INVESTIGATION THE ADSORPTION PROPERTIES OF THE NATURAL ADSORBENTS ZEOLITE AND BENTONITE TOWARDS COPPER IONS

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1 Annual of the University of Mining and Geology "St. Ivan Rilski" vol , part II, Mining and Mineral Proessing, Sofia,, pp INVESTIGATION THE ADSORPTION PROPERTIES OF THE NATURAL ADSORBENTS ZEOLITE AND BENTONITE TOWARDS COPPER IONS Valeria Коvаtheva-Ninova University of Mining and Geology St. Ivan Rilski Nina Nikolova University of Mining and Geology St. Ivan Rilski Мarin Маrinov University of Mining and Geology St. Ivan Rilski ABSTRACT The possibilities f using Bulgarian natural adsbents bentonite and zeolite is have been investigated f purifiation of odel solution of Cu + at relation of liquid to solid phase, v:=1:1. It has been found out, that the speifi surfae of the both inerals takes leading part at the adsption of Cu + fro odel solutions with onentration higher than 7 g/d 3. The ation adsption apaity is highest at size of the partiles of both adsbents,71+. The therodynais of adsption has been desribed with the ost appropriate isothers of uptake of Cu + fro different partile sizes adsbents. It has been repted, that the two natural adsbents an be used to reove Cu + fro odel solutions with onentrations not higher than 1- g/d 3 with one stage of purifiation at adsption tie 5 in f reahing the Bulgarian standards f drinking waters. Under t these onditions the optiu values of ph f the zeolite are in a wider interval fro 4,6 to 8 and f the bentonite 4,6. Key wds: zeolite, bentonite, adsption of opper ions, adsption isothers INTRODUCTION In wld-wide sale the volue of waste water reahes about 44 k 3 /year. Due to that purifiation is one of the ost wide spread tehnologial proesses. A perspetive ethod f purifiation of waste water is adsption. Using this ethod the adsbents have to answer to nuber of requireents to be ative, stable, aessible, heap, easy to regenerate and ost iptant is that the exhange ions should be harless and should not provoke seondary water pollution. The natural inerals zeolite and bentonite respond to these requireents. The big deposits of zeolite and bentonite near the town of Kurdjali, their low self value and their unique ion exhange and adsption properties, ake the attrative f purifiation of wastewater fro ions of heavy etals. Considerable aounts of ine and drain waters fro the opper ines and ineral dressing enterprises Asarel-Medet and Elazite-Med ontain ainly opper ions as well as iron, zin, aluiniu and other ions in lower quantities. Due to that the ai of the researh is: a) to opare the adsption properties of both natural inerals depending on the size of their partiles b) to find the ost appropriate equation desribing the therodynais of the adsption ) to investigate the kinetis of adsption under the sae onditions f both inerals d) to exaine the influene of ph of the solutions on the adsption of Cu ions fro odel solutions. PHYSICOCHEMICAL CHARACTERISTICS OF ZEOLITE AND BENTONITE Zeolite The linoptilolite zeolites are ost wide-spread in NE Rodopi. The ian ineral is a linoptilolite and its aount reahes up to 9% fro the oposition of the rok. The size of its grains vary fro a thousand part of the illieter up to The zeolites are built fro (AlO4) and (SiO4) tetrahedrons, whih alternate in grainy three-diensional struture. The tetrahedrons an be onneted in different ways, unified by oon tops. Coplex rystal strutures with situated in deterinate der iro-pes and anals with diaeter in oleular der are fed in this way. The strutural fula of liniptilolite is Na6[(AlO)6(SiO)3].4HO and the nuber of the tetrahedrons in the ring is 8 ading to Andronikashvili, Kirov et al. (1985). The high seletion of zeolite with respet to etal ations with large diensions is due to the existene in the struture of eight nuerial silieousoxygen rings. The linoptilolite possess the following e iptant physioheial harateristis: good ehanial strength (3,3-4 by Moos), density,16 g/ 3, ion exhange apaity.16 geq/g. The adsption ability of the zeolite is different in oparison with the ions of the heavy etals. Ading to Obal, Rozan et al. (1991) the adsption der with respet to the ounted etals is following: Pb>Cu>Zn>Ni>Fe>Cr. The seletivity der of the sae ions f the linoptilotite an be also observed in the wk of Chelishev, Bernshtein et al. (1977): Pb + >Cd + >Cu + >Zn + >>Na +. The exposed data show that the 93

2 linoptilolite zeolite reveal good seletivity with respet to the opper ions. Bentonite The bentonite deposits ainly are onentrated around Kardjali town. The bentonite is lay in whih basi lay ineral is the ontilonite. The rystal struture of ontilonite is deterinated by two layers of silieous tetrahedrons with an inserted layer of aluiniu otahedrons between the, i.e. the bentonite is also aluiniu siliate but in ontrast to zeolite possesses bedded struture. In the ontilonite rystal different exhangeable ations take part - onovalene (Na +, K +, H + ) and divalene (Ca + и Mg + ). The exhanging ability of the bentonite is deterinated not only by the kind and the quantity of these ions, but also by the stirred rystal lattie of ontilonite. The ideal heial fula of ontilonite is [Si8(Al3,34Mg,66)O(OH)4]M,66.HO, where M-ions of Na, Ca, H and Mg ading to Pironov, Stoev et al. (1991). The behavi of bentonite depends very uh on the predoinate exhange ion, f exaple, if we put Na bentonite in water it inreases his volue up to 14 ties, while Ca-bentonite pratially does not swell. In oparison to Na-bentonite the Ca-bentonite has better adsption and disolouring properties. The bentonite an be used f reoving Pb, Cd, Cu and Zn ions fro water solutions ading to Bereket, Aroguz et al. (1997). EXPERIMENTAL STUDIES Materials and ethods The natural linoptilolite is fro a big deposit Beli Past in NE Rodopi. The heial oposition by weight % is: SiO- 66,16%, AlO3-11,41%, FeO3-,8%, TiO,-,15%, MgO,6%, CaO-,8%, NaO-,%, KO-,9%. The ontent of linoptilolite is 7%, and the full exhange apaity is iniu1geq/1g. The relation of Si:Al is 5, i.e. the zeolite is highly silieous and is very stable to aid and basi solutions. The natural bentonite is fro deposit Enher near the town of Kardjali. The heial oposition of average probe by weight % is the folowing: SiO-5,7%, AlO3-15,9%, FeO3-4,5%, MgO-3,5%, CaO-4,3%, NaO-,9%, KO-1,1%. The ontent of CaO and MgO is respetively e than 1% and,5% and the relation NaO:CaO is very little. This shows that the swelling property of bentonite in water will not be deonstrated. The density of bentonite is experientally deterined and it is,3 g/ 3. Three lasses of natural inerals have been used f the aoplishent of the experients: f zeolite -,+1, - 1,+,71,71+ and f the bentonite: +,315 -,315+,71,71+. The experients have been arried out with odel solutions of CuSO4.5HO. The neessary onentrations of Cu ions are obtained by dilution with distillated water. The ontat between the natural adsbents and the solutions is realized in stati onditions with the help of shaking ahine CITRON, 15 in -1, in relation liquid:solid, v:=1:1 f all experients. The ation adsption apaity (CAC) f three lasses adsbents towards Cu ions was deterinated during 4 hours, while in the first two hours a shaking ahine is used. The oputer progra CURVE FIT 44 was used giving possibilities fro 4 types equations to hoose the best odel desribing the adsption isothers of Cu + f the three lasses of adsbents. The experients were realized at the teperature of 17 о С. The ph values of the solutions were deterinated with Metroh E588 ph-v eter and were odeled with solutions of HSO4 and NaOH. The onentration of Cu ion in solutions was deterinated by ICP-AES analysis. CAC of the natural adsbents towards Cu ions was alulated using the fula: CAC = 1 1 с V V CAC = 1 where, с1 is the onentration of the eleent in initial solution, g/d 3 is the equilibriu onentration of the eleent in solution, g/d 3 с is the quantity adsbed substane, g/d 3 V is the volue of investigated solution, d 3 is the weight of dry sbent, g CAC is ation exhange apaity, gel/g sbent. RESULTS AND DISCUSSION Influene of the adsbents partile size upon their CAC towards Cu The value of CAC shows the influene of the bentonite and zeolite partile size upon the adsption of Cu ions, reahed during the tie of ontat 4 hours. It is onsidered, that during that tie full equilibriu between the solid and the liquid phases is reahed. F this purpose 1g fro three different lasses of zeolite and bentonite ontat with 1 3 odel solution of CuSO4.5HO with different onentration of Cu +. The influene of the bentonite partile sizes is showed in fig.1 and of the zeolite in fig. on CAC depending on the onentration of Cu ions in the initial solutions. Fig.1 and fig. show that at the lower ontents of Cu ions in the initial solutions ( up to 7,6 g/d 3 ) the size of adsbent partiles does not influene essentially on CAC. But, with raise of the ontent of Cu ions in the initial solutions, CAC of both inerals raises with dereasing their partile sizes, i.e. with inreasing their speifi surfae. Coparing the dates fro the figures of both inerals one an observe higher CAC of the zeolite towards the bentonite f the three lasses at onentrations of Cu ions higher than 7,6 g/d 3. At the initial onentrations of Cu + in the solutions up to 1- g/d 3, after adsption are obtained reaining onentrations of the sae ions <, g/d 3. That shows, that both inerals an be used f purifiation of waters, ontaining this quantity Cu + with one stage of purifiation. Meover, the standards of Cu ontent are ahieved in waste waters (<, g/d 3 ), at whih they an be released into rivers and into open-air reservoirs. ANNUAL University of Mining and Geology St. Ivan Rilski, vol (), part II M I N I N G A N D M I N E R A L P R O C ESSING 94

3 CAC, gcu/g Bentonite adsption of Cu Content of Cu + in initial solution, g/d 3 lass -,71+ lass -,315+,71 lass+,315 Figure 1. Influene of bentonite partiles size on CAC towards Cu + fro odel solutions of CuSО45HO Therodynais of the opper adsption fro the natural adsbents bentonite and zeolite The adsption suh as desption depends ainly on the therodynai paraeters, teperature and onentration of adsbtive and on the ondition of the adsbent surfae. The quantity of strongly adsbed adsbate depends only on the onentration of adsbtive, at ertain teperature and established adsption equilibriu. This dependene between the quantity adsbed substane and the onentration of adsptive is expressed by the adsption isother. The adsption isothers of Cu + uptake fro natural adsbents were obtained with the help of oputer progra CURVE FIT- 44 at teperature 17 С. Fro 4 types of equations the ost suitable were hosen, desribing the Cu + adsption fro different lasses of bentonite and zeolite. The hosen equations give highest oeffiient of relation (r) of the dependene: y=f(), where y is the quantity adsbed substane () related to 1g bentonite zeolite f ontat tie 4 hours, gcu/g y=с/ с is equilibriu Cu + onentration, reahed after 4 hours, g/d 3. CAC, gcu/g Figure. Influene of zeolite partiles size on CAC towards Cu + fro odel solutions of CuSО45HO. Adsption isothers of Cu + uptake of bentonite: f lass,71+ Zeolite adsption of Cu + 11,46 34,3 7,6 19,44 17, ,5 Content of Cu + in initial solution, g/d 3 lass -,71+ lass -1,+,71 lass -,+1, 4 y = =,5378 +,14. 1,399.1 ( r =,9941),3386 y = =,839.1,9. ( r =,99 ) f lass,315+,71,169 y = = 3, , ( r =,99 ) с y = = 1,986.1,16 ( r =,9896 ) f lass +,315 y = = 1,998.,9999 ( r =,986 ),664 y = = 1,9936. r =,986 ( )..,775,671 Adsption isothers of Cu + uptake of zeolite: f lass,71+,1769 y = = exp 1,4841 +,958 ln ( r =,9845),388 y = 3,68. ( r =,9745) f lass 1,+,71,376 y = =,4115. ( r =,987) y = =,417.1,7 ( r =,9844 ) f lass,+1, y = 3,191.1,96. ( r =,997),37,367 ( r =,984),149 y = = 6,39 +, ( ), Kinetis of Cu + adsption by the natural adsbents bentonite and zeolite ANNUAL University of Mining and Geology St. Ivan Rilski, vol (), part II M I N I N G A N D M I N E R A L P R O C ESSING 95

4 Class,71+ f both adsbents was hosen f studing the kinetis of Cu + adsption. The onentration of Cu + in the initial odel solutions is 11,46 g/d 3. The experients were arried out at teperature 17 С and рн of the solutions 4,6. The ontat tie between the solid and the liquid phases is adingly: 5, 1, 5, 4 and 6 in at shaking with 15 in -1. The seletion of the ontent of Cu + in the initial solutions is based on the ahieved reaining onentration <, gcu/d 3 f all treated solutions with one stage of purifiation f both adsbents. The ahieved reaining onentration (<, gcu/d 3 ) responds to the requireents of Bulgarian standards f potable waters (<,5 gcu/d 3 ) and releasing of waste waters fro ines and ineral dressing enterprises into rivers and into open-air reservoirs (<, gcu/d 3 ). runs preipitation of Cu + at рн>5 as a result of the reoval of the reation equilibriu to the right: Cu + +HO Cu(OH)+H + An inrease of the Cu + reaining onentration at ph >8 f both adsbents was observed, whih was probably due to their partial desption fro the adsbents and the presene of unadsbed Cu(OH) in solution. The optiu ph value of the solutions at Cu + adsption f zeolite is in wider range fro 4,6 to 8 and f bentonite it is in e narrow range fro 4,6 to 6. The results show that the zeolite has better adsption qualities then bentonite. The kinetis of Cu + adsption is shown in fig.3, as relation between reaining onentration and ontat tie. Reaining onentration of Cu +, g/d 3,7,6,5,4,3,,1 Kineti of Cu + adsption Contat tie,in bentonite zeolite Figure 3. Kinetis of Cu + adsption by bentonite and zeolite., g/d 3 1,4 1, 1,8,6,4, 4 4, ph Figure 4. Influene of рн of the solutions on the Cu + adsption. CONCLUSION zeolite bentonite As we see in the figure, the kinetis of Cu + adsption is very fast f both inerals and 5 in are suffiient f reahing the reaining onentration <, g/d 3. An insignifiant desption of the opper ions fro the bentonite were observed after the 1 th in and f the zeolite after the 4 th in. A onlusion an be ade, that the Cu + adsption is stable f both inerals under the indiated onditions. Influene of ph of solution on the Cu + adsption fro bentonite and zeolite The experients were realized at the following onditions: teperature 17 С initial onentration of Cu + in the solutions 11,46 g/d 3 рн-, 4, 4,6, 6, 8, 1 ontat tie 5 in and size of the bentonite and zeolite partiles,71+. The low values of ph are reahed by aidifiation with HSO4 solution and the higher than 4,6 with a solution fro NaOH. The influene of ph of the solutions upon the adsption of Cu + is indiated in fig. 4. The hange of the reaining onentrations of Cu + in funtion fro ph of the solutions has been followed. It an be seen fro the figure, that the reaining onentration begins to derease, inreasing the ph of the solutions after the proess of adsption. F the zeolite it is lowest at ph fro 4,6 to 8 (<, g/d 3 ) and f the bentonite fro 4,6 to 6 ( fro, to,13 g/d 3 ). It is due to the fat, that besides the proess of adsption there also 1. The Bulgarian natural adsbents zeolite and bentonite an be used f reovering Cu + with onentration between 1- g/d 3 in waste water, opleting in one stage of purifiation by relation liquid:solid=1:1. Both natural inerals have good adsption properties towards Cu + with little superiity of zeolite.. The speifi surfae of the natural adsbents does not play a signifiant role on the adsption at onentrations of Cu + in the solutions up to 7 g/d 3. At higher onentrations the der of adsption, ading to the size of the partiles of zeolite, is -,71+>+1,-,>-1,+, and of bentonite is -,71+>+,71-,315>+, The therodynais of the adsption proess at different sizes of the partiles of both adsbents was desribed by the ost appropriate adsption isothers, obtained with the help of the oputer progra CurveFit The adsption proess at ontent of Cu + between 1- g/d 3 and ph of the solutions 4,6 is vary fast. The ontat tie is not e than 5 in f reahing the standard f potable waters, ading to the ontent of Cu +, whih is,5 g/d At adsption with zeolite, the ph range of the waste waters ontaining Cu + between 1- g/d 3 is wide fro 4,6 ANNUAL University of Mining and Geology St. Ivan Rilski, vol (), part II M I N I N G A N D M I N E R A L P R O C ESSING 96

5 to 8, f reahing the standards of potable waters. The tie of adsption is 5 in f ahieving reaining onentration of Cu + below, g/d 3. At adsption with bentonite f the sae ontat tie, the standards f potable waters are reahed at ph 4,6. At ph value fro 4,6 to 8 are reahed the standards f releasing waste waters ontaining Cu + in rivers and open reservoirs. REFERENCES Andronikashvili, Т.G., Кirov, G.N., Filizova, L.D Prirodnie zeoliti, Hiia, -p.. Bereket, G., Aroguz, A., Ozel, M., Reoval of Pb (II), Cd (II), Cu (II) and Zn (II) fro aqueous solutions by adsption on bentonite, J.olloid.Appl.Si., 187, (1997). Obal, M., Rozan, S., Jader, R., Kolen, M., Osojik, A., Kov.zvit.thehnol , 1-, р Pironkov, St.К., Stoev, St., Naheva, L., Marinova, S Nerudni izkopaei. Tehnologihen I ikonoiheski pregled, Tehnika. Chelishev, N.F., Bernshtein, B.G., Sola, V.I Ispolzovanie prirodnih zeolitov dlia izvlehenia islih gazov, redkih I zvetnih etallov iz proishlenih othodov, М., VEEMS, -p. 55. Reoended f publiation by Departent of Mineral Proessing, Faulty of Mining Tehnology ANNUAL University of Mining and Geology St. Ivan Rilski, vol (), part II M I N I N G A N D M I N E R A L P R O C ESSING 97