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In recent years, the discharge of various emerging pollutants, chemicals, and dyes in water and wastewater has represented one of the prominent human problems. Since water pollution is directly related to human health, highly resistant and emerging compounds in aquatic environments will pose many potential risks to the health of all living beings. Therefore, water pollution is a very acute problem that has constantly increased in recent years with the expansion of various industries. Consequently, choosing efficient and innovative wastewater treatment methods to remove contaminants is crucial. Among advanced oxidation processes, electrochemical oxidation (EO) is the most common and effective method for removing persistent pollutants from municipal and industrial wastewater. However, despite the great progress in using EO to treat real wastewater, there are still many gaps. This is due to the lack of comprehensive information on the operating parameters which affect the process and its operating costs. In this paper, among various scientific articles, the impact of operational parameters on the EO performances, a comparison between different electrochemical reactor configurations, and a report on general mechanisms of electrochemical oxidation of organic pollutants have been reported. Moreover, an evaluation of cost analysis and energy consumption requirements have also been discussed. Finally, the combination process between EO and photocatalysis (PC), called photoelectrocatalysis (PEC), has been discussed and reviewed briefly. This article shows that there is a direct relationship between important operating parameters with the amount of costs and the final removal efficiency of emerging pollutants. Optimal operating conditions can be achieved by paying special attention to reactor design, which can lead to higher efficiency and more efficient treatment. The rapid development of EO for removing emerging pollutants from impacted water and its combination with other green methods can result in more efficient approaches to face the pressing water pollution challenge. PEC proved to be a promising pollutants degradation technology, in which renewable energy sources can be adopted as a primer to perform an environmentally friendly water treatment. [ABSTRACT FROM AUTHOR]

In this study, two-dimensional incompressible steady and time-dependent magnetohydrodynamic (MHD) flows around a cylinder were simulated by applying a finite volume method. The method was first validated through fair agreement of its results with the analytical solution for MHD flows inside the channels. It was then applied to simulate the MHD flows around a cylinder at Reynolds (Re) numbers varying from 100 to 1000 and Hartmann (Ha) numbers varying from 10 to 100. According to the results, although the increase in Re number strengthens the flow instability, the magnetic field suppresses this effect. The evidence for this claim is that the increase in Ha number leads to reduce in the separation angle for each Re number. This was in such a way that no flow separation was observed at Ha number equal to 50 and above for any considered Re number. Instability and therefore unsteady flows were seen only for the cases where Ha number was equal to 10 (the minimum considered value) and Re number was 500 or above. The drag coefficient (as a constant value for steady flows) or its average value (for unsteady flows) was enhanced by increasing the Ha number. The amplitude of the drag and lift coefficient fluctuations for unsteady cases were grown up by increasing the Re number. The Strouhal number was also found as a parameter that is dependent on both Re and Ha numbers. [ABSTRACT FROM AUTHOR]

Abstract In this research Au nanoparticles, supported on Fe 3 O 4 @polyaniline as a magnetic nanocatalyst, was synthesized and its performance has been evaluated to reduce Methylene Blue (MB) and Methyl Orange (MO) from aqueous solutions. Gold nanoparticles, as a nanocatalyst with excellent activity, were prepared through the reduction of Au3+ using a wild herbal extract (Allium Sp) without any toxic chemical compounds and harmful materials. The synthesized Fe 3 O 4 @PANI-Au magnetic nanocatalyst was characterized by different instruments. To investigate the effect of nanocatalyst concentration on the degradation rate of azo dyes, two different catalyst concentrations were used at ambient temperature. According to the carried out calculations, degradation reaction of azo dyes with NaBH 4 in presence of the nanocatalyst is 103 to 104 times faster than degradation without using the catalyst. Graphical abstract Unlabelled Image [ABSTRACT FROM AUTHOR]

In this research Fe 3 O 4 @polythiophen-Ag magnetic nanocatalyst was synthesized. First Fe 3 O 4 nanoparticles were prepared in the solution and the branched polythiophene was coated on the magnetic particles. This polymer provides enough surface for precipitation of the silver nanocatalyst produced by grapefruit peel extract reduction of AgNO 3 . The synthesized catalyst was characterized by XRD, FTIR, SEM, FESEM, EDX, TEM, TGA and VSM. Finally, it was used to degrade azo dyes (methyl orange (MO) and methylene blue (MB)) in order to evaluate its catalytic performance. Ratio of the rate constants of the catalytic and non-catalytic reactions was in order of 10 5 and 10 4 for reduction reaction of MB and MO respectively. Reaction rate in the presence of catalyst was very high and just 1 min was enough to degrade the MB and MO colorant reagents. The prepared catalyst is able to take part many times in the reaction. It was recovered by a magnet after each experiment and reused 8 times without considerable loss of the activity. [ABSTRACT FROM AUTHOR]

In the last few years, many industrial sectors have generated and discharged large volumes of saline wastewater into the environment. In the present work, the electrochemical removal of nitrogen compounds from synthetic saline wastewater was investigated through a lab-scale experimental reactor. Experiments were carried out to examine the impacts of the operational parameters, such as electrolyte composition and concentration, applied current intensity, and initial ammoniacal nitrogen concentration, on the total nitrogen removal efficiency. Using NaCl as an electrolyte, the NTOT removal was higher than Na2SO4 and NaClO4; however, increasing the initial NaCl concentration over 250 mg·L−1 resulted in no benefits for the NTOT removal efficiency. A rise in the current intensity from 0.05 A to 0.15 A resulted in an improvement in NTOT removal. Nevertheless, a further increase to 0.25 A led to basically no enhancement of the efficiency. A lower initial ammoniacal nitrogen concentration resulted in higher removal efficiency. The highest NTOT removal (about 75%) was achieved after 90 min of treatment operating with a NaCl concentration of 250 mg·L−1 at an applied current intensity of 0.15 A and with an initial ammoniacal nitrogen concentration of 13 mg·L−1. The nitrogen degradation mechanism proposed assumes a series–parallel reaction system, with a first step in which NH4+ is in equilibrium with NH3. Moreover, the nitrogen molar balance showed that the main product of nitrogen oxidation was N2, but NO3− was also detected. Collectively, electrochemical treatment is a promising approach for the removal of nitrogen compounds from impacted saline wastewater. [ABSTRACT FROM AUTHOR]