Uticaj hloridnih jona na elektrohemijsku oksidaciju cijanida u otpadnim vodama

The paper describes the influence of chloride ions on the electrochemical oxidation of cyanide from wastewater. Chloride ions are added in the form of NaCl (c=0.017 mol/L), and electrochemical oxidation is carried out in a laboratory electrochemical reactor with electrodes made of steel and stainless steel (j=10 mA/cm2, t=90 min). In these conditions the removal efficiency of cyanide on steel electrodes was Eu = 91.5%, and with electrodes made of stainless steel Eu = 99.5%.U radu je prikazan uticaj hloridnih jona na elektrohemijsku oksidaciju cijanida iz otpadnih voda. Hloridni joni su dodavani u obliku NaCl (c=0,017 mol/L), a elektrohemijska oksidacija je vršena u laboratorijskom elektrohemijskom reaktoru sa elektrodama od čelika i nerđajućeg čelika (j=10 mA/cm2, t=90 min.). Pri navedenim uslovima efikasnost uklanjanja cijanida na čeličnim elektrodama je bila Eu=91,5%, a sa elektrodama od nerđajućeg čelika Eu=99,5%

Combined analytical study on chemical transformations and detoxification of model phenolic pollutants during various advanced oxidation treatment processes

Advanced oxidation processes (AOPs) have been introduced to deal with different types of water pollution. They cause effective chemical destruction of pollutants, yet leading to a mixture of transformation by-products, rather than complete mineralization. Therefore, the aim of our study was to understand complex degradation processes induced by different AOPs from chemical and ecotoxicological point of view. Phenol, 2,4-dichlorophenol, and pentachlorophenol were used as model pollutants since they are still common industrial chemicals and thus encountered in the aquatic environment. A comprehensive study of efficiency of several AOPs was undertaken by using instrumental analyses along with ecotoxicological assessment. Four approaches were compared: ozonation, photocatalytic oxidation with immobilized nitrogen-doped TiO$_2$ thin films, the sequence of both, as well as electrooxidation on boron-doped diamond (BDD) and mixed metal oxide (MMO) anodes. The monitored parameters were: removal of target phenols, dechlorination, transformation products, and ecotoxicological impact. Therefore, HPLC–DAD, GC–MS, UHPLC–MS/MS, ion chromatography, and 48 h inhibition tests on Daphnia magna were applied. In addition, pH and total organic carbon (TOC) were measured. Results show that ozonation provides by far the most suitable pattern of degradation accompanied by rapid detoxification. In contrast, photocatalysis was found to be slow and mild, marked by the accumulation of aromatic products. Preozonation reinforces the photocatalytic process. Regarding the electrooxidations, BDD is more effective than MMO, while the degradation pattern and transformation products formed depend on supporting electrolyte

Electrochemical treatment of wastewater to remove contaminants from the production and disposal of plastics

Wastewater is major source of contaminants originating from the production, usage, and disposal of plastic materials. Due to their poor biodegradability of these contaminants in municipal wastewater treatment plants, additional advanced oxidation processes such as electrochemical treatments have been developed to improve the standard biological treatment. Here we review the applications of electrochemical treatments of wastewater for the removal of the following plastic contaminants: bisphenol A, phthalic acid esters, and benzotriazoles. We present the effectiveness of treatment in terms of contaminant removal and mineralizationthe identification of transformation productstoxicity assessmentand process energy requirements. In the present review, we have focused on the applications of electrochemical treatments of wastewater for the removal of three important groups of contaminants originating mainly from plastics: bisphenol A, phthalic acid esters, and benzotriazoles. The review focuses on the research of electrochemical treatments for these contaminants from the last five years. The papers are assessed from the point of i) effectiveness of treatment in terms of contaminant removal and mineralizationii) identification of transformation productsiii) toxicity assessmentiv) processes’ energy requirements. Electrochemical treatments were confirmed to be a viable option for the removal of selected contaminants from wastewater

Electrooxidation of polar benzotriazole - The impact of supporting electrolyte

Polar benzotriazoles are heterocyclic compounds widely used in industry, and as such are easily released into the environment. These compounds show harmful and toxic effects on plants and some aquatic organisms, biodegrade quite slowly, and some, depending on the structure, have the ability to bioaccumulate. They can only be partially removed by conventional wastewater treatment, and are therefore found in a variety of waters, as well as solid waste. In this paper, synthetic wastewater containing polar benzotriazole was treated by an electrooxidation process. The efficiency of the treatment was tested depending on various parameters, such as: anode material (mixed metal oxide - MMO and boron-doped diamond - BDD), applied current density (10 and 20 mA/cm2), type of supporting electrolyte (NaCl, Na2CO3, Na2SO4, H2SO4) and treatment time (0.5 - 2.5 h). Obtained results showed the treatment was more effective at higher current density and by using BDD anode. Also, the efficiency of the treatment increases with the prolongation of the electrolysis time. After 2.5 h of treatment, 97.9% of benzotriazole was removed, in the presence of sulfuric acid as supporting electrolyte