Determination of the sodium contribution of solvent-extractable organic compounds in Bayer process liquor

Importance of the Topic

Monitoring the sodium contribution from solvent extractable organic acids in Bayer process streams is essential to troubleshoot organic related process upsets evaluate removal measures and maintain accurate sodium mass balances in alumina refineries

Objectives and Study Overview

This work presents a protocol to quantify the sodium fraction carried by weakly acidic high molecular mass organic species after solvent extraction from acidified Bayer liquor enabling process control and assessment of treatment efficiency

Methodology and Instrumentation

The procedure comprises acidification dilution and multiple solvent extractions followed by catalytic thermometric titration

• Acidify spent Bayer liquor with hydrochloric acid dilute with ultrapure water and cool
• Extract organic acids with five 25 mL aliquots of cyclohexanol
• Wash combined extracts ten times with saturated sodium chloride solution
• Dry extract overnight over anhydrous sodium sulfate at elevated temperature
• Dilute dried extract with propan-2-ol and pipette aliquot for titration
• Use paraformaldehyde as catalytic endpoint indicator
• Titrate with 0.1 mol per L potassium hydroxide in propan-2-ol to thermometric endpoint

Instrumentation

• 859 Titrotherm thermometric titrator
• 800 Dosino burette unit (10 mL)
• 804 Ti stand and 802 stirrer

Results and Discussion

Titration profiles from two Australian refinery liquors exhibit distinct endpoint shapes reflecting different organic acid distributions Non equilibrium effects around endpoint do not compromise endpoint detection The procedure delivers precise sodium contribution data with an estimated precision of 0.2 percent RSD making it suitable for process monitoring

Benefits and Practical Applications

This robust thermometric titration method enables reliable quantitation of sodium bound to extractable organic species supporting mass balance studies process trend analysis and evaluation of organic removal processes

Future Trends and Applications

Future work may broaden the range of extractable species investigated explore alternative solvents inline or automated formats and develop refined catalytic indicators to enhance sensitivity and applicability

Conclusion

A reproducible thermometric titration based protocol has been established for determining the sodium contribution of acid extractable organic compounds in Bayer process liquor with high precision and practical industrial utility

Reference

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2. Smith TK Analysis of free fatty acids in edible oils by catalyzed endpoint thermometric titrimetry Journal of the American Oil Chemists Society Vol 80 No 1 21-24 2003
3. Carneiro MJD Feres Junior MA Godinho OES Determination of acidity of oils using paraformaldehyde as thermometric endpoint indicator Journal of the Brazilian Chemical Society Vol 13 No 5 692-694 2002
4. Metrohm Application Notes AN-H-001 AN-H-029 Metrohm Products
5. Bark LS Bark SM Thermometric titrimetry Pergamon Press Oxford 1969