Study On Adsorption Models And Flotation Characteristics Of PEO-PPO-PEO Block Copolymers On The Surface Of Fluorite

Fluorite,as a global strategic mineral resource,with the rise of emerging industries such as new energy and new materials,its application value has attracted more and more attention at home and abroad.At present,flotation is the most important method for separating and recovering fluorite.Conventional fatty acid collectors have disadvantages such as poor flotation effect on fine-grained minerals.PEO-PPO-PEO block copolymer is a non-ionic surfactant with rich designability,which can change the hydrophilicity and hydrophobicity of the adsorbed mineral surface by adjusting the molecular weight and EO/PO block ratio,thereby improving mineral floating.It can be used as an adjuster to show its potential in the mineral processing industry.The thesis took PEO-PPO-PEO block copolymer as the research object,and through the flotation test system,the flotation behavior of PEO-PPO-PEO block copolymer with different structures on coarse and fine fluorite in the sodium oleate system was studied.The adsorption model and action mechanism of PEO-PPO-PEO block copolymer and sodium oleate on the surface of fluorite were further studied by combining infrared spectroscopy analysis,contact angle test,adsorption amount test and molecular dynamics simulation.（1）The flotation test showed that when the p H value was in the range of 6～10 and the dosage of sodium oleate was 1×10^-4mol/L,the coarse-grained fluorite has good floatability,but the flotation recovery rate of fine-grained fluorite was below 60%.Six different types of PEO-PPO-PEO block copolymers can improve the flotation recovery rate of fine-grained fluorspar to a certain extent without affecting the flotation of coarse-grained fluorspar.The comparison result of promoting effect was L-81>P-123>L-35>F-68>F-127>F-108.When the dosage of L-81 was 8×10^-7mol/L and the dosage of sodium oleate was 1×10^-4mol/L,the recovery rate of fine-grained fluorite flotation can be increased from 59.1%to 68.8%.（2）Infrared spectroscopy showed that L-81,P-123 and F-68 three PEO-PPO-PEO block copolymers and sodium oleates can be stably adsorbed on the fluorite surface together;The contact angle test showed that the PEO-PPO-PEO block copolymers can improve the contact angle of fluorite through the PPO hydrophobic segment in the molecular structure.When the dosage was lower than 6×10^-7mol/L,the PEO-PPO-PEO block copolymers and sodium oleate acted together on the surface of fluorite to increase its contact angle,and the effect of L-81 with lower molecular weight and EO/PO ratio was more prominent;The adsorption capacity test showed that the adsorption capacity of PEO-PPO-PEO block copolymer on the fluorite surface mainly depended on the molecular weight and the EO/PO block ratio.The block copolymer F-68 has the largest adsorption capacity on the fluorite surface,but the PEO-PPO-PEO block copolymer with low molecular weight or low EO/PO block ratio was beneficial to the adsorption of sodium oleate on the fluorite surface.（3）Molecular dynamics simulations showed that the molecular weight,EO/PO ratio and the dosing order of the combined agents all affected the adsorption configuration of the PEO-PPO-PEO block copolymer on the fluorite surface.PEO-PPO-PEO block copolymers with lower molecular weight or lower EO/PO ratio would form a pancake adsorption configuration through hydrogen bonding between the H atoms in PEO at both ends and the F atoms on the surface of fluorite,and through the molecular structure of the PEO-PPO-PEO block copolymer.The PPO hydrophobic segment enhanced the hydrophobicity of fluorite,and this adsorption model was conducive to the adsorption of sodium oleate on the surface of fluorite;The PEO-PPO-PEO block copolymers with higher molecular weight or higher EO/PO ratio tended to form a brush-like adsorption configuration on the surface of fluorite.This adsorption configuration was unstable,which was not conducive to the adsorption of sodium oleate on the surface of fluorite.When the PEO-PPO-PEO block copolymer was excessive,the agent molecules would adsorb and entangle with the sodium oleate molecules,which will weaken the adsorption strength of the sodium oleate on the fluorite surface,resulting in a decrease in the recovery rate of fluorite flotation.