Breakthroughs on tailoring membrane materials for ethanol recovery by pervaporation

Bioethanol, as a clean and renewable fuel, has gained increasing attention due to its major environmental benefits. Pervaporation(PV) is a promising and competitive technique for the recovery of ethanol from bioethanol fermentation systems due to the advantages of environmental friendliness, low energy consumption and easy coupling with fermentation process. The main challenge for the industrial application of ethanol perm-selective membranes is to break the trade-off effect between permeability and selectivity. As membrane is the heart of the pervaporation separation process, this article attempts to provide a comprehensive survey on the breakthroughs of ethanol perm-selective PV membranes from the perspectives of tailoring membrane materials to enhance PV separation performance. The research and development of polymeric and organic/inorganic hybrid membranes are reviewed to explore the fundamental structure-property-performance relationships. It is found that mixed matrix membranes with welldesigned membrane structures offer the hope of better control overphysi-/chemical microenvironment and cavity/pore size as well as size distribution, which may provide both high permeability and membrane selectivity to break the trade-off effect. The tentative perspective on the possible future directions of ethanol perm-selective membranes is also briefly discussed, which may provide some insights in developing a new generation of high-performance PV membranes for ethanol recovery.

Preparation of SGO-modified nanofiltration membrane and its application in SO_4^(2-) and Cl^- separation in salt treatment

The lack of fresh water in the world makes the search for an effective method to decontaminate water an urgent priority.An important step is to remove different multivalent ions in salt treatment.Nanofiltration(NF)has been used for treating water containing different kinds of salts.In this work,sulfonate group-modified graphene oxide(SGO)was prepared,and added during the interfacial polymerization(IP)reaction to prepare SGO-modifiedNF membranes(PA-SGO).The chemical composition,structure and surface properties of PA and PA-SGO membranes were characterized by FT-IR,XPS,SEM,AFM,contact angle and zeta potential measurements.Their water flux,salt rejection and antifouling abilities were investigated systematically.The testing results showed that the water flux of PA-SGO(0.03%SGO)was 45.85 LMH under a pressure of 0.2 MPa,and the salt rejection varied in the order of Na_2SO_4(98.99%)>MgSO_4(91.25%)>MgCl_2(42.27%)>NaCl(21.96%).An anti-fouling experiment indicated that the PA-SGO membrane had good anti-fouling properties because of its decreased roughness and increased hydrophilicity and electronegativity.The PA-SGO membrane has good potential for use in removing salt ions from water.

Drinking water treatment using a submerged internal-circulation membrane coagulation reactor coupled with permanganate oxidation

A submerged internal circulating membrane coagulation reactor （MCR） was used to treat surface water to produce drinking water. Polyaluminum chloride （PAC1） was used as coagulant, and a hydrophilic polyvinylidene fluoride （PVDF） submerged hollow fiber microfiltration membrane was employed. The influences of trans-membrane pressure （TMP）, zeta potential （ZP） of the suspended particles in raw water, and KMnO4 dosing on water flux and the removal of turbidity and organic matter were systematically investigated. Continuous bench-scale experiments showed that the permeate quality of the MCR satisfied the requirement for a centralized water supply, according to the Standards for Drinking Water Quality of China （GB B749-2006）, as evaluated by turbidity （〈1 NTU） and total organic carbon （TOC） （〈5 mE/L） measurements. Besides water flux, the removal of turbidity, TOC and dissolved organic carbon （DOC） in the raw water also increased with increasing TMP in the range of 0.01-0.05 MPa. High ZP induced by PAC1, such as 5-9 mY, led to an increase in the number of fine and total particles in the MCR, and consequently caused serious membrane fouling and high permeate turbidity. However, the removal of TOC and DOC increased with increasing ZP. A slightly positive ZP, such as 1-2 mV, corresponding to charge neutralization coagulation, was favorable for membrane fouling control. Moreover, dosing with KMnO4 could further improve the removal of turbidity and DOC, thereby mitigating membrane fouling. The results are helpful for the application of the MCR in producing drinking water and also beneficial to the research and application of other coagulation and membrane separation hybrid processes.

Effect of PEG additives on properties and morphologies of polyetherimide membranes prepared by phase inversion

This study investigated the effect of poly(ethylene glycol)(PEG)additive as a pore-former on the structure formation of membranes and their permeation properties connected with the changes in thermodynamic and kinetic properties in the phase inversion process.The membranes were prepared by using polyetherimide/Nmethyl-2-pyrrolidone/PEG(PEI/NMP/PEG)casting solution and water coagulant.The resulting membranes,prepared by changing the ratio of PEG to PEI,were characterized by scanning electron microscope(SEM)observations,measurements of water flux andγ-globin rejection.The thermodynamic and kinetic properties of the membrane-forming system were studied through viscosity.The pore radius distribution curves were especially obtained by differential scanning calorimetry(DSC).Furthermore,the membranes were characterized for pure water flux and rejection of solute and by SEM observation.The filtration results agreed well with the SEM observations.As expected,PEG with a fixed molecular weight(PEG 600)acted as a pore forming agent,and membrane porosity increased as the PEG content of the casting solution increased.