The present disclosure relates to processes for treating an aqueous composition comprising lithium sulfate and sulfuric acid. The processes comprise evaporatively crystallizing the aqueous composition comprising lithium sulfate and sulfuric acid under conditions to obtain crystals of lithium sulfate monohydrate and a lithium sulfate-reduced solution; and optionally separating the crystals of the lithium sulfate monohydrate from the lithium sulfate-reduced solution. The processes optionally further comprise concentrating the lithium sulfate-reduced solution under conditions to obtain an acidic condensate and a concentrate comprising sulfuric acid.

The present invention relates to a xylitol preparation device integrating evaporation, crystallization and centrifugation, including a xylitol tank, a cleaning liquid tank, a recycling tank and a multiple distribution system, wherein the multiple distribution system includes J groups of evaporators for evaporation concentration, K groups of vacuum crystallization kettles for vacuum crystallization and L groups of centrifuges for centrifugation, wherein 2≤J≤6, 6≤K≤12 and 2≤L≤4; the evaporator, the vacuum crystallization kettle and the centrifuge in different groups are sequentially connected in series with one another through a pipeline and a valve respectively; by controlling on and off of each valve, a xylitol exchange liquid is switched and controlled between a series-connection mode and a parallel-connection mode in the multiple distribution system to enable evaporation, crystallization and separation processes to reach an optimal effect distribution so as to improve productivity. The present invention further discloses a control method of the device. The processes and equipment of the present invention are highly integrated to realize continuous integrated production of xylitol preparation with low energy consumption and high automation degree, and full utilization of raw materials.

A method of recovering paraxylene in a pressure swing adsorption unit with varying hydrogen purge pressures. The pressure swing adsorption zone is adapted to adsorb and desorb paraxylene based on the cycling of partial pressure in the zone. A first hydrogen purge is fed concurrent to the feed. A second hydrogen purge is countercurrent to the feed.

A method of recovering paraxylene in a pressure swing adsorption unit with varying hydrogen purge pressures. The pressure swing adsorption zone is adapted to adsorb and desorb paraxylene based on the cycling of partial pressure in the zone. A first hydrogen purge is fed concurrent to the feed. A second hydrogen purge is countercurrent to the feed.

A method of recovering paraxyiene in a pressure swing adsorption unit with varying hydrogen purge pressures. The pressure swing adsorption zone is adapted to adsorb and desorb paraxyiene based on the cycling of partial pressure in the zone. A first hydrogen purge fed to the zone is within 50 psi of the adsorption pressure of paraxyiene in the zone. A second hydrogen purge fed to the zone is within 50 psi of the desorption pressure of paraxyiene in the zone. The overall amount of hydrogen necessary to operate the pressure swing adsorption zone is reduced and heat may be recovered from the effluent leaving the pressure swing adsorption zone.

Disclosed herein are systems and methods from processing flue gas desulfurization (FGD) gypsum feedstock and ash feedstocks, either separately or together. FGD gypsum conversion comprises reacting FGD gypsum (calcium sulfate) feedstock or phosphogypsum, in either batch or continuous mode, with ammonium carbonate reagent to produce commercial products comprising ammonium sulfate and calcium carbonate. A process to separate the impurities and convert the calcium carbonate to a pure precipitated calcium carbonate is disclosed. These impurities include a concentrate of valuable Rare Earth Elements, and radioactive thorium and uranium. A process to convert calcium sulfite to calcium sulfate using oxygen and a catalyst is also disclosed. Ash conversion comprises a leach process followed by a sequential precipitation process to selectively precipitate products at predetermined pHs resulting in metal hydroxides which may be converted to oxides or carbonates. The processes may be controlled by use of one or more processors.

A method for synthesizing a purified lithium (Li).sup.+ anion binding agent (ABA-F).sup.− salt and the corresponding Li.sup.+(ABA-F).sup.− are disclosed. The method includes dissolving a boron-based acid in a polar solvent to form a solution. The solution is refluxed to form an anion binding agent. A stoichiometric amount of a small fluorinated salt, such as LiF, is added to the anion binding agent to form a mixture. The mixture is subsequently crystallized to obtain a substantially pure Li.sup.+(ABA-F).sup.− salt. Example purified Li.sup.+(ABA-F).sup.− salts include Ox-Li.sup.+(ABA-F), m-Li.sup.+(ABA-F), and BF.sub.3—Li.sup.+(ABA-F).sup.−. These purified Li.sup.+(ABA-F).sup.− salts provide the benefits of increased battery thermal safety without loss of electrochemical performance.

A method of recovering paraxyiene in a pressure swing adsorption unit with varying hydrogen purge pressures. The pressure swing adsorption zone is adapted to adsorb and desorb paraxyiene based on the cycling of partial pressure in the zone. A first hydrogen purge fed to the zone is within 50 psi of the adsorption pressure of paraxyiene in the zone. A second hydrogen purge fed to the zone is within 50 psi of the desorption pressure of paraxyiene in the zone. The overall amount of hydrogen necessary to operate the pressure swing adsorption zone is reduced and heat may be recovered from the effluent leaving the pressure swing adsorption zone.

Provided is a lithium hydroxide production method for producing high-purity lithium hydroxide efficiently and at a lower energy, wherein Li ions alone are recovered in a recovery liquid from a lithium ion extract extracted from a processed member of a lithium secondary battery, using a Li permselective membrane, and lithium hydroxide is produced from the recovery liquid.

In a method for preparing a cobalt sulfate salt, a feeding solution comprising cobalt sulfate and a sulfuric acid aqueous solution is prepared. A first solution is produced by evaporation-crystallizing the feeding solution. A first cobalt sulfate salt is produced by filtering the first solution together with first purging. A second solution is produced by cooling-crystallizing an aqueous solution comprising the first cobalt sulfate salt. A second cobalt sulfate salt is produced by filtering the second solution together with second purging.