RESUMO
This study investigated the potential of a novel biomass-derived cork as a suitable catalyst after its modification with Fe@Fe2O3 for in-situ application in heterogeneous electro-Fenton (HEF) process for benzoquinone (BQ) elimination from water. No attempts on the application of modified granulated cork (GC) as a suspended heterogeneous catalyst in the HEF process for water treatment have been published yet. GC was modified by sonification approach in a FeCl3 + NaBH4 solution to reduce the ferric ions to metallic iron in order to obtain Fe@Fe2O3-modified GC (Fe@Fe2O3/GC). Results clearly demonstrated that this catalyst exhibited excellent electrocatalytic properties, such as a high conductivity as well as relatively high redox current and possessed several active sites for water depollution applications. Using Fe@Fe2O3/GC as catalyst in HEF, 100% of BQ removal was achieved in synthetic solutions by applying 33.3â¯mAâ¯cm-2 after 120â¯min. Different experimental conditions were tested to determine that best possible conditions can be as follow: 50â¯mmolâ¯L-1 Na2SO4 and 10â¯mgâ¯L-1 of Fe@Fe2O3/GC catalyst using Pt/carbon-PTFE air diffusion cell by applying 33.3â¯mAâ¯cm-2. Nevertheless, when Fe@Fe2O3/GC was used in the HEF approach to depollute real water matrices, no complete BQ concentration was removal achieved after 300â¯min of treatment, achieving between 80 and 95% of effectiveness.
Assuntos
Ferro , Poluentes Químicos da Água , Ferro/química , Carbono/química , Peróxido de Hidrogênio/química , Catálise , Poluentes Químicos da Água/análise , OxirreduçãoRESUMO
This work focuses on the electrochemical production of hydrogen peroxide in supporting electrolytes containing perchlorate ions for being used as a reagent in the reduction of chlorates to produce chlorine dioxide, as a first step in the manufacture of portable ClO2 production devices. This study evaluates the effect of the current density, pressure, and temperature on the production of hydrogen peroxide, and concentrations over 400 mg L-1 are reached. The average rate for the formation of hydrogen peroxide is 9.85 mg h-1, and the effect of increasing electrolyte concentration (3.0 and 30.0 g L-1 perchloric acid), intensity, and pressure results in values of, respectively, -2.99, -4.49, and +7.73 mg h-1. During the manufacturing process, hydrogen peroxide is decomposed through two mechanisms. The average destruction rate is 1.93 mg h-1, and the effects of the three factors results in values of, respectively, +0.07, +0.11, and -0.12 mg h-1. Solutions of this hydrogen peroxide produced electrochemically in a perchloric acid aqueous electrolyte were used to reduce chlorates in strongly acidic media and produce chlorine dioxide. Conversions of around 100% were obtained, demonstrating that this electrochemical product can be used efficiently to reduce chlorates to chlorine dioxide.
RESUMO
In this research, firstly, the treatment of soil spiked with oxyfluorfen was studied using a surfactant-aided soil-washing (SASW) process. After that, the electrochemical treatment of the washing liquid using boron doped diamond (BDD) anodes was performed. Results clearly demonstrate that SASW is a very efficient approach in the treatment of soil, removing the pesticide completely by using dosages below 5 g of sodium dodecyl sulfate (SDS) per Kg of soil. After that, complete mineralization of organic matter (oxyflourfen, SDS and by-products) was attained (100% of total organic carbon and chemical oxygen demand removals) when the washing liquids were electrolyzed using BDD anodes, but the removal rate depends on the size of the particles in solution. Electrolysis of soil washing fluids occurs via the reduction in size of micelles until their complete depletion. Lower concentrations of intermediates are produced (sulfate, chlorine, 4-(trifluoromethyl)-phenol and ortho-nitrophenol) during BDD-electrolyzes. Finally, it is important to indicate that, sulfate (coming from SDS) and chlorine (coming from oxyfluorfen) ions play an important role during the electrochemical organic matter removal.
Assuntos
Eletrólise/métodos , Éteres Difenil Halogenados/isolamento & purificação , Poluentes do Solo/isolamento & purificação , Solo/química , Poluentes Químicos da Água/isolamento & purificação , Purificação da Água/métodos , Análise da Demanda Biológica de Oxigênio , Boro/química , Diamante/química , Eletrodos , Oxirredução , Dodecilsulfato de Sódio/química , Tensoativos/químicaRESUMO
In this work, it is studied the removal of atrazine from spiked soils by soil washing using surfactant fluids, followed by the treatment of the resulting washing waste by electrolysis with boron doped diamond (BDD) anode. Results confirm that combination of both technologies is efficient for the removal and total mineralization of atrazine. Ratio surfactant/soil is a key parameter for the removal of atrazine from soil and influences significantly in the characteristic of the wastewater produced, affecting not only to the total organic load but also to the mean size of micelles. The higher the ratio surfactant soil, the lower is the size of the particles. Electrolyses of this type of waste attain the complete mineralization. TOC and COD are removed from the start of the treatment but the key of the treatment is the reduction in size of the micelles, which lead to a higher negative charge in the surface and to the faster depletion of the surfactant as compared with the pesticide.
Assuntos
Atrazina/química , Recuperação e Remediação Ambiental/métodos , Poluentes do Solo/química , Boro/química , Diamante/química , Eletrodos , Eletrólise , Caulim/química , Oxirredução , Dodecilsulfato de Sódio/química , Sulfatos/química , Tensoativos/químicaRESUMO
Scale-up of anodic oxidation system is critical to the practical application of electrochemical treatment in bio-refractory organic wastewater treatment. In this study, the scale-up of electrochemical flow system was investigated by treating petrochemical wastewater using platinized titanium (Ti/Pt) and boron-doped diamond (BDD) anodes. It was demonstrated that flow cell was successfully scaled-up because when it was compared with batch mode (Rocha et al. 2012b), higher performances on organic matter removal were achieved. Under the suitable operating conditions and better anode material, the chemical oxygen demand (COD) of petrochemical wastewater was reduced from 2,746 to 200 mg L(-1) within 5 h with an energy consumption of only 56.2 kWh m(-3) in the scaled-up BDD anode system. These results demonstrate that anode flow system is very promising in practical bio-refractory organic wastewater treatment.
Assuntos
Eliminação de Resíduos Líquidos/métodos , Poluentes Químicos da Água/química , Análise da Demanda Biológica de Oxigênio , Boro/química , Brasil , Indústria Química , Diamante/química , Eletroquímica/métodos , Eletrodos , Indústrias Extrativas e de Processamento , Resíduos Industriais , Oxirredução , Petróleo , Águas Residuárias/químicaRESUMO
Produced water (PW) is the largest waste stream generated in oil and gas industries. The drilling and extraction operations that are aimed to maximize the production of oil may be counterbalanced by the huge production of contaminated water (called PW) with pollutants, such as heavy metals, dissolved/suspended solids, and organic compounds. PW is conventionally treated through different physical, chemical, and biological methods. In offshore platforms, because of space constraints, compact physical and chemical systems are used. However, major research efforts are being developed with innovative technologies for treating PW in order to comply with reuse and discharge limits. Among them, electrochemical technologies have been proposed as a promising alternative for the treatment of this kind of wastewaters. Then, this paper presents a minireview of efficient electrochemical technologies used until now for treating PW generated by petrochemical industry.