The search for new bacterial consortia capable of removing PAH from the environment is associated with the need to employ novel, simple, and economically efficient detection methods. A fluorimetric method (FL) as well as high voltage electrochemiluminescence (ECL) on a modified surface of an aluminum electrode were used in order to determine the changes in the concentrations of PAH in the studied aqueous solutions. The ECL signal (the spectrum and emission intensity for a given wavelength) was determined with the use of an apparatus operating in single photon counting mode. The dependency of ECL and FL intensity on the concentration of naphthalene, phenanthrene, and pyrene was linear in the studied concentration range. The biodegradation kinetics of the particular PAH compounds was determined on the basis of the obtained spectroscopic determinations. It has been established that the half-life of naphthalene, phenanthrene, and pyrene at initial concentrations of 50 mg/l (beyond the solubility limit) reached 41, 75, and 130 h, accordingly. Additionally, the possibility of using ECL for rapid determination of the soluble fraction of PAH directly in the aqueous medium has been confirmed. Metagenomic analysis of the gene encoding 16S rRNA was conducted on the basis of V4 hypervariable region of the 16S rRNA gene and allowed to identify 198 species of bacteria that create the S4consortium. The consortium was dominated by Gammaproteobacteria (78.82 %), Flavobacteria (9.25 %), Betaproteobacteria (7.68 %), Sphingobacteria (3.76 %), Alphaproteobacteria (0.42 %), Clostridia (0.04 %), and Bacilli (0.03 %).

The dust removal performance of two types of modified electrode electrostatic precipitator systems was evaluated and compared with that of a conventional aluminum plate electrode using laboratory-scale experiments. In the novel electrode systems, the electrode surface was coated with activated carbon using a mixed slurry containing carbon black, polyvinyl acetate, and methanol. The modification of the electrode surface improved dust precipitation by increasing the specific capacitance of the electrode. The modification also lowered the electrode’s resistance and increased its specific surface area. The optimum electrode spacing and electric voltage supply were determined using batch-type tests. In addition, dielectric insulators were applied as a partition between the oppositely charged electrodes equipped with the modified electrode plates. Multi-layered office paper cut to the same size as the electrodes was used as an insulating material. The addition of the insulator resulted in excellent improvement in the dust removal performance by minimizing the back-corona discharge phenomenon as well as doubling the dust collecting surface. Continuous dust removal tests with the three electrode systems revealed that whereas the conventional aluminum electrode exhibited 54 % dust removal, the activated carbon (AC)-coated system showed 85 % and AC-coated + insulator system showed 90 % and higher dust removal efficiency.

The electrokinetic transport of sulfate was investigated as a means of treating and restoring a sulfate-accumulating saline soil. The electrokinetic treatment decreased the electrical conductivity of the soil, an indicator of soil salinity, to 58.6, 73.1, and 83.5 % for 7, 14, and 21 days, respectively. More than 96 % of the chloride and nitrate were removed within 7 days. However, the removal of sulfate was highly influenced by the anode material. An iron anode removed sulfate effectively, whereas sulfate was hyper-accumulated in the anodic region when an inert anode was used. The iron anode was oxidized in a sacrificial anodic reaction, which competed with the electrolysis reaction of water at the anode, and finally, the reaction prevented the severe acidification of the soil in the anodic region. However, the competing reactions produced hydrogen ions at the anode and the ions were transported toward the cathode, which, in turn, acidified the soil, especially in the anodic region. The acidification switched the surface charge of the soil from negative to positive, increasing the interaction between the soil surface and sulfate and thus inhibiting the transport of sulfate under the electric field. The zeta potential analysis of the soil provided an explanation. The results indicate that preventing severe acidification is an important factor which influences the transport of anions and iron anode for the enhanced removal of anionic pollutants by electrokinetic remediation.

The adsorbents (such as hydrous ferric oxides, HFO) generated in the electrocoagulation (EC) processing with iron electrodes are able to remove effectively inorganic arsenic (As) present in underground water. A characterization of the HFO phases produced during the arsenic removal by the EC process from low and high arsenic concentration, by using X-ray diffraction (XRD), Raman spectroscopy, Fourier transform infrared (FTIR) spectroscopy, energy dispersive X-ray spectroscopy (EDS) and scanning electron microscopy (SEM), is presented. The main HFO phase produced by this process is lepidocrocite (γ-FeOOH), and that the sorption of arsenic by this solid-state phase formed as part of the EC process was effective in removing arsenic from aqueous solution.

In this study, electrocoagulation (EC) with hybrid Fe–Al electrodes was used to remove antimony from contaminated surface water. Response surface methodology was applied to investigate the interactive effects of the operating parameters on antimony removal and optimize these variables. Results showed that the relationship between operating parameters and the response was well described by a second-order polynomial equation. Under the optimal conditions of current density 2.58 mA/cm², pH 5.24, initial concentration 521.3 μg/L, and time 89.17 min, more than 99 % antimony were removed. Besides, the antimony adsorption behavior in EC process was also investigated. Adsorption kinetics and isotherms studies suggested that the adsorption process followed well the pseudo-second-order kinetic model and the Langmuir adsorption model, respectively. Adsorption thermodynamics study revealed that the reaction was spontaneous, endothermic, and thermodynamically favorable. These results further proved that the main mechanism involved in antimony removal in EC process could be chemisorption.

The aim of this study is to develop a process that combines electrocoagulation and electroperoxidation (EC-EP) and to evaluate its performance in treating domestic wastewaters (DWW). Electrolysis was performed using a parallelepipedic electrolytic cell (0.5 L) containing one sacrificial anode (mild steel or aluminum) and one cathode (vitreous carbon). The effects of the treatment time, current density, and type of anode electrode on the process performance were examined. The experimental results revealed that a current density of 4.0 mA cm⁻² was beneficial for DWW treatment. There was a decrease in the chemical oxygen demand (COD), suspended solid (SS), turbidity, color, and total phosphorus (Pₜₒₜ) by 67 ± 9, 98 ± 2, 55 ± 10, 61 ± 9, and 97 ± 0 %, respectively, for a treatment time of 60 min in the electrolysis cell in the presence of mild steel (anode) and vitreous carbon (cathode) electrodes. The process was also determined to be effective for removing pathogens (99 ± 1 % removal), such as fecal coliform (the log-inactivation was higher than 2 units).

The novel titanium oxide/active carbon fiber (TiO₂/ACF) electrode was prepared, and electrosorptive properties for As(V) in aqueous solution were investigated. The structure of TiO₂/ACF was characterized with transmission electron microscopy (TEM), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR). Furthermore, the As(V) electrosorptive properties of TiO₂/ACF electrodes with calcination temperature, ionic species, and loaded amount of TiO₂ were measured, and the electrosorption isotherm and kinetics were investigated at the applied voltage of 1.5 V. The optimal load quality of TiO₂ was 0.80 g per ACF electrode (length × width × height = 2 cm × 1 cm × 0.4 cm, 0.30 g), and optimum calcination temperature was 450 °C. The maximum electrosorption capacity of TiO₂/ACF was 8.09 mg/g, about 200 % higher than that of ACF. Moreover, the electrode performance was stable than other materials such as pure ACF, manganese oxide/ACF, and iron oxides/ACF. It can process 100 ppb As(V) of water to 6 ppb (reach the drinking water standards of WHO), demonstrating that our novel electrode is with potential practical application.

Submerged harbor steel structures often employ cathodic protection using galvanic anodes to guard against corrosion. A laboratory experiment, with three different cathodic protection configurations by galvanic aluminum-based anodes, was performed to evaluate the potential metal transfer from the anodic alloy dissolution into the surrounding marine water. The anode dissolution rate is proportional to the imposed current demands and induced a significant Al, In, and Zn transfer in the dissolved and particulate fractions of the corrosion product layers covering the anode surface. These layers were poorly adherent, even under low hydrodynamic conditions. Consequently, at the anode vicinity, the suspended particle matter and dissolved fraction of surrounding marine waters showed strong enrichments in Al and Zn, respectively, the values of which could potentially affect the adjacent biota. After the anode activation period, however, the metal inputs from galvanic anode dissolution are rapidly diluted by seawater renewal. At regional scale, these metal fluxes should be negligible compared to river and wastewater fluxes. These results also showed that it is difficult to assess the impact of the anode dissolution on the concentrations of metals in the natural environment, especially for metals included in trace amounts in the anode alloy (i.e., Cu, Fe, In, Mn, and Si) in the aquatic compartment.

Three commercial electrodes, Ta-Ir/TiO₂, Rh-Ir/TiO₂, and PbO₂/TiO₂, were used as electrochemical anodes, and their performance was evaluated by the electrochemical oxidation of ammonia at neutral pH in a continuous electrochemical quadrangular reactor. Based on the cyclic voltammetry scans and volt-ampere relation analysis, in direct oxidation, the oxygen evolution from H₂O₂decomposition was completely inhibited, and more•OH radicals could be then generated over PbO₂/TiO₂and in the presence of powder activated carbon (PAC). PbO₂/TiO₂can be indicated as an appropriate for the direct electrooxidation of ammonia in an unpacked bed reactor. While the efficiency for direct oxidation of ammonia was similar for the three anodes in a PAC packed reactor due to the presence of PAC could avoid short circuit and enhance electric efficiency. In indirect oxidation mediated by active free chlorine, Rh-Ir/TiO₂was the most effective in ammonia removal when chloride was present in the reaction system, and the disappeared ammonia was mainly transferred to N₂, and only a small part was converted into nitrate (there was no nitrite detected during the reaction). The results indicated that Rh-Ir/TiO₂had the highest oxidation capability for ammonia compared with Ta-Ir/TiO₂and PbO₂/TiO₂. Hence, Rh-Ir/TiO₂based on a PAC packed bed reactor provides an alternative for the treatment of ammonia wastewater with high chloride concentration.

Plastics from cathode ray tube (CRT) casings were sampled in Nigeria and analysed for their polybrominated dibenzo-p-dioxin and dibenzofuran (PBDD/F) content. PBDD/Fs, consisting mainly of PBDFs, were detected in BFR containing plastic with a median (mean) concentration of 18,000 ng/g (41,000 ng/g). The PBDD/Fs levels were highest in samples containing PBDEs, but the levels of PBDFs were two orders of magnitude higher than the levels reported in the technical PBDE mixtures and where frequently exceeding 1000 μg/g of PBDE content. These higher levels are likely to arise from additional transformation of PBDEs during production, use, recycling, or storage, but the processes responsible were not identified in this study. PBDD/Fs in CRT casings containing1,2-bistribromophenoxyethane (TBPE) were dominated by tetrabrominated dibenzo-p-dioxin (TBDDs) with concentrations around 10 μg/g of the TBPE content. The PBDD/Fs in CRT casings containing tetrabromobisphenol A (TBBPA) were found at concentrations around 0.1 μg/g of TBBPA levels. Casings treated with TBPE or TBBPA often contained PBDEs (and PBDF) as impurities—probably originating from recycled e-waste plastics. It was estimated that the 237,000 t of CRT casings stockpiled in Nigeria contain between 2 and 8 t of PBDD/Fs. The total PBDD/F contamination in polymers arising from total historic PBDE production/use is estimated in the order of 1000 t. TEQ values of CRT samples frequently exceeded the Basel Convention’s provisional low POPs content of 15 ng TEQ/g. Due to the significant risks to health associated with PBDD/Fs, more detailed studies on the exposure routes from PBDD/Fs in stockpiles are needed.