This disclosure relates to membranes containing a polymer containing crown ether monomer units and a guest compound capable of binding thereto. This disclosure also relates to methods for making the membranes, and to methods for using the membranes for gas separation applications.

A membrane system includes a first membrane and a second membrane. At a given temperature and pressure: the first membrane has a permeation rate for a first gas and a selectivity for a gas mixture comprising the first gas a second gas different from the first gas; the second membrane has a permeation rate for the first gas and a selectivity for the gas mixture; the permeation rate of the first membrane is greater than the permeation rate of the second membrane; and the selectivity of the second membrane is greater than the selectivity of the first membrane.

Embodiments described herein relate generally to durable graphene oxide membranes for fluid filtration. For example, the graphene oxide membranes can be durable under high temperatures non-neutral pH, and/or high pressures. One aspect of the present disclosure relates to a filtration apparatus comprising: a support substrate, and a graphene oxide membrane disposed on the support substrate. The graphene oxide membrane has a first lactose rejection rate of at least 50% with a first 1 wt % lactose solution at room temperature. The graphene oxide membrane has a second lactose rejection rate of at least 50% with a second 1 wt % lactose solution at room temperature after the graphene oxide membrane is contacted with a solution that is at least 80° C. for a period of time.

The invention is an improved method of making an improved carbon molecular sieve (CMS) membrane in which a precursor polymer (e.g., polyimide) is pyrolyzed at a pyrolysis temperature to form a CMS membrane that is cooled to ambient temperature (about 40° C. or 30° C. to about 20° C.). The CMS membrane is then reheated to a reheating temperature of at least 250° C. to 400° C. to form the improved CMS membrane. The CMS have a novel microstructure as determined by Raman spectroscopy. The improved CMS membranes have shown an improved combination of selectivity and permeance as well as stability for separating light hydrocarbon gas molecules such as C.sub.1 to C.sub.6 hydrocarbon gases (e.g., methane, ethane, propane, ethylene, propylene, butane, butylene).

A natural gas refining apparatus including a first separation membrane unit including a first separation membrane; and a second separation membrane unit provided in a subsequent stage of the first separation membrane unit. The second separation membrane unit includes a second separation membrane that allows an amine solution to circulate through the second separation membrane unit, and the natural gas refining apparatus refines raw natural gas containing CO.sub.2 by passing the raw natural gas through the first and second separation membrane units, separating CO.sub.2-rich gas with the first and second separation membranes, and absorbing CO.sub.2 with the amine solution circulating through the second separation membrane unit.

A dehydration method is a dehydration method for selectively separating water from a mixture that contains water, using a zeolite membrane having an AFX structure, and the method includes a step of supplying the mixture to a supply side space of the zeolite membrane having an AFX structure, and a step of making a pressure difference between the supply side space and a permeation side space of the zeolite membrane having an AFX structure.

Mesoporous membranes have shown promising separation performance with a potential to lower the energy consumption, leading to a dramatic cost reduction. Recently, an extensive effort has been made on the design of membranes which brought a significant progress toward the synthesis of well-defined porous morphologies, most of which synthesized by surfactant-template methodology. Currently, the most well-designed state-of-the-art membranes using this technique are made from metals, polymers, carbon, silica, etc. In the present invention, we demonstrate mesoporous calcium-silicate particles having superior separation capacity and optimal permeability, thereby leading to reduced energy consumption for selective separation of gases/liquids and/or the combination thereof. We explore various methods to improve the calcium-silicate membranes properties by tuning pore density during the synthesis/aging process, while favoring the formation of uniformly distributed nanopores. Lowering particle density by controlling calcium to silicon ratio along with optimizing the surface area are essential in achieving our objective.

The present invention relates to a porous membrane including a polymer including a polyvinylidene fluoride-based resin as a main component, and a branched polyvinylidene fluoride-based resin as the polyvinylidene fluoride-based resin, in which the polymer has a value of a of 0.32 to 0.41 and a value of b of 0.18 to 0.42, each of which is determined by approximation according to the formula 1 below from a radius of gyration <S.sup.2>.sup.1/2 and an absolute molecular weight M.sub.w of the polymer which are measured by GPC-MALS (gel permeation chromatograph equipped with a multi-angle light scattering detector). <S.sup.2>.sup.1/2=bM.sub.w.sup.a (Formula 1)

The purpose of the present invention is to provide a porous hollow fiber membrane that can efficiently separate and remove the substances to be removed such as small-particle virus contained in a solution and, at the same time, useful recovering substances such as protein can be efficiently permeated and the decrease of its transmission rate with elapse of time is small. The porous hollow fiber membrane of the present invention is characterized in that the filtration downstream surface thereof has dot-shaped or slit-shaped pores, the filtration upstream surface thereof is a network structure or a fine particle aggregate structure, the central region of the membrane is composed of a substantially homogeneous structure, the membrane wall is composed of a structure having substantially no macrovoids, the permeability for pure water is 10 to 300 L/(h.Math.m.sup.2.Math.bar) and the permeability for a 0.1% by weight solution of bovine γ-globulin is 30 to 100% of the permeability for pure water. Also, the hollow fiber membrane is characterized in that the permeability for a 0.1% by weight solution of bovine γ-globulin in a 20 mmol/L phosphate buffer is 30 to 100% of the permeability for a 0.1% by weight solution of bovine γ-globulin in a 20 mmol/L phosphate-buffered physiological saline solution.

A separation membrane structure comprises a porous support, a first separation membrane formed on the porous support, and a second separation membrane formed on the first separation membrane. The first separation membrane has an average pore diameter of greater than or equal to 0.32 nm and less than or equal to 0.44 nm. The second separation membrane includes addition of at least one of a metal cation or a metal complex that tends to adsorb nitrogen in comparison to methane.