m · 1 · K = Exp (— △ G 0 ) m 0 — m [D] RT
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Figure 1 Relationship between adsorption capacity and pH
Figure 2 Adsorption amount and equilibrium concentration
Where [D] - the average concentration of dextrin in the medium;
Fig. 3 Schematic diagram of dextrin adsorption (a) and masking collector (b) on molybdenite
Figure 4 ξ-potential diagram of dextrin on molybdenite surface
Table dextrin inhibition effect on molybdenite
Inhibition of molybdenum by dextrin
Dextrin is called "British gum" in foreign countries and is a non-ionic, water-soluble organic polymer. It is the first step of the hydrolysis of starch by dilute acid (if it continues to hydrolyze, it will produce glucose). The molecular weight is between 800 and 7900, which is a good inhibitor of molybdenite .
J·M·Wei research found that the adsorption amount of dextrin on molybdenum ore varies with the pH value of the medium and the concentration of dextrin, as shown in Figure 1 and Figure 2.
It can be seen that the adsorption amount of dextrin on molybdenite is basically not affected by the change of pH value, and the adsorption amount varies with the concentration of dextrin, which is consistent with the Langmuir adsorption equation:
Â
M——the amount of adsorbed dextrin during equilibrium;
m 0 - saturated adsorption amount;
ΔG 0 -- adsorption free energy.
According to the measured data, ΔG 0 = 2190 kJ / mol of dextrin. [next]
Dextrin is a non-ionic large-molecular weight organic inhibitor. When it is adsorbed to molybdenum ore, it has a hydrophilic molecular chain longer, which not only directly makes the mineral surface hydrophilic, but also masks the hydrophobicity of the collector adsorbed on the mineral surface. Sex (see Figure 3).
The adsorption of dextrin on molybdenum ore is mainly due to hydrogen bonding and van der Waals. According to the calculation, the free energy of adsorption is 22.6J/mol, J·A Wei (Wie), etc., and the heat of adsorption is about 2.5kJ/mol. This order of magnitude also indicates that the interaction is hydrogen bonding and the molybdenum and dextrin molecules are pro- Water bonding (ie, the amylin molecule replaces the water adsorbed on the partially oxidized molybdenite surface to form an oriented hydrophilic hydrophilic drug adsorption layer).
The non-ionic dextrin adsorbed on the surface of the molybdenite, and the absolute value of the ξ-potential decreased, but the change was not large, and the pH value of the medium remained unchanged (see Figure 4).
Â
After molybdenum ore adsorption of dextrin, the wet contact angle and flotation recovery rate were significantly reduced, as shown in the table below.
Dextrin dosage (mg/t)
Contact angle (degrees)
Recovery rate(%)
0
86
92
0.2
67
18
1.67
42
8
8.3
0
2
16.7
Note: Harrimont tube, PH=3.8
It can be seen that when the amount of dextrin reaches a sufficient limit, it can suppress the molybdenite well. The Utah branch of Kennecott Copper Co., Ltd. relies on dextrin to inhibit molybdenum ore and talc , without affecting the floatability of copper sulfide and iron , and realizes the industrial practice of molybdenum-free copper floating. This is called using "Utah" process of the bell as well as silver copper - molybdenum processing plant.