PRECONCENTRATION OF TRACE METAL IONS FROM NATU~L WATERS: STUDIES ON me APPLICATiON. OF AN ACRYLIC ESTER MACRORETICULAR RESIN. ,By.

Transcription

1 1-<... PRECONCENTRATION OF TRACE METAL IONS FROM NATU~L WATERS: STUDIES ON me APPLICATiON. OF AN /" ACRYLIC ESTER MACRORETICULAR RESIN,By B.Sc., M.Sc. r A 'thesis ' Submitted to the School of Graduate Studies in Partial Fulfilment of the Requirements for the Degree Doctor of Philosophy McMaster University October, 1983

2 ( PRECONCENTRATION OF TRACE METAL IONS BY AN ACRYLIC ESTER RESIN «

3 ,. -..', \ DEDICATED TO -.j '1-1;.. MY FAMILY \, -. "

4 < DOCTOR OF-PHILOSOPHY (1983) (Chemistry). TITLE:.,. Preconcentratlon of Trace Metal, Stufies on the "' McMaster University Hami I ton, Ontario Ions from Natural Waters: Application of an Acrylic Ester Resin. MaL-oreticular / AUTHOR: Solomon Ying Hung Chiang B.Sc., M.Sc. (Concordia Univetsity) SUPERVISOR: Prolessor A. Corsini ṄUMBER OF PAGES: / xvi, i,... ii

5 , ABSTRACT A new preconcentration method has been developed for the determination of trace metals from natural waters. The method is based on the direct uptake of aetal ions on a column pa~ked ~ porous acrylic ester resin, XAD-7, are removed on a XAD-7~recolumn. ~ with the macro- after interfering humic substances, The retained metal ions are subsequently eluted with 1\ v/v HN0 3 and the trace metals determined by graphite-furnace atomic absorption spectroscopy. The effects of various parameters such as ph, ionic strength, anions, organic substances, flow rate, column bed-size and resin particle size on the adsorption and elution of metal ions were examined. Based on these investigations, optimal conditions for the group preconcentration of Cr, Fe, Cd, Co, Cu, Mn, Ni and Pb were established. The method was successfully applied to various natural waters,. and was found to be simpler and less ~usceptible to contamination than 'the Chelex-IOO method. In additio~~ larger preconcentration factor was obtained. The accuracy and precision of the XAD-7 method were found to be at least competitive with the.chelex-ioo method. The mechanism of adsorption was investigated and adsorption isotherms and distribution ratios of selected metal ions were measured. The adsorption process is complex and likely involves charge-dipole interactions. A simple model was developed to illustrate the rationale of the method of standard additions in a preconcentration procedure. It was shown that a high degree of spike reaction with the sample matrix iii

6 and a reasonable degree of analyte separation are vital for the success ~ ful application of standard additions. If the degree of separatfon is, very high, the method of standard additions is not required and only a simple calibration curve is necessary., J! iv

7 ACKNOWLEDGEMENTS -. I am,deeply grateful to my research supervisor, Professor Ao Corsin for his faith in my abilities and work and for his invaluable and criticism, especially d4ring the prep~tion of this thesis. I have learned many useful and long-la~ting lessons from our years of work together: Thanks are ~lso due to Professors D. Burgess,'O. E; Hileman, Jr, and R. ~. Tomlinson who, as members, of my superv~sory~ommittee, offered! many helpful suggestions. I am further indebted to Dr: Burgess for provision of advice and equipmen: ~orthe radioisotope work. "\ I also offer special thanks to Drs. R. DiFruscia and C. C. Wan and Mr~Hickling for the many enlightening conversations on topics relevant and otherwise. Although space does not allow me to cite a~l of the people who '-', have helped make life easier and more pleasant during my stay, I wish to thank Mrs. Carol Dada for her exce~lence in typing this thesis. " I takp-this opportunity to gratefully acknowledge the financial support granted me by t)le Natural Sciences and E~gi~e~ring ~. / ~ese~rch Council and by the Department of Chemistry, McMaster University; Last, b~t not least, I thank my family for their heip and 7 encouratement over the year~. " v

8 TABLE OF CONTENTS I. INTRODUCTION 1.1 General 1.2 Determination of Trace (Soluble) 3 Metals in Natural Waters (i) Methods of preconcentration 6 (ii) Method of standard additions: Effect of. incomplete reaction of spike 1.3 Metal-Ion Speciation in Natural W~ters (i) Metal-ion specie~ in natural waters (ii) Methods of speciation.j lb 1.4 Adsorption and XAD-7, a Macroreticular 20,Polymeric Adsorbent 1.5 Aim of Research 32 II. EXPERIMENTAL SECTION Laboratory Apparatus, Resins, Reagents, 35 Test Solutions Instrumentation and Techniques 36 (i) General 36 (ii) Atomic absorption and flame emission measurements 36 (iii) Radioisotope tracer techniques 42 (iv) (v) Column percolation procedure Elution recovery procedure vi.

9 p.3 (vi) Batch equilibrium procedure Preliminary Studies o~ < of Metal Ions on an XAD-7 Column. Direct Preconcen~tion Page 44 46, 1I.4.Studies on Mechanism of Metal '"'-, on XAD-7 Ions Retention 4B (i) (ii) Potentiometric titration Infrared studies 4B 49 (iii) Adsorption isotherm studies 49 (iy) Distribution ratios 51 II.5 Studies on XAD-7 Column Operation 52 (i) Breakthrough curves 52 (ii) The two-column technique 54 (iii) Elution recovery ~nd preconcentratio~ 55 'factor 11.6 Applications 57 " (i) (ii) (iii) Application to lakewater., 57 Application to seawater The analytical blank III. RESULTS AND DISCUSSION 61 IlL I Preliminary Studies on Direct Preconcentration 61 III.2 of Metal Ions on a XAD-7 Column Studies on Mechanism of Metal-Ion Retention'on XAD-7 71 (i) Potentiometric titration (ii) Infrared studies 74 (iii) Adsorption isotherm studies 76.-/ vii 72

10 (iv) (v) (vi) Langmuir iquation and adsorptiori in solution 'Microscopic model for the adsorptio~ of metal-ions Distribution ratios IlL3 Studies on XAD-7 Column Operation 106 (.(i) Breakthrough curves 106 (ii) (iii) 1be two-column technique Elution recovery and preconcentration factor IlL4 Application 122 \. (i) (ii) Application to lakewater Application to seawater 125 { 132 (iii) Statistical analysis of the XAD two-column method (iv) Method of,standard additions: effect 145 of i~~mplete reaction of spike IlL5 Surmnary 157 IV. SUGGESTIONS FOR FUTURE WORK 159 V. APPENDICES 162 V.l Mathematical and Statistical Implications of the Langmuir Equation V.2 Adsorption of Metal Complexes of Mesotetra- 165.,., i. (p-sulphophe~l)porphine (TPPS~) Column on an XAD-7.viii

11 ", Page VI. REFERENCES.. ( 170 /.".. "..,",. " ix (

12 .LIST OF TABLES Number I Title ) Decline in the Reported Concentration of Trace Metals in Seawaters, II Detection Limits of Some Trace Metals by 7 ICPAES and GFAAS ane Comparison to 2. Concentrations in Two Natural Water Samples II! Possible Physico-Chemical Forms of Metals 17 IV in Natural Waters, Summary of Speciation Scheme of Florence 21 ".\nd Batley ) V Some Chemical and Physical Pr~perties 0 29 the XAD,Resins -VI. Applicati of XAD Resins in Adsorption 30 Chromatograp y VII VII I IX X Application 0 XA~ Res~ns as Separation/- Preconcentration Agents in Trace Analysis Analytical!avelength and Temperature, Setting~ for thl' Drying, Charring and Atomization Cycle in GFAAS Percent Retention of Metal Ions on a XAD-7.' Column at Various ph Values Effect of Anions on Percent Retention of Metal Ions on XAD-7 Column at ph 2.0, 5.0 and 8.0 x

13 XI Percent Recovery of Metal Ion Spikes in DDW Page 70 XII fmax (Resin Capacity) for the Adsorption of 81 Cu(II) on Mesh XAD-7 at Various ph Values XIII fmax (Resin Capacity) for Protons and Cu(II) 86 as a Function of Particle Size XIV Langmuir Parameters for the Adsorption of Protons on XAD-7 (60-80 Mesh) as a Function XV XVI XVII XVIII XIX XX XXI XXII of Temperature Maximum DR Values for the Adsorption of Metal Ions on XAD-7 f Breakthrough Volumes for Cu(II) on 1 x 6 cm XAD-7 Column.. Recovery of-metal Ions from Aqueous Solution Containing Humic Substances by ~ingle- and Two-Column Methods Analysis of Synthetic Fresh~ater by XAD-7 Two-Column Method Analysis of Lake Ontario Water, CCIW Station 302 Analysis of Lake Ontario Water, CCIW Station. 14 Analysis of Seawater Reference Material, NRC NASS-l, by XAD-7 Two-Column Calibration Curve Method Analysis of Nova Scotia (Sandy Cove) Coastal Seawater I Il8 126 ~ , 135 xi \

14 XXIII XXIV XXV Analytical Blank Values for XAD-7 Two-Column and Chelex-IOO Procedures Test for Accuracy of XAD-7 Two-Column Method Using Calibration Curve Comparison of Analytical Data for Lake Ontario Water (Station 302) by XAD-7 Calibration Curve and Standard Additions Page Methods: Test of Significant Difference XXVI XXVII Test of Significant Difference between Chelex-IOO Standard Additions and XAD-7 Standard Additions for Sandy Cove Seawater Test of Significant Difference between Chelex-IOO Standard Additions and XAD Calibration C~rv~ for Sandy Cove Seawater XXVII I Calculation of Combined Spike and Analyte 148 Recovery for DSR=50\. F~=0.50. Original Analyte Concentration = 1.00 ~g/l XXIX Recovery (~g/l) of Original Analyte ISO.' (1.00 ~g/l) as a Function of DSR and F t \ xii. - '.

15 LIST OF FIGURES Number \ Title 1 2 Adsorption isotherm Structures of XAO-2, XAO-4 and XAD-7,~esins Structure of porphine. TPPS 4 has the group <0>- S03H substituted at the a - <I 33 positions Column configuration Effect of ph on the retention of Ni(ll), Pb(ll), Cr(III) and Fe(III) on a 1 x 7 cm XAO-7 column Effect of flow Jate on the retention of Fe(III), Cr(III), Mn(II) and Cd(II) on a 1 x 7 em XAO-7 column Profiles for the elution of some metal ions 4S from a 1 x 7 cm XAD-7 cplumn by 1\ v/v HN0 3 8 Curves for titration of (i) g of XAD in ml of F HN0 3, (ii) ml of F HN0 3.blank ph/time profile for a single point titration 7S of 10.0 g of XAD-7 in ml of U.Ol055 F HN0 3 with ml of F NaOH Infrared spectrum of XAD-7 resin Rate of adsorption of Cu(II) on XAD xiii

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