Kyllönen Hanna, Heikkinen Juha, Järvelä Eliisa, Grönroos Antti
VTT Technical Research Centre of Finland Ltd., P.O. Box 1000, FI-02044 VTT Espoo, Finland.
Membranes (Basel). 2022 Dec 5;12(12):1233. doi: 10.3390/membranes12121233.
One option for new nitrogen sources is industrial liquid side streams containing ammonium nitrogen (NH-N). Unfortunately, NH-N often exists in low concentrations in large water volumes. In order to achieve a highly concentrated NH-Nsolution, scalant removal is needed. In this study, scalant removal by precipitation was investigated. At alkali pH, sodium carbonate (NaCO) was used as a precipitation chemical while at acidic pH, the chemical used was oxalic acid (CHO). At alkali pH, high NaCO dose was needed to achieve low content of calcium, which, with sulphate, formed the main scalant in the studied mine water. NH-N at alkali pH was in the form of gaseous ammonia but it stayed well in the solution during pre-treatment for nanofiltration (NF) and reverse osmosis (RO). However, it was not rejected sufficiently, even via LG SW seawater RO membrane. At acidic pH with CaCO precipitation, NF90 was able to be used for NH-N concentration up to the volume reduction factor of 25. Then, NH-N concentration increased from 0.17 g/L to 3 g/L. NF270 produced the best fluxes for acid pre-treated mine water, but NH-N rejection was not adequate. NF90 membrane with mine water pre-treated using acid was successfully verified on a larger scale using the NF90-2540 spiral wound element.
新的氮源选择之一是含有铵态氮（NH-N）的工业液体侧流。不幸的是，NH-N在大量水体中往往浓度较低。为了获得高浓度的NH-N溶液，需要去除结垢剂。在本研究中，对通过沉淀去除结垢剂进行了研究。在碱性pH值下，使用碳酸钠（Na₂CO₃）作为沉淀剂，而在酸性pH值下，使用的化学物质是草酸（C₂H₂O₄）。在碱性pH值下，需要高剂量的Na₂CO₃才能实现低钙含量，钙与硫酸盐一起构成了所研究矿井水中的主要结垢剂。碱性pH值下的NH-N呈气态氨形式，但在纳滤（NF）和反渗透（RO）预处理过程中能很好地保留在溶液中。然而，即使通过LG SW海水RO膜，其截留效果也不够理想。在酸性pH值下通过CaCO₃沉淀，NF90能够用于将NH-N浓缩至体积减少系数为25。然后，NH-N浓度从0.17 g/L增加到3 g/L。NF270对酸预处理的矿井水产生了最佳通量，但对NH-N的截留效果不佳。使用NF90-2540螺旋卷式元件在更大规模上成功验证了用酸预处理矿井水的NF90膜。
