and auhors. IISTE Knowledge Sharing Parners EBSCO, Index Copernicus, Ulrich's Periodicals Direcory, JournalTOCS, PKP Open Archives Harveser, Bielefeld Academic Search Engine, Elekronische Zeischrifenbibliohek EZB, Open J-Gae, OCLC WorldCa, Universe Digial Library, NewJour, Google Scholar
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