The role of particle size on the conductive diamond electrochemical oxidation of soil-washing effluent polluted with atrazine

Abstract

In this work, the electrochemical oxidation of synthetic urine by anodic oxidation using boron-doped diamond (BDD) as anode and stainless steel as cathode was investigated. Results show that complete depletion of COD and TOC can be attained regardless of the current density applied in the range 20-100 mA cm-2. Oxalic and oxamic acids, and, in lower concentrations, creatol and guanidine were identified as the main intermediates. Chloride ions play a very important role as mediators and contribute not only to obtain a high efficiency in the removal of the organics but also to obtain an efficient removal of nitrogen by the transformation of the various raw nitrogen species into gaseous nitrogen through chloramine formation. Main drawback of the technology is the formation of chlorates and perchlorates as final chlorine products. The increase of current density from 20 mA cm-2 to 60 mA cm-2 led to an increase in the rate of COD and TOC removals although the process becomes less efficient in terms of energy consumption (removals of COD and TOC after applying 18 Ah dm-3 were 93.94 and 94.94%, respectively at 20 mA cm-2 and 89.17 and 86.72%, respectively, at 60 mA cm-2). The most efficient conditions are low current densities and high temperature reaching total mineralization at an applied charge as low as 20 kAh m-3. This result confirmed that the electrolysis using diamond anodes is a very interesting technology for the treatment of urine.

Solar‐powered BDD‐electrolysis remediation of soil washing fluid spiked with diesel

“…The samples were placed in a thermos‐regulated glass tank and circulated through the cell by a peristaltic pump at a 200 dm 3 h −1 flow rate. A constant applied current density ( j ) of 30 mA cm −2 provided by a power supply (MPL‐3505M, Minipa‐3505/Santa Catarina, Brazil) was used throughout the BDD‐electrolysis . However, before the BDD‐electrolysis, the electrode was polarized for 10 min in a 0.05 mol L –1 Na 2 SO 4 solution at 30 mA cm −2 to remove any impurities from its surface .…”

“…Among the used technologies, soil washing is an efficient technique which is particularly interesting due to the possibility to remove organic and inorganic compounds from the soil . Unfortunately, the high hydrophobicity of most TPH typically results in a low removal efficiency . Surfactant‐aided soil‐washing (SASW) is an ex situ process which involves excavation of contaminated soil and its subsequent treatment at the surface .…”

“…Consequently, these surfactants affect the time necessary to treat a site compared to the use of water alone. Therefore, solubilizing agents such as Tween 80, β‐cyclodextrin, Poloxamer 407, and sodium dodecyl sulfate (SDS), have been used for soil remediation …”

Anodic oxidation for the remediation of soils polluted with perchloroethylene

“…The main characteristics of the soil are shown in Table . Soil washing was carried out in a stirred batch tank as described elsewhere …”

Utilization of a new optical sensor unit to monitor the electrochemical elimination of selected dyes in water

“…Pre-treatment has been found important for significant decrease of organic content and colour of dye polluted water. In recent years, electrochemical treatment processes, especially electrochemical oxidation and electrocoagulation, have been studied as alternatives for degradation of various types of organic pollutants in wastewater [2,3]. Electrochemical oxidation is the process of oxidizing pollutants on the electrode surface, through the formation of disinfectants such as oxygen species from water itself as in equation (1- …”