Direct Acidifying and Recycling Ammonium Paratungstate Mother Liquor

To achieve the goal of shorten the process, reduce the cost and improve the recovery ratio of tungsten trioxide, reduce the pH of APT mother liquid by hydrochloric acid to realize W, P, as, Mo, Si, S₂^- separate from NH₄Cl is proposed in this paper, and filtrate can be returned directly to desorption agent, adding ammonia or liquid ammonia to increase the pH, and then returned to prepare desorption agent.

Steps are as below:
1. Adjusting pH value of APT mother liquor: turn on the stirred tank under normal temperature, and add ydrochloric acid to apt crystalline mother liquor to adjust the pH value; after H₂Soverflow from mother liquor aborted with dilute ammonia, stop stirring after H₂S volatilized completely, and clarified for 2 hours;
2. Filter: solid-liquid separation, using the cloth filter or microfiltration; filter residue return to the main flow alone or mixed with the raw materials for alkali decomposition, and filtrate can be returned directly for formulated desorption agent or adding ammonia or liquid ammonia to increase pH and then returned to prepare desorption agent.

The advantages lie in:
1. To make full use of properties of sulfur ions, made it removed from APT in the form of H₂S, and recycling as ammonium sulfide for using in recycle process, reduce the secondary pollution caused by wastewater discharge and end of pipe treatment at the same time;
2. Using hydrochloric acid to adjust pH value to make APT crystal liquor directly back to the ion exchange process of desorption agent preparation;
3. The process flow is short and simple, to realize cycle of Tungsten Hydrometallurgy, recycling WO₃ and NH₄Cl from crystallization mother liquor to achieve APT clean production.

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