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 system for treating a tetraalkylammonium hydroxide-containing liquid having a high-pressure type reverse osmosis membrane device concentrating a liquid to be treated containing tetraalkylammonium hydroxide at a concentration side, and a line for supplying the concentrated liquid to be treated by the reverse osmosis membrane device to an evaporator further concentrating the concentrated liquid to be treated.

A system for treating a tetraalkylammonium hydroxide-containing liquid having a high-pressure type reverse osmosis membrane device concentrating a liquid to be treated containing tetraalkylammonium hydroxide at a concentration side, and a line for supplying the concentrated liquid to be treated by the reverse osmosis membrane device to an evaporator further concentrating the concentrated liquid to be treated.

A water purification apparatus (1) comprising a RO-device (2) comprising a RO-membrane (2a). The RO-device (2) is configured to receive inlet water to be purified from an inlet path (19) and produce permeate water into a permeate path (22) and reject water into a reject path (23). The apparatus (1) also comprises a recirculation path (24) arranged to recirculate reject water from the reject path (23) to the inlet water. The apparatus further comprises a cooling arrangement (30) comprising a cooling device (31, 39). The cooling arrangement (30) is configured to cool the recirculated reject water in the recirculation path (24) with the cooling device (31, 39), and a control arrangement (40) configured to control the cooling arrangement (30) to cool the recirculated reject water in the recirculation path (24) in order to cool the RO-membrane (2a).

A water purification apparatus (1) comprising a RO-device (2) comprising a RO-membrane (2a). The RO-device (2) is configured to receive inlet water to be purified from an inlet path (19) and produce permeate water into a permeate path (22) and reject water into a reject path (23). The apparatus (1) also comprises a recirculation path (24) arranged to recirculate reject water from the reject path (23) to the inlet water. The apparatus further comprises a cooling arrangement (30) comprising a cooling device (31, 39). The cooling arrangement (30) is configured to cool the recirculated reject water in the recirculation path (24) with the cooling device (31, 39), and a control arrangement (40) configured to control the cooling arrangement (30) to cool the recirculated reject water in the recirculation path (24) in order to cool the RO-membrane (2a).

A process for purifying a urea-containing aqueous stream, such as the aqueous stream from the recovery section of a urea plant, comprising a step of removing biuret from the urea-containing stream by reverse osmosis in one or more reverse osmosis stages.

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.

Techniques according to the present disclosure include capturing carbon dioxide from a dilute gas source with a CO.sub.2 capture solution to form a carbonate-rich capture solution; separating at least a portion of carbonate from the carbonate-rich capture solution; forming an electrodialysis (ED) feed solution; flowing a water stream and the ED feed solution to a bipolar membrane electrodialysis (BPMED) unit; applying an electric potential to the BPMED unit to form at least two ED product streams including a first ED product stream including a hydroxide; and flowing the first ED product stream to use in the capturing the carbon dioxide from the dilute gas source with the CO.sub.2 capture solution.

Techniques according to the present disclosure include capturing carbon dioxide from a dilute gas source with a CO.sub.2 capture solution to form a carbonate-rich capture solution; separating at least a portion of carbonate from the carbonate-rich capture solution; forming an electrodialysis (ED) feed solution; flowing a water stream and the ED feed solution to a bipolar membrane electrodialysis (BPMED) unit; applying an electric potential to the BPMED unit to form at least two ED product streams including a first ED product stream including a hydroxide; and flowing the first ED product stream to use in the capturing the carbon dioxide from the dilute gas source with the CO.sub.2 capture solution.

A concentration apparatus that includes a liquid tank storing a liquid containing a filtration object, a tubular member having first and second end portions disposed in the liquid tank and forming a first circulation flow path therebetween, a circulation pump for supplying the liquid stored in the liquid tank to flow from the first end portion to the second end portion, a filtration filter disposed in a sidewall of the tubular member, a bypass pipe having first and second ends thereof connected to sidewalls of the tubular member so as to form a second circulation flow path between the first and second end portions of the tubular member, a switching valve constructed to cause the liquid to flow in one of the first or second circulation flow paths, and a control unit controlling driving of the circulation pump and a switching operation of the switching valve.