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The discharge of massive amounts of oily wastewater has become one of the major concerns among the scientific community. Membrane filtration has been one of the most used methods of treating oily wastewater due to its stability, convenience handling, and durability. However, the continuous occurrence of membrane fouling aggravates the membrane’s performance efficiency. Membrane fouling can be defined as the accumulation of various materials in the pores or surface of the membrane that affect the permeate’s quantity and quality. Many aspects of fouling have been reviewed, but recent methods for fouling reduction in oily wastewater have not been explored and discussed sufficiently. This review highlights the mitigation strategies to reduce membrane fouling from oily wastewater. We first review the membrane technology principle for oily wastewater treatment, followed by a discussion on different fouling mechanisms of inorganic fouling, organic fouling, biological fouling, and colloidal fouling for better understanding and prevention of membrane fouling. Recent mitigation strategies to reduce fouling caused by oily wastewater treatment are also discussed.

In this work, thin film composite (TFC) membrane embedded with self-synthesized layered double hydroxide (LDH) nanofillers was prepared via interfacial polymerization technique for nanofiltration (NF) process. Prior to filtration experiments, the morphologies and physicochemical properties of the prepared LDH nanofillers and TFC membranes were characterized using TEM, XRD, FESEM, FTIR, AFM, zeta potential analyzer and contact angle goniometer. The results revealed that the self-synthesized LDH nanofillers possessed layered structured materials with typical hexagonal plate-like shape. Meanwhile, it was found that the membrane contact angle decreased remarkably from 53° to 33.96° upon addition of 0.1 wt% LDH nanofillers in the active polyamide layer. TFN membrane of 0.1 wt% LDH loading possessed the highest water flux of 54.62 Lm−2 h−1 at 7 bar. The highest rejections of Na2SO4 (97.3%), MgSO4 (95.5%), MgCl2 (95.2%) and NaCl (63.7%) were also achieved by the TFN embedded with 0.1 wt% LDH in polyamide layer. In addition to the excellent water flux and rejection, incorporation of LDH also enhanced the fouling resistance, proven by the improvement of pure water flux recovery by 52% after BSA filtration. The findings indicated the potential of the newly developed TFN membrane incorporated with LDH nanofillers for efficient NF membrane in water softening and pre-desalination process.

In this work, the effect of adding manganese oxide towards polyacrylonitrile-based activated carbon nanofibers (ACNFs) was evaluated. The properties of PAN-based ACNFs/MnO2 were analyzed by using scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET), and Fourier transform infrared (FTIR). The sorption study of the electrospun ACNFs/MnO2 in comparison to neat ACNFs and commercial granular AC towards lead (Pb) was also conducted. SEM micrograph analysis displays more compact nanofibers with dispersion of beads that were observed in the ACNF/MnO2 with the diameter of 437.2 nm while aligned nanofibers with the diameter of 575.5 nm were observed in the neat ACNFs. The FTIR analysis showed the peak of Mn–O, which indicates the presence of MnO2 in the ACNFs/MnO2. In comparison to the neat ACNFs, surface area of the prepared ACNFs/MnO2 is lower. It was found out that the removal of Pb(II) using ACNFs and ACNFs/MnO2 is higher than commercial granular activated carbon with a removal rate of 100% at initial concentration of 3.5 ppm. The promising results of ACNFs/MnO2 contributed by their satisfactory specific surface area and vast presence of surface functional groups.

The wastewater discharged from dye-manufacturing industries can pose severe problems to the ecosystem and the use of conventional ultrafiltration (UF) polymeric membrane is still not capable of removing dyes from the wastewater. In this work, hybrid flat sheet mixed matrix membranes were fabricated by blending polyethersulfone (PES) with different weight percentage of ferric-based metal–organic framework (Fe-MOF), aiming to overcome the drawback of PES membrane. Findings revealed that the Fe-MOF/PES membranes attained excellent rejections (>98.5%) for cationic and anionic dyes with its optimum permeation flux as high as 165.68 L/m2h, comparable to other reported UF membranes. Moreover, the fouling study conducted using real textile wastewater revealed the potential of the hybrid membrane for reducing the levels of total suspended solid (100% rejection) and chemical oxygen demand (>92%) while exhibiting high flux recovery rate (>90%). These results suggested that the Fe-MOF/PES hybrid UF membrane has great potential for efficient industrial wastewater treatment.

PAN-based ACNFs incorporated with MgO was prepared by electrospinning process followed by appropriate activation process. The addition of MgO caused physicochemical changes in term of smaller fiber diameter with an average diameter of 520 nm and higher surface area which is up to four times (1893 m2 g−1) as compared to pristine ACNFs (478 m2 g−1). Moreover, the modified ACNFs possessed a better adsorption capacity with higher CH4 adsorption of 2.37 mmol g−1. From the experimental data, the adsorption of CH4 by composite ACNFs obeyed the pseudo-second order kinetic model with R2 value up to 0.9996 and best fitted by Freundlich isotherm model.

Activated carbon nanofibers (ACNFs) incorporated with four different types of metal oxides; magnesium oxide (MgO), manganese dioxide (MnO2), zinc oxide (ZnO), and calcium oxide (CaO) were successfully prepared via a simple electrospinning and pyrolysis process. Optimum electrospinning and pyrolysis parameters were performed to obtain porous ACNFs composites for CO2 capture. The porous and textural characteristics of the resultant ACNFs composites were performed using N2 adsorption isotherms at 77 K, while the features and morphologies were observed using TEM and FE-SEM. The EDX and Raman analysis were used to determine and analyse the elemental composition in the ACNFs. It was observed that ACNFs incorporated MgO (ACNF2) exhibited the largest surface area (413 m2/g) and the highest micropore volume (0.1777 cm3/g) as compared to pristine ACNF (ACNF1) and other ACNFs composites. ACNF2 also possessed the smallest fiber diameter of 357.8 ± 16.7 nm as compared to other samples. The successful incorporation of all metal oxides in electrospun fibers were proven by EDX analysis. All resultant ACNFs exhibited D- and G-peaks in Raman spectra indicating the carbon-based materials structure. As expected, the ACNF2 attained the highest CO2 adsorption of 60 cm3/g at 298 K as compared to other ACNFs samples which is correspond to N2 adsorption capacity. The CO2 adsorption/desorption isotherms of the best composite sample (ACNF2) was measured at three different temperatures (273, 298, and 318 K) at 1 bar through a volumetric adsorption process and this result was compared to ACNF1. It shown that the CO2 adsorption capacity is inversely proportional to the increasing temperature in which as the adsorption temperature increased, the adsorbed amounts of CO2 decreased. These results indicated that the incorporation of MgO into ACNFs shows the best improvement in their physicochemical properties for enhanced adsorption performance of CO2 under practical conditions.

In forward osmosis (FO) process, reverse solute flux (RSF) is considered as a major disadvantage that limits the potential of FO. In this study, an innovative approach to reduce RSF was developed by introducing complexing agent into draw solution (DS) containing magnesium chloride (MgCl2). A water-soluble complexing agent namely poly(sodium 4-styrenesulfonate) (PSS) was chosen for this study and its affinity towards complexation with MgCl2 was investigated in terms of its loadings (0.1–5.0 w/w%) and pH condition (3.0, 5.0, 7.0 and 9.0). It was found out that the addition of PSS was able to reduce the effect of RSF due to its complexation with MgCl2 which enhanced the molecular weight and inhibited the movement of MgCl2 across thin film composite (TFC) membrane. Under pH studies, it is demonstrated that the optimum DS condition for complexation affinity was at none-adjusted pH. Compared to RSF value without the PSS addition, reduced RSF value (0.3 g / m 2 . h ) was achieved at 1.0 w/w% PSS. When copper(II) sulphate was used as feed solution, the rejection was maintained at an average value of 95%. Based on these findings, this study promotes the feasibility of polymer-complex DS to be used in FO process for heavy metals removal.

In this work, activated carbon nanofibers (ACNFs) from precursor polyacrylonitrile (PAN) and magnesium oxide (MgO) were prepared via electrospinning process. The morphological properties of the PAN/MgO - based ACNFs were characterized by using Scanning Electron Microscopy (SEM) and the specific surface area (SSA) were investigated using nitrogen adsorption, Brunauer - Emmett - Teller (BET) methods. Moreover, the functional groups were analyzed by using Fourier Transform Infrared (FTIR). Besides that, the sorption study has been conducted in order to determine the adsorption capacity between electrospun ACNFs/MgO, pristine ACNFs and granular activated carbon (GAC) towards cadmium (II) i ons. The results showed that the SSA of modified ACNFs (198.80 m 2 /g) is significantly higher compared to the precursor ACNFs (15.43 m 2 /g), however the SSA obtained is quite lower compared to the average theoretical value. SEM micrograph of pristine ACNFs depicted more compact nanofibers compared to aligned nanofibers with average diameter of 200 - 700 nm. Under batch adsorption study, it was found out that Cd(II) removal of both ACNFs and ACNFs/MgO is higher compared to the commercial GAC. It has been demonst rated that the adsorption capacity of both electrospun ACNFs (ACNFs/MgO and pristine ACNFs) is higher when compared to the adsorption capacity of commercial GAC towards Cd (II) ions.

This study aimed to investigate the effects of cooperative membrane surface charge of thin film composite (TFC) membranes for removal of Cu(II) from aqueous solution using nanofiltration (NF) and forward osmosis (FO) process. A total of five composite membranes with different piperazine/polyethyleneimine (PIP/PEI) ratio (1.0-PIP, 0.3-PEI, 0.5-PEI, 0.7-PEI, 1.0-PEI) were fabricated and the physicochemical properties of these membranes were characterized using scanning electron microscope (SEM), attenuated total reflection -Fourier transform infra-red (ATR-FTIR), zeta potential and contact angle analysis. Physicochemical analysis confirmed the formation of polyamide (PA) layer for all TFC membranes. Result of zeta potential analysis revealed that 1.0-PEI is positively charged surface whereas 1.0-PIP is negatively charged. Consequently, 1.0-PEI exhibits higher flux compared to 1.0-PIP owing to its higher hydrophilicity. Interestingly, 1.0-PEI demonstrates the highest copper (Cu) (II) ion rejection of more than 95% and 99% in NF and FO operation respectively, outperforming the other produced TFCs. Result of the elemental diffraction x-ray (EDX) further explained that the copper rejection was facilitated by the cooperative surface charge.

In this present study, adsorptive membranes for Cr(VI) ion removal were prepared by blending polyethersulfone (PES) with hydrous ferric oxide (HFO) nanoparticles (NPs). The effects of HFO NPs to PES weight ratio (0–1.5) on the physicochemical properties of the resultant HFO/PES adsorptive membranes were investigated with respect to the surface chemistry and roughness as well as structural morphologies using different analytical instruments. The adsorptive performance of the HFO NPs/PES membranes was studied via batch adsorption experiments under various conditions by varying solution pH, initial concentration of Cr(VI), and contact time. The results showed that the membrane made of HFO/PES at a weight ratio of 1.0 exhibited the highest adsorption capacity which is 13.5 mg/g. Isotherm and kinetic studies revealed that the mechanism is best fitted to the Langmuir model and pseudo-second-order model. For filtration of Cr(VI), the best promising membranes showed improved water flux (629.3 L/m2 h) with Cr(VI) ion removal of 75%. More importantly, the newly developed membrane maintained the Cr(VI) concentration below the maximum contamination level (MCL) for up to 9 h.

This chapter discusses carbon-based polymer nanocomposites including carbon nanotubes, carbon nanofibers, graphene, graphene oxide, and reduced graphene oxide as filler elements in the nanocomposites for the removal of various dyes and pigments. The carbon-based nanocomposites are discussed in general followed by critical review of their performance on dye and pigment removal via adsorption, membrane separation, and photocatalytic processes in which the advantages and limitations of each processes are addressed. At the end of this chapter, the future direction of the application of these nanocomposites is also included.

This paper reported the production of precursor PAN/MnO2 nanofibers via electrospinning method and studying its microstructural properties. The nanofibers were prepared by electrospun the polymer solution of polyacrylonitrile (PAN) and Manganese Oxide (MnO2) in, N, N-Dimethylformamide as its solvent. The factors considered in this study were polymer PAN/ MnO2 concentration which will significantly affect the specific surface area, nanofibers morphology, micropore volume and diameter of the nanofibers. The nanofibers were characterized using Scanning Electron Microscopy (SEM), Brunauer Emmett and Teller (BET) surface area, and Fourier Transmission Infrared Spectroscopy (FTIR). The addition of MnO2 in polymer solution increased the specific surface area of the nanofibers up to 3.5 wt % which found to be its optimum loading. In conclusion, the precursor PAN/ MnO2 -based ACNF were successfully produced with the optimization of metal oxide loading resulting to nanofibers with higher specific surface area which will further increased its adsorption performance.

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.

The recent growth of oil and gas industry has led to the increase of oily wastewater release. Membrane technology has been in the spotlight in recent advancement to treat the oily wastewater. Fouling due to surfactant adsorption and/or oil droplets plugging the pore has become one of the major hindrances in most of the research on oily wastewater treatment. In this work, self-synthesized hydrous ferric dioxide nanoparticles (HFO NPs) via chemical precipitation method were incorporated in polyethersulfone (PES) to fabricate a novel nanocomposite mixed matrix membranes (MMMs) for ultrafiltration (UF). The morphologies and physicochemical properties of prepared HFO NPs and MMMs were characterized using Scanning Electron Microscopy (SEM) and Transmission electron microscope (TEM), contact angle goniometer, before further subjected to water permeation test and oil rejection test. It was found that contact angle of membrane decreased remarkably with an increase in HFO nanoparticle loading from 70° to 38° at which proved its improved hydrophilicity which led to a significant rise in permeate flux, achieving 168.06 L/m2h bar in comparison to 63.67 L/m2h bar shown by the plain PES membrane. Total rejection of oil (100% rejection) demonstrated by the MMMs has confirmed the superior potential of PES/HFO UF membrane for total purification of oily wastewater especially to be reused in oilfield and refinery processes as well as to be released to the environment.

This research reports the production of precursor polyacrylonitrile (PAN)/ manganese dioxide (MnO2) nanofibers (NFs) via electrospinning method followed by stabilization and carbonization processes. Nowadays, electrospinning has become a suitable method in manufacturing continuous NFs, thus it is employed to fabricate NFs in this study. The microstructural properties and adsorption competencies of the produced NFs were also studied. The NFs were prepared by electrospinning the polymer solution of Polyacrylonitrile (PAN) and Manganese Dioxide (MnO2) in, N, N-Dimethylformamide (DMF) solvent. The factors considered in this study were various polymer PAN/MnO2 concentrations which will significantly affect the specific surface area, fiber morphology and the diameter of the NFs prepared. Subsequently, heat treatment is applied by setting up the stabilization temperature at 275 oC and carbonization temperature at 800 oC with constant dwelling time (30 min). Nitrogen gas at constant rate 0.2 L/min was used for stabilization and carbonization with the stabilization rate (2 oC/min) and carbonization rate (5 oC/min). The CNFs produced were characterized using Scanning Electron Microscopy (SEM), Brunauer Emmett and Teller (BET) surface area and Fourier Transmission Infrared Spectroscopy (FTIR). It was found that the PAN/MnO2 CNFs were successfully produced with the carbonization temperature of 800 oC. The prepared PAN/MnO2 CNFs prepared showed an enhanced in specific surface area about two times compared to it precursor NFs.