A composite that includes an expanded polytetrafluoroethylene (ePTFE) membrane having a porous microstructure. The porous microstructure of the ePTFE membrane is impregnated with a stiffening polymer. An acoustic device assembly that includes the composite and an acoustic device is also described. The composite and the acoustic device assembly can exhibit an insertion loss of less than 7 dB at 1 kHz when measured by the Acoustic Response Measurement (“ARM”) Test.

A composite that includes an expanded polytetrafluoroethylene (ePTFE) membrane having a porous microstructure. The porous microstructure of the ePTFE membrane is impregnated with a stiffening polymer. An acoustic device assembly that includes the composite and an acoustic device is also described. The composite and the acoustic device assembly can exhibit an insertion loss of less than 7 dB at 1 kHz when measured by the Acoustic Response Measurement (“ARM”) Test.

A filtration method that includes a cleaning step using a chemical agent, wherein provided is the filtration method with excellent chemical resistance performance. The filtration method pertaining to the present invention comprises a filtration step in which a liquid to be filtered is filtered by being passed through a porous membrane formed of a resin, and a cleaning step in which the membrane interior of the porous membrane is cleaned after the filtration step, wherein a porous membrane for which the area ratio of a resin part having an area of 1 μm.sup.2 or less included in a cross section of the membrane interior is at least 70% of the total area of the entire resin part included in the cross section, and said cleaning step includes a step in which an aqueous solution of at least 1% sodium hydroxide is passed through the porous membrane.

A filtration method that includes a cleaning step using a chemical agent, wherein provided is the filtration method with excellent chemical resistance performance. The filtration method pertaining to the present invention comprises a filtration step in which a liquid to be filtered is filtered by being passed through a porous membrane formed of a resin, and a cleaning step in which the membrane interior of the porous membrane is cleaned after the filtration step, wherein a porous membrane for which the area ratio of a resin part having an area of 1 μm.sup.2 or less included in a cross section of the membrane interior is at least 70% of the total area of the entire resin part included in the cross section, and said cleaning step includes a step in which an aqueous solution of at least 1% sodium hydroxide is passed through the porous membrane.

Process for the removal of particulate matter from an aqueous stream containing a concentrated acid, preferably concentrated sulfuric acid, the process including mechanical filtration by passing the aqueous stream through a filter unit, the filter unit including a metallic, ceramic or polymeric filter, or a filter including a filter aid on a septum. The aqueous stream is the exit stream of a sulfuric acid condenser, optionally the exit stream of a sulfuric acid concentrator arranged downstream the sulfuric acid condenser.

Process for the removal of particulate matter from an aqueous stream containing a concentrated acid, preferably concentrated sulfuric acid, the process including mechanical filtration by passing the aqueous stream through a filter unit, the filter unit including a metallic, ceramic or polymeric filter, or a filter including a filter aid on a septum. The aqueous stream is the exit stream of a sulfuric acid condenser, optionally the exit stream of a sulfuric acid concentrator arranged downstream the sulfuric acid condenser.

A gas sensor includes a support structure with a cavity, a sensing element sensitive to a gas and arranged in the cavity, and a filter spanning the cavity. The filter is a size selective filter.

A gas sensor includes a support structure with a cavity, a sensing element sensitive to a gas and arranged in the cavity, and a filter spanning the cavity. The filter is a size selective filter.

Disclosed herein are systems and methods for purifying aqueous solutions. For example, disclosed herein are flexible membrane distillation systems comprising one or more stages stacked on top of each other, wherein each stage comprises: a feedwater layer; a membrane distillation layer; a distillate layer; and a thermally conductive layer. The systems further comprise substantially impermeable top surface, bottom surface, and perimeter. Each feedwater layer is independently receives a portion of a contaminated aqueous solution (a feed solution). Each feedwater layer further receives heat from a heat source to distill at least a portion of the feed solution through the membrane distillation layer, thereby producing a distillate in the distillate layer. Distilling said portion of the feed solution through the membrane distillation layer purifies said portion of the feed solution to produce a purified aqueous solution, which is condensed in the distillate layer to form a condensate.

Disclosed herein are systems and methods for purifying aqueous solutions. For example, disclosed herein are flexible membrane distillation systems comprising one or more stages stacked on top of each other, wherein each stage comprises: a feedwater layer; a membrane distillation layer; a distillate layer; and a thermally conductive layer. The systems further comprise substantially impermeable top surface, bottom surface, and perimeter. Each feedwater layer is independently receives a portion of a contaminated aqueous solution (a feed solution). Each feedwater layer further receives heat from a heat source to distill at least a portion of the feed solution through the membrane distillation layer, thereby producing a distillate in the distillate layer. Distilling said portion of the feed solution through the membrane distillation layer purifies said portion of the feed solution to produce a purified aqueous solution, which is condensed in the distillate layer to form a condensate.