In the current study, a novel approach for separating ethanol-water mixture by microbubble distillation technology was investigated. Traditional distillation processes require large amounts of energy to raise the liquid to its boiling point to effect removal of volatile components. The concept of microbubble distillation by comparison is to heat the gas phase rather than the liquid phase to achieve separation. The removal of ethanol from the thermally sensitive fermentation broths was taken as a case of study. Consequently the results were then compared with those which could be obtained under equilibrium conditions expected in an "ideal" distillation unit. Microbubble distillation has achieved vapour compositions higher than that which could be obtained under traditional equilibrium conditions. The separation was achieved at liquid temperature significantly less than the boiling point of the mixture. In addition, it was observed that the separation efficiency of the microbubble distillation could be increased by raising the injected air temperature, while the temperature of the liquid mixture increased only moderately. The separation efficiency of microbubble distillation was compared with that of pervaporation for the recovery of bioethanol from the thermally sensitive fermentation broths. The technology could be controlled to give high separation and energy efficiency. This could contribute to improving commercial viability of biofuel production and other coproducts of biorefinery processing.

The progress in textile industrial technologies comes along with a massive increase in the discharge of dyes in the wastewater which considers a serious environmental problem. In this regard, a new electrochemical system has been developed for the treatment of simulated dye solutions of permanent methylene blue dye by an electrochemical cyclic ring reactor. An aluminum rod and a stainless steel mesh were used as the anode and cathode. The experiments on the artificial dye solutions have been carried out in a 6-liter electrochemical cell containing 50 ppm neutral dye solutions. The effects of various parameters such as electrolysis time applied current density (2, 3.32, 5.31, 6.64, and 7.46 mA cm−2), electrolyte concentrations (600, 900, 1200, 1500, and 1800 ppm), and flow rates (1, 1.5, 2, 2.5, and 3 Lh−1) on the process removal efficiency were examined. The results demonstrated that the removal efficiency reached 94–99% within 40–50 minutes of electrolysis time. The removal efficiency increased by increasing the flow rates until it reaches a maximum value at a flow rate of 2 Lh−1; thereafter, it declined with the farther augment of recirculation speed. It is indicated that raising the applied current resulted in increasing the removal efficiency. However, the power consumption builds up to the maximum value by increasing the applied current, where the power consumption rose from 8.51 to 30.3 kWh kg−1 with an increase in the current density from 2 to 7.46 mA cm−2, and a removal efficiency increased from 94% to 99%, accordingly. The results also showed that by increasing the electrolyte concentration, the power consumption can be reduced to its minimum value and the removal efficiency increased remarkably.

The characteristics of microbubble distillation of binary system of ethanol and water have been investigated. The study describes the use of a fluidic oscillator used to generate microbubbles. The effects of air temperature and liquid level on separation performance have been studied. The results demonstrate that ethanol concentration in the distilled phase decreases with increasing liquid level. Increasing air temperature enhances the separation efficiency of the two components. It is shown that the ethanol fraction in distilled phase and the evaporation ratio increases by increasing the air temperature. Furthermore, the concentration of ethanol in the residual liquid shows a corresponding decrease. The vapour-liquid composition of microbubble distillation can exceed the isothermal equilibrium vapour-liquid composition by controlling the liquid level and the air temperature within the process.

Oil/water emulsions are one of the major threats to environment nowadays, occurs at many stages in the production and treatment of crude oil. The oil recovery process adopted will depend on how the oil is present in the water stream. Oil can be found as free oil, as an unstable oil/water emulsion and also as a highly stable oil/water emulsion. The current study was dedicated to the application of microbubble air flotation process for the removal of such oily emulsions for its characters of cost-effective, simple structure, high efficiency and no secondary pollution. The influence of several key parameters on the process removal efficiency was examined, namely, initial oil concentration, pH value of the emulsion, and the effect of adding sodium chloride. The effect of bubble size on the performance of the separation process and its impact on removal efficiency was also investigated. The results demonstrated that removal efficiency obtained by using microbubbles flotation was higher by factor of 1.72 in comparison with that achieved with fine bubbles. The removal efficiency of oil droplets was increased with the increasing of flotation time and initial oil concentration. The removal efficiency reached up 60.68% under alkaline conditions (pH≈9), and it increased to around 75% by decreasing the emulsion acidity to around (pH≈3). The addition of sodium chloride has a significant influence to the efficiency of the flotation process. The efficiency could be reached to about 84% by adding 1 gL−1 of NaCl to the emulsion. While increasing the NaCl concentration to 9 gL−1 resulted in reduction in removal efficiency to around 80%.

The cost of microalgae harvesting constitutes a heavy burden on the commercialization of biofuel production. The present study addressed this problem through economic and parametric comparison of electrochemical harvesting using a sacrificial electrode (aluminum) and nonsacrificial electrode (graphite). The harvesting efficiency, power consumption, and operation cost were collected as objective variables as a function of applied current and initial pH of the solution. The results indicated that high harvesting efficiency obtained by using aluminum anode is achieved in short electrolysis time. That harvesting efficiency can be enhanced by increasing the applied current or the electrolysis time for both electrodes materials, where 98% of harvesting efficiency can be obtained. The results also demonstrated that the power consumption with graphite anode is higher than that of aluminum. However, at 0.2 A the local cost of operation with graphite (0.036US$/m3), which is distinctly lower than that of aluminum (0.08US$/m3). Furthermore, the harvesting efficiency reached its higher value at short electrolysis time at an initial pH of 6 for aluminum, and at an initial pH of 4 for graphite. Consequently, the power consumption of the harvesting process could be reduced at acid- nature conditions to around 0.46KWh/Kg for aluminum and 1.12KWh/Kg for graphite.