Modification of Liquid Separation Membranes Using Multidimensional Nanomaterials: Revealing the Roles of Dimension Based on Classical Titanium Dioxide

Membrane technology has become increasingly popular and important for separation processes in industries, as well as for desalination and wastewater treatment. Over the last decade, the merger of nanotechnology and membrane technology in the development of nanocomposite membranes has emerged as a rapidly expanding research area. The key motivation driving the development of nanocomposite membranes is the pursuit of high-performance liquid separation membranes that can address the bottlenecks of conventionally used polymeric membranes. Nanostructured materials in the form of zero to three-dimensions exhibit unique dimension-dependent morphology and topology that have triggered considerable attention in various fields. While the surface hydrophilicity, antibacterial, and photocatalytic properties of TiO₂ are particularly attractive for liquid separation membranes, the geometry-dependent properties of the nanocomposite membrane can be further fine-tuned by selecting the nanostructures with the right dimension. This review aims to provide an overview and comments on the state-of-the-art modifications of liquid separation membrane using TiO₂ as a classical example of multidimensional nanomaterials. The performances of TiO₂-incorporated nanocomposite membranes are discussed with attention placed on the special features rendered by their structures and dimensions. The innovations and breakthroughs made in the synthesis and modifications of structure-controlled TiO₂ and its composites have enabled fascinating and advantageous properties for the development of high-performance nanocomposite membranes for liquid separation.

Nanocrystalline cellulose incorporated biopolymer tailored polyethersulfone mixed matrix membranes for efficient treatment of produced water

Membrane technology is a sustainable method to remove pollutants from petroleum wastewater. However, the presence of hydrophobic oil molecules and inorganic constituents can cause membrane fouling. Biomass derived biopolymers are promising renewable materials for membrane modification. In this study, fouling resistant biopolymer N-phthaloylchitosan (CS)- based polythersulfone (PES) mixed matrix membranes (MMMs) incorporated with nanocrystalline cellulose (NCC) was fabricated via phase inversion method and applied for produced water (PW) treatment. The morphological and Fourier-transform infrared spectroscopy (FTIR) analyses of the as-prepared NCC evidenced the formation of fibrous sheet-like structure and the presence of hydrophilic group. The membrane morphology and AFM analysis showed that the NCC altered the surface and cross-sectional morphology of the CS-PES MMMs. The tensile strength of NCC-CS-PES MMMs was also enhanced. 0.5 wt% NCC-CS-PES MMMs displayed a water permeability of 1.11 × 10^-7 m/s.kPa with the lowest contact angle value of 61°. It affirmed that its hydrophilicity increased through the synergetic interaction between CS biopolymer and NCC. The effect of process variables such as transmembrane pressure (TMP) and synthetic produced water (PW) concentration were evaluated for both neat PES and NCC-CS-PES MMMs membranes. 0.5 wt% NCC-CS-PES MMMs exhibited the highest PW rejection of 98% when treating 50 mgL^-1 of synthetic PW at a transmembrane pressure (TMP) of 200 kPa. The effect of nano silica and sodium chloride on the long-term PW filtration of NCC-CS-PES MMMs was also investigated.

Co-Adsorptive Removal of Creatinine and Urea by a Three-Component Dual-Layer Hollow Fiber Membrane

The development of wearable artificial kidney demands an efficient dialysate recovery, which relies upon the adsorption process. This study proposes a solution to solve the problem of competitive adsorption between the uremic toxins by employing two adsorptive components in a membrane separation process. Dual-layer hollow fiber (DLHF) membranes, which are composed of a polysulfone (PSf)/activated carbon (AC) inner layer and a PSf/poly(methyl methacrylate) (PMMA) outer layer, were prepared for co-adsorptive removal of creatinine and urea from aqueous solution. The DLHF membranes were characterized in terms of morphological, physicochemical, water transport, and creatinine adsorption properties. The membrane was then subjected to an ultrafiltration adsorption study for performance evaluation. The incorporation of AC in membrane, as confirmed by microscopic and surface analyses, has improved the pure water flux up to 25.2 L/(m² h). A membrane with optimum AC loading (9 wt %) demonstrated the highest maximum creatinine adsorption capacity (86.2 mg/g) based on the Langmuir adsorption isotherm model. In the ultrafiltration adsorption experiment, the membrane removed creatinine and urea with a combined average percent removal of 29.3%. Moreover, the membrane exhibited creatinine and urea uptake recoveries of 98.8 and 81.2%, respectively. The combined action of PMMA and AC in the PSf DLHF membrane has made the adsorption of multiple uremic toxins possible during dialysate recovery.

ZrO2-TiO2 Incorporated PVDF Dual-Layer Hollow Fiber Membrane for Oily Wastewater Treatment: Effect of Air Gap

Dual-layer hollow fiber (DLHF) nanocomposite membrane prepared by co-extrusion technique allows a uniform distribution of nanoparticles within the membrane outer layer to enhance the membrane performance. The effects of spinning parameters especially the air gap on the physico-chemical properties of ZrO2-TiO2 nanoparticles incorporated PVDF DLHF membranes for oily wastewater treatment have been investigated in this study. The zeta potential of the nanoparticles was measured to be around -16.5 mV. FESEM-EDX verified the uniform distribution of Ti, Zr, and O elements throughout the nanoparticle sample and the TEM images showed an average nanoparticles grain size of ~12 nm. Meanwhile, the size distribution intensity was around 716 nm. A lower air gap was found to suppress the macrovoid growth which resulted in the formation of thin outer layer incorporated with nanoparticles. The improvement in the separation performance of PVDF DLHF membranes embedded with ZrO2-TiO2 nanoparticles by about 5.7% in comparison to the neat membrane disclosed that the incorporation of ZrO2-TiO2 nanoparticles make them potentially useful for oily wastewater treatment.

Effects of long-term inhaled corticosteroid treatment on fragility fractures in older women: the Manitoba BMD registry study

The effects of inhaled corticosteroids (ICS) on fracture risk in older women with chronic respiratory diseases are not well established. Our results indicate long-term ICS use in this population does not increase the risk of major osteoporotic fracture. This finding further elucidates the long-term safety of ICS in older women.

INTRODUCTION

Inhaled corticosteroids (ICS) are frequently used in older women with chronic respiratory diseases. There is insufficient evidence regarding the association between long-term ICS use and the risk of fragility fractures in this population.

METHODS

We used linked Manitoba health administrative databases and the provincial bone mineral density (BMD) registry (1996-2013) to identify women ≥ 40 years of age with asthma and/or chronic obstructive pulmonary disease (COPD) within 3 years preceding the baseline BMD test. We followed them until the first major osteoporotic fracture or end of study, whichever came first. ICS use, stratified by exposure tertiles, was measured within the 12-month period following the baseline BMD test (by total days and quantity, primary outcome), and over the entire follow-up period (by medication possession ratio (MPR) and average annual dose, secondary outcome). The hazard ratio of fracture with ICS use was estimated using a Cox proportional hazards model, controlling for baseline determinants of fracture.

RESULTS

Of 6880 older women with asthma (38%) or COPD (62%), 810 (12%) experienced a major osteoporotic fracture over a mean follow-up of 7.7 years (SD = 3.9). ICS use at any tertile was not associated with an increased risk of fracture (dispensed days, p = 0.90; dispensed quantity, p = 0.67). Similarly, ICS use at any tertile during the entire follow-up period was not associated with an increased risk of fracture (MPR, p = 0.62; average annual dose, p = 0.58).

CONCLUSION

Our findings do not support an increased risk of major osteoporotic fracture in older women with chronic respiratory diseases due to long-term ICS use.

Polysulfone hemodialysis membrane incorporated with Fe2O3 for enhanced removal of middle molecular weight uremic toxin

Removing middle molecular weight uremic toxin remains as one of the most challenging tasks in hemodialysis. Hence, in this study a high performance polysulfone (PSf) hemodialysis membrane was developed by incorporating iron oxide (Fe2O3) nanoparticles. The PSf/Fe2O3 hemodialysis membrane and pristine PSf membrane were prepared via dry-wet spinning process. The membranes were characterized by scanning electron microscopy, water contact angle, average pore size, and porosity measurements. The biocompatibility profiles of the membranes were also evaluated in terms of protein adsorption and blood coagulation time. Next, the performance of the membranes was determined by measuring pure water permeability (PWP), bovine serum albumin rejection, and removal of various solutes such as urea and lysozyme. The incorporation of Fe2O3 resulted in significant increment of the PWP from 40.74 L/m2/h/bar to 58.6 L/m2/h/bar, mainly due to the improved water transport properties of the membrane. Moreover, the percent removal of urea and lysozyme was reported to be 75.1% and 35.6%, respectively. PSf/Fe2O3 hemodialysis membrane is proven to have a bright prospect for enhanced blood purification process.

Adsorptive nanocomposite membranes for heavy metal remediation: Recent progresses and challenges

Heavy metal contamination in aqueous system has attracted global attention due to the toxicity and carcinogenicity effects towards living bodies. Among available removal techniques, adsorptive removal by nanosized materials such as metal oxide, metal organic frameworks, zeolite and carbon-based materials has attracted much attention due to the large active surface area, large number of functional groups, high chemical and thermal stability which led to outstanding adsorption performance. However, the usage of nanosized materials is restricted by the difficulty in separating the spent adsorbent from aqueous solution. The shift towards the use of adsorptive composite membrane for heavy metal ions removal has attracted much attention due to the synergistic properties of adsorption and filtration approaches in a same chamber. Thus, this review critically discusses the development of nanoadsorbents and adsorptive nanocomposite membranes for heavy metal removal over the last decade. The adsorption mechanism of heavy metal ions by the advanced nanoadsorbents is also discussed using kinetic and isotherm models. The challenges and future prospect of adsorptive membrane technology for heavy metal removal is presented at the end of this review.

Synthesis and characterisation of composite sulphonated polyurethane/polyethersulphone membrane for blood purification application

Polyurethane (PU) with three different functional groups: carboxyl, hydroxyl and sulphonyl group on its molecular structure were synthesised in this work. The synthesised material suppresses blood clotting and exhibits anticoagulant characteristics due to the presence of the important anionic groups. The synthesised PU was blended with polyethersulphone (PES) and fabricated into flat-sheet membrane to study the physico-chemical and biocompatibility properties of the PES membrane for blood purification application. PES-PU flat-sheet membranes were fabricated via the dry-wet phase separation technique. Different loading of PU (0, 1, 2, 3, 4, and 5%) blended with PES was studied and compared. Based on the in-vitro biocompatibility analysis of the membrane, it can be suggested that the membrane incorporated with PU has better anticoagulant properties compared to the pristine PES membrane. PU incorporation prolonged the clotting time, decreased the formation of thrombin, decreased soluble complement component 3a (C3a) generation and suppressed platelet adhesion and aggregation. The anionic groups on the membrane surface might bind to coagulation factors (antithrombin) and the calcium ions, Ca²⁺ and thus improve anticoagulant ability. Based on both physico-chemical and in-vitro studied, 4% loading of PU is the optimum loading for incorporation with PES membrane. These results suggested that the blended PES-PU membranes with good haemocompatibility allowed practical application in the field of blood purification.

Degradation of PVDF-based composite membrane and its impacts on membrane intrinsic and separation properties

In this work, an attempt was made to evaluate the effects of ultraviolet (UV) irradiation period on the intrinsic and separation properties of composite membrane composed of organic polyvinylidene fluoride and inorganic titanium dioxide (TiO2) nanoparticles by exposing the membrane to UV-A light for up to 250 h. The changes on membrane structural morphologies and chemical characteristics upon UV exposure were studied by field-emission scanning electron microscope and Fourier transform infrared, respectively. It was observed that some cracks and fractures were formed on the membrane outer surface when it was exposed to 120-h UV light. Further increase in UV irradiation time to 250 h had caused membrane structure to collapse, turning it into powder form. Filtration experiments showed that the permeate flux of irradiated membrane was significantly increased from 10.89 L/m2 h to 21.84 L/m2 h (>100% flux increment) while oil rejection decreased with increasing UV exposure time from 0 h to 120 h. Furthermore, the mechanical strength and thermal stability of irradiated membrane were also reported to decrease with increasing UV exposure time, suggesting the negative impacts of UV light on the membrane overall stability. This research is of particular importance to evaluate the suitability and sustainability of polymeric membrane, which is widely considered as the host for photocatalyts and used for wastewater treatment process under UV irradiation.

Impedance and structural studies on plasticized PCL-LiSO3CF3-SiO2 polymer electrolytes

Plasticized polymer electrolytes in this study are consist of biodegradable polycaprolactone (PCL) as a host, ethylene carbonate (EC) as a plasticizer, lithium triflate (LiSO3CF3) as salt and nanocomposite silicon dioxide (SiO2) as filler. Solution cast technique is used in the preparation of the plasticized polymer electrolytes. The electrical properties of the plasticized polymer electrolytes with different composition of lithium salt, plasticizer and nano-sized filler are reported in this paper. Conductivity as high as 4.30 x 10(-3) S cm(-1) is obtained in ambient temperature. Ionic conductivity of the plasticized polymer electrolytes are measured using electrochemistry impedance spectroscopy (EIS). The structural and complex formations are studied by X-ray diffraction (XRD) and Fourier Transform Infrared (FTIR) spectroscopy. The ionic conductivity result can be further verified and supported by XRD and FTIR reading in which the ionic conductivity is directly proportional to the amorphous phase behaviour of the sample.

The cerebro-costo-mandibular syndrome: 9-year follow-up of a case

Cerebro-costo-mandibular syndrome (CCMS) is a rare multiple congenital anomaly with a low survival rate. There are few reports of long-term survival in this condition. We describe the findings and management of a 9-year-old survivor of CCMS, outline the importance of early intervention and multidisciplinary team approach. The child presented in the neonatal period in respiratory distress with classical features of the syndrome. Aggressive initial respiratory management was later followed up with an integrated multidisciplinary team approach. He has been carefully followed up for nine years now, illustrating well, the course of the syndrome.

Treatment and rehabilitation of drug addicts in Singapore 1977-1982

In Singapore, the treatment and rehabilitation of drug addicts consist of detoxification, recuperation and orientation, indoctrination, physical training and work programme. This is followed by a Day Release Scheme to bridge the gap between the strict disciplinary regime and the free environment of the outside world. The addicts are given the opportunities to pursue academic studies. Two review committees monitor their progress. There has been a significant decrease in the total number of admission from 7084 in 1977 to 2043 in 1982. Over this period, there appears to be a drop in the number of youths recruited into drug abuse. At the same time, more and more of those who have been previously treated are coming into the drug scene.

A radioimmunoassay of 15 (S) 15 methyl prostaglandin F-2alpha

A sensitive and relatively specific radioimmunoassay for 15 (S) 15 methyl prostaglandin F-2alpha has been developed to enable the measurements of the concentrations of the drug in biological fluids after its administration for therapeutic abortion. The precision, accuracy and specificity of the assay are described.