As for inorganic inhibitors, sodium silicate, water glass + metal ions, water glass + ammonium salt, salufer, pyrophosphate, calgon and phosphorous acid are mostly used. Each of them has its advantage. Inorganic depressing agent of tungsten ore –water glass modified by metal icon is basically introduced in this part.

 

AS a popular regulator, water glass can be directly applied to the flotation process, serving as an inhibitor of calcic gangue. However, only water glass itself cannot fully cause the inhibition of gangue minerals. For that reason, researchers usually accidate the water glass or add metal ion (Al³⁺、Mg²⁺、Cu²⁺、Fe²⁺、Co²⁺、Pb²⁺ 、Ca²⁺…) to modified it before use, increasing the content of active ingredient after the water glass hydrolyzed and enhancing the inhibitory effect.

 

Research shows that the mixed usage of water glass and alkaline metal ions , Al³⁺、Mg²⁺、Cu²⁺、Fe²⁺、Co²⁺、Pb²⁺ and Ca²⁺ for example, can improve the suppression performance of water glass on the calcareous gangue. There are two possible reasons that cause this phenomenon. One is that, the water glass reacts with metal ions in the pulp, generating weak alkali hydroxides and promoting the hydrolysis of water glass. Thereby, more silicic colloids are produced, and then mix together with water glass colloid, enhancing the water glass’s inhibitory effect. Another possible reason is that, reacting with metal ions, the water glass generates the macaloid, of which the selective adsorption performance is better. Thus the selectivity is increased.

 

Additionally, the researchers conducted comprehensive test on water glass modified by metal ions such as Al³⁺、Mg²⁺、Cu²⁺、Fe²⁺、Co²⁺、Pb²⁺ and Ca²⁺. The conclusion is that divalent metal ions and trivalent metal ions have different effects on floatabilities of calcium gangues, the sizes of difference are as follows: scheelite > fluorite > calcite. The inhibitory effects of divalent metal ions and trivalent metal ions on water glass are also different, orders are: Pb²⁺＞Cu²⁺＞Zn²⁺、Al³⁺＞Cr³⁺≥Fe³⁺. Metal ions effect the performance of water glass mainly by changing the contents of effective components in aqueous solution and adsorbing on the surface of scheelite to enhance the scheelite’s adsorption to anionic collector agent.