A filter medium of the present invention includes a porous carbon material having a value of a specific surface area by a nitrogen BET method of 1×10.sup.2 m.sup.2/g or more, a volume of fine pores by a BJH method of 0.3 cm.sup.3/g or more, and a particle size of 75 μm or more, alternatively, a porous carbon material having a value of a specific surface area by a nitrogen BET method of 1×10.sup.2 m.sup.2/g or more, a total of volumes of fine pores having a diameter of from 1×10.sup.−9 m to 5×10.sup.−7 m, obtained by a non-localized density functional theory method, of 1.0 cm.sup.3/g or more, and a particle size of 75 μm or more.

A filter medium of the present invention includes a porous carbon material having a value of a specific surface area by a nitrogen BET method of 1×10.sup.2 m.sup.2/g or more, a volume of fine pores by a BJH method of 0.3 cm.sup.3/g or more, and a particle size of 75 μm or more, alternatively, a porous carbon material having a value of a specific surface area by a nitrogen BET method of 1×10.sup.2 m.sup.2/g or more, a total of volumes of fine pores having a diameter of from 1×10.sup.−9 m to 5×10.sup.−7 m, obtained by a non-localized density functional theory method, of 1.0 cm.sup.3/g or more, and a particle size of 75 μm or more.

A purification system is for purifying a mixture containing a first solvent, a second solvent, and an impurity. The purification system includes a first membrane separation device including a pervaporation membrane and a second membrane separation device including a filtration membrane. The pervaporation membrane separates the mixture into a first permeated fluid and a first concentrated fluid. The first permeated fluid has a lower concentration of the impurity than that in the mixture, and the first concentrated fluid has a higher concentration of the impurity than that in the mixture. The filtration membrane separates the first concentrated fluid into a second permeated fluid and a second concentrated fluid. The second permeated fluid has a lower concentration of the impurity than that in the first concentrated fluid, and the second concentrated fluid has a higher concentration of the impurity than that in the first concentrated fluid.

A method of concentrating lithium containing solutions includes inputting a feed brine solution to an initial separation stage, the feed brine solution including lithium sulfate and one or more of sodium sulfate, potassium sulfate, calcium sulfate, and sodium chloride dissolved in water. In the initial separation stage, the feed brine solution is introduced to a pre-treatment membrane at a pressure that is less than the osmotic pressure of the feed brine solution. An initial permeate that passes through the pre-treatment membrane becomes the feed to a final separation stage, and an initial retentate that does not pass through the pre-treatment membrane includes a precipitate of at least one of the salts other than lithium sulfate. In the final separation stage, the initial permeate is introduced to a nanofiltration membrane at a pressure that is less than the osmotic pressure of the initial permeate. A final retentate that does not pass through the nanofiltration membrane is combined with the initial retentate to obtain a product solution having a higher concentration of dissolved lithium sulfate than the feed brine solution.

A method of concentrating lithium containing solutions includes inputting a feed brine solution to an initial separation stage, the feed brine solution including lithium sulfate and one or more of sodium sulfate, potassium sulfate, calcium sulfate, and sodium chloride dissolved in water. In the initial separation stage, the feed brine solution is introduced to a pre-treatment membrane at a pressure that is less than the osmotic pressure of the feed brine solution. An initial permeate that passes through the pre-treatment membrane becomes the feed to a final separation stage, and an initial retentate that does not pass through the pre-treatment membrane includes a precipitate of at least one of the salts other than lithium sulfate. In the final separation stage, the initial permeate is introduced to a nanofiltration membrane at a pressure that is less than the osmotic pressure of the initial permeate. A final retentate that does not pass through the nanofiltration membrane is combined with the initial retentate to obtain a product solution having a higher concentration of dissolved lithium sulfate than the feed brine solution.

Biocide can be controllably added to a feed stream for a membrane. In some examples, the feed stream is separated into a primary feed stream and a secondary feed stream, for example, with the secondary feed stream having a lower flow rate than the primary feed stream. The secondary feed stream may be used to monitor and control the addition of the biocide, which is then diluted when the secondary feed stream is combined with the primary feed stream to form a combined stream for delivery to the membrane.

A system and process for concentrating a lithium stream is disclosed. The lithium stream is directed to a reverse osmosis unit which produces a concentrate containing lithium compounds. The RO concentrate is directed through two pressure retarded osmosis (PRO) modules connected in series. The two PRO modules further concentrate the RO concentrate and at the same time yield a diluted brine that is effective to drive an energy recovery device. The RO concentrate leaving the PRO modules is directed to an osmotically assisted reverse osmosis (OARO) module which also further concentrates the RO concentrate.

A preparation method and use of a modified hydroxyethyl cellulose scale inhibitor for inhibiting silica scale are provided. The scale inhibitor is prepared by grafting reaction with hydroxyethyl cellulose as a raw material, ammonium persulfate as an initiator and N-(3-dimethylaminopropyl) methyl acrylamide as a graft monomer. The grafting reaction can introduce grafting chains containing amide group and tertiary amine group into a cellulose molecular chain, so that it can effectively disperse scale forming substances and obtain the efficient environment-friendly scale inhibitor. The scale inhibitor can effectively inhibit the generation of silica scale and prevent the increase of scale particle size, the scale inhibitor is used in a reverse osmosis system, which can effectively alleviate the decline of the membrane flux. The scale inhibitor has a good application prospect in controlling the silica scale on the surface of the reverse osmosis membrane.

A reverse osmosis apparatus for a seawater desalination system is provided. The reverse osmosis apparatus includes: a barrel in which a plurality of reverse osmosis membrane units with a reverse osmosis membrane wrapped in each reverse osmosis membrane unit are arranged; an inflow and outflow portion provided at a first end of the barrel and connected to a seawater inlet a high salinity water outlet; a partition wall configured to partition an inner space of the inflow and outflow portion into a first stage and a second stage; and a transport space portion provided in a second end of the barrel and configured to guide water being moved from a plurality of reverse osmosis membrane units arranged in the first stage to move to a plurality of reverse osmosis membrane units arranged at the second stage, wherein part of seawater fed to the inflow and outflow portion is fed around the tubes in the barrel and insulates the plurality of reverse osmosis membrane units in the barrel from external high temperature while being moved, and flows into the transport space portion.

A reverse osmosis apparatus for a seawater desalination system is provided. The reverse osmosis apparatus includes: a barrel in which a plurality of reverse osmosis membrane units with a reverse osmosis membrane wrapped in each reverse osmosis membrane unit are arranged; an inflow and outflow portion provided at a first end of the barrel and connected to a seawater inlet a high salinity water outlet; a partition wall configured to partition an inner space of the inflow and outflow portion into a first stage and a second stage; and a transport space portion provided in a second end of the barrel and configured to guide water being moved from a plurality of reverse osmosis membrane units arranged in the first stage to move to a plurality of reverse osmosis membrane units arranged at the second stage, wherein part of seawater fed to the inflow and outflow portion is fed around the tubes in the barrel and insulates the plurality of reverse osmosis membrane units in the barrel from external high temperature while being moved, and flows into the transport space portion.