Abstract: The kinetics of the extraction of Nd(Ⅲ) by di-(1-methyl heptyl)methyl phosphonate (P₃₅₀) in nitric acid solution has been studied by using the constant-interface cell technique. The effects of the stirring speed,interfacial area between two phases,temperature,and concentration of P₃₅₀,NO₃^-,amd H⁺ on the extraction rate have been examined. The apparent activation energy was found to be 11.8kJ/mol. The experimental results showed that the rate-controlling step may be the chemical reaction at the interface. A cation exchange mechanism has been proposed.

Key words: di-(1-methyl heptyl)methyl phosphonate, neodymium, kinetics, extraction