Combined electrocoagulation processes as a novel approach for enhanced pollutants removal: A state-of-the-art review.

A novel approach using the integration of electrocoagulation, with one or more treatment processes has been recently practiced to improve the removal of colloidal and non-biodegradable pollutants. Several treatment processes including adsorption, chemical coagulation, magnetic field, reverse osmosis, and membrane filtration have been combined with electrocoagulation treatment step to improve pollutants removal efficiency. These combined systems showed the potential to improve the performance of the treatment process. This paper presents a state-of-the-art review for the recent processes available in the literature that combine treatment electrocoagulation with one of the previously mentioned treatment processes. It is found that the removal efficiency of any combined processes is higher than that of any single treatment process and the combined process has up to 20% higher removal efficiency compared to electrocoagulation alone. However, most reported studies were conducted at bench-scale level with synthetic wastewater instead of real wastewater. The main aspects of these combined systems including process mechanism, kinetic models, cost and the scale up of combined processes were discussed and summarized. Finally, several concluding remarks were drawn in view of the literature investigations and the gaps that suggest more studies and insights for future development were addressed.

Degradation of dissolved diazinon pesticide in water using the high frequency of ultrasound wave.

This article aims to apply the ultrasound technique in the field of clean technology to protect environment. The principle of sonochemistry is conducted here to degrade pesticides in simulated industrial wastewater resulted from a factory manufacturing pesticides namely diazinon. Diazinon pesticide selected in this study for degradation under high frequency ultrasound wave. Three different initial concentrations of diazinon (800, 1200, and 1800 ppm), at different solution volumes were investigated in to degrade dissolved diazinon in water. Ultrasound device with 1.7 MHz, and 0.044 cm diameter, was used to study the degradation process. It is found that as the concentration of diazinon increased, the degradation is also increasing, and when the solution volume increases, the ability to degraded pesticides decreases. The experimental results showed an optimum condition achieved for degradation of diazinon at 1200 ppm as initial concentration and 50 ml solution volume. Kinetic modeling applied for the obtained results showed that the degradation of diazinon by high ultrasound frequency wave followed a pseudo-first-order model with apparent rate constant of around of 0.01 s(-1).

Batch adsorption of cadmium ions from aqueous solution by means of olive cake.

The use of natural adsorbent such as olive cake to replace expensive imported synthetic adsorbent is particularly appropriate for developing countries such as Jordan. In this study, batch adsorption experiments were carried out for the removal of cadmium ions from its aqueous solution using olive cake as adsorbent. Parameters effects such as temperature, pH and adsorbent dose on the adsorption process were studied. The adsorbent used in this study exhibited as good sorption at approximately pH 6 at temperatures 28, 35 and 45 degrees C. The removal efficiency was found to be 66% at pH 6 and temperature 28 degrees C. The equilibrium data were analyzed using Langmuir and Freundlich isotherm models to calculate isotherm constants. The experimental results were in a good agreement with these models. Results show that when an increasing in temperature from 28 to 45 degrees C, the maximum adsorption capacity (qmax) is decreased from 65.4 to 44.4 mg/g and Freundlich constant (Kf) decreased from 19.9 to 15.7. The thermodynamic parameters for the adsorption process data were evaluated using Langmuir isotherm. The free energy change (DeltaG degrees) and the enthalpy change (DeltaH degrees) showed that the process was feasible and exothermic, respectively. The dynamic data fitted to the first order, Lagergren-first order and pseudo second-order kinetic models. The experimental results indicated that the pseudo second-order reaction model provided the best description for these data with a correlation coefficient of 0.99. The adsorption rate constant was calculated as 8.4x10(-3) g mg(-1) min(-1) at 28 degrees C.

The application of high frequency ultrasound waves to remove ammonia from simulated industrial wastewater.

This article aims at applying the ultrasound technique in the field of clean technology to protect environment. The principle of ultrasound was conducted here to remove and recover ammonia from industrial wastewater. Three different concentrations of ammonia namely 5%, 15% and 25% (vol.%) were used to study the efficiency of removing ammonia from water. These concentrations are exactly similar to what may be found in wastewater resulting from strippers at petroleum refinery. High ultrasound frequency device with 2.4 and 1.7 MHz was conducted to study the effect of waves on the removal of ammonia. It was found that the ultrasound has the ability to remove ammonia with 5% concentration to meet the local standard of treated wastewater within less than 2 h for 0.080 L solution. It was also found that as the concentration of the ammonia increases the removing of ammonia within 2 h decreases, still the concentration of the ammonia meets the standard of the treated wastewater. The ability of the ultrasound to remove the ammonia failed to produce any mist when the height of the liquid solution increased, namely when the height reached (0.0337 m). This is equivalent to liquid volume of 0.150 L. It means that the device capacity to remove ammonia has certain limitations based on liquid heights. The best condition for ammonia removal was obtained at 5% concentration and 0.080 L liquid volume (equivalent to 0.0165 m).

Prediction of the critical micelle concentration in a lattice model for amphiphiles using a single-chain mean-field theory.

A single-chain mean-field theory is used to predict the properties of binary surfactant solutions including the critical micelle concentration (cmc). In particular, the cmc of two symmetric nonionic amphiphiles is calculated as a function of temperature in order to analyze the validity of the ideal mixing assumption, often employed in the mass action model. On comparing against literature Monte Carlo results for the same lattice model we find that although it is applicable at low temperatures and hence cmcs at low amphiphile concentrations, at higher temperatures it becomes necessary to correct for the nonideal mixing of the free chain-free chain bulk interaction. We find that a simplistic model taking into account only the repulsive interaction is sufficient to restore the excellent quantitative agreement found between a single-chain mean-field theory calculations and literature molecular simulation results at the low temperature limit.