nan Khoiruddin

Combined ultrafiltration-electrodeionization technique for production of high purity water

Electrodeionization (EDI) is the most common method to produce high purity water used for boiler feed water, microelectronic, and pharmaceutical industries. Commonly, EDI is combined with reverse osmosis (RO) to meet the requirement of EDI feed water, with hardness less than 1 ppm. However, RO requires a relatively high operating pressure and ultrafiltration (UF) as pretreatment which results in high energy consumption and high complexity in piping and instrumentation. In this work, UF was used as the sole pretreatment of EDI to produce high purity water. Tap water with conductivity 248 μS/cm was fed to UF-EDI system. The UF-EDI system showed good performance with ion removal more than 99.4% and produced water with low conductivity from 0.2 to 1 μS/cm and total organic compounds less than 0.3 ppm. Generally, product conductivity decreased with the increase of current density of EDI and the decrease of feed velocity and UF pressure. The energy consumption for UF-EDI system in this work was 0.89-2.36 kWh/m3. These results proved that UF-EDI system meets the standards of high purity water for pharmaceutical and boiler feed water with lower investment and energy consumption than RO-EDI system.

LTA zeolite membranes: current progress and challenges in pervaporation

Linde Type A (LTA) zeolite-based membranes have demonstrated excellent selectivity in pervaporation due to their unique structural framework and interaction with water. The development of LTA zeolite membranes for commercial application is limited by some parameters, particularly the complexity of the membrane preparation required to produce reproducible defect-free membranes and the high costs required for the membrane materials. In addition, the high content of Al in the zeolite framework makes the LTA zeolite membrane unsuitable for acidic conditions. A number of modification techniques have been proposed to produce a thin, defect-free, and high permselectivity LTA zeolite membrane with high reproducibility. Two major approaches are generally used to produce defect-free zeolite membranes, i.e. modifying either the seeding step or the synthesis process. Since the self-supported zeolite membrane has low mechanical stability, the LTA zeolite membrane is usually synthesized on an inorganic support to give better properties. Zeolite membrane costs can be reduced by several methods such as replacing the support, manufacturing a higher flux zeolite membrane, and fabricating a polymer–zeolite membrane. One should consider, however, that changing the support can dramatically influence and even reverse the obtained separation behavior. Despite various techniques used to prepare dense LTA zeolite membranes, a facile mass production technique with a highly reproducible result remains a significant challenge. To present a clear background for LTA zeolite and its performances in pervaporation, this paper includes a brief discussion on the recent trends related to LTA zeolite membranes. Some topics are discussed, including the features inherent to LTA zeolite, the transport phenomena in zeolite structures, preparation methods of LTA zeolite membranes, and the challenges associated with preparation. Furthermore, critical issues related to LTA zeolite membranes in pervaporation will be discussed to develop the topic further.

Functionalized carbon nanotube (CNT) membrane: progress and challenges

The role of carbon nanotube (CNT) as filler in a membrane matrix became popular recently. CNT is believed to solve the trade-off issue between permeability and selectivity, and also fouling problems in membrane filtration applications. Their fullerene form is a key point to provide a higher pore size on membrane surface as well as empty space called porosity in membrane structures. However, the hydrophobicity characteristic of CNT has made it difficult to distribute and it tends to agglomerate with each other which leads to a decrease in the dispersion ability in a solvent and, in the same way, a decline in the compatibility of a membrane structure. Functionalization of CNT is expected to solve those problems. Moreover, membrane hydrophilicity, which is provided by the existence of hydrophilic functionalized CNT, is aimed to achieve the anti trade-off between permeability and selectivity based on a electrostatic repulsion concept. By an electrostatic repulsion process, a pollutant will be repelled from attaching to a membrane surface while water will be strongly attracted and be transported through the membrane. Therefore, various approaches have been investigated to functionalize CNT for achieving a high dispersion of CNT as well as high compatibility between CNT and a polymer matrix which lead to improvement of modified membrane properties and performances. This paper reviews the progress of CNT functionalization applied in membrane filtration during the years 2006 up to 2016. The influence of functionalized CNT in improving membrane properties as well as membrane performances is specifically highlighted.

The role of ion-exchange membrane in energy conversion

Ion-exchange membrane (IEM) may play an important role in the future of electrical energy generation which is considered as renewable and clean energy. Fell cell (FC) is one of the promising technologies for solving energy issues in the future owing to the interesting features such as high electrical efficiency, low emissions, low noise level, and modularity. IEM-based processes, such as microbial fuel cell (MFC) and reverse electrodialysis (RED) may be combined with water or wastewater treatment into an integrated system. By using the integrated system, water and energy could be produced simultaneously. The IEM-based processes can be used for direct electricity generation or long term energy storage such as by harnessing surplus electricity from an existing renewable energy system to be converted into hydrogen gas via electrolysis or stored into chemical energy via redox flow battery (RFB). In this paper, recent development and applications of IEM-based processes in energy conversion are reviewed. In add...

Study on the influence of applied voltage and feed concentration on the performance of electrodeionization in nickel recovery from electroplating wastewater

Wastewaters from electroplating industries are usually contaminated with nickel up to 1000 mg/L. According to environmental regulations worldwide, nickel concentration on wastewaters must be controlled to an acceptable level before being discharged to the environment. This paper offers an alternative way to develop an efficient effluent-free technology to reduce the nickel content of rinse water so that the treated water could be recycled for rinsing and subsequently to workout methodology to recover nickel by electrodeionization (EDI). Electrical voltage and initial nickel concentration were varied to study the effect of the parameters. Results showed that EDI could remove nickel effectively which gives an outstanding result in terms of product quality. Nickel concentration on diluate chamber decreased up to 99% after 60 and 180 minutes for nickel concentration of 300 and 1000 mg/L, respectively. Meanwhile, the increase of electrical voltage led to faster nickel removal.

Preparation and characterization of polysulfone/PEG heterogeneous ion exchange membrane for reverse electrodialysis (RED)

Heterogeneous cation-exchange membrane is synthesized using solution casting method. The casting solution is prepared by dispersing finely ground cation-exchange resin particles in N,N-dimethylacetamide (DMAc) solutions of polysulfone (PSf) while polyethylene glycol (PEG400) is used as a modifier. The results show that the PEG400 can increase water uptake, conductivity, and ion-exchange capacity (IEC) of the heterogeneous cation-exchange membrane due to the hydrophilic nature of PEG400. The more hydrophilic membrane results in higher water uptake and wider access for functional sites. However, when the concentration of PEG400 is increased further, the IEC and conductivity tend to decrease. This tendency is more pronounced when the ion-exchange resin particle is increased from 50 to 60%-wt. It could be attributed to the washed out of some ion-exchange particle during membrane immersion due to lower bonding between membrane matrix and the particles.

Improving ion-exchange membrane properties by the role of nanoparticles

Extensive application of synthetic ion-exchange membrane (IEM) in many areas has necessitated the improvement of their properties. Recently, the introduction of nanoparticles into polymeric membrane has attracted growing interest since the combination of both materials results in better properties. This well-known mixed-matrix membrane exhibits superior characteristics compared to an individual polymeric membrane. Properties of the nanoparticles such as electrical conductivity, hydrophilicity, and adsorption capacity can be utilized to produce the IEM with better physicochemical, electrochemical, and mechanical characteristics. The nanoparticles may also be used to achieve a specific characteristic such as an antibacterial property and monovalent ion permselectivity. In this paper, preparation, the role of inorganic materials and performance of mixed-matrix IEM are reviewed. In addition, challenges facing mixed-matrix IEM and strategies taken to overcome those challenges and future perspectives are discussed.Extensive application of synthetic ion-exchange membrane (IEM) in many areas has necessitated the improvement of their properties. Recently, the introduction of nanoparticles into polymeric membrane has attracted growing interest since the combination of both materials results in better properties. This well-known mixed-matrix membrane exhibits superior characteristics compared to an individual polymeric membrane. Properties of the nanoparticles such as electrical conductivity, hydrophilicity, and adsorption capacity can be utilized to produce the IEM with better physicochemical, electrochemical, and mechanical characteristics. The nanoparticles may also be used to achieve a specific characteristic such as an antibacterial property and monovalent ion permselectivity. In this paper, preparation, the role of inorganic materials and performance of mixed-matrix IEM are reviewed. In addition, challenges facing mixed-matrix IEM and strategies taken to overcome those challenges and future perspectives are discussed.