Habis Al-zoubi - Academia.edu (original) (raw)

Papers by Habis Al-zoubi

Desalination and water treatment

Acid mine drainage (AMD) is recognized as one of the more critical environmental problems in the ... more Acid mine drainage (AMD) is recognized as one of the more critical environmental problems in the mining industry, with the potential of severe contamination of surface and groundwater, as well as soils. Different conventional methods are used to treat AMD such as lime neutralization, in which lime is added to AMD to raise pH and then precipitate the dissolved toxic heavy metals. In addition to a high concentration of sulphate, the sludge produced by this process has no economic value and has to be disposed of in large areas of land. Nanofiltration (NF) membranes are a new alternative method employed to treat AMD in this work. First, neutralization of AMD collected from the copper mine in Chile using both sodium hydroxide and lime will be investigated to find the optimum formed sludge. Then, three commercial NF membranes (NF99, DK, GE) have been used to filter AMD at two different pressures of 20 and 30 bar and at two different concentrations. The results showed that NF membranes suc...

Modern water desalination membranes are largely based on crosslinked polyamides chemistry, which ... more Modern water desalination membranes are largely based on crosslinked polyamides chemistry, which are susceptible to degradation by exposure to chlorine compounds, which are often necessary to act as a biocide to prevent fouling of the membranes. Sulfonated polysulfones show promising water/salt separation properties and significant resistance to degradation by chlorine compounds. These materials consist of randomly copolymerized charged and uncharged monomers, and these charge groups directly affect the salt and water transport and separation performance. One challenge of these materials is that they show reduced sodium chloride rejection when even relatively low amounts of divalent salts (such as calcium chloride or magnesium chloride) are added to the feed. This work investigates the effect of the chemistry and concentration of salts in the feed on different transport properties: water and salt permeability, water and salt partition coefficients, and water diffusivity. These prope...

Separation Science and Technology, 2005

Nanofiltration (NF) membranes have been employed in pre-treatment unit operations in both thermal... more Nanofiltration (NF) membranes have been employed in pre-treatment unit operations in both thermal and membrane seawater desalination processes. This has resulted in reduction of chemicals used in pretreatment processes as well as lowering the energy consumption and water production cost and, therefore, has led to a more environmentally friendly processes. In order to predict NF membrane performance, a systematic study on the filtration performance of selected commercial NF membranes against brackish water and seawater is required. In this study, three commercial nanofiltration membranes (NF90, NF270, N30F) have been used to treat highly concentrated different salts solutions (MgCl 2 , Na 2 CO 3 , and CaSO 4 ) at salinity level similar to that of brackish water and seawater. The main parameters studied in this paper are salt concentration and feed pressure. The experimental data were correlated and analysed using the Spiegler-Kedem model. In particular, the reflection coefficient (s) of all studied membranes and the solute permeability (P s ) have been determined for all membranes and at different salinity levels of studied salts. All the studied membranes fitted the model well for all investigated salts except the experimental data of MgCl 2 using N30F membrane, which did not fit well at low rejection. The results showed that NF90 produced a high rejection around 97% for all salts with medium permeate flux while NF270 gave a high flux with medium rejection and N30F gave low rejection and flux.

Separation Science and Technology, 2007

Page 1. Performance of Nanofiltration Membranes in the Treatment of Synthetic and Real Seawater N... more Page 1. Performance of Nanofiltration Membranes in the Treatment of Synthetic and Real Seawater Nidal Hilal and Habis Al-Zoubi Centre for Clean Water Technologies, School of Chemical, Environmental and Mining Engineering, The University of Nottingham, UK ...

Separation Science and Technology, 2010

Mine Water and the Environment, 2012

Korean Journal of Chemical Engineering, 2009

Recently, Nanofiltration (NF) membranes have been employed in pre-treatment unit operations in bo... more Recently, Nanofiltration (NF) membranes have been employed in pre-treatment unit operations in both thermal and membrane seawater desalination processes. This has resulted in reduction of chemicals used in pretreatment processes as well as lowering the energy consumption and water production cost and, therefore, has led to a more environmentally friendly processes. In order to predict NF membrane performance, a systematic study on the filtration performance of selected commercial NF membranes against brackish water and seawater is required. In this study, three commercial nanofiltration membranes (NF90, NF270, N30F) have been used to treat highly concentrated (NaCl) salt solutions up to 25,000 ppm, a salinity level similar to that of seawater. The membranes were firstly characterized using the Atomic Force Microscopy (AFM) technique. Pore size and pore size distribution obtained from AFM measurements were used to analyse both experimental data of pure water permeation and data obtained from salt rejection. The main parameters studied in this paper are feed pressure and salt concentration. The experimental data of this work was correlated and analysed using the Spigler-Kedem model. In particular, the reflection coefficient () of all studied membranes and the solute permeability of the salt (P s ) have been determined for all membranes and at all salinity levels studied. For a salinity of 5000 ppm and a pressure of 9 bars, the experimental results showed that NF90 could achieve a salt rejection up to 95%, whereas its rejection dropped to 41% at a salinity of 25,000 ppm and the same pressure. Rejection levels achieved by NF270 have been in range of 11-29%, while N30F gave the lowest rejection in the range of 3-6%.

Journal of Membrane Science, 2007

In this work, the Donnan-steric-pore-model-dielectric-exclusion (DSPM-DE) model was used to predi... more In this work, the Donnan-steric-pore-model-dielectric-exclusion (DSPM-DE) model was used to predict permeate fluxes and rejections of various single salts solutions in NF90 nanofiltration membrane. The salts used were NaCl, KCl, MgCl2, Na2SO4, Na2CO3, MgSO4 and CaSO4. The concentration of salts used in this study was generally higher than in previous reported studies. The concentrations were chosen to represent typical ions

Journal of the American Oil Chemists' Society, 1998

International Journal of Mineral Processing, 2012

The effluent ponds from phosphoric acid and fertilizer industries are a worldwide problem. Wastew... more The effluent ponds from phosphoric acid and fertilizer industries are a worldwide problem. Wastewater in these ponds contains high concentration of acids and heavy metals that seriously contaminates the environment and underground water. On the other hand, it contains valuable components such as phosphoric acid, fluorine and flousilicic acid. In this work, wastewater samples from effluent pond of the Indo Jordan Chemicals (IJC) plant were collected. These samples were characterized for their pH, and chemical composition. The pH of pond water was found to be about 0.8 due to its high content of HF, H 2 SiF 6 and H 3 PO 4 . Potentiometric titration, chloride and fluoride ion selective electrodes and other acid base titration methods were employed to determine the content of the above acids. AAS was also used to determine the content of heavy metals in this waste water. Potentiometric titration curves were produced to determine the optimum neutralization conditions for several synthetic mixtures made from the above acids, and for real effluent wastewater. XRD, XRF and SEM analyses were employed for analysis of the products of calcium hydroxide neutralizations. It was found that fluorine is present in effluent pond water in two forms: HF and H 2 SiF 6 . Precipitation experiments revealed that the reaction of H 2 SiF 6 with Ca(OH) 2 yielded only CaF 2 with no CaSiF 6 . Furthermore, it was found that it is possible to separate sulfate in an initial precipitation stage. Additionally, it is possible to remove almost all fluoride in the form of CaF 2 leaving at least 60% of H 3 PO 4 in water. Amorphous silica could be removed by aging the solution after fluoride removal.

Desalination and Water Treatment, 2009

A B S T R A C T The seeding crystallization of calcite and aragonite in seawater was evaluated th... more A B S T R A C T The seeding crystallization of calcite and aragonite in seawater was evaluated theoretically and experimentally. The level of supersaturation with respect to calcium carbonate, which is the driving force for the crystal growth, was found to be influenced by the pH value of seawater, the temperature and the seed morphology. It was proven

Desalination and Water Treatment, 2009

Wastewater produced from many industries such as dyeing, textile industry, minerals processing/ph... more Wastewater produced from many industries such as dyeing, textile industry, minerals processing/phosphate beneficiation, food processing and deinking is either reused after being treated by conventional treatment methods or pumped to drainage systems without treatment. This represents a serious environmental problem and causes challenges to the countries which face water shortages. A hybrid dissolved air flotation (DAF)-membrane process is a promised technology which can be used for treatment of many types of wastewater. Froth flotation is usually used to remove large proportion of suspended or dissolved solids while the membrane cell can reject very small particles. In this paper, a comprehensive review on the treatment of wastewater using DAF process alone as well as a hybrid flotation membrane was discussed. Various ways of hybrid flotation-membrane filtration such as flotation-microfiltration (MF), flotation-ultrafiltration (UF), flotation-nanofiltration (NF), and flotation-reverse osmosis (RO) are also addressed. The review showed that the hybrid flotation membrane system can achieve high separation performance with reasonable price compared with the traditional DAF or membrane-based filtration systems. This extends the use of this emerging technology to treat new types of wastewater or improving the existing technologies which reduce the effect of harmful effluents on the surrounding environment. Moreover, using flotation in combination with MF/UF has reduced membrane fouling and extended their useful working time. This leads to a reduction in operation cost and improves the efficiency of membrane performance. Hybrid flotation-NF/RO is a new technology for wastewater treatment which produces high quality water with greater recovery and lower energy and reagents consumption. Finally, the review also addressed the new application of DAF as pretreatment for the desalination processes.

Desalination, 1992

Atomic force microscopy (AFM) has been used to characterize five commercial nanofiltration (NF) m... more Atomic force microscopy (AFM) has been used to characterize five commercial nanofiltration (NF) membranes from three companies. High-resolution 3D images of the membranes were obtained without preparative treatment that may affect the membrane surface. Obtained images have been filtered to overcome the effect of tip convolution and the noises. Two sizes of the images were obtained 2 I~m x 2 gm and small sizes. The first images were used to find the surface morphology data such as average roughness, mean height, root mean square (RMS), and maximum peak-to-valley. The small size images showing visible pores were used to determine the pore size and pore size distributions, which were used to calculate porosity of membranes. A fitted line using lognormal distributions was used to represent the pore size distribution of the nanofiltration membranes. The results show that the Iognormal distribution is fitted well with AFM experimental data.

Desalination, 2007

This paper presents experimental data and modelling for three commercial nanofiltration membranes... more This paper presents experimental data and modelling for three commercial nanofiltration membranes (NF90, NF270, N30F) used to treat highly concentrated different salts solutions (KCl, Na 2 SO 4 , and MgSO 4 ) in a crossflow filtration set-up at a salinity level similar to that of seawater. The main parameters that have been studied in this work are feed pressure and salt concentration. The experimental data were correlated and analysed using artificial neural network (ANN) and Spiegler-Kedem model. Through the latter model, the reflection coefficient of all studied membranes and the solute permeability have been determined for all membranes at different salinity levels. The ANN's prediction of rejection vs. pressure and rejection vs. permeate flux for all investigated salt solutions is discussed. The results showed that both NF90 and NF270 produced a high rejection in the range of 95-99% at a pressure greater than 5 bar for Na 2 SO 4 , and MgSO 4 salts, while for KCl the rejection was in the range of 30-89%. N30F gave relatively medium rejection and flux for Na 2 SO 4 and MgSO 4 salts and very low rejection and flux for KCl. A good agreement has been obtained using the ANN predictions and the experimental data with a deviation not more than 5% for most of the cases considered. The ANN interpolative performance for the medium concentration H. Al-Zoubi et al. / Desalination 206 (2007) 42-60 43 levels (which were not represented in the training phase) is shown to be of lesser quality. A comparison between ANN model and Spiegler-Kedem model is also discussed.

Desalination, 2004

Nanofiltration membranes (NF) have applications in several areas. One of the main applications ha... more Nanofiltration membranes (NF) have applications in several areas. One of the main applications has been in water treatment for drinking water production as well as wastewater treatment. NF can either be used to treat all kinds of water including ground, surface, and wastewater or used as a pretreatment for desalination. The introduction of NF as a pretreatment is considered a breakthrough for the desalination process. NF membranes have been shown to be able to remove turbidity, microorganisms and hardness, as well as a fraction of the dissolved salts. This results in a significantly lower operating pressure and thus provides a much more energy-efficient process. Similar to other membrane processes, a major problem in NF membrane applications is fouling. Several studies have investigated the mechanisms of fouling in NF membranes and suggested methods to minimize and control the fouling of NF membranes. For NF membrane characterizations and process prediction, modeling of NF processes and the use of atomic force microscopy (AFM) are very important. The ability to predict the performance of NF processes will lead to a lower number of experiments, saving of time and money, and help to understand the separation mechanisms during NF. A comprehensive review of NF in water treatments is presented including a review of the applications of NF in treating water as well as in the pretreatment process for desalination; the mechanism as well as minimization of NF membrane fouling problems; and theories for modelling and transport of salt, charged and noncharged organic compounds in NF membranes. The review will also address the application of AFM in studying the morphology of membrane surfaces as part of the NF membrane characterization.

Desalination, 2005

Two microfiltration membranes made of polyvinilidene fluoride (PVDF) and polyethersulfone (PES) o... more Two microfiltration membranes made of polyvinilidene fluoride (PVDF) and polyethersulfone (PES) of the same nominal pore size have been modified by photo-initiated graft copolymerisation of quaternary salt of dimethylamino ethyl methacrylate (qDMAEM). Atomic force microscopy (AFM) has been used to characterise changes in surface morphology with variation of the degree of polymer grafting and therefore the process of modification. Comparative analysis of pore size distribution (PSD) of the initial and modified membranes has revealed differences in the modification process. Although polymer grafting resulted in PSD shifting towards smaller pore sizes, modification of PES membrane narrowed PSD, whereas modified PVDF showed wider PSD. This was attributed to different free-radical density for photo-reactive PES and more inert PVDF with possible contribution of the surface roughness.

Desalination, 2005

Recently, Nanofiltration (NF) membranes have been employed in pre-treatment unit operations in bo... more Recently, Nanofiltration (NF) membranes have been employed in pre-treatment unit operations in both thermal and membrane seawater desalination processes. This has resulted in reduction of chemicals used in pretreatment processes as well as lowering the energy consumption and water production cost and, therefore, has led to a more environmentally friendly processes. In order to predict NF membrane performance, a systematic study on the filtration performance of selected commercial NF membranes against brackish water and seawater is required. In this study, three commercial nanofiltration membranes (NF90, NF270, N30F) have been used to treat highly concentrated (NaCl) salt solutions up to 25,000 ppm, a salinity level similar to that of seawater. The membranes were firstly characterized using the Atomic Force Microscopy (AFM) technique. Pore size and pore size distribution obtained from AFM measurements were used to analyse both experimental data of pure water permeation and data obtained from salt rejection. The main parameters studied in this paper are feed pressure and salt concentration. The experimental data of this work was correlated and analysed using the Spigler-Kedem model. In particular, the reflection coefficient () of all studied membranes and the solute permeability of the salt (P s ) have been determined for all membranes and at all salinity levels studied. For a salinity of 5000 ppm and a pressure of 9 bars, the experimental results showed that NF90 could achieve a salt rejection up to 95%, whereas its rejection dropped to 41% at a salinity of 25,000 ppm and the same pressure. Rejection levels achieved by NF270 have been in range of 11-29%, while N30F gave the lowest rejection in the range of 3-6%.

Chemical Engineering Research and Design, 2007

Artificial neural network (ANN) simulation is used to predict the rejection of two salts (NaCl an... more Artificial neural network (ANN) simulation is used to predict the rejection of two salts (NaCl and MgCl 2 ) at typical seawater concentrations in a cross-flow nanofiltration membrane process. Rejections are predicted as a function of feed pressure and permeate flux with the salt concentration as a parameter. ANN predictions of the two salts' rejections are compared with experimental results obtained using three different nanofiltration membranes (NF90, NF270 and N30F) in a cross flow filtration set-up. The experimental program spans a concentration range of 5000 to 25 000 ppm for NaCl solution and of 5000 to 20 000 ppm for MgCl 2 solution at pressures covering the range of 2-9 bars. The effects of the training algorithm, neural network architectures and transfer function on the ANN performance, as reflected by the percentage average absolute deviation are discussed. A network with one hidden layer comprising four neurones is found to be adequate for mapping input -output relationships and providing a good interpolative tool. Algorithms based on the conjugate gradient, regularization and quasi-Newton principles were found to outperform those based on the gradient descent and variable momentum gradient descent. The former algorithms gave an average absolute percentage deviation up to 5% whereas deviations up to 20% are obtained from the latter algorithms. For most of the cases considered, the ANN proved to be an adequate interpolation tool, where an excellent prediction was obtained for some concentration levels not represented in the training data set. For very limited cases, the ANN predictive performance was poor. However, the network's performance in these extreme cases didn't improve even with increasing the data points in the training data set.

Chemical Engineering Journal, 2000

Jojoba oil extraction by pressing alone, pressing followed by leaching, and leaching alone were i... more Jojoba oil extraction by pressing alone, pressing followed by leaching, and leaching alone were investigated. The extraction process by first and second pressing followed by leaching gave about 50% by weight oil with reference to total seed, which is in agreement with what has been reported previously. The extraction by leaching process was carried out using different solvents. These solvents were; hexane, benzene, toluene, petroleum ether, chloroform, and isopropanol. Hexane, benzene, and petroleum ether gave the highest yield (all about 50% by weight oil with reference to total seed), but when cost is considered, petroleum ether is recommended as the best solvent to leach jojoba oil. The yield obtained in this work for leaching by hexane and benzene are 3-5% and about 10% for isopropanol more than those reported in the literature. Traces of solvent remained with the extracted oil after simple distillation followed by a second stage distillation via a Rotavapour apparatus. These traces slightly affected some of the oil properties such as pour point and flash point.

Desalination and water treatment

Acid mine drainage (AMD) is recognized as one of the more critical environmental problems in the ... more Acid mine drainage (AMD) is recognized as one of the more critical environmental problems in the mining industry, with the potential of severe contamination of surface and groundwater, as well as soils. Different conventional methods are used to treat AMD such as lime neutralization, in which lime is added to AMD to raise pH and then precipitate the dissolved toxic heavy metals. In addition to a high concentration of sulphate, the sludge produced by this process has no economic value and has to be disposed of in large areas of land. Nanofiltration (NF) membranes are a new alternative method employed to treat AMD in this work. First, neutralization of AMD collected from the copper mine in Chile using both sodium hydroxide and lime will be investigated to find the optimum formed sludge. Then, three commercial NF membranes (NF99, DK, GE) have been used to filter AMD at two different pressures of 20 and 30 bar and at two different concentrations. The results showed that NF membranes suc...

Modern water desalination membranes are largely based on crosslinked polyamides chemistry, which ... more Modern water desalination membranes are largely based on crosslinked polyamides chemistry, which are susceptible to degradation by exposure to chlorine compounds, which are often necessary to act as a biocide to prevent fouling of the membranes. Sulfonated polysulfones show promising water/salt separation properties and significant resistance to degradation by chlorine compounds. These materials consist of randomly copolymerized charged and uncharged monomers, and these charge groups directly affect the salt and water transport and separation performance. One challenge of these materials is that they show reduced sodium chloride rejection when even relatively low amounts of divalent salts (such as calcium chloride or magnesium chloride) are added to the feed. This work investigates the effect of the chemistry and concentration of salts in the feed on different transport properties: water and salt permeability, water and salt partition coefficients, and water diffusivity. These prope...

Separation Science and Technology, 2005

Nanofiltration (NF) membranes have been employed in pre-treatment unit operations in both thermal... more Nanofiltration (NF) membranes have been employed in pre-treatment unit operations in both thermal and membrane seawater desalination processes. This has resulted in reduction of chemicals used in pretreatment processes as well as lowering the energy consumption and water production cost and, therefore, has led to a more environmentally friendly processes. In order to predict NF membrane performance, a systematic study on the filtration performance of selected commercial NF membranes against brackish water and seawater is required. In this study, three commercial nanofiltration membranes (NF90, NF270, N30F) have been used to treat highly concentrated different salts solutions (MgCl 2 , Na 2 CO 3 , and CaSO 4 ) at salinity level similar to that of brackish water and seawater. The main parameters studied in this paper are salt concentration and feed pressure. The experimental data were correlated and analysed using the Spiegler-Kedem model. In particular, the reflection coefficient (s) of all studied membranes and the solute permeability (P s ) have been determined for all membranes and at different salinity levels of studied salts. All the studied membranes fitted the model well for all investigated salts except the experimental data of MgCl 2 using N30F membrane, which did not fit well at low rejection. The results showed that NF90 produced a high rejection around 97% for all salts with medium permeate flux while NF270 gave a high flux with medium rejection and N30F gave low rejection and flux.

Separation Science and Technology, 2007

Page 1. Performance of Nanofiltration Membranes in the Treatment of Synthetic and Real Seawater N... more Page 1. Performance of Nanofiltration Membranes in the Treatment of Synthetic and Real Seawater Nidal Hilal and Habis Al-Zoubi Centre for Clean Water Technologies, School of Chemical, Environmental and Mining Engineering, The University of Nottingham, UK ...

Separation Science and Technology, 2010

Mine Water and the Environment, 2012

Korean Journal of Chemical Engineering, 2009

Recently, Nanofiltration (NF) membranes have been employed in pre-treatment unit operations in bo... more Recently, Nanofiltration (NF) membranes have been employed in pre-treatment unit operations in both thermal and membrane seawater desalination processes. This has resulted in reduction of chemicals used in pretreatment processes as well as lowering the energy consumption and water production cost and, therefore, has led to a more environmentally friendly processes. In order to predict NF membrane performance, a systematic study on the filtration performance of selected commercial NF membranes against brackish water and seawater is required. In this study, three commercial nanofiltration membranes (NF90, NF270, N30F) have been used to treat highly concentrated (NaCl) salt solutions up to 25,000 ppm, a salinity level similar to that of seawater. The membranes were firstly characterized using the Atomic Force Microscopy (AFM) technique. Pore size and pore size distribution obtained from AFM measurements were used to analyse both experimental data of pure water permeation and data obtained from salt rejection. The main parameters studied in this paper are feed pressure and salt concentration. The experimental data of this work was correlated and analysed using the Spigler-Kedem model. In particular, the reflection coefficient () of all studied membranes and the solute permeability of the salt (P s ) have been determined for all membranes and at all salinity levels studied. For a salinity of 5000 ppm and a pressure of 9 bars, the experimental results showed that NF90 could achieve a salt rejection up to 95%, whereas its rejection dropped to 41% at a salinity of 25,000 ppm and the same pressure. Rejection levels achieved by NF270 have been in range of 11-29%, while N30F gave the lowest rejection in the range of 3-6%.

Journal of Membrane Science, 2007

In this work, the Donnan-steric-pore-model-dielectric-exclusion (DSPM-DE) model was used to predi... more In this work, the Donnan-steric-pore-model-dielectric-exclusion (DSPM-DE) model was used to predict permeate fluxes and rejections of various single salts solutions in NF90 nanofiltration membrane. The salts used were NaCl, KCl, MgCl2, Na2SO4, Na2CO3, MgSO4 and CaSO4. The concentration of salts used in this study was generally higher than in previous reported studies. The concentrations were chosen to represent typical ions

Journal of the American Oil Chemists' Society, 1998

International Journal of Mineral Processing, 2012

The effluent ponds from phosphoric acid and fertilizer industries are a worldwide problem. Wastew... more The effluent ponds from phosphoric acid and fertilizer industries are a worldwide problem. Wastewater in these ponds contains high concentration of acids and heavy metals that seriously contaminates the environment and underground water. On the other hand, it contains valuable components such as phosphoric acid, fluorine and flousilicic acid. In this work, wastewater samples from effluent pond of the Indo Jordan Chemicals (IJC) plant were collected. These samples were characterized for their pH, and chemical composition. The pH of pond water was found to be about 0.8 due to its high content of HF, H 2 SiF 6 and H 3 PO 4 . Potentiometric titration, chloride and fluoride ion selective electrodes and other acid base titration methods were employed to determine the content of the above acids. AAS was also used to determine the content of heavy metals in this waste water. Potentiometric titration curves were produced to determine the optimum neutralization conditions for several synthetic mixtures made from the above acids, and for real effluent wastewater. XRD, XRF and SEM analyses were employed for analysis of the products of calcium hydroxide neutralizations. It was found that fluorine is present in effluent pond water in two forms: HF and H 2 SiF 6 . Precipitation experiments revealed that the reaction of H 2 SiF 6 with Ca(OH) 2 yielded only CaF 2 with no CaSiF 6 . Furthermore, it was found that it is possible to separate sulfate in an initial precipitation stage. Additionally, it is possible to remove almost all fluoride in the form of CaF 2 leaving at least 60% of H 3 PO 4 in water. Amorphous silica could be removed by aging the solution after fluoride removal.

Desalination and Water Treatment, 2009

A B S T R A C T The seeding crystallization of calcite and aragonite in seawater was evaluated th... more A B S T R A C T The seeding crystallization of calcite and aragonite in seawater was evaluated theoretically and experimentally. The level of supersaturation with respect to calcium carbonate, which is the driving force for the crystal growth, was found to be influenced by the pH value of seawater, the temperature and the seed morphology. It was proven

Desalination and Water Treatment, 2009

Wastewater produced from many industries such as dyeing, textile industry, minerals processing/ph... more Wastewater produced from many industries such as dyeing, textile industry, minerals processing/phosphate beneficiation, food processing and deinking is either reused after being treated by conventional treatment methods or pumped to drainage systems without treatment. This represents a serious environmental problem and causes challenges to the countries which face water shortages. A hybrid dissolved air flotation (DAF)-membrane process is a promised technology which can be used for treatment of many types of wastewater. Froth flotation is usually used to remove large proportion of suspended or dissolved solids while the membrane cell can reject very small particles. In this paper, a comprehensive review on the treatment of wastewater using DAF process alone as well as a hybrid flotation membrane was discussed. Various ways of hybrid flotation-membrane filtration such as flotation-microfiltration (MF), flotation-ultrafiltration (UF), flotation-nanofiltration (NF), and flotation-reverse osmosis (RO) are also addressed. The review showed that the hybrid flotation membrane system can achieve high separation performance with reasonable price compared with the traditional DAF or membrane-based filtration systems. This extends the use of this emerging technology to treat new types of wastewater or improving the existing technologies which reduce the effect of harmful effluents on the surrounding environment. Moreover, using flotation in combination with MF/UF has reduced membrane fouling and extended their useful working time. This leads to a reduction in operation cost and improves the efficiency of membrane performance. Hybrid flotation-NF/RO is a new technology for wastewater treatment which produces high quality water with greater recovery and lower energy and reagents consumption. Finally, the review also addressed the new application of DAF as pretreatment for the desalination processes.

Desalination, 1992

Atomic force microscopy (AFM) has been used to characterize five commercial nanofiltration (NF) m... more Atomic force microscopy (AFM) has been used to characterize five commercial nanofiltration (NF) membranes from three companies. High-resolution 3D images of the membranes were obtained without preparative treatment that may affect the membrane surface. Obtained images have been filtered to overcome the effect of tip convolution and the noises. Two sizes of the images were obtained 2 I~m x 2 gm and small sizes. The first images were used to find the surface morphology data such as average roughness, mean height, root mean square (RMS), and maximum peak-to-valley. The small size images showing visible pores were used to determine the pore size and pore size distributions, which were used to calculate porosity of membranes. A fitted line using lognormal distributions was used to represent the pore size distribution of the nanofiltration membranes. The results show that the Iognormal distribution is fitted well with AFM experimental data.

Desalination, 2007

This paper presents experimental data and modelling for three commercial nanofiltration membranes... more This paper presents experimental data and modelling for three commercial nanofiltration membranes (NF90, NF270, N30F) used to treat highly concentrated different salts solutions (KCl, Na 2 SO 4 , and MgSO 4 ) in a crossflow filtration set-up at a salinity level similar to that of seawater. The main parameters that have been studied in this work are feed pressure and salt concentration. The experimental data were correlated and analysed using artificial neural network (ANN) and Spiegler-Kedem model. Through the latter model, the reflection coefficient of all studied membranes and the solute permeability have been determined for all membranes at different salinity levels. The ANN's prediction of rejection vs. pressure and rejection vs. permeate flux for all investigated salt solutions is discussed. The results showed that both NF90 and NF270 produced a high rejection in the range of 95-99% at a pressure greater than 5 bar for Na 2 SO 4 , and MgSO 4 salts, while for KCl the rejection was in the range of 30-89%. N30F gave relatively medium rejection and flux for Na 2 SO 4 and MgSO 4 salts and very low rejection and flux for KCl. A good agreement has been obtained using the ANN predictions and the experimental data with a deviation not more than 5% for most of the cases considered. The ANN interpolative performance for the medium concentration H. Al-Zoubi et al. / Desalination 206 (2007) 42-60 43 levels (which were not represented in the training phase) is shown to be of lesser quality. A comparison between ANN model and Spiegler-Kedem model is also discussed.

Desalination, 2004

Nanofiltration membranes (NF) have applications in several areas. One of the main applications ha... more Nanofiltration membranes (NF) have applications in several areas. One of the main applications has been in water treatment for drinking water production as well as wastewater treatment. NF can either be used to treat all kinds of water including ground, surface, and wastewater or used as a pretreatment for desalination. The introduction of NF as a pretreatment is considered a breakthrough for the desalination process. NF membranes have been shown to be able to remove turbidity, microorganisms and hardness, as well as a fraction of the dissolved salts. This results in a significantly lower operating pressure and thus provides a much more energy-efficient process. Similar to other membrane processes, a major problem in NF membrane applications is fouling. Several studies have investigated the mechanisms of fouling in NF membranes and suggested methods to minimize and control the fouling of NF membranes. For NF membrane characterizations and process prediction, modeling of NF processes and the use of atomic force microscopy (AFM) are very important. The ability to predict the performance of NF processes will lead to a lower number of experiments, saving of time and money, and help to understand the separation mechanisms during NF. A comprehensive review of NF in water treatments is presented including a review of the applications of NF in treating water as well as in the pretreatment process for desalination; the mechanism as well as minimization of NF membrane fouling problems; and theories for modelling and transport of salt, charged and noncharged organic compounds in NF membranes. The review will also address the application of AFM in studying the morphology of membrane surfaces as part of the NF membrane characterization.

Desalination, 2005

Two microfiltration membranes made of polyvinilidene fluoride (PVDF) and polyethersulfone (PES) o... more Two microfiltration membranes made of polyvinilidene fluoride (PVDF) and polyethersulfone (PES) of the same nominal pore size have been modified by photo-initiated graft copolymerisation of quaternary salt of dimethylamino ethyl methacrylate (qDMAEM). Atomic force microscopy (AFM) has been used to characterise changes in surface morphology with variation of the degree of polymer grafting and therefore the process of modification. Comparative analysis of pore size distribution (PSD) of the initial and modified membranes has revealed differences in the modification process. Although polymer grafting resulted in PSD shifting towards smaller pore sizes, modification of PES membrane narrowed PSD, whereas modified PVDF showed wider PSD. This was attributed to different free-radical density for photo-reactive PES and more inert PVDF with possible contribution of the surface roughness.

Desalination, 2005

Recently, Nanofiltration (NF) membranes have been employed in pre-treatment unit operations in bo... more Recently, Nanofiltration (NF) membranes have been employed in pre-treatment unit operations in both thermal and membrane seawater desalination processes. This has resulted in reduction of chemicals used in pretreatment processes as well as lowering the energy consumption and water production cost and, therefore, has led to a more environmentally friendly processes. In order to predict NF membrane performance, a systematic study on the filtration performance of selected commercial NF membranes against brackish water and seawater is required. In this study, three commercial nanofiltration membranes (NF90, NF270, N30F) have been used to treat highly concentrated (NaCl) salt solutions up to 25,000 ppm, a salinity level similar to that of seawater. The membranes were firstly characterized using the Atomic Force Microscopy (AFM) technique. Pore size and pore size distribution obtained from AFM measurements were used to analyse both experimental data of pure water permeation and data obtained from salt rejection. The main parameters studied in this paper are feed pressure and salt concentration. The experimental data of this work was correlated and analysed using the Spigler-Kedem model. In particular, the reflection coefficient () of all studied membranes and the solute permeability of the salt (P s ) have been determined for all membranes and at all salinity levels studied. For a salinity of 5000 ppm and a pressure of 9 bars, the experimental results showed that NF90 could achieve a salt rejection up to 95%, whereas its rejection dropped to 41% at a salinity of 25,000 ppm and the same pressure. Rejection levels achieved by NF270 have been in range of 11-29%, while N30F gave the lowest rejection in the range of 3-6%.

Chemical Engineering Research and Design, 2007

Artificial neural network (ANN) simulation is used to predict the rejection of two salts (NaCl an... more Artificial neural network (ANN) simulation is used to predict the rejection of two salts (NaCl and MgCl 2 ) at typical seawater concentrations in a cross-flow nanofiltration membrane process. Rejections are predicted as a function of feed pressure and permeate flux with the salt concentration as a parameter. ANN predictions of the two salts' rejections are compared with experimental results obtained using three different nanofiltration membranes (NF90, NF270 and N30F) in a cross flow filtration set-up. The experimental program spans a concentration range of 5000 to 25 000 ppm for NaCl solution and of 5000 to 20 000 ppm for MgCl 2 solution at pressures covering the range of 2-9 bars. The effects of the training algorithm, neural network architectures and transfer function on the ANN performance, as reflected by the percentage average absolute deviation are discussed. A network with one hidden layer comprising four neurones is found to be adequate for mapping input -output relationships and providing a good interpolative tool. Algorithms based on the conjugate gradient, regularization and quasi-Newton principles were found to outperform those based on the gradient descent and variable momentum gradient descent. The former algorithms gave an average absolute percentage deviation up to 5% whereas deviations up to 20% are obtained from the latter algorithms. For most of the cases considered, the ANN proved to be an adequate interpolation tool, where an excellent prediction was obtained for some concentration levels not represented in the training data set. For very limited cases, the ANN predictive performance was poor. However, the network's performance in these extreme cases didn't improve even with increasing the data points in the training data set.

Chemical Engineering Journal, 2000

Jojoba oil extraction by pressing alone, pressing followed by leaching, and leaching alone were i... more Jojoba oil extraction by pressing alone, pressing followed by leaching, and leaching alone were investigated. The extraction process by first and second pressing followed by leaching gave about 50% by weight oil with reference to total seed, which is in agreement with what has been reported previously. The extraction by leaching process was carried out using different solvents. These solvents were; hexane, benzene, toluene, petroleum ether, chloroform, and isopropanol. Hexane, benzene, and petroleum ether gave the highest yield (all about 50% by weight oil with reference to total seed), but when cost is considered, petroleum ether is recommended as the best solvent to leach jojoba oil. The yield obtained in this work for leaching by hexane and benzene are 3-5% and about 10% for isopropanol more than those reported in the literature. Traces of solvent remained with the extracted oil after simple distillation followed by a second stage distillation via a Rotavapour apparatus. These traces slightly affected some of the oil properties such as pour point and flash point.