Cognizurecreating knowledge for future

In order to dispose the ammonium chloride (NH₄Cl) recovered from rare-earth wastewater, a series of experiments were conducted to examine the feasibility of converting the recovered ammonium chloride to ammonium sulfate, a product that could then be reused in the mining of rare-earth. Experimental results showed that the NH₄Cl conversion efficiency rises on lowering the NH₄Cl:H₂SO₄ molar ratio and on increasing the reaction temperature and initial concentration of the NH₄Cl mass. Reaction time influences the increase of the NH₄Cl conversion efficiency, but declines to negligible levels when its duration exceeds 1 h. The NH₄Cl conversion efficiency of adding concentrated H₂SO₄ before ammonium chloride is higher than that of adding ammonium chloride before concentrated H₂SO₄. Stirring and maintaining a negative pressure during the course of reaction too exert an influence although slightly on the conversion. Based on these findings, a process was designed to convert the ammonium chloride recovered from the rare-earth wastewater to ammonium sulfate. An economic evaluation of this process revealed that a payoff of $1.445 million per year is possible.