Concentration and separation process utilizing combination of reverse osmosis membrane and nanofiltration membrane

The invention discloses a concentration and separation process utilizing combination of a reverse osmosis membrane and a nanofiltration membrane. The process specifically comprises the following steps: concentrating ions in a solution through the reverse osmosis membrane; processing concentrated liquid drained by the reverse osmosis membrane by a first circulating concentrating manner until reaching extreme concentration, and further concentrating through the nanofiltration membrane by a second circulating concentrating manner until reaching the ion concentration as requirement; or concentrating the solution through the nanofiltration membrane, concentrating the concentrated liquid drained by the nanofiltration membrane by the second circulating concentrating manner until reaching the extremely concentration and then draining to the outside of a system; respectively feeding the clear liquid drained by the nanofiltration membrane into the reverse osmosis membrane or the nanofiltration membrane according to the ion concentration from high to low to further concentrate; draining the clear liquid from the reverse osmosis membrane to the outside of the system. According to the concentration and separation process, the ion concentration can be 10% or higher by concentrating through the combination of the reverse osmosis membrane and the nanofiltration membrane; the process is high in concentration efficiency, low in cost and low in energy consumption.