Research On Nanofiltration Enrichment Process Of Rare Earth Mother Liquid Precipitation Supernatant Rare Earth Leaching Solution

The experiment,taking he South Weathered Crust Rare Earth ore leaching supernatant liquid precipitation?Rare earth mother liquor clear liquid precipitation?as study object,investigated the effects of operation pressure difference??P?,temperature,pH value and running time?T?on the separation and enrichment of rare earth ions and recycling ammonium ions by Nanofiltration.Meanwhile,the experiment,based on film theory model and combined Spiegler-Kedem model,detailedly estimate membrane transport parameters and enrichment factors and concentration polarization modulus and study the separation characteristics of polyamide composite membrane NF-1812 on Rare earth mother liquor clear liquid precipitation.?1?With the increase of pressure,nanofiltration membrane flux increased from 7.05L/?m²?h?to 42.86L/?m²?h?,which showed the tendency of increasing gradually,but the increasing trend was more and more slowly.The retention rate of rare earth ion RE³⁺ and the impurity ions Ca²⁺?Mg²⁺?Mn²⁺ and Zn²⁺ presented a trend of reducing the rise.The retention rate of rare earth ion RE³⁺ was not particularly evident,remaining at more than 96%.Under the pressure of certain circumstances,flux had not much changed with pH value.When pH was exceeding 5.5,the retention rate of rare earth ion RE³⁺ and the impurity ions Ca²⁺?Mg²⁺?Mn²⁺ and Zn²⁺ had increased because of forming complex.With the increase of temperature,flux increased linearly,while the retention rate falled flat before 25? and decreased significantly after 25?.Because of concentration polarization,membrane flux gradually reduced with run time and the rejection of rare earth ions and the impurity ions reduced first and increased.?2?With the increase of pressure,Ammonium ion concentration in permeate was gradually increasing,and the increasing trend was growing which the transmittance increased from 53.37% to 86.59%.Within the scope of the system operation of pH,ammonia nitrogen concentration presented the trend of increaseing first then decreaseing with pH value.When the temperature was between 10 and 30 ?,the retention rate of ammonia nitrogen maintained at about 38%,which was on the rise as the temperature rise further.Considering membrane flux,membrane life,retention and economic such as factors,the experiment taked 25? as the optimum.Osmotic liquid ammonia nitrogen concentration increased with running time,but little changed in the 120 min.?3?When the system runs for 240 min,the concentration of rare earth ions concentrated from 0.1429 g/L to 0.777 g/L,concentrating 5.437 times;ammonium ion concentration concentrated from 346.1 mg/L to 957.59 mg/L,concentrating 3.63 times.The results showed that rare earth ions and ammonium ions can be concentrated by nanofiltration membrane.?4?Combined film theory combined with Spiegler-Kedem model?CFSK?was description the nanofiltration separation process of rare earth mother liquid precipitation supernatant.The results showed that the retention rate of rare earth ion was equally fitting,the impurity ions Ca²⁺?Mg²⁺?Mn²⁺ and Zn²⁺ were also consistent,the calculation result of ammonium ions was not most consistent,there was a certain deviation between model data and experimental data.