The toxicity of heavy metals can cause water pollution and has harmful effects on human health and the environment. Various methods are used to overcome this pressing issue and each method has its own advantages and disadvantages. Membrane filtration technology such as nanofiltration (NF) produces high quality water and has a very small footprint, which results in lower energy usage. Nanofiltration is a membrane-based separation technique based on the reverse osmosis separation process developed in the 1980s. NF membranes have a pore size of 1 nm and molecular weight cut off (MWCO) of 300 to 500 Da. The properties of NF membranes are unique since the surface charge of the membranes is dependent on the functional groups of the membrane. The rejection mechanism of NF membrane is unique as it is a combination of various rejection mechanisms such as steric hindrance, electric exclusion, dielectric effect, and hydration mechanism. However, these mechanisms have not been studied in-depth due to their complexity. There are also many factors contributing to the rejection of NF membrane. Many junior researchers would face difficulty in studying NF membrane. Therefore, this paper is designed for researchers new to the field, and will briefly review the rejection mechanisms of NF membrane by both sieving and non-sieving separation processes. This mini-review aims to provide new researchers with a general understanding of the concept of the separation process of charged membranes.

Polypyrrole (PPy) has been widely used as a sensing material in many studies as PPy gives out noticeable reactions towards varieties of vapours of acids, bases, alcohols, alkanes, and chemical warfare agent (CWA) simulants. However, due to dispersion and mechanical properties limitation, PPy in nanoparticles (PPy NPs) has been introduced. The combinations between PPy NPs and nanosized metal oxide have shown promising improvement in the sensitivity of a sensor due to the larger total surface area of detection. In this study, the potential of PPy NPs and polypyrrole‐iron oxyhydroxide (PFFs) nanocomposite as sensing materials in detecting the CWA simulant, dimethyl methylphosphonate (DMMP), is investigated. PPy NPs and modified PFFs nanocomposite were successfully synthesised using chemical oxidative polymerisation. The formation of PPy NPs and the effect of iron‐oxyhydroxide (FeOOH) on the chemical interaction, morphology, and size of PPy NPs were investigated using attenuated total reflection‐Fourier transform infrared (ATR‐FTIR), field emission scanning electron microscopy (FESEM), and transmission electron microscopy (TEM). ATR‐FTIR analysis showed that the modified PFFs nanocomposite was successfully produced through the presence of a sharp –OH peak. The size of the prepared PPy NPs and PFFs nanocomposite was observed in the range of 50 to 70 nm and 110 to 160 nm, respectively, through TEM analysis. The electrochemical behaviour of PPy NPs and PFFs nanocomposite towards DMMP was investigated using cyclic voltammetry (CV) where, in the presence of DMMP, PPy NPs and PFFs nanocomposite showed 24% and 21% current signal reduction, respectively. This suggests that both PPy NPs and PFFs nanocomposite are able to discriminate an electrical signal both with and without the presence of DMMP.

The utilization of membranes has been extensively employed in the treatment of water and wastewater. Membrane fouling, attributed to the hydrophobic nature of membranes, constitutes a noteworthy concern in the realm of membrane separation. The mitigation of fouling can be achieved through the modification of membrane characteristics, including but not limited to hydrophilicity, morphology, and selectivity. In this study, a nanohybrid polysulfone (PSf) membrane embedded with silver–graphene oxide (Ag-GO) was fabricated to overcome problems related to biofouling. The embedment of Ag-GO nanoparticles (NPs) is the aim towards producing membranes with antimicrobial properties. The fabricated membranes at different compositions of NPs (0 wt%, 0.3 wt%, 0.5 wt%, and 0.8 wt%) are denoted as M0, M1, M2, and M3, respectively. These PSf/Ag-GO membranes were characterized using FTIR, water contact angle (WCA) goniometer, FESEM, and salt rejection. The additions of GO significantly improved the hydrophilicity of PSf membranes. An additional OH peak at 3380.84 cm⁻¹ of the nanohybrid membrane from FTIR spectra may be related to hydroxyl (-OH) groups of GO. The WCA of the fabricated membranes decreased from 69.92° to 54.71°, which confirmed the improvement in its hydrophilicity. In comparison to the pure PSf membrane, the morphology of the finger-like structure of the fabricated nanohybrid membrane slightly bent with a larger bottom part. Among the fabricated membranes, M2 achieved the highest iron (Fe) removal, up to 93%. This finding proved that the addition of 0.5 wt% Ag-GO NPs enhanced the membrane water permeability together with its performance of ionic solute removal (Fe²⁺) from synthetic groundwater. In conclusion, embedding a small amount of Ag-GO NPs successfully improved the hydrophilicity of PSf membranes and was able to achieve high removal of Fe at 10–100 mg L⁻¹ towards purification of groundwater for safe drinking water.

Green polymer electrolytes based on chitosan as the polymer matrix and ionic liquid 1-butyl-3-methylimidazolium acetate [Bmim][OAc] as charge carriers were prepared by solution casting technique. Complexes with various amount of ionic liquid loading were investigated as possible ionic conducting polymers. The ionic conductivity was found to increase with increasing weight percent of ionic liquid. The highest ionic conductivity of the charged chitosan-[Bmim][OAc] was 2.44 × 10−3 S cm−1 at 90 wt.% of [Bmim][OAc] content at ambient temperature. Attenuated Total Reflection Fourier Transform infrared (ATR-FTIR) spectroscopy has proven the interaction between chitosan and [Bmim][OAc]. X-ray Diffraction (XRD) has shown that the amorphosity of the complexes increase as the amount of [Bmim][OAc] increase.