Fahmi A. Abu Al-Rub

Desalination by vacuum membrane distillation: sensitivity analysis

Abstract In order to enhance the performance of the vacuum membrane distillation process in desalination, i.e. to get more flux, it is necessary to study the effect of operating parameters on the yield of distillate water. Simple techniques including the normalized dimensionless sensitivity factor and temperature polarization coefficient as well as the solution of the transport models were used for this purpose. The sensitivity of the mass flux to the process operating parameters including downstream pressure, feed temperature, feed flow rate, and membrane permeability were investigated. The mass flux of distillate water was highly sensitive to the feed temperature especially at high values of vacuum pressure. The mass flux was more sensitive to the vacuum pressure at low feed temperature levels than at the high ones. Since lowering the temperature polarization coefficient is essential to enhance the process performance considerable efforts should be directed toward maximizing the heat transfer coefficient through better module design. The predictions of the normalized dimensionless sensitivity analysis were in agreement with the results obtained from solving the transport model of the process.

Nickel Removal from Aqueous Solutions Using Sheep Manure Wastes

This paper reports a study on the potential use of sheep manure waste (SMW) for the removal of nickel ions from aqueous solutions. The adsorption of nickel ions from aqueous solutions on SMW has been studied as functions of contact time, initial pH, amount of sorbent, sorbent particle size, initial concentration of nickel ions, salt, and chelating agents. The experimental results showed that the SMW has a high affinity for nickel binding, where 79 % removal of 100 ppm initial nickel ions concentration was obtained using 8.0 mg SMW/mL, at pH 6.5 in 4 minutes equilibrium time. The equilibrium adsorption data were analyzed using four different isotherms: the Langmuir, Freundlich, Redlich‐Peterson, and Sips isotherm equations. The results of the kinetic studies showed that the adsorption of nickel ions on SMW is a pseudo‐first order with respect to the nickel ions solution concentration.

Adsorption of Lead Ions from Aqueous Solution onto Activated Carbon and Chemically-modified Activated Carbon Prepared from Date Pits

Date pits, i.e. agricultural wastes, were converted into activated carbon by air and phosphoric acid activation. The surfaces of some of the prepared activated carbons were modified chemically using 8-hydroxyquinoline. The carbons prepared by both air and phosphoric acid activation showed surface areas of 864.8 m2/g and 502.2 m2/g, respectively, and micropore volumes of 0.298 cm3/g and 0.126 cm3/g, respectively. The adsorption of Methylene Blue onto the prepared activated carbon demonstrated its very high adsorption capacity. The adsorption of lead ions on both carbons, i.e. activated and chemically-modified, was studied under different conditions. The experimental results showed that both types of carbon gave a relatively large maximum lead ion uptake, the increase in the uptake as a result of chemical modification being insignificant. Lead ion uptake was found to increase by increasing the solution pH — whereby the maximum adsorption of lead ions was obtained at pH 5.2 — and by increasing the initial lead ion concentration. Equilibrium studies showed that the adsorption of lead ions on both adsorbents could be described by the Langmuir and Freundlich isotherm models. Kinetic studies showed that the adsorption of lead ions on the prepared activated carbons followed pseudo-second-order kinetics. The presence of EDTA, acetic acid or citric acid led to a significant decrease of lead ion uptake by the activated carbons.

Biosorption of Zinc on Palm Tree Leaves: Equilibrium, Kinetics, and Thermodynamics Studies

Abstract The efficiency of using palm tree leaves to remove zinc ions from aqueous solution was studied. Adsorption isotherms, kinetics, and thermodynamics studies were conducted. The influence of different experimental parameters, such as equilibrium pH, shaking rate, temperature, and the presence of other pollutants such as chelating agents on the biosorption of zinc on palm tree leaves was investigated. Batch biosorption experiments showed that palm tree leaves used in this study proved to be suitable for the removal of zinc from dilute solutions where a maximum uptake capacity of 14.7 mg/g was obtained at 25°C. Zinc biosorption on palm tree leaves was found to be highly pH dependent. The biosorption process was found to be rapid with 90% of the adsorption completed in about 10 min. Dynamics studies of the biosorption of zinc on palm tree leaves showed that the biosorption process followed the pseudo second‐order kinetics with little intraparticle diffusion mechanism contribution. The equilibrium results indicated that zinc biosorption on palm tree leaves could be described by the Langmuir, Freundlich, Gin et al., and Sips models. Using the Langmuir equilibrium constants obtained at different temperatures, the thermodynamics properties of the biosorption (ΔG0, ΔH0, and ΔS0) were also determined. The values of these parameters indicated the spontaneous and endothermic nature of zinc biosorption on palm tree leaves.

Competitive Adsorption of Nickel and Cadmium on Sheep Manure Wastes: Experimental and Prediction Studies

Sheep manure wastes (SMW) previously have been shown to be very efficient in removing nickel and cadmium from single-component, dilute aqueous solutions. Simultaneous removal of nickel and cadmium ions from aqueous solutions using SMW has been investigated in this study. The experimental results showed that the SMW has a relatively higher affinity for cadmium binding than that for nickel. Different multicomponent-isotherm models; extended Langmuir, modified Langmuir, extended Redlich–Peterson, and extended Sips isotherm models, were used to predict the removal of either ions using single metal isotherm data.

Modeling of dilute ethanol-water mixture separation by membrane distillation

Abstract The effect of membrane distillation process parameters on ethanol–water separation has been investigated using a comprehensive mathematical model. Three mass transfer solutions are considered in the model, namely: the exact solution of the Stefan–Maxwell equations developed by Krishna and Standart; the approximate solution of the Stefan–Maxwell equations suggested by Krishna and Wesselingh; and the binary Fickian solution. Temperature and concentration variation along the flow and diffusion paths are accounted for in the model. Though the exact and approximate solutions of the Stefan–Maxwell equations are coincident with each other, some differences are noticed between them and the Fickian-based solution. The difference between the three mass transfer-based solutions, as well as the process performance under several process parameters, are discussed.

PARAMETRIC SENSITIVITY ANALYSIS OF DIRECT CONTACT MEMBRANE DISTILLATION

Membrane distillation is a thermally driven mass transfer in which a porous hydrophobic membrane separates two liquid phases and a temperature difference is maintained as the driving force. In this study, the technique of direct contact membrane distillation (DCMD) process, where the liquid phases are in direct contact with both sides of the membrane, has been investigated for the case of pure water production. Parametric sensitivity analysis and temperature polarization factor are used to study the sensitivity of the mass flux to the different parameters associated with DCMD for water production, and the effect of these parameters on the thermal efficiency of the DCMD process has been investigated. The results obtained show that the mass flux of pure water production is highly sensitive to the feed bulk temperature, and at low flow rates of hot and cold fluids, to the heat transfer coefficients. Results also show that increasing membrane thickness decreases the mass flux of pure water and decreases temperature polarization effect. In addition, results show that temperature polarization effect becomes significant as feed bulk temperature increases.

On the effect of inert gases in breaking the formic acid-water azeotrope by gas-gap membrane distillation

Abstract The effect of inert gases, such as helium, air, and sulfur hexafluoride, in breaking the formic acid–water azeotrope by gas-gap membrane distillation process is theoretically investigated under the process relevant operating conditions. A Stefan–Maxwell-based mathematical model that includes all necessary vapor–liquid equilibrium, heat, and mass relations is used for this purpose. According to the model predictions, heavy inert gases such as sulfur hexafluoride help more in breaking the azeotrope than lighter ones such as air and helium. This phenomenal behavior is discussed along with the effect of other associated process parameters.

Experimental Study of the Salt Effect in Vapor/Liquid Equilibria Using Headspace Gas Chromatography

The salt effect on vapor/liquid equilibrium for an ethanol/water system was studied at 70 °C using the Headspace Gas Chromatography technique. The azeotropic point of the system was eliminated in the presence of the salts studied. All the salts investigated in this work exhibited a salting out effect which followed the order of NH4Cl > NaCl > CaCl2 and which increased with increasing salt concentration. Good agreement with Furters equation was observed for the experimental data with unsaturated NaCl salt. The salt effect parameter, determined from Furters equation, was found to be a function of the liquid concentration.

Modeling of Desalination Using Tubular Direct Contact Membrane Distillation Modules

A fully predictive mathematical model based on first principles of heat and mass transfer as well as vapor–liquid equilibrium was developed for desalination application via tubular direct contact membrane distillation. The model took into account the temperature and the effect of concentration polarization. The models prediction in terms of distillate flux were validated with previously published experimental data for such process parameters as saline water and cooling water flow rates and temperatures, and feed salt concentration. The models results agreed well with previously published experimental and theoretical work.