1·A soft silver-white univalent element of the alkali metal group; the lightest metal known; occurs in several minerals.
一种银白色软质单价元素，碱金属属，已知最轻的金属，存在于许多矿物中。
2·The result showed that bivalent and multivalent cations could be removed effectively, while the rejection of univalent cations was very low.
实验表明，所制备的纳滤膜能有效截留二价和多价阳离子，对单价阳离子的截留率极低。