In flotation process, the harm of excessive reagent is often ignored. Practical experience has proved that the decline of flotation index is caused by excessive flotation reagents in many cases. The harm of excessive flotation reagents mainly includes the following aspects

(1) The harm of excessive collector.

① The selectivity of flotation process is destroyed. A large number of tests and production practice have proved that when the collector dosage exceeds a certain range, the concentrate grade will obviously decline. Even if the recovery rate increases slightly, the gain is not worth the loss;

(2) excessive collectors will cause difficulties in further selection of foam concentrate and separation of mixed concentrate. In this case, the scene often take more adjustment agent to remedy. Due to the addition of regulator, the middlings containing excessive reagent return to the process, forming a vicious circle. The flotation process is confused and the flotation index is reduced. In addition, because of the excessive collector, the amount of inhibitor will also increase. For example, if the xanthate is excessive, the amount of inhibitor cyanide will also increase, which not only wastes the reagent, but also increases the content of toxic reagent in tailings, causing public hazards;

③ The floatability of some minerals can be reduced by excessive collector. For example, excessive fatty acid collectors can reduce the floatability of oxide ores. The reason is that the collector forms a reverse layer of multi-layer adsorption on the mineral surface, and the polar group is outward instead, making the mineral surface hydrophilic;

(4) excessive collectors will also form a large amount of foam, which makes it difficult for the concentrate and tailings to dehydrate, resulting in difficulties in concentration and filtration.

(2) The harm of excessive inhibitors. When the inhibitor is excessive, the minerals to be floated and the minerals to be restrained may be inhibited at the same time, resulting in the decrease of recovery. At this time, in order to improve the floating ability of the floating minerals, the amount of collector must be increased.

(3) The harm of excessive activator. This will not only destroy the selectivity of flotation process, but also may react with collectors to form precipitates and consume a lot of collectors. For example, when the sphalerite is activated, such as excessive copper sulfate, the copper ion generated by excessive copper sulfate will form copper xanthate precipitation with xanthate in the pulp, thus increasing unnecessary consumption.

(4) The harm of excessive foaming agent. It will cause a large number of sticky and fine bubbles, which will easily make gangue minerals adhere to the bubbles and affect the concentrate grade. If there is more mud in the original ore, a lot of viscous foam will be formed, which will easily cause the "running slot" accident. A lot of concentrate will overflow the foam tank, causing confusion in the production operation. Strict control of reagent dosage is an important factor to improve flotation process index. Excessive reagent destroys the selectivity of flotation process, increases the cost of mineral processing, and directly or indirectly brings difficulties to the regulation of flotation process.