A new method is reported for the-determination of trace

levels of Ti(IV) in water by cofiotation and polargraphy.

Ti(IV) is preconcentrated and separated by cofiotation

using aluminium hydroxide as coprecipitant and sodium

oleate as surfactant. Polarographic determination of

titanium content in the froth is based on the catalytic wave

ofTi(IV) in the presenceof chlorate and oxalate. The effect

ofvarious cations and anions on the fiotation and

determination of titanium has been investigated. The

method has been applied to estimation of titanium in

natural fresh water samples

Basu, Bharathibai J

Padma, DK

English

National Aerospace Laboratories Institutional Repository

Indian Journal of ChemistryYo.!. 34A, April 1995, pp. 320-322Catalytic current polarographicdetermination of traces of titanium in waterafter preconcentration by coflotationBharathibai J Basu & S R Rajagopalan*Materials Science Division, National Aerospace Laboratories,Bangalore 560017, IndiaandD K Padma*Department of Inorganic and Physical Chemistry,Indian Institute of Science, Bangalore 560012, IndiaReceived 27 December 1993; revised 19 April 1994;accepted 28 October 1994A newmethod is reported'for the-determinationof tracelevelsof Ti(IV) in water by cofiotation and polargraphy.Ti(IV) is preconcentrated and separated by cofiotationusing aluminium hydroxide as coprecipitant and sodiumoleate as surfactant. Polarographic determination oftitanium content in the froth isbased on the catalyticwaveofTi(IV) in the presenceof chlorate and oxalate. The effectofvarious cations and anions on the fiotation anddetermination of titanium has been investigated. Themethod has been applied to estimation of titanium innatural fresh water samples.This paper describes a method for the estimation oftrace amounts of titanium(lV) by catalytic currentpolarography after preconcentration by coflotation.Coprecipitation with ferric hydroxide! has been usedearlier for the preconcentrationof traces of titanium.However, the bulky amorphous precipitates aredifficult to filter and centrifugation is cumbersome forlarge volumes. Flotation technique for the separationof trace elements is free from these disadvantages andI has been widely used to preconcentrate several traceelements from aqueous systems- -7. But flotation'separation of traces of titanium has rarely beenreported". We have exploited the high concentrationfactor involved in separation by coflotation toimprove the detection limits for the determination oftitanium(IV) by catalytic current polarography.ExperimentalThe polarography as well as the flotationapparatus used have been described in our earlierpublication", All the polarograms were recorded at25°C.All reagents, except the surfactants, were of ARgrade. Sodium oleate (SO) was obtained from LobaChemie and soidum lauryl sulphate (SLS) fromFluka. Stock solution of Ti(IV) (1.0 mg/ml, wasprepared by dissolving pure titanium dioxide insulphuric acid and standardised gravimetrically",Working solutions were prepared daily by dilutingthe stock solution. Stock solutions of aluminiumnitrate (10 mg/ml AI), zirconium nitrate (10 mg/mlZr), SLS (2 mgjml), SO (2 mgjrnl), sodium chlorate(1 M) and oxalic acid (0.8 M) were also prepared.ProcedureTo an aqueous solution (1000 ml) of the samplecontaining traces of Ti(IV), was added AI(III)solution (5ml). The pH was adjusted to 8.0 by addingaqueous ammonia solution with stirring. Stirring wascontinued for 5 min, after which SO solution (5 ml)was added and the solution was transferred to theflotation cell. Nitrogen was bubbled through thesolution for 2 min, and the mother liquor wasdrained through the side arm. The froth wascollected, dissolved in 5ml of hot 2M sulphuric acidand the volume was made up to 10m!.Polarographic measurements-An aliquot of thissolution was pipetted into a polarographic cell.Oxalic acid (12.5 ml, 0.8 M), sulphuric acid (2 ml,2.5 M) and sodium chlorate (2 ml, I M) were added.The contents were diluted to 20ml and de" rated for5 min. The polarogram was recorded between 0 and- 0.40 V. The titanium concentration in the solutionwas determined by the standard addition method.Results and discussionIt has been reported earlier that SLS and SO areable to float aluminium hydroxide in the pH ranges5-7.5 and 7.0-9.5 respectively". In this study, wefound that the colloidal precipitate Jf zirconiumhydroxide could be floated by SLS and SO in the pHranges 3-7.5 and 7.0-9.5 respectively.The effect of pH on the recovery of Ti(IV) fromsynthetic solutions oflow ionic strength (u < 0.10) bycoflotation with aluminium hydroxide andzirconium hydroxide was studied. SLS and SO wereused assurfactants in the pH ranges 4.0-7.0 and1.0-9.5 respectively. The flotation behaviour' wasalmost similar on both collectors. The recovery ofTi(IV) increased with increase in pH and 100%recovery was obtained in the pH range 7.0-9.0 onboth the collectors. This indicates that themechanism of collection ofTi(IV) is coprecipitation.Titanium(lV) hydroxide is coprecipitated onaluminium hydroxide or zirconium hydroxide whichis then floated by the surfactant. The high solubilityproduct of titanium hydroxide is favourable forcomplete recovery even at very low concentrations ofTi(IV). In this study, aluminium hydroxide and SOwere chosen as the coprecipitant and the surfactantrespectively for the coflotation separation of Ti(IV)at an optimum pH of8.0 due to easier dissolution offroth.The optimum concentrations of coprecipitant andsurfactant required to obtain maximum recovery atpH 8.0 were found to be 50-100 ppm and 10-15 ppmrespectively. A short stirring time of 5 min wassufficient to bring about the complete recovery oftitanium.Determination of Ti(lV) by catalytic currentpolarographyThe composition of the supporting electrolyte hasto be carefully controlled to obtain a linear relation-ship between the catalytic current and the con-centration of Ti(IV). Sodium chlorate (0.10 MY,oxalic acid (0.50 M) and sulphuric acid (0.25 M) as thesupporting electrolyte gave a linear calibration forTi(IV) in the concentration range 0.01-1.0 ppm.A comparison of the sensitivities of the catalyticcurrent of Ti(IV) by DPP and charging currentcompensated de polarography (CCCDCP) showedthat the de catalytic current was 2.8 times moresensitive than the DPP catalytic current. This valueagrees well with the theoretical ratio of i(CCCDCP)to i(DPP) calculated for n = 1 under the polarogra-phicconditions, t = 0.5 s and ilE = 50 mV (ref. 10).Even though CCCDCP was more sensitive thanDPP, the latter gave better resolution. Hence, DPPwas preferred attitanium concentrations less than 0.1ppm where it is necessary to resolve the titaniumcatalytic current from the large current due to theirreversible reduction of excess of chlorate (The twopeaks were separated by about 200 mV). It was alsoseen that the inteferencefrom the chlorate peakdecreased as the drop time was increased 11, This isbecause catalyttic current is a function of i-/3, whereasthe irreversible current due to the reduction ofchlorate does not increase much with increase in droptime. A higher drop time was preferred also becauseit gave a linear curve.The effect of surfactants (SLS and SO) on thecatalytic current of Ti(IV) was studied. The Ti(IY)concentration in the supporting electrolyte was 1.0ppm. The catalytic current was suppressed by thepresence of both surfactants, but the effect was lesssevere in the case of SO. It was observed that thereduction of DPP catalytic current by 40 ppm ofsurfactant was 18% and 70% in the case of SO andNOTES 321Table l-e-Determination of Ti(IV) in natural fresh watersamplesTi(IV) addted Ti(lVj found' Ti(IV) in the sample(~g) (ug) (ug/I)Laboratory lap water0 0.65 0.659·5 1.18 0.681.0 1.70. 0.70Bore-well water0 0.81 0.810.5 1.34 0.840.1 1.80 0.80tAverage of 6 replicate measurents.SLS respectively. But at surfactant concentrationsless than 10ppm, the change in the peak curren twasnegligibly small and within the limits of experimentalerror.Effect of various cations and anions on the coflotationand determination of Ti(lV)The influence of known amounts of added cationsand anions on the coflotation ofTi(IV) in the presenceof 100 ppm Al(IlI) and 10 ppm SO at pH 8.0 wasstudied. A solution containing 0.1 ppm Ti(IV) wasused for this study. Fe(III), Zr(IV), Bi(III), Cufll),Pb(II), Ni(II), Co(II), Zn(II) and Cd(II) floated alongwith Ti(IV), but the recovery ofTi(V) was not affectedby the presence of these ions. Except for Fe(III),Bi(III) and Cu(II), 100-fold amounts of the ions did,not interfere with the polarographic determination ofTi(IV). Cu(II) and Bi(III) did not interfere whenpresent in up to lO-fold excess. However, largeramounts of these ions were found to decrease thecatalytic peak since the reduction of Cu(II) and .Bi(III) occurs at more positive potentials than that of .Ti(IV). There was no interference from up to 20 ppmFe(III) in the supporting electrolyte. But if theconcentration of Fe(III) was increased above thislevel, the catalytic current of Ti(IV) increased.Mo(VI), Cr(VI) and Sb(III) were not floated al allunder the conditions used for the coflotation ofTi(IV).The effect of anions such as chloride, nitrate,sulphate, silicate and phosphate on the coflotation oftitanium was studied by adding known amounts ofthese ions to the solution before flotation. It wasobserved that flotation was incomplete above 5 ppmeach-of phosphate and silicate and hence recovery ofTi(IV) was about 60%. Up to 0.2 M, chloride andnitrate did not interfere with the coflotation oftitanium. Sulphate was tolerated only up to 0.05 M.322 INDIAN J Cl{EM. SEe. A, APRIL 1995Determination ofTi(IV) in synthetic solutions and realsamples. Synthetic water samples were prepared by adding0.2, 0.5, 1.0, 2.0, 4.0 and 10.0 I1g of Ti(IV) to 1.01distilled water. Ti(IV) was determined in these samplesolutions by the coflotation-DPP procedure des-cribed in the experimental section. It was found thatthe recoveries were> 95%. The relative standarddeviation calculated for six replicate measurementsat 1.0 I1g/1 was 4%.Samples of tap water and well water (11) were alsoanalyzed and the results are shown in Table I. Therelative standard deviation for 6 replicatemeasurements was found tobe 5%. .ReferencesJ Griel J V.& ..Robinson R J. J mar Res. II (1952) 173.2 Hiraide M & Mizuike A, Rev anal Chern, 6 (1982) 151.3 Mizuike A & Hiraide M, Pure & appl Chern, 54'(1982) 1956.4 Caballero M,Cela R & Perez-Bustamante J A, Ta/anta, 37(1990) 275.5 Kim Y S & Zeitlin H, Sep Sci, 1 (1972) 861.6 Kim Y S & Zeitlin H, Sep Sci, 6 (1971) 505.7 Hiraide M, Ito.T, Baba M, Kawaguchi H &Mizuike A, Ana/ytChern, 52 (1980) 804.8 Bharathibai J Basu, Padma D K & Rajagopalan S R, Talanta,38 (1991) 1431.9 Standardrnethods of chemical analysis, Vol. 1. edited by N HFurman (Van Nostrand, New York) 1962, p.1107.10 Rodriguez-Monge L M, Munez E, Avila J L & Camacho L,An/yt Chern, 57 (1985) 2269.II Bharathibai J Basu & Rajagopalan S R, Bull Electrochem, 9(1993) 35...------~--

Catalytic current polarographic determination of traces of titanium in water after preconcentration by coflotation

A new method is reported for the-determination of trace\ud
levels of Ti(IV) in water by cofiotation and polargraphy.\ud
Ti(IV) is preconcentrated and separated by cofiotation\ud
using aluminium hydroxide as coprecipitant and sodium\ud
oleate as surfactant. Polarographic determination of\ud
titanium content in the froth is based on the catalytic wave\ud
ofTi(IV) in the presenceof chlorate and oxalate. The effect\ud
ofvarious cations and anions on the fiotation and\ud
determination of titanium has been investigated. The\ud
method has been applied to estimation of titanium in\ud
natural fresh water samples

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Catalytic current polarographic determination of traces of titanium in water after preconcentration by coflotation

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