For most complex sulphide minerals, sodium ethyl xanthate (SEX) are often used due it its low collecting power and maximum selectivity as compare to PEX. To increase grade and recover fine particles of the sulphide, SEX is used as a helping collector with one of the powerful xanthates. PEX is powerful but least selective.

You right. I find that SEX is has a lower price at the market, and lower molecular weight. But I want know more, some experience from processes, comparison from flotation plants. I hope that our colleagues are wanted to divide real data with us.

I am not talking about the low in price; the low collecting power here is the power of adsorption onto the hydrophobic mineral surface. SEX is much selective and can help improve grade of a mineral as compare to PEX. It means it attacks specific mineral of interest leaving the unwanted unlike PEX

Thanks for your comment. I understand completely. Finally, in concentrators is very important to implement economical scheme for froth flotation. Task is optimum process.

I see many engineers talk about Capex and material cost. I wonder how and without basic cost benefit analysis some one can say anything they like or understand, and confuse the listener or observer. An unknown person/ Business man will think on CAPEX only or material cost as he is interested to reduce cost of production. I say the cost of minerals i.e. sales value is much higher than chemical, where you get more profit by adding costly and quality chemicals -rather than loosing minerals with cheap chemicals or equipment’s. Before deciding any new change you need to do 100 lab tests and compare the results. Based on some one's recommendation you cannot decide. All minerals behave differently in different mines. It needs microscopic and petrological study followed by lab, pilot plant tests. Last concluding remarks are used for COMMERCIAL operation.

An properly structured on/off plant trial over several days should generate enough data to make an informed decision (that is with a statistically significant justification) on the effect of a new collector (there may not actually be a difference, only that the new collector maybe half the price, in which case the new collector would win).

Okay, some extra work will probably be required (an initial laboratory study for example) to determine the addition ratio between the new and old collector, and to confirm that it will not immediately destroy your flotation kinetics or selectivity.

I repeat that cost/quality plays major role in chemical purchase. I give one example-

Case study-

Cheap chemical PEX, & SEX

Quality-High moisture, different colored chemical with green, white, yellow colors. Consumption 3 times higher than normal. Grade, recovery-50% reduced. Can I accept this chemical because it is cheap? Can you give reason for such chemicals?

After investigation it was found that manufacturer is ignorant of filtration and drying the chemical. He simply copied the process and started production. 50% cost goes for Filtration and drying in suitable atmosphere to be created.

Please don't deviate from good quality chemical norms, grade, and recovery advantages in metals.

You will need to educate me on this one: since the collector fully dissolves and dissociates in water, it is difficult to see how the cation plays any role in the behavior and subsequent attachment of the anion i.e. ethyl xanthate onto a mineral surface.

Of course, I am assuming that by 'PEX' Robert means KEX! I appreciate the universal warning about assumptions; however I am unaware of 'PEX' as a collector. Again, I may need some re-education! The main advantage is cost as noted by others: sodium salts are a lot cheaper to make than potassium salts.

Purity is a very important (and the water quality is mixed with) and can cause grief in many ways other than just poor metallurgy! 

I think that in this discussion there may be some confusion between PEX (potassium ethyl xanthate) and PAX (potassium amyl xanthate). PEX is a weak collector. PAX is a strong collector.

From the Cytec Mining Chemicals Handbook 2010, with my comments added [in square parentheses]:

"Xanthates are available in a range of carbon chain lengths, generally from C2 to C5. The collecting power generally increases with increase in chain length, but the selectivity decreases.

AERO 303 xanthate – Potassium ethyl xanthate [PEX]. Shortest carbon chain of the available AERO xanthates. [I cannot see how the carbon chain length differs from SEX] Particularly useful where maximum selectivity is desired. [I cannot see how this would differ in performance from SEX but I have no experience with using PEX]

AERO 325 xanthate – Sodium ethyl [SEX]. Used on complex ores for maximum selectivity! Most frequently used to float galena with Pb/Zn ores.

AERO 343 xanthate – Sodium isopropyl [SIPX]. Most widely used in the flotation of sulfide minerals of copper, molybdenum and zinc. Good compromise between collecting power and selectivity.

AERO 317 xanthate – Sodium isobutyl [SIBX]. A relatively strong collector used in the flotation of Cu, Pb, Ni, Zn, and PGM ores.

AERO 350 xanthate – Potassium amyl [PAX]. The most powerful and least selective xanthate. Often used as a scavenger collector following a more selective rougher collector. Used widely in the flotation of Cu, Ni, Zn, and Au-containing iron sulfides.

The selection of collectors can be very complex, depending on the concentrator. The comments above allude to this. In complex sulphide applications, it is not unusual to find 3 or 4 different collectors applied in different circuit sections as well as used for different ore types when they reach the mill. I worked at one operation where 3 different ore types were treated separately such that the reagent scheme had to be changed for each one. It was a great challenge.

Personally, I have used both PEX and SEX in the lab as well as other potassium and sodium versions of xanthates and never noticed a difference. I can say that I have seen sodium salts act as dispersants where potassium salts did not, hydroxide anion.

I support when he says " a properly structured on/off plant trial" should demonstrate the difference. Although I think it would take a few more days than he is suggesting teasing out a statistical difference. I think it represents the greatest difference. "Please don't deviate from good quality chemicals"! 

All collectors are hydro carbon chins with inorganic tip. There is no chemical reaction in any flotation. Minerals surface adsorbs inorganic element to keep hydro carbon free. Then mineral becomes hydrophobic, and aerophilic. When air bubbles come in contact with them H-C chain gets attached to air. When bubble goes up mineral also goes up along with bubble. It is similar to washing clothes. Sodium or potassium getting adsorbed on Pb, Zn, Cu all depends on surface character and surface tension. Hence while preparing Chemicals due care is taken to see that chemicals are dry, and water added is pure and normal.

Case study:

In HZL for lead flotation PEX and Zinc flotation SIX is used. Differential flotation found more economical and suitable.

Case study: Pb and Zn minerals are different from each other in different mines and require different flow sheet and chemical dosage. For xanthates the process of preparing is very important as it controls Quality and recovery of minerals. It is my 100% bitter experience.

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