A method includes contacting a metallic compound comprising a first metallic cation, with a melt comprising a metallic polysulfide comprising a second metallic cation, thereby forming a molten metallic polysulfide of the first metallic cation. The method also includes cooling the melt to form a sulfur phase and a solid phase comprising the molten metallic polysulfide of the first metallic cation.

A method includes contacting a metallic compound comprising a first metallic cation, with a melt comprising a metallic polysulfide comprising a second metallic cation, thereby forming a molten metallic polysulfide of the first metallic cation. The method also includes cooling the melt to form a sulfur phase and a solid phase comprising the molten metallic polysulfide of the first metallic cation.

A sorbent based monitoring system for measuring the solute concentration of at least one component of a fluid. The system has a sorbent regeneration system for regeneration of the fluid and has a sorbent cartridge that has at least one material layer. The fluid is conveyed through the sorbent cartridge and contacts at least one sensor after having contacted at least one material layer.

A sorbent based monitoring system for measuring the solute concentration of at least one component of a fluid. The system has a sorbent regeneration system for regeneration of the fluid and has a sorbent cartridge that has at least one material layer. The fluid is conveyed through the sorbent cartridge and contacts at least one sensor after having contacted at least one material layer.

Provided are an apparatus and a method for ion-exchange extraction of lithium from natural or technological brine by using a lithium-selective inorganic sorbent operating on a principle of an ion sieve. The apparatus contains a plurality of ion-exchange columns arranged and interconnected in sequence. Flows of the brine, flush water, acidic desorption solution, and outputs, of the processed products are controlled via switchable shut-off valves. The method can be carried out by operating the apparatus in a parallel or a serial mode of column operations. In the parallel mode, all columns work simultaneously in the same manner. In the serial mode of operation, the columns work individually with a shift of the sorption-flushing-desorption-flushing cycles sequentially and with a transfer of the processed brined sequentially from the first column to the last column and from the last column to the first one thus providing continuity of the lithium-extraction process.

Provided are an apparatus and a method for ion-exchange extraction of lithium from natural or technological brine by using a lithium-selective inorganic sorbent operating on a principle of an ion sieve. The apparatus contains a plurality of ion-exchange columns arranged and interconnected in sequence. Flows of the brine, flush water, acidic desorption solution, and outputs, of the processed products are controlled via switchable shut-off valves. The method can be carried out by operating the apparatus in a parallel or a serial mode of column operations. In the parallel mode, all columns work simultaneously in the same manner. In the serial mode of operation, the columns work individually with a shift of the sorption-flushing-desorption-flushing cycles sequentially and with a transfer of the processed brined sequentially from the first column to the last column and from the last column to the first one thus providing continuity of the lithium-extraction process.

A water softening device includes a filter configured to decrease hardness of a first stream of raw water to produce a second stream of water with decreased hardness, a first sensor that measures an electrical property of the first stream, a second sensor that measures an electrical property of the second stream, and optionally, a third sensor that detects a water flow through the filter, wherein the filter includes an ion exchange resin operated in H.sup.+-mode, and the filter is buffered with at least one salt selected from the group of a potassium salt (K.sup.+), a sodium salt (Na.sup.+) and a lithium salt (Li.sup.+).

A water softening device includes a filter configured to decrease hardness of a first stream of raw water to produce a second stream of water with decreased hardness, a first sensor that measures an electrical property of the first stream, a second sensor that measures an electrical property of the second stream, and optionally, a third sensor that detects a water flow through the filter, wherein the filter includes an ion exchange resin operated in H.sup.+-mode, and the filter is buffered with at least one salt selected from the group of a potassium salt (K.sup.+), a sodium salt (Na.sup.+) and a lithium salt (Li.sup.+).

A water softening device includes a filter configured to remove hardness from a first stream of raw water to produce a second stream of softened water. The filter includes an ion exchange material which is loaded with a first cationic ion species deriving from a tracer salt and with a second cationic ion species deriving from a regenerant salt. The IEX material shows a lower affinity to the first cationic ion species than to the hardness. At the same time the IEX material shows a higher affinity to the first cationic ion species than to the second cationic species. An electrical property of the second stream is monitored by a sensor. A change in the monitored electrical property can be used as an indicator for the exhaustion state of the filter.

A water softening device includes a filter configured to remove hardness from a first stream of raw water to produce a second stream of softened water. The filter includes an ion exchange material which is loaded with a first cationic ion species deriving from a tracer salt and with a second cationic ion species deriving from a regenerant salt. The IEX material shows a lower affinity to the first cationic ion species than to the hardness. At the same time the IEX material shows a higher affinity to the first cationic ion species than to the second cationic species. An electrical property of the second stream is monitored by a sensor. A change in the monitored electrical property can be used as an indicator for the exhaustion state of the filter.