SLIP VELOCITY IN PULSED DISC AND DOUGHNUT EXTRACTION COLUMN

In the present work, slip velocity has been measured in a 76 mm diameter pulsed disc and doughnut extraction column for four different liquid-liquid systems. The effects of operating variables including pulsation intensity and dispersed and continuous phase flow rates on slip velocity have been investigated. The existence of three different operational regimes, namely mixersettler, transition, and emulsion regimes, was observed when the energy input was changed. Empirical correlations are derived for prediction of the slip velocity in terms of operating variables, physical properties of the liquid systems, and column geometry for different regimes. Good agreement between prediction and experiments was found for all operating conditions that were investigated

Pressure drop in pulsed extraction columns with internals of discs and doughnuts

A study on the pressure drop in pulsed extraction columns with internals of immobile discs and rings, usually called Discs and Doughnuts Columns (DDC) is carried out. The local pressure at a desired level of the column is obtained by resolving of turbulent flow model based on Reynolds equations coupled with k–ε model of turbulence. Consequently, the pressure drop for a column stage or for a unit of column length is determined. The results are used for development of correlations for determination of pressure drop as a function of plate free area, interplate distance and pulsation parameters - amplitude and frequency. Good correspondence to experimental data is observed. The developed quantitative relations are useful for non-experimental numerical optimization of stage geometry in view of lesser energy consumption

Valorization of lemon peel waste as biosorbent for the simultaneous removal of nickel and cadmium from industrial effluents

The valorization of agricultural waste as biosorbent requires studies dealing with aqueous systems containing coexisting heavy metals. Batch adsorption experiments were carried out to study the competitive biosorption of Ni(II) and Cd(II) on alkalimodified lemon peel. The biosorption kinetic analysis indicated that the uptake of Ni(II) on lemon peel was better described by pseudo first-order model whereas for Cd(II) results were no conclusive. A rapid uptake of both metals on alkali-modified lemon peel was detected during the first 10 min obtaining more than 90% of the maximum sorption. The maximum adsorption capacity of Ni(II) and Cd(II) for single metal systems at optimum conditions (pH = 5, S/L = 5 g L−1, 25 ◦C), which were obtained from Langmuir model, reached as high as about 0.626 and 0.726 mmol g−1, respectively. These values were reduced 30 and 20 % in the presence of 100 mg L−1 of Cd and Ni, respectively. Regarding the reusability of the biosorbent, after five consecutives adsorption–desorption cycles using HNO3 and H2SO4 as desorption reagents percentages of 90 and 70 % were recovered for Ni and Cd. The promising results obtained through this work are expected to promote the use of lemon peel as an efficient biosorbent for industrial applications.Universidad de Málaga/CBUA: Funding for open access charg

Experimental analysis and mathematical prediction of Cd(II) removal by biosorption using support vector machines and genetic algorithms

We investigated the bioremoval of Cd(II) in batch mode, using dead and living biomass of Trichoderma viride. Kinetic studies revealed three distinct stages of the biosorption process. The pseudo-second order model and the Langmuir model described well the kinetics and equilibrium of the biosorption process, with a determination coefficient, R2 > 0.99. The value of the mean free energy of adsorption, E, is less than 16 kJ/mol at 25°C, suggesting that, at low temperature, the dominant process involved in Cd(II) biosorption by dead T. viride is the chemical ion-exchange. With the temperature increasing to 4050°C, E values are above 16 kJ/mol, showing that the particle diffusion mechanism could play an important role in Cd(II) biosorption. The studies on T. viride growth in Cd(II) solutions and its bioaccumulation performance showed that the living biomass was able to bioaccumulate 100% Cd(II) from a 50 mg/L solution at pH 6.0. The influence of pH, biomass dosage, metal concentration, contact time and temperature on the bioremoval efficiency was evaluated to further assess the biosorption capability of the dead biosorbent. These complex influences were correlated by means of a modeling procedure consisting in data driven approach in which the principles of artificial intelligence were applied with the help of support vector machines (SVM), combined with genetic algorithms (GA). According to our data, the optimal working conditions for the removal of 98.91% Cd(II) by T. viride were found for an aqueous solution containing 26.11 mg/L Cd(II) as follows: pH 6.0, contact time of 3833 min, 8 g/L biosorbent, temperature 46.5°C. The complete characterization of bioremoval parameters indicates that T. viride is an excellent material to treat wastewater containing low concentrations of metal

Biosorption of lanthanum and cerium from aqueous solutions using tangerine (Citrus reticulata) peel: Equilibrium, kinetic, and thermodynamic studies

Biosorption of lanthanum (III) and cerium (III) from aqueous solution by tangerine (Citrus reticulate) peel has been investigated in a batch system as a function of pH, biosorbent dosage, contact time, and temperature. The equilibrium pH was found to severely affect the biosorption performance; pH 5.0 is found to be an optimum pH for favorable biosorption of La (III) and Ce (III). The biosorption of lanthanum and cerium was investigated by the Langmuir, Freundlich and Dubinin-Radushkevich (D-R) isotherm models. Maximum biosorption uptakes, according to the Langmuir model, were obtained as 154.86 and 162.79 (mg/g) for La(III) and Ce(III), respectively. The biosorption kinetic was tested with pseudo-first order and pseudo-second order models. The results showed that the kinetic of biosorption process was described by the pseudo-second order model very well. Thermodynamic parameters including the change of Gibbs free energy (ΔG°), enthalpy change (ΔH°) and entropy change (ΔS°) for both sorption systems were determined at four different temperatures. The results showed that the biosorption of La(III) and Ce(III) on tangerine (C. reticulate) peel is a spontaneous and endothermic process. FTIR analysis demonstrated that carboxyl and hydroxyl groups were involved in the biosorption of the metal ions