Removal of manganese from water by electrocoagulation: Adsorption,kinetics and thermodynamic studies

The present study provides an electrocoagulation process for the removal of manganese (Mn) from water using magnesium as anode and galvanised iron as cathode. The various operating parameters like effect of initial pH, current density, electrode configuration, inter‐electrode distance, coexisting ions and temperature on the removal efficiency of Mn were studied. The results showed that the maximum removal efficiency of 97.2% at a pH of 7.0 was achieved at a current density 0.05 A/dm² with an energy consumption of 1.151 kWhr/m³. Thermodynamic parameters, including the Gibbs free energy, enthalpy and entropy, indicated that the Mn adsorption of water on magnesium hydroxides was feasible, spontaneous and endothermic. The experimental data were fitted with several adsorption isotherm models to describe the electrocoagulation process. The adsorption of Mn preferably fitting the Langmuir adsorption isotherm suggests monolayer coverage of adsorbed molecules. In addition, the adsorption kinetic studies showed that the electrocoagulation process was best described using the second‐order kinetic model at the various current densities. © 2012 Canadian Society for Chemical Engineering     

The Electrocapillary Behaviour and the Corrosion-Inhibitive Nature of some Organic Sulphur Compounds

The effects of different organic radicals attached to the sulphide group in dimethyl sulphide,di-n-butyl sulphide, di-phenyl sulphide and thiophene on their electrocapillary behaviour with mercury surface and on their corrosion inhibitive nature with respect to steel in 1N sulphuric acid have been examined. It has been found that (i) there is a qualitative correlation between the electrocapillary behaviour and corrosion inhibitive effect of only some of these sulphides, (ii) the inductive effect of methyl groups enhances the effectiveness of the sulphur atom both in its adsorption on mercury surface and in corrosion- inhibition and (iii) the direct linkage of the sulphur atom to aromatic groups or its incorporation in the aromatic ring brings down the electrocapillary adsorption and the corrosion inhibitive effects of the organic sulphides.     

In vivo confocal fluorescence imaging of skin surface cellular morphology: a pilot study of its potential as a clinical tool in skin research

The cellular morphology of the stratum corneum was studied in vivo using a novel imaging technique that uses confocal fluorescence microscopy in combination with topical application of a fluorescent contrast agent. Images obtained with this method show a strong variation in skin surface cellular morphology among healthy subjects. The results of several clinical studies suggest that cellular morphology is affected by the efficiency of the process of desquamation. As such, cellular morphology shows strong potential to serve as an indicator of skin health that yields mechanistic insight into the origins of skin ailments, such as xerosis, and the effectiveness of their treatments.     

Experimental investigation with optimal prediction of emission in diesel engine using combined NSR–SCR catalyzer

Clean Technologies and Environmental Policy - The utilization of catalytic converters is one of the well-known strategies to clean the exhaust. The catalytic converters oxidize the destructive...     

Effects of alternating and direct current in electrocoagulation process on the removal of cadmium from water

In practice, direct current (DC) is used in an electrocoagulation processes. In this case, an impermeable oxide layer may form on the cathode as well as corrosion formation on the anode due to oxidation. This prevents the effective current transfer between the anode and cathode, so the efficiency of electrocoagulation processes declines. These disadvantages of DC have been diminished by adopting alternating current (AC) in electrocoagulation processes. The main objective of this study is to investigate the effects of AC and DC on the removal of cadmium from water using aluminum alloy as anode and cathode. The results showed that the removal efficiency of 97.5 and 96.2% with the energy consumption of 0.454 and 1.002 kWh kl⁻¹ was achieved at a current density of 0.2 A/dm² and pH of 7.0 using aluminum alloy as electrodes using AC and DC, respectively. For both AC and DC, the adsorption of cadmium was preferably fitting Langmuir adsorption isotherm, the adsorption process follows second order kinetics and the temperature studies showed that adsorption was exothermic and spontaneous in nature.     

The influence of radioactive n-dibutyl sulphide on the corrosion and polarization of steel and its electrocapillary behaviour in in sulphuric acid

The corrosion and polarization of steel have been investigated in 1N sulphuric acid, containing n-dibutyl sulphide labelled with radioactive sulphur atom. In addition, the electrocapillary behaviour of the radioactive substance on a mercury surface in the acid has been tested. Similar experiments employing non-radioactive dibutyl sulphide (d.b.s.) and hydrogen peroxide have been carried out.The inhibition of corrosion of steel in IN sulphuric acid by d.b.s. is significantly reduced and under some conditions corrosion is accelerated by the radioactive form. The polarization and the electrocapillary behaviour of radioactive d.b.s. solutions are clearly different from that of the non-radioactive compound. There is some similarity in the effects produced by radioactive d.b.s. and by a combination of non-radioactive d.b.s. and hydrogen peroxide, in respect of corrosion inhibition and electrocapillary behaviour. It is concluded that the effects produced by radioactive d.b.s. can be attributed mainly to the hydrogen peroxide produced by radiolysis, though the radioactivity can also affect the electrical characteristics at the metal-solution interface.     

Effects of alternating and direct current in electrocoagulation process on the removal of fluoride from water

BACKGROUND: When direct current (DC) is used in electrocoagulation processes, an impermeable oxide layer may form on the cathode and corrosion of the anode may occur due to oxidation. This prevents effective current transfer between the anode and cathode, so the efficiency of the electrocoagulation process declines. These disadvantages of DC have been reduced by adopting alternating current (AC). The main objective of this study is to investigate the effects of AC and DC on the removal of fluoride from water using an aluminum alloy as anode and cathode. RESULTS: Results showed that removal efficiencies of 93 and 91.5% with energy consumption of 1.883 and 2.541 kWh kL^?1 was achieved at a current density of 1.0 A dm^?2 and pH 7.0 using an aluminum alloy as electrodes using AC and DC, respectively. For both AC and DC, the adsorption of fluoride fitted the Langmuir adsorption isotherm. The adsorption process follows second‐order kinetics and temperature studies showed that adsorption was exothermic and spontaneous in nature. CONCLUSIONS: The aluminum hydroxide generated in the cell removed the fluoride present in the water and reduced it to a permissible level thus making it drinkable. It is concluded that an alternating current prevents passivation of the aluminum anode during electrocoagulation and avoids the additional energy wasted due to the resistance of the aluminum oxide film formed on the anode surface. Copyright © 2010 Society of Chemical Industry     

Optimization of the process parameters for the removal of boron from drinking water by electrocoagulation—a clean technology

BACKGROUND: There are a number of articles related to removal of boron by electrocoagulation using aluminium electrodes, but there are fewer articles describing the use of magnesium as the anode material. The main disadvantage of aluminium electrodes is the residual aluminium present in the treated water due to cathodic dissolution, which can create health problems. In the case of magnesium electrodes, there is no such disadvantage. This paper presents the results of studies on the removal of boron using magnesium and stainless steel as anode and cathode, respectively. RESULTS: Results show that a maximum removal efficiency of 86.32% was achieved at a current density of 0.2 A dm^?2 and pH of 7 using magnesium as the anode and stainless steel as the cathode. The adsorption of boron fitted the Langmuir adsorption isotherm, suggesting monolayer coverage of adsorbed molecules. The adsorption process follows second‐order kinetics. Temperature studies showed that adsorption was endothermic and spontaneous in nature. CONCLUSIONS: The magnesium hydroxide generated in the cell remove the boron present in the water and reduced to a permissible level and making it drinkable. The process scale up results was consistent with the results obtained from the laboratory scale, showing the robustness of the process. Copyright © 2010 Society of Chemical Industry     

Effects of alternating current (AC) and direct current (DC) in electrocoagulation process for the removal of iron from water

In practice, direct current (DC) is used in an electrocoagulation processes. In this case, an impermeable oxide layer may form on the cathode as well as corrosion formation on the anode due to oxidation. This prevents the effective current transfer between the anode and cathode, so the efficiency of electrocoagulation processes declines. These disadvantages of DC have been diminished by adopting alternating current (AC) in electrocoagulation processes. The main objective of this study is to investigate the effects of AC and DC on the removal of iron from water using zinc as anode and cathode. The results showed that the optimum removal efficiency of 99.6% and 99.1% with the energy consumption of 0.625 and 0.991 kWh kL^?1 was achieved at a current density of 0.06 A dm^?2, at pH of 7.0 using AC and DC, respectively. For both AC and DC, the adsorption of iron was preferably fitting Langmuir adsorption isotherm, the adsorption process follows second order kinetics and the temperature studies showed that adsorption was exothermic and spontaneous in nature. © 2011 Canadian Society for Chemical Engineering     

Electrochemical removal of boron from water: Adsorption and thermodynamic studies

The present work provides an electrochemical removal of boron from water and its kinetics, thermodynamics, isotherm using mild steel and stainless steel as anode and cathode respectively. The various operating parameters on the removal efficiency of boron were investigated, such as initial boron ion concentration, initial pH, current density and temperature. The results showed that the optimum removal efficiency of 93.2% was achieved at a current density of 0.2 A dm^?2 at pH of 7.0. First‐, second‐order rate equations, Elovich and Intraparticle models were applied to study adsorption kinetics. Adsorption isotherms of boron on Fe(OH)₃ were determined and correlated with isotherm equations such as Langmuir, Freundlich and D‐R models. Thermodynamic parameters, such as standard Gibb's free energy (ΔG°), standard enthalpy (ΔH°) and standard entropy (ΔS°), were also evaluated by Van't Hoff equation. The adsorption process follows second‐order kinetics. The adsorption of boron preferably fits with Langmuir adsorption isotherm suggesting monolayer coverage of adsorbed molecules. The adsorption of boron onto Fe(OH)₃ was found to be spontaneous and endothermic. © 2011 Canadian Society for Chemical Engineering