Synthesis of PES membranes modified with polyurethane-paraffin wax nanocapsules and performance of bovine serum albumin and humic acid rejection.

Membrane fouling is a serious handicap of membrane-based separation, as it reduces permeation flux and hence increases operational and maintenance expenses. Polyurethane-paraffin wax (PU/PW) nanocapsules were integrated into the polyethersulfone membrane to manufacture a composite membrane with higher antifouling and permeability performance against humic acid (HA) and bovine serum albumin (BSA) foulants. All manufactured membranes were characterized by scanning electron microscopy (SEM), scanning electron microscopy-energy dispersive spectrometry (SEM-EDS), and contact angle. The contact angle of the pristine polyethersulfone (PES) membrane was measured 73.40 ± 1.32. With the embedding of nanocapsules, the contact angle decreased to 64.55 ± 1.23 for PES/PU/PW 2.0 wt%, and the pure water flux of all composite membranes increased when compared to pristine PES. The pristine PES membrane also has shown the lowest steady-state fluxes at 45.84 and 46.59 L/m2h for BSA and HA, respectively. With the increase of PU/PW nanocapsule ratio from 0.5 to 1.0 wt%, steady-state fluxes increased from 51.96 to 71.61 and from 67.87 to 98.73 L/m2h, respectively, for BSA and HA. The results depicted that BSA and HA rejection efficiencies of PU/PW nanocapsules blended PES membranes increased when compared to pristine PES membranes.

Antifouling and antibacterial performance evaluation of polyethersulfone membranes modified with AZ63 alloy.

Antibacterial membranes have attracted researchers' interest in recent years as a possible approach for dealing with biofouling on the membrane surface. This research aims to see if blending AZ63 Mg alloy into a polyethersulphone (PES) membrane can improve antifouling and separation properties. The composite membranes' pure water flux continued to increase from pristine PES to PES/AZ63 2.00 wt%. The results showed that PES/AZ63 2.00 wt% membrane supplied the highest permeate flux of E. coli. The steady-state fluxes of AZ63 composite membranes were 113.24, 104.38 and 44.79 L/m2h for PES/AZ63 2.00 wt%, 1.00 wt%, and 0.50 wt%, respectively. The enhanced biological activity of AZ63 was studied based on antioxidant activity, DNA cleavage, antimicrobial, anti-biofilm, bacterial viability inhibition and photodynamic antimicrobial therapy studies. The maximum DPPH scavenging activity was determined as 81.25% with AZ63. AZ63 indicated good chemical nuclease activity and also showed moderate antimicrobial activity against studied strains. The highest biofilm inhibition of AZ63 was 83.25% and 71.63% towards P. aeruginosa and S. aureus, respectively. The cell viability inhibition activity of AZ63 was found as 96.34% against E. coli. The photodynamic antimicrobial therapy results displayed that AZ63 demonstrated 100% bacterial inhibition when using E. coli.

Antimicrobial and antioxidant activity of phenolic extracts from walnut (Juglans regia L.) green husk by using pressure-driven membrane process.

In this study, antioxidant (DPPH and metal chelating), DNA cleavage, biofilm, and antimicrobial properties of extracted phenol from the walnut green husk (WGH) and its different concentrate and permeate samples were evaluated. For maximum phenolic compound extraction from the WGH first, the effects of solvent type (deionized water, methanol, n-hexane, acetone, and ethanol), solvent temperature (25-75 °C), and extraction time (0.5-24 h) were optimized. Then to concentrate phenolic compounds a pressure-driven membrane process was used with four different membrane types. The phenol contents of the concentrate samples were found to be microfiltration (MF) concentrate 4400 mg/L, ultrafiltration (UF) concentrate 4175 mg/L, nanofiltration (NF) concentrate 8155 mg/L, and reverse osmosis (RO) concentrate 8100 mg/L. LC-MSMS was used to determine the quantification of phenolic compounds in permeate and concentrate streams. In addition, all of the concentrate samples with high phenol content showed a high antioxidant activity as 100% with MF concentrate, UF concentrate, NF concentrated and RO concentrated. Likewise, concentrate samples were found to have very high antibiofilm activity as 82.86% for NF concentrate againts S. aureus, 85.80% for NF concentrate against P. aureginosa, 80.95% for RO concentrate against S. aureus, and 83.61% for RO-concentrate against P. aureginosa. When the antimicrobial activity of the extracted phenol from WGH and its different concentrate and permeate samples were evaluated by micro dilution and disk diffusion methods, it was found that the ability of the concentrate samples to inhibit bacterial growth was much higher than permeate ones. In addition, extracted phenol from WGH and its different concentrate and permeate samples showed significant DNA nuclease activity. Supplementary Information: The online version contains supplementary material available at 10.1007/s13197-022-05588-w.

Investigation of diode laser effect on the inactivation of selected Gram-negative bacteria, Gram-positive bacteria and yeast and its disinfection on wastewater and natural milk.

Disinfection can be accomplished by adding external chemical agents to kill harmful microorganisms or by removing them using membranes. However, most chemicals are toxic for humans and animals if it is consumed above a certain concentration. Likewise, membranes have fouling problems. The aim of this study is to investigate the effect of diode laser, which is an environmentally friendly application, on pathogenic microorganisms such as Escherichia coli (ATCC 10536), Staphylococcus aureus (ATCC 6538) and Candida albicans. To reveal the effect of diode laser on aforementioned, various parameters have been studied on how diode laser type, laser irradiation time, laser power density, laser penetration efficiency and biofilm inhibition affect microorganisms. As a result of the study, it was observed that the blue laser was more effective than red and green lasers, and the inhibition rates for 15 min at 0.36 W/cm2 laser power density were 65.9% > 34.52% > 43.63% for S. aureus, E. coli and C. albicans, respectively. After 30 min of blue laser irradiation, the microbial growth inhibitions were found as 85.39%, 41.18% and 54.55% for S. aureus, E. coli and C. albicans, respectively. The highest biofilm inhibition was 94.61% when S. aureus cells were exposed to blue laser irradiation for 60 min. The microbial growth kinetics on three microorganisms were tested by using at 0.54 W/cm2 laser power density for 28 h, and there were not observed any microbial development in microbial cultures. Moreover, blue laser irradiation was successfully disinfected wastewater and natural milk at 0.54 W/cm2 laser power density.

Investigation of two different size microplastic degradation ability of thermophilic bacteria using polyethylene polymers.

There are several studies stating that many types of microplastics cannot be retained completely by conventional wastewater treatment systems. Therefore, it is necessary to prevent the discharge of these microplastics to the ecological system. The objective of this study was to investigate the biodegradation ability of two different size of PE (50 and 150 µm) by using two Gram-positive, spore-forming, rod-shaped, and motile thermophilic bacteria, called strain Gecek4 and strain ST5, which can hydrolyse starch, were isolated from the soil's samples of Gecek and Ömer hot-springs in Afyonkarahisar, Turkey, respectively. Phenotypic features and 16S rRNA analyzing of strains also studied. According to these results, Gecek4s and ST5 were identified as Anoxybacillus flavithermus Gecek4s and Bacillus firmus ST5, respectively. Results showed that A. flavithermus Gecek4s could colonise the polymer surface and cause surface damage whereas B. firmus ST5 could not degrade bigger-sized particles efficiently. In addition, morphological changes on microplastic surface were investigated by scanning electron microscopy (SEM) where dimensional changes, irregularities, crack, and/or holes were detected. This finding suggests that there is a high potential to develop an effective integrated method for plastic bags degradation by extracellular enzymes from bacteria.

A hybrid process for leachate wastewater treatment: Evaporation and reverse osmosis/sequencing batch reactor.

In this study, a hybrid process for leachate wastewater treatment including evaporation and reverse osmosis (RO) membrane or biological treatment systems was suggested. Experiments were performed on a real landfill leachate wastewater. The leachate was subjected to evaporation; as a result, a distillate was obtained containing less organic matter and less substantial amounts of other pollutants, as ammonium salts and total phenols were removed. Tests were carried out at different evaporation temperatures and times. The initial leachate pH was adjusted and optimized. For optimum conditions, each of chemical oxygen demand (COD), total phenol, and ammonium salt concentrations were reduced to 99.99%, 95.00%, and 83.00%, respectively. The distillate of the first stage of the proposed process was then exposed to RO membrane system, as a first study, under different transmembrane pressure of 20, 30, and 40 bar and at different pH values of 7, 8, and 9. As a second suggested treatment system, the distillate was subjected to a biological treatment process for 30 days as a retention time, pH = 6, and room temperature 25°C ± 1°C. At the end of the research study, a comparison was conducted between results obtained with RO membrane separation and biological treatment system as two distinct treatment systems proposed for leachate landfill wastewater treatment. Although both systems were effective for landfill leachate wastewater treatment, however, with the RO membrane separation system, COD removal efficiency reached 99.99%. In the other hand, with biological treatment process, COD elimination was as much as 90.00%. Certainly, evaporation and RO are not novel ways of landfill leachate treatment; however, few studies have attempted to use similar combined system for landfill leachate wastewater treatment and attained effective results of treated water. PRACTITIONER POINTS: A hybrid process of evaporation and RO membrane or biological treatment systems was suggested for leachate wastewater treatment. For optimum conditions, COD, total phenols, and ammonium salt reductions were achieved to 99.99%, 95%, and 83%, respectively, after the first evaporation stage. The distillate of the first stage of the proposed process was then exposed to RO membrane system and biological treatment system. Different transmembrane pressure and different pH values were optimized for RO.

The effect of pre-treatment methods on membrane flux, COD, and total phenol removal efficiencies for membrane treatment of pistachio wastewater.

In this study, the effect of pre-treatment methods was investigated for membrane treatment of pistachio processing wastewater (PPW). Chemical coagulation, electrocoagulation, and electrooxidation processes were tested as the pretreatment methods to understand the effect of pretreatment on membrane performance. Alum (Al2(SO4)3·18H2O), iron (III) chloride (FeCl3·6H2O) and iron(II) sulfate (Fe(SO4)·7H2O) were used as coagulant and anionic polyelectrolyte was used as flocculant. Al-Al and Fe-Fe electrode pairs were used in the electrocoagulation experiments while platinum (Pt), boron doped diamond (BDD), and graphite were used in the electrooxidation experiments. UP150, NF270, and NF90 were used as the membranes. Chemical oxygen demand (COD) and total phenol removal efficiencies from wastewater were determined by considering membrane flux. For chemical coagulation experiments, the highest COD removal efficiency was determined as 44.9% for Al2(SO4)3.18H2O at 1000 mg/L when the wastewater pH value was 8.0. However, the highest total phenol removal efficiencies were obtined as 62.5% at 4000 mg/L for FeCl3.6H2O at pH 8. For electrocoagulation experiments, the highest COD and total phenol removal efficiencies were determined as 63.9% at pH 4.0 and 74.2% at pH 7.0, respectively, for 100 A/m2 current density when aluminum electrode pairs were used. For electrooxidation experiments, the highest COD and total phenol removal efficiencies were determined as 61.2% at pH 4.0 and 83.1% at pH 10, respectively, for 200 A/m2 current density when BDD-Pt electrode pairs were used. Raw PPW and pre-treated PPW with chemical coagulation, electrocoagulation, and electrooxidation processes were progressively further treated with ultrafiltration (UP150) and nanofiltration (NF270, NF90) membranes to improve COD and total phenol removal efficiencies. The results showed that the permeate of NF90 membrane supplied the highest COD (96.0%) and total phenol removal (97.5%) efficiencies for the raw wastewater. However, COD and total phenol removal efficiencies were determined as 98.6% and 100% for electrocoagulation + NF90, 97.9% and 100% for electrooxidation + NF90, 96.6% and 100% for chemical coagulation + NF90, respectively. The steady-state fluxes for NF90 membranes were 2.9, 7.0, and 8.6 L/m2h after chemical coagulation, electrooxidation, and electrocoagulation, respectively. The results depicted that electrocoagulation and electrooxidation were the most suitable pre-treatment methods for water recovery using NF90 membrane.

Preparation of composite polyethersulfone membrane containing basalt powder and optimization of the parameters using response surface methodology.

In this study, environmental-friendly composite polyethersulfone (PES) membranes based on basalt powder were prepared by phase inversion method. The effects of polymer percentage, the basalt percentage, and the thickness of the membrane were investigated on the distilled water flux, compaction factor, bovine serum albumin (BSA) rejection, contact angle, fouling factor and the parameters were modelled by response surface methodology (RSM). The distilled water flux increased when the basalt was added to the membrane up to 6% percentage of the polymer amount. The blending of basalt also provided resistance against the membrane compaction. The BSA rejection experiments approved the positive effects of basalt on the rejections efficiencies. At higher basalt percentages, the rejection efficiencies increased from 78% at the raw membrane to 99% for the composite membranes had 10% basalt. The adding of basalt to the membranes decreased the contact angles. The hydrophilicity of the membranes contained basalt in their structures was higher than those which had not basalt. By comparison with the neat membranes and the basalt added membrane, it can be said that the basalt increased the flux recovery and decreased the irreversible fouling factors. The basalt increased the antifouling properties for the composite membranes. Finally, the prepared membranes were characterized by scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX).

Effects of hydrogen peroxide, temperature and treatment time on degradation properties of polyethersulfone ultrafiltration membrane.

Oxidative cleaning agents such as hydrogen peroxide (H2O2) and sodium hypochlorite (NaClO) used in water and wastewater treatment play an important role in the degradation and rapid aging of the polymeric membranes. In addition, when the temperature is above the maximum operating range of the membrane, it negatively affects the membrane performance. H2O2, which is also known as a green and environmentally friendly strong oxidant because of releasing only water as a by-product, can provide good cleaning efficiency under temperature, but its influence on membrane aging is not fully understood. In this study, the aging of polyethersulfone (PES) ultrafiltration (UF) membrane using H2O2 under high-temperature conditions and degradation of the polymeric membrane were systematically investigated using response surface methodology (RSM). The effects of H2O2 concentration, temperature, and treatment time were tested on membrane flux, contact angle, pore size, and porosity for decomposed membrane. The results showed that normalized permeability was significantly changed approximately 2.34-folds by H2O2 concentration at an exposure dose of 5 mM and 373 K temperature. Moreover, the largest pore sizes as 161.23 nm and 160.73 nm were obtained at the conditions of 2.5 mM H2O2 concentration and 373 K temperature. The lowest contact angle (54.76°) and porosity (61.88%) were obtained at the same conditions. The results depicted that H2O2 can be used for membrane cleaning with minimum membrane degradation at moderate conditions.

Investigation of the usage potential of calcium alginate beads functionalized with sodium dodecyl sulfate for wastewater treatment contaminated with waste motor oil.

In this study, calcium alginate (Ca-Alg) beads, an inexpensive, easily available, biodegradable material, were activated with anionic surfactant and used for the treatment of wastewater contaminated with waste motor oil. First, polyethyleneimine (PEI) was used to bind sodium dodecyl sulfate (SDS) onto the Ca-Alg beads' surface. Three different SDS concentrations (25, 50, & 100 mg/L) were prepared and treated with Ca-Alg beads for 1, 2, 4, 6, and 24 h. SDS binding yield reached equilibrium at the end of the 24 h, and the binding efficiencies of 25, 50, and 100 mg SDS/L were determined 84%, 72%, and 48%, respectively. The effect of pH between 2 and 10 was also investigated on oil adsorption. Maximum adsorption efficiency (77%) was obtained in the range of pH 6-8. After determining the optimum pH value for oil adsorption, the effect of beads amount (2.5-30 g/L) was also investigated on oil removal efficiency. When the amount of beads increased from 2.5 to 30 g/L, the oil adsorption efficiency increased from 77% to 95%. It was also observed that the oil adsorption efficiency increased when the size of the beads decreased from 4 to 1 mm. For the kinetic calculation, three different concentrations (250, 500, &1000 mg/L) of oily solution were prepared, and oil adsorption was investigated versus time. The kinetic studies for the adsorption of the oily solution using SDS functionalized Ca-Alg beads showed the second-order kinetics. When the initial oil concentration increased from 250 to 1000 mg/L, the amount of adsorbed oil molecules increased from 8.34 to 22.12 mg/g. Langmuir and Freundlich isotherm models were used to explain the relationship between adsorbent and adsorbate, and Langmuir isotherm was the most suitable model because of its high regression coefficient (r2 ) value. Column studies were also carried out, and it was concluded that the proposed adsorbent can be used effectively in the treatment of oily wastewater. PRACTITIONER POINTS: Although there are numerous adsorption studies and studies on the use of alginate beads in various fields in the literature, its use in oil treatment has not been found to our knowledge. The study aims to produce a selective adsorbent for the removal of oil from water by functionalizing the surface of the alginate beads with active agents. In conventional adsorption studies, pollutants are transported from liquid phase to solid phase. With the proposed new adsorbent material, oils will be specifically removed from wastewater and used as fuel. Thus, obtaining an organic origin adsorbent with high calorific value constitutes the original value of the study. In addition, no secondary pollutants will emerge after the adsorption process.

Investigation of the antifouling properties of polyethersulfone ultrafiltration membranes by blending of boron nitride quantum dots.

This study aims to investigate the modification of polyethersulfone (PES) membrane with boron nitride quantum dots (BNQD) for improving the antifouling performance. The composite membranes were synthesized by blending different amounts of BNQD (0.50, 1.00, and 2.00 wt.%) into PES with the non-solvent induced phase separation (NIPS) method. UV-vis absorption, X-ray diffraction (XRD), and transmission electron microscopy (TEM) were used to characterize BNQD. Moreover, porosity, pore size, contact angle, permeability, bovine serum albumin (BSA) rejection, and antifouling properties were determined for composite membranes. The enhanced biological activity of BNQD was investigated based on antioxidant, antimicrobial, anti-biofilm, bacterial viability inhibition, and DNA cleavage studies. The BNQD showed 19.35 % DPPH radical scavenging activity and 76.45 % ferrous ion chelating activity at 500 mg/L. They also exhibited good chemical nuclease activity at all concentrations. BNQD had moderate antibacterial activity against all tested microorganisms. Biofilm inhibition percentage of BNQD was determined as 82.31 % at 500 mg/L. Cell viability assay demonstrated that the BNQD showed strong cell viability inhibition 99.9 % at the concentration of 1000 mg/L. The porosity increased from 56.83 ± 1.17%-61.83 ± 1.17 % while BNQD concentration increased from 0 to 2.00 wt%. Moreover, the hydrophilicity of BNQD nanocomposite membranes also increased from 75.42 ± 0.56° to 65.34 ± 0.25°. The mean pore radius is far slightly changed from 16.47 ± 0.35 nm to 19.16 ± 0.22 nm. The water flux increased from 133.5 ± 9.5 L/m2/h (for pristine membrane) to 388.6 ± 18.8 L/m2/h (for PES/BNQD 2.00 wt% membrane). BSA flux increased from 38.8 ± 0.9 L/m2/h to 63.2 ± 2.7 L/m2/h up to 1.00 wt% amount of BNQD nanoparticles.

Green synthesis of Quercus coccifera hydrochar in subcritical water medium and evaluation of its adsorption performance for BR18 dye.

In this study, we investigated the production conditions of Quercus coccifera hydrochar, which is an inexpensive and easy available adsorbent, for the adsorption of Basic Red 18 (BR18) azo dye. The hydrochar was produced in the eco-friendly subcritical water medium (SWM). The effects of the pH (2-10), adsorbent size (45-106 µm), adsorbent dose (0.5-1.5 g/L), dye concentration (40-455 mg/L), and contact time (5-120 min) were studied via optimization experiments. The optimum conditions were pH 10, particle size of 45 µm, particle amount of 1.5 g/L, dye concentration of 455 mg/L, and 60 min. The removal efficiency increased sharply for the first 5 min; after that the removal efficiency reached a steady state at 60 min, with a maximum removal of 88.7%. The kinetic studies for the adsorption of BR18 dye in aqueous solution using hydrochar showed pseudo-second-order kinetics. The Langmuir and Freundlich isotherm models were used to explain the relationship between adsorbent and adsorbate, and Freundlich isotherm was the most suitable model because of its high regression coefficient (R2) value. The intraparticle diffusion model was used to determine the adsorption mechanism of BR18 onto Q. coccifera acorn hydrochar. Desorption studies were also carried out using different types of acid and different molarities.

Electrocoagulation and electrooxidation pre-treatment effect on fungal treatment of pistachio processing wastewater.

The effect of electrochemical pre-treatment on fungal treatment of pistachio processing wastewater (PPW) was investigated. Electrocoagulation (EC) and electrooxidation (EO) were used as electrochemical pre-treatment step before fungal treatment of PPW. Aluminum (Al/Al), iron (Fe/Fe), and stainless steel (SS/SS) electrode pairs were selected as anode/cathode for EC whereas boron doped diamond (BDD/SS) was preferred as anode/cathode electrode pairs for EO experiments in this study. The impact of current density (50-300 A/m2) and operating time (0-240 min) were tested for chemical oxygen demand (COD) and total phenol removal. After pre-treatment of PPW, four different fungus species (Coriolus versicolor, Funalia trogii, Aspergillus carbonarius, and Penicillium glabrum) were tested for further treatment. Penicillium glabrum supplied maximum COD and total phenol removal efficiency compared to other fungus strains. The combined electrochemical-assisted fungal treatment process supplied 90.1% COD and 88.7% total phenol removal efficiency when supported with EO pre-treatment. Pre-treatment of PPW with EO method provided better results than EC method for fungal treatment. Operating cost of the combined process was calculated as 6.12 US$/m3. The results indicated that the proposed combined process supplied higher pollutant removal compared to the individual electrocoagulation, electrooxidation, and fungal treatment process.

The adsorption and Fenton behavior of iron rich Terra Rosa soil for removal of aqueous anthraquinone dye solutions: kinetic and thermodynamic studies.

Adsorption and advanced oxidation processes are being extensively used for treatment of wastewater containing dye chemicals. In this study, the adsorption and Fenton behavior of iron rich Terra Rosa soil was investigated for the treatment of aqueous anthraquinone dye (Reactive Blue 19 (RB19)) solutions. The impact of pH, initial dye concentration, soil loading rate, contact time and temperature was systematically investigated for adsorption process. A maximum removal efficiency of dye (86.6%) was obtained at pH 2, soil loading of 10 g/L, initial dye concentration of 25 mg/L, and contact time of 120 min. Pseudo-first-order, pseudo-second-order, Elovich, and Weber-Morris kinetic models were applied to describe the adsorption mechanism and sorption kinetic followed a pseudo-second-order kinetic model. Moreover, Langmuir, Freundlich and Temkin isotherm models were used to investigate the isothermal mechanism and equilibrium data were well represented by the Langmuir equation. The maximum adsorption capacity of soil was found as 4.11 mg/g using Langmuir adsorption isotherm. The effect of soil loading and hydrogen peroxide (H2O2) dosage was solely tested for Fenton oxidation process. The highest removal efficiency of dye (89.4%) was obtained at pH 2, H2O2 dosage of 10 mM, soil loading of 5 g/L, initial dye concentration of 50 mg/L, and contact time of 60 min. Thermodynamic studies showed that when the adsorption dosage of dye was 25 mg/L at 293-313 K, adsorption enthalpy (ΔH) and entropy (ΔS) were negative and adsorption free energy (ΔG) was positive. This result indicated that the adsorption was exothermic. Morphological characteristics of the soil were evaluated by X-ray fluorescence (XRF), scanning electron microscopy (SEM), and attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy before and after the adsorption and oxidation process.

Synthesis and performance of antifouling and self-cleaning polyethersulfone/graphene oxide composite membrane functionalized with photoactive semiconductor catalyst.

This study was performed to synthesize membranes of polyethersulfone (PES) blended with graphene oxide (GO) and PES blended with GO functionalized with photoactive semiconductor catalyst (TiO2 and ZnO). The antifouling and self-cleaning properties of composite membranes were also investigated. The GO was prepared from natural graphite powder by oxidation method at low temperature. TiO2 and ZnO nanopowders were synthesized by anhydrous sol-gel method. The surface of TiO2 and ZnO nanopowders was modified by a surfactant (myristic acid) to obtain a homogeneously dispersed mixture in a solvent, and then GO was functionalized by loading with these metal oxide nanopowders. The PES membranes blended with GO and functionalized GO into the casting solution were prepared via phase inversion method and tested for their antifouling as well as self-cleaning properties. The composite membranes were synthesized as 14%wt. of PES polymer with three different concentrations (0.5, 1.0, and 2.0%wt.) of GO, GO-TiO2, and GO-ZnO. The functionalization of membranes improved hydrophilicity property of membranes as compared to neat PES membrane. However, the lowest flux was obtained by functionalized membranes with GO-TiO2. The results showed that functionalized membranes demonstrated better self-cleaning property than neat PES membrane. Moreover, the flux recovery rate of functionalized membranes over five cycles was higher than that of neat membrane.

Electrocoagulation and nanofiltration integrated process application in purification of bilge water using response surface methodology.

Marine pollution has been considered an increasing problem because of the increase in sea transportation day by day. Therefore, a large volume of bilge water which contains petroleum, oil and hydrocarbons in high concentrations is generated from all types of ships. In this study, treatment of bilge water by electrocoagulation/electroflotation and nanofiltration integrated process is investigated as a function of voltage, time, and initial pH with aluminum electrode as both anode and cathode. Moreover, a commercial NF270 flat-sheet membrane was also used for further purification. Box-Behnken design combined with response surface methodology was used to study the response pattern and determine the optimum conditions for maximum chemical oxygen demand (COD) removal and minimum metal ion contents of bilge water. Three independent variables, namely voltage (5-15 V), initial pH (4.5-8.0) and time (30-90 min) were transformed to coded values. The COD removal percent, UV absorbance at 254 nm, pH value (after treatment), and concentration of metal ions (Ti, As, Cu, Cr, Zn, Sr, Mo) were obtained as responses. Analysis of variance results showed that all the models were significant except for Zn (P > 0.05), because the calculated F values for these models were less than the critical F value for the considered probability (P = 0.05). The obtained R(2) and Radj(2) values signified the correlation between the experimental data and predicted responses: except for the model of Zn concentration after treatment, the high R(2) values showed the goodness of fit of the model. While the increase in the applied voltage showed negative effects, the increases in time and pH showed a positive effect on COD removal efficiency; also the most effective linear term was found as time. A positive sign of the interactive coefficients of the voltage-time and pH-time systems indicated synergistic effect on COD removal efficiency, whereas interaction between voltage and pH showed an antagonistic effect.