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Produced water (PW) is a by-product of oil and gas extraction, of which it is deemed as the primary contributor of wastewater stream in oil production. Conventional treatment such as membrane separation is favoured due to its sustainability and cost effectiveness. On the other hand, oceanic litters such as abandoned fishing nets endangered the marine life ecosystem, despite of its potential to be raw material for fabrication of nanofiber membrane (NFM). This study explores the potential usage of electrospun nylon 6,6 waste NFM for treatment of real PW. In terms of modelling, it is found that feed concentration is the dominant factor with R2 of 0.94 for permeate concentration response and 0.91 for average flux response. Moreover, the optimized system with average flux of 216.5 L/m 2 h with low specific power consumption of ca. 0.09 kWh/m 3 is proven to be economically feasible with less than 5% error from predicted model. As for technoeconomic analysis, it is found that permeate flux plays the major role in controlling total capital cost (CAPEX) and operating cost (OPEX) of the system. The lowest total CAPEX and OPEX to achieve 10 ppm of permeate concentration, also was found to be RM 3.7 M and RM/year 1660, hence proving the economic feasibility of the proposed system.

Textile industry, one of the largest exporting industries in Malaysia, generates azo dyes wastewater which cannot be easily decomposed biologically due to its high stability and xenobiotic nature. Conventional electrocoagulation (EC) system requires high energy consumption, resulting in higher operating cost while membrane system suffers from fouling. To eliminate these drawbacks, an integrated electrocoagulation - membrane (ECM) system has been proposed as one of the emerging methods for treating dye wastewater. However, feasibility analysis of the proposed system is yet to be conducted. This study proposes a statistical technique to evaluate the techno-economic feasibility of the system via John's Macintosh Project (JMP) software. From JMP, an equation represents the whole model had been obtained for each of the system, EC standalone and ECM system. The models have been validated experimentally it is proven all the models can reach dye removal efficiency of 96%. Overall, the total cost for ECM system (1 V and 1.0 g of NaCl) was 40.44% cheaper than the conventional dye treatment method with total cost of 1.079 million MYR. EC standalone system at 1 V and 1.0 g however were found to be more economically feasible with 0.325 million MYR or 82.07% cheaper compared to conventional photocatalytic method. EC standalone system was also more economical than ECM system due to lower capital cost expended for installation of membrane tank and additional membrane purchase., (Copyright © 2022. Published by Elsevier Ltd.)

Membrane fouling deteriorates membrane filtration performances. Hence, mitigating membrane fouling is the key factor in sustaining the membrane process, particularly when treating fouling-prone feed, such as oil/water emulsions. The use of spacers has been expanded in the membrane module system, including for membrane fouling control. This study proposed a rotating spacer system to ameliorate membrane fouling issues when treating an oil/water emulsion. The system's effectiveness was assessed by investigating the effect of rotating speed and membrane-to-disk gap on the hydraulic performance and the energy input and through computational fluid dynamics (CFD) simulation. The results showed that the newly developed rotary spacer system was effective and energy-efficient for fouling control. The CFD simulation results proved that the spacer rotations induced secondary flow near the membrane surface and imposed shear rate and lift force to exert fouling control. Increasing the rotation speed to an average linear velocity of 0.44 m/s increased the permeability from 126.8 ± 2.1 to 175.5 ± 2.7 Lm -2 h -1 bar -1 . The system showed better performance at a lower spacer-to-membrane gap, in which increasing the gap from 0.5 to 2.0 cm lowered the permeability from 175.5 ± 2.7 to 126.7 ± 2.0 Lm -2 h -1 bar -1 . Interestingly, the rotary system showed a low energy input of 1.08 to 4.08 × 10 -3 kWhm -3 permeate when run at linear velocities of 0.27 to 0.44 ms -1 . Overall, the findings suggest the competitiveness of the rotary spacer system as a method for membrane fouling control.

Nanostructure adsorbents namely nanofibers have been demonstrated to have a high adsorption rate and are efficient to treat wastewater. Herein, chitosan/poly(vinyl alcohol) (PVA) blend nanofiber membranes prepared by electrospinning method were crosslinked using glutaraldehyde and functionalized with 1-allyl-3-methylimidazolium chloride to be used as a potential bio-sorbent for heavy metal ions removal. The chitosan was first hydrolyzed before electrospinning with PVA, followed by crosslinking and further functionalized by ionic liquid to overcome the limitation of chitosan which has low adsorption capacity and unsuitable physical properties for the adsorption process. The morphology and the chemical bond formed were investigated by using field emission scanning electron microscopy with energy dispersive x-ray spectroscopy (FESEM-EDX) and Fourier transform infrared (FTIR) showing that the hydrolyzed chitosan/PVA nanofiber membranes were successfully crosslinked and functionalized. The synthesized adsorbent was evaluated in pure heavy metal ions solutions namely Pb(II), Mn(II), and Cu(II) and shown best performance for Pb(II) ions. The highest adsorption capacity recorded for Pb(II) ions was 166.34 mg/g and are well fitted to the Freundlich isotherm model and pseudo-second-order kinetic model to describe the adsorption equilibrium and kinetic rate of the Pb(II) uptake, respectively. The synthesized adsorbent clearly shows a great capability to remove Pb(II) ions., (Copyright © 2021 Elsevier B.V. All rights reserved.)

This study focuses on the effect of modified silica fillers by [EMIN][Tf 2 N] via physical adsorption on the CO 2 separation performance of a mixed matrix membrane (MMM). The IL-modified silica was successfully synthesized as the presence of fluorine element was observed in both Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectrometer (XPS) analyses. The prepared MMMs with different loadings of the IL-modified silica were then compared with an unmodified silica counterpart and neat membrane. The morphology of IL-modified MMMs was observed to have insignificant changes, while polymer chains of were found to be slightly more flexible compared to their counterpart. At 2 bar of operating pressure, a significant increase in performance was observed with the incorporation of 3 wt% Sil-IL fillers compared to that of pure polycarbonate (PC). The permeability increased from 353 to 1151 Barrer while the CO 2 /CH 4 selectivity increased from 20 to 76. The aforementioned increment also exceeded the Robeson upper bound. This indicates that the incorporation of fillers surface-modified with ionic liquid in an organic membrane is worth exploring for CO 2 separation.

Malaysia is one of the countries that is well known for its palm oil based products and exports all over the world. Over the years, palm oil mill has been rising at alarming rate in Malaysia, causing palm oil-based wastes to increase especially palm oil mill effluent (POME). POME in Malaysia are channelled into water bodies such as rivers after treated mostly with conventional biological method. However, with current technologies and knowledge, conventional POME treatments are seen to be outdated and require major improvements as greenhouse gaseous are emitted to the environment as well as being less cost effective. Integrated systems that combine two or more conventional methods are introduced and reviewed to provide insights on the advantages and disadvantages of the system if it is to be implemented in real life plant. Integrated systems that focus on combining conventional methods are compiled and reviewed specifically for POME treatment. Among the integrated methods that are reviewed includes biological with membrane, adsorption with magnetic field exposure, adsorption with membrane and electrocoagulation with membrane. The systems are seen to give excellent color, chemical oxygen demand (COD) and total suspended solids (TSS) removal with average of higher than 90%. Reduction in space utilization, improved treatment time as well as simplified operating system were reported when integrated systems are applied as compared to conventional treatment of POME., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

The textile industry provides for the needs of people especially in apparel and household items. The industry also discharges dye-containing wastewater that is typically challenging to treat. Despite the application of the biological and chemical treatments for the treatment of textile wastewater, these methods have their own drawbacks such as non-environment friendly, high cost and energy intensive. This research investigates the efficiency of the celestine blue dye removal from simulated textile wastewater by electrocoagulation (EC) method using iron (Fe) electrodes through an electrolytic cell, integrated with nylon 6,6 nanofiber (NF) membrane filtration for the separation of the flocculants from aqueous water. Based on the results, the integrated system achieves a high dye removal efficiency of 79.4%, by using 1000 ppm of sodium chloride as the electrolyte and 2 V of voltage at a constant pH of 7 and 10 ppm celestine blue dye solution, compared to the standalone EC method in which only 43.2% removal was achieved. Atomic absorption spectroscopy analysis was used to identify the traces of iron in the residual EC solution confirming the absence of iron. The EC-integrated membrane system thus shows superior performance compared to the conventional method whereby an additional 10-30% of dye was removed at 1 V and 2 V using similar energy consumptions.

This paper reports the fabrication of polyethersulfone membranes via in situ hydrogen peroxide-assisted polymerization of dopamine. The dopamine and hydrogen peroxide were introduced into the dope solution where the polymerization occurred, resulting in a single-step additive formation during membrane fabrication. The effectivity of modification was evaluated through characterizations of the resulting membranes in terms of chemical functional groups, surface morphology, porosity, contact angle, mechanical strength and filtration of humic acid solution. The results confirm that the polydopamine was formed during the dope solution mixing through peroxide-assisted polymerization as proven by the appearance of peaks associated OH and NH groups in the resulting membranes. The presence of polydopamine residual in the membrane matric enhances the pore properties in terms of size and porosity (by a factor of 10), and by lowering the hydrophilicity (from 69° to 53°) which leads to enhanced filtration flux of up to 217 L/m 2 h. The presence of the residual polydopamine also enhances membrane surface hydrophilicity which improve the antifouling properties as shown from the flux recovery ratio of > 80%.

A petroleum refinery heavily depends on crude oil as its main feedstock to produce liquid fuels and chemicals. In the long term, this unyielding dependency is threatened by the depletion of the crude oil reserve. However, in the short term, its price highly fluctuates due to various factors, such as regional and global security instability causing additional complexity on refinery production planning. The petroleum refining industries are also drawing criticism and pressure due to their direct and indirect impacts on the environment. The exhaust gas emission of automobiles apart from the industrial and power plant emission has been viewed as the cause of global warming. In this sense, there is a need for a feasible, sustainable, and environmentally friendly generation process of fuels and chemicals. The attention turns to the utilization of biomass as a potential feedstock to produce substitutes for petroleum-derived fuels and building blocks for biochemicals. Biomass is abundant and currently is still low in utilization. The biorefinery, a facility to convert biomass into biofuels and biochemicals, is still lacking in competitiveness to a petroleum refinery. An attractive solution that addresses both is by the integration of bio- and petroleum refineries. In this context, the right decision making in the process selection and technologies can lower the investment and operational costs and assure optimum yield. Process optimization based on mathematical programming has been extensively used to conduct techno-economic and sustainability analysis for bio-, petroleum, and the integration of both refineries. This paper provides insights into the context of crude oil and biomass as potential refinery feedstocks. The current optimization status of either bio- or petroleum refineries and their integration is reviewed with the focus on the methods to solve the multi-objective optimization problems. Internal and external uncertain parameters are important aspects in process optimization. The nature of these uncertain parameters and their representation methods in process optimization are also discussed.

The competitiveness of algae as biofuel feedstock leads to the growth of membrane filtration as one of promising technologies for algae harvesting. Nanofiber membrane (NFM) was found to be efficient for microalgae harvesting via membrane filtration, but it is highly limited by its weak mechanical strength. The main objective of this study is to enhance the applicability of nylon 6,6 NFM for microalgae filtration by optimizing the operational parameters and applying solvent vapor treatment to improve its mechanical strength. The relaxation period and filtration cycle could be optimized to improve the hydraulic performance. For a cycle of 5 min., relaxation period of ≤2 min shows the highest steady-state permeability of 365 ± 14.14 L m -2 h -1 bar -1 , while for 10 min cycle, 3 min. of relaxation period was found optimum that yields permeability of 402 ± 34.47 L m -2 h -1 bar -1 . The treated nylon 6,6 NFM was also used to study the effect of aeration rate. It is confirmed that the aeration rate enhances the steady-state performance for both intermittent and continuous mode of aeration. Remarkably, intermittent aeration shows 7% better permeability than the full aeration for all tested condition, which is beneficial for reducing the total energy consumption., Competing Interests: The authors declare no conflict of interest.

In this study, a series of TiO 2 nanotubes (NTs) were synthesized employing electrochemical anodization of titanium foil in an ionic liquid solution containing a mixture of glycerol and choline chloride, acting as electrolyte. The as-synthesized TiO 2 NTs were calcined at 350, 450, or 550 °C for a 2 h duration to investigate the influence of calcination temperature on NTs formation, morphology, surface properties, crystallinity, and subsequent photocatalytic activity for visible light photodegradation of gaseous formaldehyde (HCHO). Results showed that the calcination temperature has a significant effect on the structure and coverage of TiO 2 NTs on the surface. Freshly synthesized TiO 2 NTs showed better-ordered structure compared to calcined samples. There was significant pore rupture with increasing calcination temperature. The transformation from anatase to rutile phase appeared after calcination at 450 °C and the weight fraction of the rutile phase increased from 19% to 36% upon increasing the calcination temperature to 550 °C. The band gaps of the TiO 2 NTs were in the range from 2.80 to 2.74 eV, shifting the active region of the materials to visible light. The presence of mixed anatase-rutile TiO 2 phases in the sample calcined at 450 °C showed enhanced photoactivity, which was confirmed by the 21.56 mg∙L -1 ∙g -1 removal of gaseous formaldehyde under 120 min of visible light irradiation and displayed enhanced quantum yield, ∅ HCHO of 17%.

Electrospun nanofiber membrane (NFM) has a high potential to be applied as a filter for produced water treatment due to its highly porous structure and great permeability. However, it faces fouling issues and has low mechanical properties, which reduces the performance and lifespan of the membrane. NFM has a low integrity and the fine mat easily detaches from the sheet. In this study, nylon 6,6 was selected as the polymer since it offers great hydrophilicity. In order to increase mechanical strength and separation performance of NFM, solvent vapor treatment was implemented where the vapor induces the fusion of fibers. The fabricated nylon 6,6 NFMs were treated with different exposure times of formic acid vapor. Results show that solvent vapor treatment helps to induce the fusion of overlapping fibers. The optimum exposure time for solvent vapor is 5 h to offer full retention of dispersed oil (100% of oil rejection), has 62% higher in tensile strength (1950 MPa) compared to untreated nylon 6,6 NFM (738 MPa), and has the final permeability closest to the untreated nylon 6,6 NFM (733 L/m 2 .h.bar). It also took more time to get fouled (220 min) compared to untreated NFM (160 min).

Phthalates are endocrine disruptors frequently occurring in the general and industrial environment and in many industrial products. Moreover, they are also suspected of being carcinogenic, teratogenic, and mutagenic, and they show diverse toxicity profiles depending on their structures. The European Union and the United States Environmental Protection Agency (US EPA) have included many phthalates in the list of priority substances with potential endocrine-disrupting action. They are: dimethyl phthalate (DMP), diethyl phthalate (DEP), dibutyl phthalate (DBP), butylbenzyl phthalate (BBP), diethylhexyl phthalate (DEHP), di-iso-nonyl phthalate (DINP), di-iso-decyl phthalate (DIDP), di-n-decyl phthalate (DnDP), and dioctyl phthalate (DOP). There is an ever-increasing demand for new analytical methods suitable for monitoring different phthalates in various environmental, biological, and other matrices. Separation and spectrometric methods are most frequently used. However, modern electroanalytical methods can also play a useful role in this field because of their high sensitivity, reasonable selectivity, easy automation, and miniaturization, and especially low investment and running costs, which makes them suitable for large-scale monitoring. Therefore, this review outlines possibilities and limitations of various analytical methods for determination of endocrine-disruptor phthalate esters in various matrices, including somewhat neglected electroanalytical methods.