Interaction forces between colloidal starch and quartz and hematite particles in mineral flotation

In this study, we present theoretical and experimental data on the interaction forces between starch and particles of hematite and quartz as well as their implications for flotation and aggregation. The individual Hamaker constant for starch acting through vacuum, A(11), was calculated, and its value, 6.27 x 10(-20)J, demonstrates the highly hydrophilic character of gelatinized starch. The Hamaker constants for quartz/water/starch and for hematite/water/starch, A(132), were also calculated, and these values were 6.07 x 10(-21)J and 17.90 x 10(-20)J, respectively. It was confirmed that starch strongly adsorbs onto hematite, whereas on quartz, starch may adsorb onto only silicon surface sites. In fact, AFM images of quartz surfaces showed non-adsorbed areas or areas with a thin layer of starch that certainly do not interfere in subsequent adsorption by the collector (etheramine). The interaction energies between gelatinized starch and the hematite and quartz surfaces were estimated based on DLVO theory at pH 10.5 and a constant ionic strength (10(-3) moLL(-1) NaCl). The repulsion electrostatic energy was higher for the quartz-starch system than for the interactions between hematite and starch. The calculated total energy of interaction between quartz and starch revealed that there is no possibility of aggregation for the individual colloids of starch and quartz particles. On the other hand, spontaneous adhesion between the colloids and hematite particles was confirmed by DLVO theory.