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Al-Amoudi A.,Saline Water Desalination Research Institute
Separation and Purification Technology | Year: 2013

In membrane process industries, membrane cleaning is one of the most important concerns from both economic and scientific points of view. Though cleaning is important to restore membrane performance, the inappropriate selection of cleaning agents may result in unsatisfactory cleaning or irreparable membrane damage. In this study, the cleaning performance was studied by measuring membrane pore size; by positron annihilation spectroscopy and salt rejection as well as by flux measurement. Thin film composite nanofiltration (NF) membranes, supplied by GE Osmonics NF-DK were used in this study. Tests were carried out on virgin membranes. Several different cleaning agents were investigated. Some of them were of analytical grade such as HCl and NaOH. Others such as SDS and mixed agents were of commercial grade already in use in commercial plants. Pore size and salt rejection as well as the flux of virgin membranes before and after chemical cleaning were measured and compared. After the chemical cleaning of the virgin membranes, the membrane pore size was measured revealing interesting results, which may be used to characterize membrane surface cleanliness. The membrane pore size results showed that the cleaning agents affect membrane surface properties by enlarging the pore size of the treated virgin membranes. The flux and rejection were correlated with pore size after low and high pH cleaning, and these findings were investigated and reported in this paper. © 2013 Elsevier Ltd. All rights reserved. Source

Al-Amoudi A.S.,Saline Water Desalination Research Institute
Desalination | Year: 2010

Membrane fouling is a major problem in brackish and seawater desalination as well as in membrane mediated waste water reclamation. Fouling of nanofiltration (NF) membranes is typically caused by inorganic and organic materials present in water that adhere to the surface and pores of the membrane and results in deterioration of performance (reduced membrane flux) with a consequent increase in costs of energy and early membrane replacement. Natural organic matter (NOM) fouling of NF membranes involves interrelationship between physical and chemical interactions and it is described in this review. Membrane fouling in the presence of NOM can be influenced by: membrane characteristics, including surface structure as well as surface chemical properties, chemistry of feed solution including ionic strength, pH and concentration of monovalent ions and divalent ions, NOM properties, including molecular weight and polarity, and hydrodynamic and operating conditions including permeate flux, pressure, concentration polarization, and the mass transfer properties of the fluid boundary layer. These factors will be discussed in details in this review.Inorganic fouling due to scale formation of sparingly soluble inorganic salts occurs whenever the ionic salt concentration stream exceeds the equilibrium solubility. Scale formation take place by homogenous or heterogeneous crystallization and its factors will be also investigated in this review. © 2010 Elsevier B.V. Source

Al-Hamzah A.A.,University of New England of Australia | Al-Hamzah A.A.,Saline Water Desalination Research Institute | East C.P.,Queensland University of Technology | Doherty W.O.S.,Queensland University of Technology | Fellows C.M.,University of New England of Australia
Desalination | Year: 2014

The ability of poly(acrylic acid) (PAA) with different end groups and molar masses prepared by Atom Transfer Radical Polymerization (ATRP) to inhibit the formation of calcium carbonate scale at low and elevated temperatures was investigated. Inhibition of CaCO3 deposition was affected by the hydrophobicity of the end groups of PAA, with the greatest inhibition seen for PAA with hydrophobic end groups of moderate size (6-10 carbons). The morphologies of CaCO3 crystals were significantly distorted in the presence of these PAAs. The smallest morphological change was in the presence of PAA with long hydrophobic end groups (16 carbons) and the relative inhibition observed for all species were in the same order at 30°C and 100°C. As well as distorting morphologies, the scale inhibitors appeared to stabilize the less thermodynamically favorable polymorph, vaterite, to a degree proportional to their ability to inhibit precipitation. © 2014 Elsevier B.V. Source

Alhamzah A.,University of New England of Australia | Alhamzah A.,Saline Water Desalination Research Institute | Fellows C.M.,University of New England of Australia
Desalination | Year: 2014

The thermal decomposition of the hydrogencarbonate ion has been previously described by a bimolecular mechanism or a unimolecular mechanism. In this work the Gibbs free energy of the competing reactions for both the unimolecular and bimolecular mechanisms was calculated for typical concentrations found in thermal desalination plants. Activity coefficients were estimated using the Pitzer equations. At low temperature the bimolecular mechanism is thermodynamically favored, while above 80°C the unimolecular mechanism is favored, consistent with observations of alkaline scale formation in thermal desalination plants. The rate coefficient of thermal decomposition of HCO3- at 97.2°C in the absence and presence of 10ppm of poly(acrylic acid) (PAA) with different end groups and molar mass was determined. PAA was found to retard the rate of decomposition by up to 49% and for all end groups of PAA the rate coefficient of thermal decomposition of 40ppm HCO3- increased with increasing molar mass. The results are consistent with PAA preventing heterogeneous decomposition of HCO3- on interfaces. The rate of partitioning of PAA to these interfaces should increase with decreasing molar mass and resulting mobility of PAA, and may also be affected by self-assembly behavior. © 2013 Elsevier B.V. Source

Saline Water Desalination Research Institute | Date: 2011-09-02

The removal of boron from saline water based using alkalized NF membrane pretreatment can be adopted at 90% recovery and pH 8-9.5 to produce softened and alkalized NF permeate having SDI<1 with significant reduction in feed boron, TDS and scale-forming ions, depending on the properties of the NF membrane polymer structure. NF process acts as a softening process, as well as a boron removal process. An additional RO membrane alkalization can be adopted at a wide range of RO feed at pH 8.5-10, resulting in production of desalinated water with almost nil boron content.

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