Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
  • B29C48/03—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor characterised by the shape of the extruded material at extrusion
  • B29C48/09—Articles with cross-sections having partially or fully enclosed cavities, e.g. pipes or channels
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D69/00—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
  • B01D69/08—Hollow fibre membranes
• • B29C47/0023—
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D67/00—Processes specially adapted for manufacturing semi-permeable membranes for separation processes or apparatus
  • B01D67/0002—Organic membrane manufacture
  • B01D67/0006—Organic membrane manufacture by chemical reactions
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D69/00—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
  • B01D69/02—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor characterised by their properties
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D69/00—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
  • B01D69/08—Hollow fibre membranes
  • B01D69/087—Details relating to the spinning process
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D69/00—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
  • B01D69/08—Hollow fibre membranes
  • B01D69/087—Details relating to the spinning process
  • B01D69/088—Co-extrusion; Co-spinning
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D69/00—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
  • B01D69/10—Supported membranes; Membrane supports
  • B01D69/107—Organic support material
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D69/00—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
  • B01D69/10—Supported membranes; Membrane supports
  • B01D69/107—Organic support material
  • B01D69/1071—Woven, non-woven or net mesh
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D69/00—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
  • B01D69/12—Composite membranes; Ultra-thin membranes
  • B01D69/125—In situ manufacturing by polymerisation, polycondensation, cross-linking or chemical reaction
  • B01D69/1251—In situ manufacturing by polymerisation, polycondensation, cross-linking or chemical reaction by interfacial polymerisation
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
  • B01D71/06—Organic material
  • B01D71/56—Polyamides, e.g. polyester-amides
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
  • B01D71/06—Organic material
  • B01D71/66—Polymers having sulfur in the main chain, with or without nitrogen, oxygen or carbon only
  • B01D71/68—Polysulfones; Polyethersulfones
• • B29C47/0004—
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
  • B29C48/022—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor characterised by the choice of material
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2323/00—Details relating to membrane preparation
  • B01D2323/40—Details relating to membrane preparation in-situ membrane formation
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2325/00—Details relating to properties of membranes
  • B01D2325/04—Characteristic thickness
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2325/00—Details relating to properties of membranes
  • B01D2325/20—Specific permeability or cut-off range
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2325/00—Details relating to properties of membranes
  • B01D2325/24—Mechanical properties, e.g. strength
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
  • B29K2081/00—Use of polymers having sulfur, with or without nitrogen, oxygen or carbon only, in the main chain, as moulding material
  • B29K2081/06—PSU, i.e. polysulfones; PES, i.e. polyethersulfones or derivatives thereof
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29L—INDEXING SCHEME ASSOCIATED WITH SUBCLASS B29C, RELATING TO PARTICULAR ARTICLES
  • B29L2023/00—Tubular articles
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29L—INDEXING SCHEME ASSOCIATED WITH SUBCLASS B29C, RELATING TO PARTICULAR ARTICLES
  • B29L2031/00—Other particular articles
  • B29L2031/731—Filamentary material, i.e. comprised of a single element, e.g. filaments, strands, threads, fibres

Definitions

• Pressure retarded osmosis is a membrane-based separation process for harvesting osmotic power, a renewable marine resource.
• An ideal semi-permeable membrane used in a PRO process has both a high mechanical strength (i.e., capable of withstanding a high transmembrane pressure) and a high pure water permeability (PWP) rate. Yet, a higher mechanical strength typically requires a higher density or a greater thickness of the membrane, which adversely affects the PWP rate.
• This invention relates to a thin film composite (TFC) hollow fiber that can withstand an unexpectedly high pressure while maintaining a high water permeability rate. As such, it is suitable as a PRO membrane for use in developing osmotic energy.
• TFC thin film composite
• One aspect of this invention relates to a TFC hollow fiber that includes an outer support layer and an inner thin film layer adherent to the outer support layer.
• the outer support layer or the support has a thickness of 10 to 10000 ⁇ m (preferably, 50-1000 ⁇ m, and, more preferably, 100-300 ⁇ m) and the inner thin film layer has a thickness of 1 to 10000 nm (preferably, 20-1000 nm, and, more preferably, 50-500 nm).
• the outer support layer of a TFC hollow fiber can be made of polyethersulfone (PES), polysulfone, polyphenylsulfone, polyacrylonitrile, polyimide, polyether imide, polyamide-imde, polyvinylidene fluoride, cellulose triacetate, polyetherketone, or polyetheretherketone.
• PES polyethersulfone
• polysulfone polysulfone
• polyphenylsulfone polyacrylonitrile
• polyimide polyether imide
• polyamide-imde polyvinylidene fluoride
• cellulose triacetate cellulose triacetate
• polyetherketone or polyetheretherketone
• the outer support layer is made of PES.
• the inner thin film layer of a TFC hollow fiber can be made of cross-linked polyamide.
• the TFC hollow fiber of this invention exhibits a transmembrane pressure resistance rate of higher than 15 bar and a pure water permeability (PWP) rate of higher than 0.8 Lm ⁇ 2 h ⁇ 1 bar ⁇ 1 .
• the TFC hollow fiber has a transmembrane pressure resistance rate of higher than 20 bar and a PWP rate of higher than 3.3 Lm ⁇ 2 h ⁇ 1 bar ⁇ 1 .
• Another aspect of this invention relates to a method of preparing the above-described support of a TFC hollow fiber.
• the method includes the following steps: (i) dissolving a polymer in a solvent containing N-methyl-2-pyrrolidone (NMP), polyethylene glycol (PEG), and water to obtain a spinning dope, (ii) providing a triple orifice spinneret that has an external orifice, a middle orifice, and an internal orifice, and (iii) extruding the spinning dope through the middle orifice into a coagulation bath and at the same time passing a first solvent and a second solvent through the external orifice and the internal orifice, respectively.
• the polymeric hollow fiber support thus formed has a lumen.
• the polymer used for this support is 5 to 50 wt % (preferably, 10-40 wt %, and, more preferably, 15-30 wt %)
• the NMP is 5 to 95 wt % (preferably, 20-90 wt %, and, more preferably, 30-70 wt %)
• the PEG is 0 to 60 wt % (preferably, 0-40 wt %, and, more preferably, 10-40 wt %)
• the water is 0 to 60 wt % (preferably, 0-40 wt %, and, more preferably, 10-40 wt %).
• the first solvent and the second solvent can be NMP, water, alcohols, dimethylformamide, dimethyl sulfoxide, dimethylacetamide, or a combination thereof.
• the first solvent is NMP and the second solvent is water.
• the above-described method can include a step of coating the inner surface, i.e., the luminal surface, of the support with a thin film layer made of cross-linked polyamide to form a TFC hollow fiber. More specifically, a polyamide thin film layer is formed on the inner surface via interfacial polymerization between a first monomer solution and a second monomer solution.
• the TFC hollow fiber thus prepared has an outer support layer and an inner polyamide thin film layer.
• the first monomer solution examples include a solution containing m-phenylenediamine (MPD), p-phenylenediamine, p-xylylenediamine, or branched or dendrimeric polyethylenimine.
• MPD m-phenylenediamine
• a specific example is an aqueous or alcohol solution or a water-alcohol solution containing MPD 0.1 to 20 wt % (preferably, 0.1-5 wt %, and, more preferably, 1-3 wt %).
• the second monomer solution can be a solution containing trimesoyl chloride (TMC), benzene-1,3-dicarbonyl chloride or benzene-1,4-dicarbonyl chloride.
• TMC trimesoyl chloride
• benzene-1,3-dicarbonyl chloride benzene-1,4-dicarbonyl chloride.
• a specific example is a hexane
• TFC hollow fiber that includes an outer support layer and an inner thin film layer.
• the TFC hollow fiber has a transmembrane pressure resistance rate of higher than 15 bar and a PWP rate of higher than 0.8 Lm ⁇ 2 h ⁇ 1 bar ⁇ 1 .
• the transmembrane pressure resistance rate i.e., the burst pressure rate
• the transmembrane pressure resistance rate is measured in a lab-scale PRO process, in which deionized (DI) water, acting as a feed solution, and seawater (1M NaCl), acting as a draw solution, are separated by a PRO membrane, i.e., a TFC hollow fiber. Due to the salinity gradient across the membrane, water permeation is observed from the feed solution side to the draw solution side. A gradually increasing hydraulic pressure is applied at the draw solution until at one certain hydraulic pressure the direction of water permeation is reversed. This hydraulic pressure is recorded as the transmembrane pressure resistance rate.
• DI deionized
• (1M NaCl acting as a draw solution
• a gradually increasing hydraulic pressure is applied at the draw solution until at one certain hydraulic pressure the direction of water permeation is reversed. This hydraulic pressure is recorded as the transmembrane pressure resistance rate.
• the PWP rate is determined in a lab-scale reverse osmosis (RO) process. More specifically, DI water is pumped into the lumen side of a hollow fiber at the flow rate of 0.15 ml/min and pressurized at 2 bar for 20 min before the permeate was collected from the shell side of the hollow fiber.
• the PWP rate i.e., A, is calculated using the following equation:
• Q is the water permeation volumetric flow rate (L/h)
• a m is the effective filtration area (m 2 )
• ⁇ P is the transmembrane pressure (bar).
• the PWP rate is repeatedly tested until a stable reading is obtained when the transmembrane pressure is at 2 bar. Then the pressure is gradually increased by an interval of 3 bar below 14 bar and after that 1 bar per increase. At each pressure, the PWP rate is determined until its reading is stabilized.
• the hollow fiber typically has a salt permeability rate of lower than 0.5 Lm ⁇ 2 h ⁇ 1 and a NaCl rejection rate of higher than 88%.
• it typically has a power density rate of higher than 8 Wm ⁇ 2 .
• it has a power density rate of higher than 20 Wm ⁇ 2 .
• the salt permeability rate and the NaCl rejection rate are measured in a RO process similar to the PWP rate.
• the power density rate (W) is measured in a PRO process similar to the transmembrane pressure. It is a product of the water flux (J w ) and the hydraulic pressure ( ⁇ P) applied at the draw solution:
• Described below is an exemplary procedure for preparing a TFC hollow fiber of this invention.
• a triple orifice spinneret is used to prepare the support of the hollow fiber.
• a spinning dope is prepared by dissolving a polymer in a solution containing NMP and, optionally, PEG and water.
• NMP is a solvent for the polymer.
• PEG is commonly employed as a weak non-solvent additive to improve pore connectivity and enhance pore formation.
• Water is added in a relatively small amount to increase the dope viscosity and lead the polymer solution close to a binodal decomposition, resulting in sponge-like structure.
• the spinning dope is extruded through the middle orifice of the spinneret into a coagulation bath while the NMP and the water are passed through the external orifice and the internal orifice, respectively.
• the polymer in the spinning dope coagulates to form a polymeric support. More specifically, a relatively dense layer, i.e., an inner skin, is formed near the inner surface of the support as a result of co-extruding with water from the internal orifice, and a more porous outer surface of the support is formed as a result of co-extruding with NMP from the external orifice.
• a relatively dense layer i.e., an inner skin
• the polymeric support thus prepared has a lumen.
• the inner surface, i.e., the luminal surface, of the support is then coated with a thin film layer formed of cross-linked polyamide.
• a thin film layer formed of cross-linked polyamide.
• a tube having a proximal end, a distal end, and a lumen diameter the same as that of the support is prepared, the distal end of which is reversibly connected to one end of the support.
• an MPD aqueous solution is pumped from the proximal end of the tube to the support to coat the inner surface of the support, followed by blowing air from the proximal end of the tube to the support to remove excess MPD aqueous solution.
• a TMC hexane solution is pumped from the proximal end of the tube to the support to coat the MPD aqueous solution.
• a polyamide thin film layer is formed via interfacial polymerization between MPD and TMC on the inner surface of the support.
• a TFC hollow fiber having an outer support layer and an inner polyamide thin film layer is thus formed.
• the TFC hollow fiber of this invention can also be employed in low pressure RO and forward osmosis processes.
• Table 1 Listed in Table 1 below are the detailed spinning conditions for preparing these three supports and the parameters of the triple orifice spinneret.
• Supports L, MM, and N were prepared from different spinning dopes, each of which was made using PES of the same wt %, water of increasing wt % (0.0 to 6.4 wt %), and both PEG and NMP of decreasing wt %.
• Each of the supports was prepared by extruding NMP through the external orifice of the spinneret to promote high porosity at the outer surface of the support, extruding the spinning dope through the middle orifice, and extruding water, an internal coagulant, through the internal orifice to promote formation of an inner skin at the inner surface of the support.
• the NMP, spinning dope, and water were extruded at a free-fall speed through an air gap before entering a coagulation bath where water acted as an external coagulant.
• the hollow fiber PES support thus formed included a lumen.
• FESEM Field emission scanning electron microscopy
• the pore size and pore size distribution of a PES support were measured by a solute transport study, in which rejection by the PES support against polyethylene glycol (PEG) and polyethylene oxide (PEO) polymers of different molecular weights was tested under a transmembrane hydraulic pressure of 1.0 bar.
• PEG polyethylene glycol
• PEO polyethylene oxide
• pore size and pore size distribution were quantified as the mean pore diameter and the geometric standard deviation, respectively.
• d s is related to the molecular weight M of the polymer as described in the following equations:
• OD and ID were the outer diameter and inner diameter of a support, respectively.
• ⁇ p was the polymer density (1.37 g/cm 2 ).
• l and m were the length and weight of the PES support piece, respectively.
• the mechanical properties of the PES support including maximum tensile strength, Young's modulus, and extension, i.e., elongation at break, were measured by an Instron tensiometer (Model 5542, Instron Corp.). A constant elongation rate of 10 mm/min with a starting gauge length of 50 mm was applied.
• the mean pore diameters of the PES supports decreased from L to MM and then increased from MM to N. See Table 2, row 2. Notably, the pore size distributions quantified as the geometric standard deviation ⁇ for all supports were low (less than 1.5), indicating uniform distribution of pores in the supports. See Table 2, row 3. Support MM showed the highest porosity, whereas support N, which had the sponge-like structure, showed the lowest porosity among all three supports.
• a polyamide thin film layer was coated on each of the inner surfaces of PES supports L, MM, and N via the interfacial polymerization reaction between MPD and TMC.
• the coating was conducted as follows.
• a tube which had a proximal end, a distal end, and a lumen diameter the same as that of the support, was reversibly connected, at its distal end, to one end of the support.
• an aqueous solution containing MPD 2 wt % was pumped for 3 min from the proximal end of the tube to the support to coat the inner surface of the support, followed by blowing air for 5 min from the proximal end of the tube to the support to remove excess aqueous solution.
• a hexane solution containing TMC 0.1 wt % was pumped from the proximal end of the tube to the support to coat the aqueous solution, thereby forming a polyamide thin film layer via interfacial polymerization between MPD and TMC on the inner surface of the support.
• TFC hollow fibers thus formed were purged with air for 30 sec to remove any residual hexane solution and stored in DI water before further characterization.
• hollow fibers had a PWP rate of higher than 0.8 Lm ⁇ 2 h ⁇ 1 bar ⁇ 1 .
• hollow fiber MM had a PWP rate of higher than 3.3 Lm ⁇ 2 h ⁇ 1 bar ⁇ 1 .
• all of the hollow fibers had a salt permeability rate of lower than 0.5 Lm ⁇ 2 h ⁇ 1 .
• hollow fiber N had a lower PWP rate and a higher salt permeability rate than L′ and MM′, which might account for a lower power density in a PRO test described below.
• the transmembrane pressure resistance rates of hollow fibers L′, MM′, and N′ (17.5, >20.0, and 20.0 bar, respectively) were closely related to those of their corresponding supports L, MM, and N (17.8, 22.0, and 21.0 bar, respectively, see Table 2, row 9), indicating the mechanical strength of a TFC hollow fiber is highly dependent on its support.
• L′, MM′, and N′ were all found to break slightly earlier than their corresponding supports L, MM, and N.
• MM′ showed the highest transmembrane pressure resistance rate (>20 bar) among all three.
• TFC hollow fibers prepared in Example 3 unexpectedly exhibited transmembrane pressure resistance rates that were much higher than those of any other membranes reported in the literature so far. See Table 4, column 3.
• Hollow fibers L′, MM′, and N′ were stabilized at their highest stable pressure for 30 min before their PRO performances were tested.
• 1 M NaCl, representing synthetic brine was employed as the draw solution and DI water, representing river water, was used as the feed solution.
• the flow rate for the draw solution and the feed solution were 0.2 and 0.15 L/min, respectively, and the operation was performed at room temperature ( ⁇ 23° C.).
• hollow fiber MM′ Due to both a high water flux and a high mechanical strength, hollow fiber MM′ showed the highest power density in a PRO process among all the three tested, having an unexpectedly high power density rate of 24.0 Wm ⁇ 2 at >20 bar when 10 mM NaCl was used as the feed solution. Its power density remained as high as 19.2 Wm ⁇ 2 when synthetic brackish water of a higher salinity, i.e., 40 mM NaCl, was employed as the feed solution.
• hollow fiber MM′ regardless of which feed solution was used, is unexpectedly exhibited a power density rate that was much higher than those of any other membranes reported in the literature. See Table 4, columns 5 and 6.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Manufacturing & Machinery (AREA)
• Separation Using Semi-Permeable Membranes (AREA)
• Dispersion Chemistry (AREA)
• Laminated Bodies (AREA)

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• 2014
  • 2014-06-17 SG SG11201509816QA patent/SG11201509816QA/en unknown
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