Impacts of Secondary Mixed Monomer on Properties of Thin Film Composite (TFC) Nanofiltration and Reverse Osmosis Membranes: A Review.

Polyamide (PA) Thin-Film Composite (TFC) membranes are widely used for large-scale water and wastewater treatment processes worldwide owing to their good balance between water permeability and dissolved solutes separation rate. The physicochemical properties of the cross-linked PA layer are the main criteria determining the filtration performance of the resultant TFC membrane, and this selective layer can be created through Interfacial Polymerization (IP) between two immiscible active monomers, i.e., amine monomer in aqueous solution and acyl chloride monomer in organic solution. This patent review article intends to provide insights to researchers in fabricating improved properties of TFC membranes through the utilization of secondary monomers during IP process. To the best of our knowledge, this is the first review that gives a state-of-the-art account of the subject matter by emphasizing the impacts of secondary monomers (both amine and acyl chloride monomers) on the properties of conventional TFC membranes for nanofiltration and reverse osmosis applications. Our review indicated that the introduction of secondary monomers into either aqueous or organic solution could alter the physical and chemical properties of PA layer, which led to variations in membrane filtration performance. Nevertheless, more research is still required, as most of the secondary monomers reported in the literature did not overcome the membrane trade-off effect between permeability and selectivity. The subject of improved PA layer development is a multi-disciplinary study that requires researchers with different backgrounds (e.g., materials science, chemistry, physics and engineering) to work together.

Occupational and Environmental Risk Factors Influencing the Inducement of Erythema among Nigerian Laboratory University Workers with Multiple Chemical Exposures.

: The chemicals from laboratories pose a significant risk forinducing erythema, an abnormal redness of the skin, as a result of poor occupational and environmental factors that promote hypersensitivity to a chemical agent. The aim of this present study was to determine the occupational and environmental risk factors influencing the inducement of erythema in laboratory workers due to exposure to chemicals. This was a cross-sectional study on a population-based sample of Nigerian university laboratory workers. Data were collected using the erythema index meter and an indoor air control meter. The study included 287 laboratory workers. The laboratory workers who properly used personal protective equipment (PPE) were 60% less likely to have induced erythema (adjusted odds ratio (AOR) = 0.40; 95% confidence interval CI: 0.22-0.77; probability value p = 0.011). The chemical mixture exceeding the permissible exposure limit (PEL) was found to have a small effect in inducing the erythema (AOR = 4.22; 95%CI: 2.88-12.11; p = 0.004). Most of the sampled laboratories where the respondents worked had unsuitable temperatures (AOR = 8.21; 95% CI: 4.03-15.01; p = 0.001). Erythema was more frequently found in the respondents who spent 4-5h in the laboratory (AOR = 3.11; 95%CI: 1.77-9.23; p = 0.001). However, high levels of ventilation reduce the likelihood of erythema in a laboratory by 82% (0.18). Multiple logistic regressions revealed that PPE, PEL, exposure time, temperature, and ventilation were the probable predictive factors associated with the inducement of erythema. Providing better educational knowledge and improving the attitude towards hazards and safety in a laboratory would lead to reduced rates of new cases.

Performance of PES/LSMM-OGCN Photocatalytic Membrane for Phenol Removal: Effect of OGCN Loading.

In designing a photocatalytic oxidation system, the immobilized photocatalyst technique becomes highly profitable due to its promising capability in treating organic pollutants such as phenols in wastewater. In this study, hydrophiLic surface modifying macromolecules (LSMM) modified polyethersulfone (PES) hybrid photocatalytic membranes incorporated with oxygenated graphitic carbon nitride (OGCN) was successfully developed using phase inversion technique. The effectiveness of the hybrid photocatalytic membrane was determined under different loading of OGCN photocatalyst (0, 0.5, 1.0, 1.5, 2.0, and 2.5 wt%). The best amount of OGCN in the casting solution was 1.0 wt% as the agglomeration did not occur considering the stability of the membrane performance and morphology. The highest flux of 264 L/m²·h was achieved by PES/LSMM-OGCN1.5wt% membrane. However, the highest flux performance was not an advantage in this situation as the flux reduced the rejection value due to open pores. The membrane with the highest photocatalytic performance was obtained at 1.0 wt% of OGCN loading with 35.78% phenol degradation after 6 h. Regardless of the lower rejection value, the performance shown by the PES/LSMM-OGCN1.0wt% membrane was still competent because of the small difference of less than 1% to that of the PES/LSMM-OGCN0wt% membrane. Based on the findings, it can be concluded that the optimisation of the OGCN loading in the PES hybrid photocatalytic membrane indeed plays an important role towards enhancing the catalyst distribution, phenol degradation, and acceptable rejection above all considerations.

Characterizations of Polysulfone/Ferrihydrite Mixed Matrix Membranes for Water/Wastewater Treatment.

This study aimed to investigate the effects of ferrihydrite (Fh) nanoparticle loading on the physicochemical properties of polysulfone (PSf) membranes fabricated via the phase inversion method. The morphologies and physicochemical properties of prepared Fh and PSf/Fh mixed matrix membranes (MMMs) were characterized using transmission electron microscopy (TEM), X-ray diffraction analysis (XRD), Fourier transmission infra-red (FTIR), scanning electron microscopy (SEM), atomic force microscopy (AFM), pure water flux analysis, contact angle measurement, and membrane porosity analysis. FTIR study indicated that a new O-H band was formed when Fh was added into the membrane matrix. SEM analysis showed the formation of typical asymmetric membrane structures with elongated fingerlike and looser porous layers. Increasing the loading of Fh significantly enhanced membrane pure water flux from 230.2 L/m2•h (M-Fh 0%) to 726.6 L/m2•h (M-Fh 15.3%), attributed to the improved membranes structures, membranes wettability, surface roughness, and overall porosity. The findings suggest incorporation of Fh into PSf membranes improves physicochemical properties of the membranes which are applicable for water/wastewater treatment.