Recent advances in membrane bioreactors (MBRs): membrane fouling and membrane material.

Membrane cleaning in membrane bioreactors: A review

Colloidal interactions and fouling of NF and RO membranes: A review

Developing a feasible and efficient separation membrane for the purification of highly emulsified oily wastewater is of significance but challenging due to the critical limitations of low flux and serious membrane fouling. Herein, a biomimetic and superwettable nanofibrous skin on an electrospun fibrous membrane via a facile strategy of synchronous electrospraying and electrospinning is created. The obtained nanofibrous skin possesses a lotus-leaf-like micro/nanostructured surface with intriguing superhydrophilicity and underwater superoleophobicity, which are due to the synergistic effect of the hierarchical roughness and hydrophilic polymeric matrix. The ultrathin, high porosity, sub-micrometer porous skin layer results in the composite nanofibrous membranes exhibiting superior performances for separating both highly emulsified surfactant-free and surfactant-stabilized oil-in-water emulsions. An ultrahigh permeation flux of up to 5152 L m−2 h−1 with a separation efficiency of >99.93% is obtained solely under the driving of gravity (≈1 kPa), which was one order of magnitude higher than that of conventional filtration membranes with similar separation properties, showing significant applicability for energy-saving filtration. Moreover, with the advantage of an excellent antioil fouling property, the membrane exhibits robust reusability for long-term separation, which is promising for large-scale oily wastewater remediation.

Biomimetic and Superwettable Nanofibrous Skins for Highly Efficient Separation of Oil-in-Water Emulsions

Membrane-based techniques for the separation and purification of proteins: an overview.

Pore blocking is one of the critical factors governing the overall performance of membrane filtration systems. Pore blockage leads to a large resistance to filtration, giving rise to a sharp decline in the filtrate flux rate under constant pressure conditions and a severe increase in the pressure for operation under constant flux conditions during membrane filtration. In membrane filtration work, blocking filtration laws are widely used to interpret the membrane fouling in membrane filtration. This article presents a systematic review on the theoretical developments of mechanistic models related to the blocking filtration laws for describing the membrane fouling in membrane filtration. Equations for constant pressure and constant flux separations in the interstices of a membrane and on the surface are reported for the filtrate flow of Newtonian and power-law non-Newtonian fluids. The blocking filtration laws are useful also in the evaluation of the reduced pore size, maximum filtrate volume, and fouling p...

A Review on Modeling of Pore-Blocking Behaviors of Membranes During Pressurized Membrane Filtration

Blocking filtration laws consist of four different filtration mechanisms: complete blocking, standard blocking, intermediate blocking, and cake filtration. Blocking filtration laws for describing both the pore blocking and cake formation have been extensively employed over the past several decades to evaluate the increase in filtration resistance with the progress of filtration in the field of classical particulate filtration. In recent years, blocking filtration laws become widely used also in membrane filtration such as microfiltration and ultrafiltration of colloids. This paper gives an overview of the developments of blocking filtration laws and equations under constant pressure and constant rate conditions reported for the filtrate flow of Newtonian and non-Newtonian fluids. The fouling index evaluating the degree of membrane fouling was examined on the basis of the blocking filtration equations. The blocking filtration laws were reexamined to extend the range of their application. Moreover, various combined models developed based on the blocking filtration laws were introduced for describing more rigorously the complicated filtration behaviors controlled by more than one mechanism which occurs successively or simultaneously.

Developments of Blocking Filtration Model in Membrane Filtration

Flux decline behavior in dead-end microfiltration of protein solutions

The effects of pH and the addition of such salts as NaCl on the structure of the gel-cake in dead-end ultrafiltration of BSA solutions are examined by using a batchwise filter which has an abrupt reduction in its filtration area. Both the average porosity eav and the average specific filtration resistance αav of the gel-cake may be determined accurately on the basis of measurements of the variation of filtrate volume with time. The most compact gel-cake, which provides a large flow resistance, forms on the membrane around the isoelectric pH. By the addition of NaCl at pH extremes the gel-cake structure becomes compact, thereby decreasing the filtration rate. Such internal structures as the solute concentration and the compressive pressure acting on the solutes within the gel-cake, which may serve as a basis for evaluating the sweeping performance of the gel-cake in crossflow ultrafiltration, are evaluated on the basis of the overall filtration characteristics obtained under various filtration pressure conditions.

Effect of solution environment on unstirred dead-end ultrafiltration characteristics of proteinaceous solutions

Upward dead-end ultrafiltration of aqueous solutions of mixtures of bovine serum albumin (BSA) and egg white lysozyme was conducted using membranes which are almost completely retentive for BSA but permeable for lysozyme. The dependence of lysozyme rejection and the filtration flux rate on pH and the addition of salts has been investigated. The experimental data obtained in this study clearly demonstrate that the electrostatic interactions between dissimilar molecules may control the solute rejection and the filtration rate in upward ultrafiltration of binary protein mixtures. For instance, the BSA and lysozyme molecules have opposite electric charges at pH 7. Consequently, lysozyme rejection is large because both molecules within the filter cake pack more tightly due to heterocoagulation. On the other hand, the BSA and lysozyme molecules have the same electric charge at pH 4. Thus, lysozyme is rejected by the filter cake of the retained BSA molecules due to repulsive electrostatic interactions b...

Eiji Iritani

Papers

A Review on Modeling of Pore-Blocking Behaviors of Membranes During Pressurized Membrane Filtration

Developments of Blocking Filtration Model in Membrane Filtration

Flux decline behavior in dead-end microfiltration of protein solutions

Effect of solution environment on unstirred dead-end ultrafiltration characteristics of proteinaceous solutions

Upward Dead-End Ultrafiltration of Binary Protein Mixtures