Precise and instrumental measurement of thermodynamics and kinetics of froth flotation by langmuir-blodgett technique

Abstract

Froth flotation is most common means in mineral separation, and the in-situ measurement of flotation is of significance. However there were no instrumental means of measuring kinetics and thermodynamics for this process up to date. Herein, for the first time a facile method was developed by using Langmuir-Blodgett (LB) technique to get precise recording of kinetics and thermodynamics for adsorption process of Langmuir hybrid layer at the air/water interface. The formation of hybrid Langmuir monolayer was assumed to simulate the adsorption of mineral particles by frother/collector bubbles in the micro-flotation although this was a semi-static adsorption process. The kinetic parameters including time constant (τ1/e, 32.0∼139.0 s) and adsorption rate constant (k, 0.0315∼0.00718 s−1) were precisely determined according to surface pressure vs. time (π-t) plots of Langmuir monolayer which consisted of floated minerals particles and collector molecules. The thermodynamic data such as partition coefficient (Kd, 0.221−0.339), Gibbs free energy of adsorption ΔG (2.68∼3.74 kJ mol−1), and minimum dosages of collector molecules (potassium butylxanthate) were derived from the surface pressure vs. molecular area (π-A) isotherms. Taking the major mineral of pyrite with minor of dolomite and quartz as a froth flotation model, the recovery yield of concentrate pyrite obtained from LB technique was found in good agreement with the common tests used micro-flotation, suggesting the consistency of the new-developed LB method in predicting kinetics and thermodynamics for froth flotation.