Flux Removal Research Articles

Phenol Removal by Novel Choline Chloride Blended Cellulose Acetate-Fly Ash Composite Membrane

A novel composite membrane (CM) was prepared by coating choline chloride (ChCl) blended cellulose acetate (CA) on fly-ash based ceramic substrate for phenol removal. Different amount (0-1 g) of ChCl was blended with CA to synthesize various CMs. Amount of ChCl in CA increases the contact angle, average pore radius, permeability of CM from 55.15° to 71.55°, 1.6 to 6.83 nm and 0.0057 to 0.0152 L·m−2·h−1·kPa−1, respectively. Phenol rejection increased from 56 to 93 % while increasing ChCl amount in CA. Phenol removal decreased from 94.26-64.23 % and 91.09-78.62 % with increase in applied pressure (69-483 kPa) and feed concentration (50-200 mg·L−1). However, removal rate increased from 80.46-92.47 % with increase in pH 2-12. Among all CMs, CC5 is identified as best CM with maximum phenol removal efficiency (92.7 %) and flux (1.86 L·m−2·h−1) at 207 kPa applied pressure and 100 mg·L−1 of feed phenol concentration. The obtained results reveal that blending of 0.9 % ChCl with CA can significantly enhances the phenol removal efficiency and this could be used as potential CM for treatment of phenol bearing wastewater.

Dissolved oxygen has no inhibition on methane oxidation coupled to selenate reduction in a membrane biofilm reactor

Methane oxidation coupled to selenate reduction has been suggested as a promising technology to bio-remediate selenium contaminated environments. However, the effect of dissolved oxygen (DO) on this process remained unclear. Here, we investigate the feasibility of selenate removal at two distinct DO concentrations. A membrane biofilm reactor (MBfR) was initially fed with ∼5 mg Se/L and then lowered to ∼1 mg Se/L of selenate, under anoxic condition containing ∼0.2 mg/L of influent DO. Selenate removal reached approximately 90% without selenite accumulation after one-month operation. Then 6–7 mg/L of DO was introduced and showed no apparent effect on selenate reduction in the subsequent operation. Electron microscopy suggested elevated oxygen exposure did not affect microbial shapes. 16S rDNA sequencing showed the aerobic methanotroph Methylocystis increased, while possible selenate reducers, Ignavibacterium and Bradyrhizobium, maintained stable after oxygen boost. Gene analysis indicated that nitrate/nitrite reductases positively correlated with selenate removal flux and were not remarkably affected by oxygen addition. Reversely, enzymes related with aerobic methane oxidation were obviously improved. This study provides a potential technology for selenate removal from oxygenated environments in a methane-based MBfR.

Investigations of the effect of pore size of ceramic membranes on the pilot-scale removal of oil from oil-water emulsion

Oil-water emulsions are one of the most serious pollutants because of the large quantities produced by various industries, such as the petrochemical, oil and gas industries. One of the major methods to remove oil from wastewater is filtration using ceramic tubular microfiltration membranes. However, such membranes are vulnerable to fouling, which causes operational impairment. The aims of this work are to study the influence of membrane pore size on permeate flux and oil removal efficiency at different operating parameters and the reduction in fouling when used in combination with hybrid Coagulation/sand filter-MF pre-treatment process. The droplet size of the oil-water emulsion has an interaction with the pore size of the ceramic membrane. Therefore, each pore size may be optimal, depending upon the concentration of oil in the emulsion, and hence droplet size. Steady-state flux and oil removal efficiency were found to b highest for hybrid coagulation/sand filter –MF due to a reduction of membrane fouling by reducing the oil concentration in the inlet emulsion to the ceramic membrane.

Giant Protostellar Flares: Accretion-driven Accumulation and Reconnection-driven Ejection of Magnetic Flux in Protostars

Abstract Protostellar flares are rapid magnetic energy release events associated with the formation of hot plasma in protostars. In the previous models of protostellar flares, the interaction between a protostellar magnetosphere with the surrounding disk plays crucial role in building-up and releasing the magnetic energy. However, it remains unclear if protostars indeed have magnetospheres because vigorous disk accretion and strong disk magnetic fields in the protostellar phase may destroy the magnetosphere. Considering this possibility, we investigate the energy accumulation and release processes in the absence of a magnetosphere using a three-dimensional magnetohydrodynamic simulation. Our simulation reveals that protostellar flares are repeatedly produced even in such a case. Unlike in the magnetospheric models, the protostar accumulates magnetic energy by acquiring large-scale magnetic fields from the disk by accretion. Protostellar flares occur when a portion of the large-scale magnetic fields are removed from the protostar as a result of magnetic reconnection. Protostellar flares in the simulation are consistent with observations; the released magnetic energy (up to ∼3 × 1038 erg) is large enough to drive observed flares, and the flares produce hot ejecta. The expelled magnetic fields enhance accretion, and the energy build-up and release processes are repeated as a result. The magnetic flux removal via reconnection leads to redistribution of magnetic fields in the inner disk. We therefore consider that protostellar flares will play an important role in the evolution of the disk magnetic fields in the vicinity of protostars.

Enhanced Water Flux by Fabrication of Polysulfone/Alumina Nanocomposite Membrane for Copper(II) Removal

In the current study, polysulfone (PSF) membranes incorporated with nano alumina (Al2O3) were synthesized by a phase inversion method to improve the efficiency of the PSF membrane for wastewater treatment. Dimethylformamide was used as solvent while polyvinylpyrrolidone was used as a pore former. Different concentrations of nanoparticles of Al2O3 were used in the casting solution to get an optimum condition for the highest water flux. Cross section morphology of the membranes was investigated through scanning electron microscope. Membranes were characterized by pure water flux, permeability, hydrophilicity, porosity, and retention of Cu(II). All the mixed matrix nanocomposite membranes showed higher water flux than the nascent PSF membrane due to their increased porosity and hydrophilicity with the addition of nano alumina. Cu(II) rejection was also enriched by composite membranes due to a high number of adsorption sites on membranes surface as a result of better hydrophilicity and dispersion of nano alumina. The membrane with 0.1 wt% nano Al2O3showed the best performance in terms of water flux (32.60 L·m-2·h-1) and significant Cu(II) removal (61.95%) compared to other membranes after continuous treatment of 150 min. The reusability test of the PAl0.1 membrane confirmed the durability of the composite membranes after several cycles using ethylenediaminetetraacetic acid as a regenerator.

Effect of Activated Alkanolamine for CO2 Absorption using Hollow Fiber Membrane Contactor

Hollow Fiber Membrane Contactor (HFMC) technology has been widely developed as an alternative technology to separate CO2 gas. HFMC technology combines gas absorption process with absorbent and membrane technology. Membrane contactor technology has advantages than conventional technology such as larger gas-liquid contact area, smaller equipment, modularity, and gas-liquid flow rates adjusted independently. In this research, the CO2 absorption experiments was conducted for absorption process at 30°C temperature and various gas flow rate from 200 - 600 mL/min, feed gas of CO2 20%vol. flowed into shell side and the absorbents flowed in tube side of membrane contactor. Piperazine (PZ) and monosodium glutamate (MSG) as activators with 1%w/w concentration, added into methyldiethanolamine (MDEA) 30% w/w solution to form aqueous solutions of activated MDEA. The membrane material used in this experiment was hydrophobic polypropylene membrane. The effect of liquid flow rate and various activators used to get CO2 absorption flux and CO2 removal in HFMC. The results showed that the best of CO2 absorption process using activated alkanolamine was MDEA-PZ, where the highest flux value was 5.5x10−4 mole/m2.s and CO2 removal reached 96.9% at a gas flow rate of 600mL/min.

Trends and resource recovery in biological wastewater treatment system

Nutrient removal from wastewater is an essential task to protect natural water resource and its excess results in eutrophication. Faster resource depletion and environmental sustainability paves the way for wastewater treatment and resource recovery and bioelectrochemical systems (BES) were employed to attain the goal. The first generation, BES, microbial fuel cell (MFC), microbial electrochemical cell (MEC) and microbial desalination cells (MDC) were getting really good with wastewaters. However, to achieve improved performance, BESs with membrane systems (OsMFC and FO-OMBR) and combination systems (MFC-MEC; MEDCC) were introduced. This review pointed out that high strength wastewaters can enhance nutrient recovery and electricity generation. This review aims to explore the recovered sources in various states of matter as solid, liquid, gas and energy. Moreover, limiting factors for resource recovery such as membrane fouling, reverse solute flux, internal resistance, substrate type and COD removal efficiency are highlighted. Finally, future research prospects have been discussed.

Chromium removal and water recycling from electroplating wastewater through direct osmosis: Modeling and optimization by response surface methodology

Background: Considering the carcinogenic effects of heavy metals, such as chromium, it is essential to remove these elements from water and wastewater. Direct osmosis is a new membrane technology, which can be a proper alternative to conventional chromium removal processes. Methods: The wastewater samples were collected from an electroplating unit, located in Alborz industrial city, Qazvin, Iran. Magnesium chloride was used as the draw solution, and a semipermeable membrane (Aquaporin) was used in this study. The experiments were designed, using response surface methodology (RSM) and central composite design (CCD) with draw solution concentration (0.5- 1.5 M), feed solution concentration (4-12 mg/L), and experiment time (30-90 minutes) as variable factors. The chromium concentration and water flux were also measured, based on atomic absorption spectrophotometry and water flux equation, respectively. Results: Direct osmosis was highly efficient in chromium removal and water recycling. Water flux and chromium removal efficiency were 15.6 LMH and 85.58%, respectively, under optimal conditions (draw solution = 1.27 mol/L, feed solution = 4 mg/L, and experiment time = 90 min). In terms of validity, the results predicted by the quadratic polynomial model were in good agreement with the responses reported in the laboratory. Conclusion: In direct osmosis, the use of magnesium chloride as the draw solution resulted in the acceptable chromium removal from electroplating wastewater. Using this method, chromium concentration in wastewater reduced to a level lower than the discharge standards, established by Iran’s Department of Environment.

Data-driven modeling of phosphorus (P) dynamics in low-P stormwater wetlands

The ability to simulate wetland phosphorus (P) concentration dynamics in the low-P domain (<20 μg/L of total P) has been poor. This paper develops a new model algorithm to describe P removal in Stormwater Treatment Areas (STAs) for Everglades restoration. It includes a performance review of previous low-P models. Analysis of inflow-outflow pulse responses at daily and monthly time steps in the STAs revealed surprisingly counterintuitive dynamics (lowest outflow concentrations occurring during highest flow events). Analysis of internal P concentration and flux data (from within STAs) informed new flow-dependent P removal and zero-order return flux formulations. The resulting parsimonious model is based directly on these two core equations. Calibration and testing are presented, using four independent datasets (6–36 month duration) including outflow P time series and internal water treatment profiles. This data-driven approach significantly improved dynamic simulations (R2 = 0.4–0.7) and identified the determinant role of internal P loading in low-P wetlands.

Antiwettability enhancement of PVDF-HFP membrane via superhydrophobic modification by SiO2 nanoparticles

Pore wetting is undesirable in the membrane gas–liquid separation process as it deteriorates the gas removal flux. To alleviate the affinity of a membrane surface toward a liquid solvent, its hydrophobicity needs to be enhanced. In this study, a superhydrophobic polyvinylidene fluoride-co-hexafluoropropylene membrane was synthesized via a simple and facile nonsolvent-induced phase inversion process. Hydrophobic nano-SiO2 particles were used as solvent additives to improve the wetting resistance of the membrane. The results revealed that blended nano-SiO2 membranes exhibited enhanced surface hydrophobicity in terms of water contact angle. Such improvement was attributed to the enhancement of surface roughness via the formation of hierarchical multilevel protrusions. Besides, the embedment of nanoparticles in polymer spherulitic globules also contributed to the reduction in surface energy of the membrane. As a result, the blended nano-SiO2 membrane achieved superhydrophobicity with a water contact angle of up to 151°.

Preparation of adsorptive nanoporous membrane using powder activated carbon: Isotherm and thermodynamic studies

Adsorptive polyethesulfone (PES) membranes were prepared by intercalation of powder activated carbon (PAC) with and without functionalization. Accordingly, PAC was aminated with 1,5-diamino-2-methylpentane, and the physicochemical properties of the functionalized PAC were analyzed. Intercalation of PAC within the PES scaffold changed the porosity and mean pore size of the aminated membrane (AC-NH2) from 52.6% to 92.5% and from 22.6 nm to 3.5 nm, respectively. The effect of temperature on the performance of the modified membranes was monitored by the flux and chemical oxygen demand (COD) removal of leachate. At ambient temperature, the COD removal of the neat, AC-containing, and AC-NH2 membranes was 47%, 52%, and 58.5%, respectively. A similar increment was obtained for the membrane flux, which was due to the synergistic effect of the high porosity and large number of hydrophilic functional groups. The experimental leachate adsorption data were analyzed by Langmuir, Freundlich, and Dubinin-Radushkevich isotherm models. For all membranes, the significant thermodynamic parameters (ΔH, ΔS, and ΔG) were calculated and compared. The isosteric heat of adsorption was lower than 80 kJ∙mol–1, indicating that the interaction between the membranes and the leachate is mainly physical, involving weak van der Waals forces.

Performance of Ultrafiltration–Ozone Combined System for Produced Water Treatment

Oil exploration waste, also called produced water, contains hazardous pollutants, such as benzene; benzene, toluene, and xylene (BTX); naphthalene, phenanthrene, and dibenzothiophene (NDP); polyaromatic hydrocarbons (PAHs); and phenol. Produced water is characterized by high chemical oxygen demand (COD) and oil content, which exceed the standard limits of regulation. In this study, the combination of ultrafiltration (UF) and ozone pre-treatment and post-treatment were applied for treatment of produced water to minimize its environmental impact. Produced water and membrane were characterized, and their ultrafiltration performance for removal of oil content, benzene, toluene, xylene, and COD. Two commercial Polyethersulfone membranes, with molecular-weight cut-off values of 10 and 20 kDa, were used. The membrane flux profile illustrated that ozone pre-treatment had higher normalized flux than UF only. Separation performance was evaluated based on flux profile and removal of COD, oil and grease content, toluene, and xylene. Significant finding was found where the combination of UF with ozone pre-treatment and post-treatment could significantly eliminate COD, oil content, toluene, and xylene. The rejection of these components was found higher than conventional process, which was in the range of 80 % to 99 %. In addition, almost oil and grease can be removed by using this combined system. Permeate quality of this system confirmed the acceptable level as water discharge.

Development of tungsten armored high heat flux plasma facing components for ITER like divertor application

The dome and reflector plate are the parts of divertor plasma facing components (PFCs) of ITER tokamak which are mainly aimed for the removal of heat load of maximum 5 MW/m2 in steady state condition. The dome is a curved tungsten armoured component and the reflector plate is a straight component. These components have multi-layered joints made of various materials such as tungsten (W), OFHC copper (Cu), copper alloy (CuCrZr) and stainless steel (SS316LN). Joining of such multi-layered joints is known to be problematic due to joining of several dissimilar materials. In this paper, we report the indigenous development of medium size dome and reflector plate via vacuum brazing route for ITER like tokamak application. In order to evaluate the performance of the dome against ITER-like scenarios (maximum heat flux removal of 5MW/m2), the dome has been successfully tested for 1000 number of steady-state thermal cycles at incident heat fluxes of 3.87 MW/m2 in the High Heat Flux Test Facility (HHFTF) at IPR. Subsequent testing of additional 200 thermal cycles was also done at incident heat flux of 6 MW/m2. During the High heat flux (HHF) tests, surface temperature of W tiles reached 640oC and the beam power was restricted at 6MW/m2 to limit the temperature below 450oC at the CuCrZr heat sink. Total 1200 steady-state thermal cycles have been completed. At 6 MW/m2, the absorbed heat flux was 4 MW/m2. Engineering analysis on the HHFT of the dome has been performed using Finite element method (FEM) and Computational Fluid Dynamics (CFD) to simulate and to correlate with the experimental data. Ultrasonic immersion technique – Non destructive testing (NDT) was used to inspect the brazed joint quality of the dome before and after the HHFT. The results of the experimental details, engineering analysis and methodology adopted to fabricate the medium size dome and reflector plate are presented here.

Integrated simple ceramic filter and waste stabilization pond for domestic wastewater treatment

Abstract A laboratory scale study was undertaken to investigate the applicability of a simple ceramic filter (SCF) when integrated into a Waste Stabilization Pond (WSP) system and was operated under different experimental conditions. The SCF was made of locally available materials: 80% soil and 20% rice bran on weight basis. Scanning electron microscope with energy-dispersive X-ray spectrometry (SEM/EDS) analysis indicated mainly the presence of C, O, Si, Fe and Al. The SCF was submerged in rectangular pond reactors made of glass sheets. Synthetic wastewater was fed continuously into the reactors that contained algae (mainly Scenedesmus) mixed liquor; effluent through the integrated filter was collected using a suction pump. Filtration efficiency, organic removal performance, flux and HRT effects, organic loading rate optimization and SCF maintenance were investigated through different experimental conditions. High organic removal was achieved due to efficient filtration performance. Nitrogen removal was critically dependent on organic carbon availability. A linear relationship between flux, HRT, BOD loads and clogging frequency was obtained. Reversible fouling of SCF was observed during the experiment and simple physical cleaning was found effective for its maintenance. In general, the results of this study indicated that the low cost SCF can be integrated with WSP for treating domestic wastewater, after identifying optimum hydraulic loadings and associated size and shape.

Droplet-Based Microfluidic Thermal Management Methods for High Performance Electronic Devices

Advanced thermal management methods have been the key issues for the rapid development of the electronic industry following Moore’s law. Droplet-based microfluidic cooling technologies are considered as promising solutions to conquer the major challenges of high heat flux removal and nonuniform temperature distribution in confined spaces for high performance electronic devices. In this paper, we review the state-of-the-art droplet-based microfluidic cooling methods in the literature, including the basic theory of electrocapillarity, cooling applications of continuous electrowetting (CEW), electrowetting (EW) and electrowetting-on-dielectric (EWOD), and jumping droplet microfluidic liquid handling methods. The droplet-based microfluidic cooling methods have shown an attractive capability of microscale liquid manipulation and a relatively high heat flux removal for hot spots. Recommendations are made for further research to develop advanced liquid coolant materials and the optimization of system operation parameters.

Incorporation of UiO-66-NH2 MOF into the PAN/chitosan nanofibers for adsorption and membrane filtration of Pb(II), Cd(II) and Cr(VI) ions from aqueous solutions.

In the present study, the UiO-66-NH2 MOF synthesized by microwave heating method was incorporated into the PAN/chitosan nanofibers for the removal of Pb(II), Cd(II) and Cr(VI) ions through the adsorption and membrane filtration processes. The synthesized MOFs and nanofibers were characterized using XRD, BET, FTIR, SEM, and DSC analysis. The effect of UiO-66-NH2 MOF content (0-15 wt.%), pH (2-7), contact time(5-90 min), metal ions initial concentration (20-1000 mg/L) and temperature (25-45 °C) was studied on the metal ions adsorption using PAN/chitosan/UiO-66-NH2 nanofibrous adsorbent. The kinetic, isotherm and thermodynamic parameters were evaluated to understand the metal ions adsorption mechanism using nanofibers. The Pseudo-second-order kinetic and Redlich-Peterson isotherm model were well described the experimental sorption data. In the heavy metal ions membrane filtration process, the different parameters such as MOF concentration (2-15 wt.%), membrane thickness (10-70 μm), metal ions concentration (5-50 mg/L), temperature (25-45 °C) and filtration time (1-24 h) were investigated on the performance of PVDF/ PAN/chitosan/UiO-66-NH2 nanofibrous membrane toward metal ions removal. The high water flux and high metal ions removal within 18 h filtration time showed the high potential of PVDF/ PAN/chitosan/UiO-66-NH2 membrane for the removal of metal ions from aqueous solutions.

Effects of plant diversity on carbon dioxide emissions and carbon removal in laboratory-scale constructed wetland.

Previous studies have shown that plant diversity can enhance methane (CH4) emission and nitrogen purification efficiency in constructed wetlands (CWs), but effect of plant diversity on carbon dioxide (CO2) flux and carbon removal efficiency in CWs is unknown. Therefore, we established four plant diversity levels (each level containing 4, 3, 2, and 1 species, respectively) in laboratory-scale wetland microcosms fed with simulated wastewater. Results showed that plant species richness enhanced CO2 emissions (84.7-124.7mg CO2 m-2h-1, P < 0.01), carbon fixation rate (P < 0.05), and microbial biomass carbon (P < 0.001), but did not improve carbon removal (P > 0.05). The presence of Pontederia cordata increased CO2 emissions, carbon fixation rate of belowground, and microbial biomass carbon (P < 0.05), whereas the presence of Phragmites australis only enhanced CO2 emission (P < 0.05). However, the presence of Typha orientalis or Lythrum salicaria did not show an influence on CO2 emissions and carbon removal (P > 0.05). Hence, our study highlights the importance of plant diversity in mediating CO2 emission intensity and carbon processes but not carbon removal in CWs.

Fluorosilaned-TiO2/PVDF Membrane Distillation with Improved Wetting Resistance for Water Recovery from High Solid Loading Wastewater

Membrane distillation (MD) has emerged as an important technology for applications in industries such as seawater desalination and wastewater treatment due to its low energy requirement and theoretically low fouling propensity. However, the main obstacle to obtain high separating efciency in MD lies on the availability of porous hydrophobic membrane that can withstand pore wetting and membrane fouling. In this work, a dual coagulation bath method was introduced to alter the membrane morphology by increasing its porosity, surface roughness as well as polymer crystallinity. To increase the membrane hydrophobicity, membrane roughness was induced by adding TiO2 nanoparticles. However, this has brought concomitant impacts by lowering its porosity due to the pore blocking and reducing hydrophobicity due to the presence of hydroxyl group on TiO2 surface. Introduction of silanized TiO2 modifed at pH 7 gave higher contact angle (131.7±4) that could withstand the pore wetting and at the same time maintained its high permeation flux (12kg/m2.h) and excellent nutrient removal efciency of 99.65%. Consistent flux around 6 kg/m2.h for Paper Mill Sequence Batch Reactor (PMSE) could be achieved showing that the membrane wetting and fouling resistance towards solids were good. The system efciency was around 55% which was comparable to the pure water treatment process (50%). However, the membrane was not suitable to be used for treatment of the oil-rich Palm Oil Mill Efuent (POME) as the flux dropped from 6 to 2 kg/m2.h after 7 hours of operation with thermal efciency dropped to 26% due to fouling phenomena.

Two-phase cooling system with controlled pulsations

One of the promising ways of removing large heat fluxes from the surface of heat-stressed elements of electronic devices is the use of evaporating thin layer of liquid film, moving under the action of the gas flow in a flat channel. In this work, a prototype of evaporative cooling system for high heat flux removal with forced circulation of liquid and gas coolants with controlled pulsation, capable to remove heat flux of up to 1,5 kW/cm2 and higher was presented. For the first time the regime with controlled pulsation is used. Due to pulsations, it is possible to achieve high values of critical heat flux due to a brief increase in the flow rate of the liquid, which allows to "wash off" large dry spots and prevent the occurrence of zones of flow and drying.

Effects of multiple-nozzle distribution on large-scale spray cooling via numerical investigation

Spray cooling has been widely employed in many applications due to its high flux removal ability. A previous study has been conducted to reveal the large-scale spray cooling performance of an industrial used single nozzle. Continuously, influence of multiple-nozzle distribution has also been numerically investigated in present work. The mean heat flux and its standard deviation and uniformity are used to qualify the cooling performance. A flat wall with 1.6 m in length and 1.0 m in width has been taken as the research object. Effects of nozzle number, distance and offset have been parametrically compared. It is found that increasing nozzle number could promote mean heat flux, improve the uniformity of cooling patterns and enhance heat transfer performance. A best nozzle number of 10 could be obtained by an equation fitting. Decreasing nozzle distance turns out to be detrimental to heat transfer. The reason comes from the collisions and interactions of two too adjacent nozzles. Based on choices in real practice, two types of arrays i. e. perpendicular and skew array have been discussed and compared. It is concluded that the skew array could obtain higher heat flux with more uniform distribution.