Adsorption of Sb(V) on Goethite: Effect of ph, Ionic Strength, and Competition with Phosphate Jianhong Xi Supervised by Liping Weng
Outline General introduction Material and methods Experimental results Conclusions
Chemical properties Toxicity Sb(III) > Sb(V) Sb(III) --Sb(OH) Sb(V) --Sb(OH) 6 -
Eh ph diagram of antimony in the Sb S H O system at a dissolved antimony concentration of 0-8 mol/l and a dissolved sulfur concentration of 0 mol/l. From Filella et al. (00)
Antimony pollution and potential risk to human Mining and smelting activities
Heavy pollution and potential risk to human waters bottled in PET containers had as much as 550 ppt of Sb. Even highly purified deionized waters contained in PET bottles had antimony concentrations up to 60 ppt.
Retention of antimony in soils and sediments Brannon and Patrick. 985, Fixation and Mobilization of Antimony in Sediments. Environmental Pollution Takahashi et al. 00, Contribution of Amorphous Iron Compounds to Adsorptions of Pentavalent Antimony by Soils. Water, Air, and Soil Pollution Scheinose et al. 006, Quantitative antimony speciation in shooting-range soils by EXAFS spectroscopy. Geochimica et Cosmochimica Acta Sb(V)
Literature review 5 4 Leuz et al. 006 Sorption of Sb(III) and Sb(V) to Goethite: Influence on Sb(III) Oxidation and Mobilization. Environmental Science & Technology Sb adsorbed (µmol/m ) 0 Adsorption isotherms ph= 0 0 40 60 80 00 0 40 60 Sb in solution (µmol/l) McComb et al. 007 ATR-IR Spectroscopic Study of Antimonate Adsorption to Iron Oxide. Langmuir Schematic representation of Sb(OH) 6 - adsorption onto iron(iii) oxide under acidic conditions followed by desorption under alkaline conditions
Research objectives Adsorption isotherms on goethite Effect of ph and ionic strength Comparison with PO 4 and As(V) Competitive adsorption of Sb(V) and PO 4
Materials and Methods
Materials Compounds Sb(V) PO4 As(V) KSb(OH) 6 Na HPO 4 H O Na HAsO 4 7H O Iron-oxide Specific surface area PZC Goethite 96 m /g ph=9.
Adsorption experiments Samples addition Shaking in dark Centrifugation N days Determination Filtrate Filter ICP-MS ICP-AES
Experimental Results
Adsorption isotherms 5 Normal scale 0.8 log scale 0.0 M NaCl 0. M NaCl Sb adsorbed (umol/m ) Sb adsorbed (umol/m ) 5 4 4 0 lg(qe) 0 50 00 50 00 50 00 50 Sb(OH) 6 in solution (umol/l) lg(qe) 0.6 0.4 0. 0.0-0. 0.7 0.6 0.5 0.4 0. 0. - - 0 lg(ce) ph=4 ph=6 ph=7. 0 00 00 00 400 Sb(OH) 6 in solution (umol/l) 0. - 0 lg(ce)
Comparison with PO4 and As(V) 5 Normal scale 0.8 0.7 lg scale ph=4 I=0.0 M PO 4 AsO 4 Adsorbed (µmol/m ) Sb(OH) 6 4 0 50 00 50 00 50 00 50 Ce (µmol/l) lg(qe) 0.6 0.5 0.4 0. 0. 0. 0.0 0.5 - - 0 lg(ce) ph=6 I=0.0 M Adsorbed (µmol/m ) lg(qe) 0.4 0. 0. 0. 0 50 00 50 00 50 00 50 Ce (µmol/l) 0.0 - - 0 lg(ce)
Effect of ph and ionic strength Change of adsorbed amount Change of solution concentration 4 Sb adsorbed (µmol/m ) lg Ce 0-4 5 6 7 8 9 ph Filled symbols 0.0 M Open symbols 0. M 4 5 6 7 8 9 ph ph has a negative effect on Sb(V) adsorption - C0=74.5 µm C0=8. µm C0=6.79 µm C0=05.4 µm
Effect of ionic strength 4 Change of adsorbed amount Change of solution concentration Sb adsorbed (µmol/m ) lg Ce 0-4 5 6 7 8 9 ph - 4 5 6 7 8 9 ph Filled symbols 0.0 M Open symbols 0. M C0=74.5 µm C0=05.4 µm High Sb(V) loadings, high ph, increase of IS has increased Sb(V) adsorption Low Sb(V) loading, low ph, increase of IS has decreased Sb(V) adsorption
Competitive adsorption of Sb(V) and PO 4 0. mm PO 4, a range of Sb(V) 0.0 M NaCl Sb(V) adsorbed (µmol/m ) 5 4 0 ph=4 No PO 4 0. mm PO 4 0 50 00 50 00 50 00 50 Sb(OH) 6 in solution (µmol/l) Sb(V) Sb(V) adsorbed (µmol/m ) 0 ph=6 No PO 4 0. mm PO 4 0 50 00 50 00 50 00 50 Sb(OH) 6 in solution (µmol/l) PO 4 adsorbed (µmol/m ).8.7.6.5.4....0 ph=4 PO 4 ph=6 0 Molar ratio of Sb(V) to P(V) Sb(V) adsorption was decreased strongly by PO 4 PO 4 adsorption was also decreased due to competition ph dependency of PO 4 adsorption was reversed by the presence of Sb(V)
Competitive adsorption of Sb(V) and PO 4 0. mm Sb(V) + 0. mm PO 4 0.0M NaCl Sb/P adsorbed (umol/m ) 0 Sb(V), no PO 4 Sb(V) PO 4-4 5 6 7 8 9 ph Sb(V) adsorption decreases strongly with the increase of ph; In the presence of PO 4, ph effect on Sb(V) adsorption becomes stronger; At the same molar concentration added, PO 4 adsorption is stronger than Sb(V); In the presence of Sb(V), ph has had little effect on PO 4 adsorption (under the exp. conditions)
Conclusions. In single adsorbate systems, Sb(V) > PO 4 As(V). Sb(V) adsorption decreases with ph increase, ph dependency is stronger than As(V) and PO 4. Ionic strength dependency is small and depends on ph and Sb(V) concentration 4. In binary systems of Sb(V) and PO 4 adsorption of both Sb(V) and PO 4 were decreased, and Sb(V) showed a stronger decrease.
Thank you for your attention Acknowledgements: André van Leeuwen Gerlinde Vink Miranda Vlag Peter Nobels Jaap Nelemans Johan Uijtenbroek
Experimental setup Isotherms Background Single system Binary system 0.0M NaCl Sb(V)-goethite at ph 4, 6, 7. Sb(V)-PO4-goethite at ph 4, 6 As(V)-goethite at ph 4, 6 PO4-goethite at ph 4, 6 0. M NaCl Sb(V)-goethite at ph 4, 6 Effect of ph Background Single system Binary system 0.0M NaCl Sb(V)-goethite Sb(V)-PO4-goethite 0. M NaCl Sb(V)-goethite