A KINETIC INVESTIGATION OF THE DISSOLUTION OF POWELLITE IN OXALIC ACID SOLUTIONS


Ilhan S. , Kalpakli A. O. , Kahruman C. , Yusufoglu I.

T T Chen Honorary Symposium on Hydrometallurgy, Electrometallurgy and Materials Characterization held during the 141st TMS Annual Meeting and Exhibition, Florida, United States Of America, 11 - 15 March 2012, pp.629-639 identifier identifier

  • Publication Type: Conference Paper / Full Text
  • Volume:
  • City: Florida
  • Country: United States Of America
  • Page Numbers: pp.629-639

Abstract

The effects of oxalic acid concentration, temperature, stirring rate and particle size on the dissolution rate of synthetically prepared calcium molybdate were investigated. Dissolution of calcium molybdate in oxalic acid solutions takes place as a series - parallel type reaction. In the first reaction step, which proceeds according to the "Langmuir - Hinshelwood Mechanism", calcium aqua oxalato molybdate is formed as a complex chelate intermediate product. In the second reaction step, molybdic acid is formed during the slow hydrolysis of calcium aqua oxalato molybdate, and it reacts rapidly with oxalic acid to form the polymeric hydrogen oxalate dimolybdate chelate as an end product. Activation energies were calculated as 41.4 and 49.9 kJ mol(-1) for the first and zero order reactions. The fractional conversion versus time relationship can be given by the following equation.