IRON & MANGANESE

1. IRON& MANGANESE ENVE 201 Dr. Aslıhan Kerç http://sites.google.com/site/marmaraengineer/my-forms http://translate.google.com.tr/translate?hl=tr&sl=en&u=http://sites.google.com/site/marmaraengineer/

2. IRON & MANGANESE Problems in groundwater, surface water certain seasons. Some underground waters are free of Fe, Mn, but some have Biochemical changes effect Fe, Mn content Changes in environmental condition brought by biological reactions effect Fe, Mn content.

3. IRON & MANGANESE Mainly Fe,Mn  insoluble form in soilhow converted to soluble? Fe is found in soils and minerals as : insoluble ferric oxide ironsulfide (pyrite) (slightly soluble) Ferrous carbonate (siderite)

4. Mn  in soil as manganese dioxide (insoluble) in water containing CO2 Under anaerobic cond. : oxidation state changes ΙV  ΙΙ These changes occur due to biological rxns: 1) G.W. containing Fe, Mn low D.O high CO2 in the form Fe2+ , Mn2+ High CO2 bacterial oxidation of organic matter. Absence of D.O anaerobic cond.

5. 2) Wells producing good water change to poor quality in time. What is the reason? Organic wastes discharge aroundanaerobic conditions occur in soil. 3) In surface waters (reservoirs) anaerobic conditions occur in hypolimnion. Fe,Mn released from bottom mud. Distributed to the whole lake during fall overturn. 4) Mn (IV) , Fe (III) stable oxidation states for aerobic. Reduced to soluble Mn(II) , Fe(II) under highly anaerobic conditions.

6. G.W. contain CO2 FeCO3 + CO2 + H2O  Fe2+ + 2HCO3- like dissolution of calcium and magnesium carbonates More problems w/ insoluble ferric compounds. Under anaerobic (reducing) condition : Fe3+ Fe2+ (ferric) (ferrous)

7. 5) Certain bacteria use Fe (III) and Mn(IV) as electron acceptor. (?) When O2 containing water injected into G.W for recharge  soluble Fe content may increase. O2 consumed by pyriteFeS2  leading to anaerobic conditions again 2FeS2 + 7O2 + 2H2O  2Fe2+ + 42SO42- + 4H+

8. No harmful affect in drinking water When exposed to air become turbid, form colloidal precipitants unaccepted aestheticaly oxidation rate  not rapid Form stable complexes with humic substances more resistant to oxidation Interfere with laundering. Environmental Significance

9. Difficulties in distribution sys.  growth of iron bacteria Imparts taste to water Fe: 0.3 mg/L SMCL Mn: 0.05 mg/L Environmental Significance

10. Interferences : Phosphate Heavy metals 1,10 phenonthroline combines with Fe2+ to form complex ion orange in red color Color produced confirms Beer’s Law Visual Photometric comparison Measurement of Iron (Phenanthroline Method)

11. Sample exposed to atmospfere contains Fe2+ , Fe3+ , ppt of ferric hydroxide. All iron  must be in soluble form HCl is used Fe(OH)3 + 3 H+ Fe3+ + 3 H2O 1,10 phenonthroline  specific for measuring Fe(II) Fe3+is reduced to Fe2+ Hydroxylamine is used as reducing agent 4Fe(III) + 2 NH2OH  4Fe(II) + N2O + H2O + 4 H+ 3 molecules of 1,10 phenantrhroline complex with each Fe2+ Phenanthroline Method

12. Colorimetric method  depend upon oxidation of Mn to  VII forms highly colored permanganete ion Obeys Beer’s Law Visual or photometric comparison AAS ICP Manganese measurement

13. Ammonium persulphate  oxidizing agent Cl- interference: Because of reducing action in acid medium. use Hg2+for interference. HgCl2 complex is formed Ag2+ is used as catalyst Oxidation of Mn in lower valence to permanganete by persulfate. Ag+ 2Mn2++5S2O82- +8H2O 2MnO4- +10SO42- +16H+ (permanganete colored) Manganese measurement (Persulphate Method)