Person: Khayet Souhaimi, Mohamed
Universidad Complutense de Madrid
Faculty / Institute
Estructura de la Materia, Física Térmica y Electrónica
Now showing 1 - 10 of 81
PublicationModeling and optimization of sweeping gas membrane distillation(Elsevier Science BV, 2012-02-15) Khayet Souhaimi, Mohamed; Cojocaru, C.; Baroudi, A.A central compositional orthogonal design has been applied for modeling and optimization of sweeping gas membrane distillation process. The effects of the operational parameters, liquid temperature, gas temperature, liquid flow rate and gas flow rate and their binary interactions on the membrane distillate flux (i.e. permeate flux) have been investigated. The developed model has been statistically validated by analysis of variance and further used to predict the distillate flux. The optimum operating conditions have been determined by Monte Carlo method finding a liquid inlet temperature of 71.6 degrees C, a gas inlet temperature of 17.3 degrees C, a water circulation velocity of 0.16 m/s (i.e. flow rate of 165 L/h) and a gas circulation velocity of 211 m/s (i.e. flow rate of 36 L/min). Under these optimal conditions the measured water distillate flux was 2.789 x 10(-3) kg/m(2).s, while the predicted distillate flux was only 2% higher confirming the developed model. Desalination experiments were performed under the optimum conditions using a feed 30 g/L NaCl solution and Mediterranean seawater. The obtained distillate fluxes were 2.31 x 10(-3) kg/m(2).s and 2.05 x 10(-3) kg/m(2).s for NaCl solution and seawater, respectively; and the salt rejection factors were 99.94% for 30 g/L NaCl solution and 99.48% for seawater. PublicationPerformance assessment and modeling of an SWRO pilot plant with an energy recovery device under variable operating conditions(Elsevier Science Bv, 2023-06-01) Ruiz García, A.; Nuez, I.; Khayet Souhaimi, MohamedReverse osmosis (RO) is one of the most widespread desalination technologies in use today due to its good performance and reliability. Given that it is an energy intensive technology, using variable renewable energy sources (VRES) to power RO systems is an interesting option. Work with the RO system under variable operating conditions is one of the strategies that can be employed to take advantage of all the energy that is available at any given time from an off-grid renewable system. However, this will entail additional challenges in terms of, among other factors, plant maintenance and permeate production rate and quality. In grid-connected seawater RO (SWRO) desalination plants, energy recovery devices (ERD) are commonly used to increase energy efficiency performance. In these cases, the ERD usually operates under constant operating conditions. This work aims to assess the performance of an SWRO system with an ERD under widely variable operating conditions. The SWRO system has six membrane elements in pressure vessels. The ERD is a Pelton turbine connected to a generator to measure the energy produced by the turbine. An artificial neural network (ANN) based model was developed to estimate the performance of the SWRO-ERD system under variable operating conditions. According to the results, power savings of between 2.9 and 6.08 kW can be achieved for a wide range of operating conditions, allowing an increase in the produced permeate flux (Qp). The proposed ANN-based model is able to estimate Qp and permeate electrical conductivity with error intervals of 1.56 x 10-6 -8.49 x 10-2 m3 h-1 and 8.33 x 10-5 -31.06 mu S cm-1, respectively. The experimental data and the developed model could help to obtain a better performance pre-diction of VRES-powered SWRO systems that are operating under variable operating conditions and with ERDs. PublicationPoly(2,6-dimethyl-1,4-phenylene oxide) mixed matrix pervaporation membranes(Elsevier B. V., 2006-11-20) Khayet Souhaimi, Mohamed; García Villaluenga, Juan Pedro; Valentín, Juan L.; López Manchado, Miguel Ángel; Mengual Cabezón, Juan Ignacio; Seoane Rodríguez, Benjamín PublicationModelling and optimization of coagulation of highly concentrated industrial grade leather dye by response surface methodology(Elsevier B. V., 2011-02-15) Khayet Souhaimi, Mohamed; Zahrim, A. Y.; Hilal, N.High consumption of process water and water scarcity has motivated industry to reuse their wastewater. Membrane processes are vital to produce water for reuse from dyeing baths in the tanning industry. In this regard, synthetic dye was recognised as the major foulant. To minimise the membrane fouling, coagulation/flocculation process is an important pre-treatment. Due to the complex nature of the process involving dyes-coagulant, the modelling is challenging. In this study, statistical experimental design and response surface methodology, RSM, have been applied to optimize removal of C.I. Acid Black 210 dye from highly concentrated solutions by means of a coagulation/floculation process. Aluminium sulphate was used as the coagulant. Central composite design (CCD) using as input variables the experimental temperature, the concentration of aluminium sulphate and the initial pH of the solution have been considered. Based on the design of experiment the quadratic response surface models have been developed to link the output response, which is the dye removal factor, with the input variables via mathematical relationships. The constructed response model has been tested using the analysis of variance (ANOVA). A Monte Carlo simulation method has been conducted to determine the optimum operating conditions. The obtained optimal point corresponds to a temperature of 40 degrees C, a concentration of aluminium sulphate of 0.82 g/L and an initial pH value of 5.61. The maximal value of the dye removal obtained under optimal process conditions has been confirmed experimentally. PublicationNovel porous composite hydrophobic/hydrophilic polysulfone membranes for desalination by direct contact membrane distillation(Elsevier B. V., 2009-09-30) Qtaishat, M.; Khayet Souhaimi, Mohamed; Matsuura, T.Novel composite membrane distillation membranes were prepared by blending the hydrophilic polysulfone with hydrophobic surface modifying macromolecules (SMMs). Three different types of SMMs were tested. These SMMs were synthesized and characterized for fluorine content, molecular weights and glass transition temperature. Phase inversion method in a single casting step was used to prepare the composite membranes. The membranes were characterized by means of different techniques such as contact angle measurement, gas permeation test, liquid entry pressure of water and scanning electron microscopy. Finally, these membranes were tested for desalination by direct contact membrane distillation (DCMD). Different membrane preparation conditions affecting membrane morphology, structure and DCMD performance were investigated. The parameters studied were the SMMs type, polysulfone concentration, solvent type and non-solvent additive concentration in the casting solution. Attempts linking the membrane morphology to its DCMD performance have been made. it was found that increasing the polymer concentration or the non-solvent additive concentration decreased the permeate flux of the porous composite hydrophobic/hydrophilic membranes since the liquid entry pressure of water increased and the ratio of the membrane pore size time the porosity over the effective pore length (r epsilon/L(p)) decreased. Furthermore, the stoichiometric ratio of the SMMs, type of SMMs, was found to affect considerably the characteristics and permeate flux of the composite membranes. In general, the composite membranes with higher liquid entry pressure of water exhibited smaller permeate fluxes. Moreover, the obtained results were compared to those of a commercial polytetrafluoroethylene membrane and it was observed that some of the SMMs blended polysulfone membranes achieved better DCMD fluxes than those of the commercial membrane. A permeate flux 43% higher than that of the commercial membrane was achieved with 99.9% NaCl separation factor. PublicationTreatment of olive mill wastewater by membrane distillation using polytetrafluoroethylene membranes(Elsevier Science BV, 2012-09-19) El Abbassi, A.; Kiai, H.; Hafidi, A.; García Payo, María del Carmen; Khayet Souhaimi, MohamedDirect contact membrane distillation (DCMD) process was applied for olive mill wastewater (OMW) treatment. Three commercial polytetrafluoroethylene (PTFE) membranes with different pore sizes (TF200 of 0.2 mu m, TF450 of 0.45 mu m and TF1000 of 1 mu m) were tested under different temperatures, namely, temperature difference and mean temperature. The aim of this study is to investigate the possibility of pure water production and concentration of natural polyphenols from OMW for further valorization. The results demonstrated the efficiency of DCMD process for OMW treatment by the three PTFE membranes. The permeate flux increased with the increase of the membrane pore size, the mean temperature and the temperature difference. However, no significant effect was detected between the pore size and the polyphenol separation coefficient, which remains close to 100% after 8 h of DCMD operating time. The DCMD processing of OMW using PTFE membranes allow to reach a concentration factor higher than 1.78 after 8 h of operating time, obtaining the best performance index for the membrane TF1000 with the greatest pore size. In addition, the effect of high temperatures on the phenolic content of OMW and its free radical-scavenging ability (DPPH assay) was also evaluated with time. It was found that a treatment of OMW by DCMD at high temperatures have no undesirable effects on the phenolic content and its antioxidant activity. PublicationAnalysis of the membrane thickness effect on the pervaporation separation of methanol/methyl tertiary butyl ether mixtures(Elsevier Science BV, 2005-12) García Villaluenga, Juan Pedro; Khayet Souhaimi, Mohamed; Godino Gómez, María Paz; Seoane Rodríguez, Benjamín; Mengual Cabezón, Juan IgnacioThe effect of the membrane thickness on the pervaporation separation of methanol and methyl tertiary butyl ether mixtures through membranes was studied. Membranes of a wide range of thicknesses were prepared from two different polymers: cellulose acetate and poly(2,6-dimethyl-1,4-phenylene oxide). For each membrane, the experiments were performed at the same feed pressure, feed temperature and permeate pressure. The results showed that the permeate flux through both membrane types decreased markedly with increasing the membrane thickness, while the separation factor remained nearly constant. This behavior was discussed in terms of a resistance-in-series model. PublicationGas transport properties of polypropylene/clay composite membranes(Elsevier, 2007-04) García Villaluenga, Juan Pedro; Khayet Souhaimi, Mohamed; Lopez Manchado, M. A.; Valentin, J. L.; Seoane Rodríguez, Benjamín; Mengual Cabezón, Juan IgnacioPolypropylene membranes modified with natural and organically modified montmorillonite clays were prepared. The permeability, diffusivity and solubility of helium, oxygen and nitrogen were determined for the unfilled and filled membranes over the temperature range 25-65 degrees C. Physical properties of polypropylene membranes were investigated using X-ray diffraction, thermogravimetric analyser, tensile testing and differential scanning calorimetry. The results showed that the filled membranes exhibit lower gas permeability compared to the unfilled polypropylene membrane. For helium, a reduced diffusivity is mainly responsible for the reduction in the permeability, in contrast, for nitrogen and oxygen, both diffusivity and solubility were reduced by the presence of fillers. The X-ray diffraction spectra showed that the incorporation of the unmodified and modified clay did not affect the crystallographic nature of polypropylene. PublicationStructural and performance studies of poly(vinyl chloride) hollow fiber membranes prepared at different air gap lengths(Elsevier B. V., 2009-03-20) Khayet Souhaimi, Mohamed; García Payo, María del Carmen; Qusay, F. A.; Zubaidy, M. A.Poly(vinyl chloride) hollow fiber membranes were prepared by the dry/wet and wet/wet spinning technique at different air gap lengths keeping all other spinning parameters constants. Mean pore size, pore size distribution and mean roughness of both the internal and external surfaces of the hollow fibers were determined by atomic force microscopy. Cross-sectional structure was studied by scanning electron microscopy. Ultrafiltration experiments of pure water and aqueous solutions of different solutes having different molecular weights (bovine serum albumin, polyethylene glycol and polyvinyl pyrrolidone) were carried out. It was found that the inner and outer diameters of the PVC fiber membranes decreased with the increase of the air gap distance due to the gravitational force effect. The hollow fiber membranes prepared without and with air gap distances up to 7 cm exhibited a quite symmetric cross-structure consisting of four layers, two small finger-like structure layers at both edges of the hollow fibers and two larger finger-like voids mixed with macrovoids layers in the middle of the cross-section. The outer-middle layer thickness decreased when the air gap distance was increased to 10 cm and disappeared from the cross-section of the hollow membranes prepared with higher air gap lengths than 15 cm. For all dry/wet spun PVC hollow fibers, the outer pore size and the pure water permeation flux both increased with the increase of the air gap distance. In contrast, the solute separation factor decreased with the air gap distance. This was related to the pore size of the external surface of the PVC hollow fibers. PublicationPreparation and application of dense poly(phenylene oxide) membranes in pervaporation(Elsevier, 2004-10-15) Khayet Souhaimi, Mohamed; García Villaluenga, Juan Pedro; Godino Gómez, María Paz; Mengual Cabezón, Juan Ignacio; Seoane Rodríguez, Benjamín; Khulbe, K. C.; Matsuura, T.Dense flat-sheet membranes were prepared from poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) using the casting solvents chloroform and 1,1,2-trichloroethylene. X-ray diffraction, tapping mode atomic force microscopy (TM-AFM), and contact angle studies were used to characterize the membranes. The surface energy and the solubility parameters of the PPO membranes were determined from the measured contact angles and compared with the predicted ones from the group contribution method. Swelling experiments and pervaporation separation of methanol from its mixture with ethylene glycol over the entire range of concentration, 0-100%, were conducted using these membranes. Flory-Huggins theory was used to predict the sorption selectivity. The results are discussed in terms of the solubility parameter approach and as function of the morphological characteristics of the membranes. It was found that PPO membranes prepared with chloroform exhibited better pervaporation performance than PPO membranes prepared with 1, 1,2-trichloroethylene.