Research On Reverse Osmosis Concentration Of Rare-Earth Ammonium Chloride Waste Water

This paper is based on the research of the rare-earth chlorine ammonium wastewater treatment and recycling in Baotou, Inner Mongolia. The Rare-earth chlorine ammonium wastewater, including the mother liquor and cleaning solution, is formed in the production of unitary rare earth carbonate. In practice, many enterprises now directly evaporate and crystallize the mother liquor of high concentration for Ammonium chloride products. However, currently, there is no effective treatment available for the cleaning solution yet. Because of its large liquid volume, low concentration, and high energy consumption,when evaporated and crystallized, it will be too costly for the related enterprises. If untreated before discharged, the cleaning solution will pollute the Yellow River in Baotou. In the project in this paper, the technique of reverse osmosis (RO) concentration is adopted to concentrate and crystallize the cleaning solution.The RO membrane imposes high standards on the quality of the influent water. When it comes to how to prevent the RO membrane from being polluted and being blocked by the scales formed by calcium or magnesium ions in the after-concentration wastewater, it still remains a huge problem in the reverse osmosis concentration of rare-earth Ammonium chloride wastewater. The key to guarantee the long-term stability of RO technique lies in strict pre-cautions.The RO pretreatment experiment introduced in this paper include mainly the following specific experiments:coagulation sedimentation experiment, oil filtration and removal experiment via oil-absorbing blanket, filtration experiment via dual-media filter feed,activated carbon absorption experiment, and scale inhibition experiment.Coagulation Sedimentation Experiment: The result shows that PFS, as its small but sufficient dosage is concerned, is obviously superior in removing turbidity and COD. Besides, the turbidity of the supernatant liquid is below 2.0 NTU, which meets the requirements of the RO membrane. Since PFS can remove COD and oil to certain degree, it can be used as an assisted treatment.Oil Filtration and Removal Experiment via Oil-Absorbing Blankets: The experiment shows that the oil-absorbing blankets are characterized with a remarkably high removal rate to the oil in the water. And, the oil volume can be reduced to 6.5mg/L.Activated Carbon Absorption Experiment: Activated carbon has been used as adsorbent in the experiment, the result of which shows that after the absorption, oil concentration was reduced below 0.2 mg/L, and that of COD below 10mg/L. It meets entirely the standard of the RO membrane on RO Influent water.Scale Inhibition Experiment: The wastewater concentration quadruples and no scale forms when 3.1mg/L membrane scale inhibitor (MDC220) is added in the wastewater. After the above-mentioned process, the quality of the treated wastewater meets the standard of the RO membrane. It indicates that the application of the cleaning solution in RO concentration of rare-earth ammonium chloride wastewater is feasible.Then, this paper elaborates on the design of the RO concentration system, and the validation of the RO parameter, the type, the number as well as the permutation and combination of the RO membrane.Finally, the RO concentration experiment based on the current ESPA1-4040 system has been conducted. The result shows that the maximum recycling rate of the two-section ESPA1-4040 RO system is 2.36%, which is far below the expected rate. Therefore, it is definitely not suitable for the RO concentration treatment of ammonium chloride wastewater.