In this study, a novel rotating anode-based reactor (RAR) was designed to investigate its effectiveness in removing dissolved salts (i.e., Br⁻, Cl⁻, TDS, and SO₄²⁻) from saline water samples. Two configurations of an impeller’s rotating anode with various operation factors, such as operating time (min), rotating speed (rpm), current density (mA/cm²), temperature (°C), pH, and inter-electrode space (cm), were used in the desalination process. The total cost consumed was calculated on the basis of the energy consumption and aluminum (Al) used in the desalination. In this respect, operating costs were calculated using optimal operating conditions. Salinity was removed electrochemically from saline water through electrocoagulation (EC). Results showed that the optimal adjustments for treating saline water were carried out at the following conditions: 150 and 75 rpm rotating speeds for the impeller’s rod anode and plate anode designs, respectively; 2 mA/cm² current density (I), 1 cm² inter-electrode space, 25 °C temperature, 10 min operation time, and pH 8. The results indicated that EC technology with impeller plates of rotating anode can be considered a very cost-effective technique for treating saline water.

Pore water is a crucial storage medium and a key source of sediment phosphorus. A novel equipment based on electrokinetic geosynthetics (EKGs) was used for isolating phosphorus from eutrophic lake sediments through pore water drainage. Three mutually independent indoor group experiments (A, B, and C) were conducted to investigate the effects of voltage gradient (0.00, 0.25, and 0.50 V/cm) on pore water drainage capacity, phosphorus removal performance, sediment physicochemical properties, and phosphorus storage dynamics. The average reduction in the sediment moisture and total phosphorus content was 2.5%, 4.3%, and 4.6% and 28.15, 75.95, and 112.65 mg/kg after 6 days of treatment for A, B and C, respectively. Efficient pore water drainage through gravity and electroosmotic flow and electromigration of phosphate were the main drivers of sediment-dissolved and mobilized phosphorus separation. A high voltage gradient facilitated the migration of pore water and the phosphorus in it. The maximal effluent total phosphorous (TP) concentration was up to 27.9 times that in the initial pore water samples, and negligible effluent TP was detected when the pore water pH was less than 2.5. The TP concentration was exponentially and linearly related to the pH and electronic conductivity of the electroosmotic flow, respectively. The migration of H⁺ within the sediment matrix promoted the liberation of metals bounded to phosphorus, particularly of Ca–P and Fe–P. Pore water drainage through an EKG resulted in Ex–P separation of up to 87.50% and a 13.84 mg/kg decrease in Ca–P and 125.35 mg/kg accumulation of low mobile Fe–P in the weak acid anode zone.

In this study, response of the microbial communities associated with the bioremediation of crude oil contaminated marine sediments was addressed using sediment microbial fuel cells (SMFCs). Crude oil was spiked into marine sediments at 1 g/kg of dry sediment to simulate a heavily contaminated marine environment. Conventional SMFCs were used with carbon fiber brushes as the electrode components and were enhanced with ferric iron to stimulate electrochemically active bacteria. Controls were operated under open circuit with and without ferric iron stimulation, with the latter condition simulating natural attenuation. Crude oil removal in the Fe enhanced SMFCs reached 22.0 ± 5.5% and was comparable to the measured removal in the control treatments (19.2 ± 7.4% in natural attenuation SMFCs and 15.2 ± 2.7% in Fe stimulated open circuit SMFCs), indicating no major enhancement to biodegradation under the applied experimental conditions. The low removal efficiency could be due to limitations in the mass transfer of the electron donor to the microbes and the anodes. The microbial community structure showed similarity between the iron stimulated SMFCs operated under the open and closed circuit. Natural attenuation SMFCs showed a unique profile. All SMFCs showed high relative abundances of hydrocarbon degrading bacteria rather than anode reducers, such as Marinobacter and Arthrobacter in the case of the natural attenuation SMFCs, and Gordonia in the case of iron stimulated SMFCs. This indicated that the microbial structure during the bioremediation process was mainly determined by the presence of petroleum contamination and to a lesser extent the presence of the ferric iron, with no major involvement of the anode as a terminal electron acceptor. Under the adopted experimental conditions, the absence of electrochemically active microbes throughout the biodegradation process indicates that the use of SMFCs in crude oil bioremediation is not a successful approach. Further studies are required to optimize SMFCs systems for this aim.

In this work, the electrochemical degradation of antibiotic ceftazidime has been studied using a novel rare earth metal Ce and carbon nanotubes codoped PbO₂ electrode. A competitively high oxygen evolution potential (2.4 V) and enhanced catalytic surface area were obtained, evidence by LSV and CV electrochemical characterization. The G/CNT-Ce/PbO₂–Ce electrode possessed a more compact structure and a smaller grain size than the other PbO₂ and Ce–PbO₂ electrodes, exhibiting a prolonged service lifetime, evidence by accelerated lifespan test and recycling degradation experiment. As electrolysis time reached 120 min, the removal efficiency of ceftazidime and TOC arrived at 100.0% and 54.2% respectively in 0.05 M Na₂SO₄ solution containing 50 mg⋅L⁻¹ ceftazidime. The effect of applied current density, pH value, initial ceftazidime concentration and chloride contents on the degradation performance were systematically evaluated. The results demonstrated that electrochemical oxidation of ceftazidime over the G/CNT-Ce/PbO₂–Ce electrode was highly effective, and the mineralization rate was greatly improved, compared with pristine PbO₂ electrode. Considering the toxicity was increased after 30 min electrolysis, the intermediates were quantitatively investigated through HPLC-MS, GC-MS and IC technology. According to the identified products, a reaction mechanism has been proposed and pyridine and aminothiazole were detected with concentration from approximately 1 to 3 mg⋅L⁻¹, which were regarded as toxic byproducts during electrooxidation. Further electrocatalyzing by ring cleavage reaction and complete mineralization to CO₂, NO₃⁻ and NH₄⁺ was proposed, which demonstrated the G/CNT-Ce/PbO₂–Ce electrode exhibited high efficiency for ceftazidime removal in mild conditions.

Remediation of heavy metal contaminated soils remains a global challenge. Here, low-molecular-weight organic acids were used to extract Cu and Zn from polluted soils, and the extracted heavy metals were subsequently adsorbed by activated carbon electrodes. The electrochemical adsorption mechanism as well as the influence of pH, organic acid type and voltage were investigated, and the soil remediation effect was further evaluated by the cultivation of rape. After extraction by citrate at initial pH 8.3 and electrochemical adsorption at 0.9 V for 7 d, the concentrations of total and bioavailable Cu in soils decreased from 1090 to 281 to 391 and 52 mg kg⁻¹, and those of Zn decreased from 262 to 39 to 208 and 30 mg kg⁻¹, respectively. Cu and Zn ions were mainly electrochemically adsorbed on the carbon cathode and anode, respectively, resulting in decreases of their concentrations to below 1 mg L⁻¹ in the leachate. The presence of organic acids improved the remediation performance in the order of citrate > oxalate > acetate. The decrease in the initial pH of citrate solution enhanced the removal rate of Zn, while seemed to have no effect on that of Cu. The removal capacity for heavy metals decreased with decreasing cell voltage from 0.9 to 0.3 V. In the rape cultivation experiment, the Cu and Zn contents in shoot and root were decreased by more than 50%, validating the soil remediation effect. The present work proposes a facile method for heavy metal removal from contaminated soils.

Sacrificial anodes are attached to the hulls of boats and marine structures to prevent corrosion. Their use inevitably leads to release of zinc as well as impurities in the zinc alloy such as cadmium to the saline environment. Risk assessments and source apportionment exercises require accurate assessments of the potential loads of chemicals into the environment. This research has surveyed a wide variety of zinc anodes for their composition to compare against a reported industry standard as well as using differing methodologies to determine the dissolution rate of zinc and cadmium from anodes. A zinc dissolution rate of 477 g/yr/kg of anode is proposed. Although most anodes tested had concentrations of cadmium within the prescribed limits set by the reported standard, calculated leaching rates from laboratory dissolution experiments suggested as much as 400 g per year of cadmium could leach from zinc anodes used on leisure vessels within UK waters.

This work aimed to remove sulfate and acidity from mine-impacted water (MIW) via electrocoagulation (EC), a technique which stands as an advanced alternative to chemical coagulation in pollutant removal from wastewaters. The multiple electrochemical reactions occurring in the aluminum anode and the stainless steel cathode surfaces can form unstable flakes of metal hydroxysulfate complexes, causing coagulation, flocculation, and floatation; or, adsorption of sulfate on sorbents originated from the electrochemical process can occur, depending on pH value. Batch experiments in the continuous mode of exposition using different current densities (35, 50, and 65 A m⁻²) were tested, and a statistical difference between their sulfate removals was detected. Furthermore, the intermittent mode of exposure was also tested by performing a 2²-factorial design to verify the combination with different current densities, concluding that better efficiencies of sulfate removal were obtained in the continuous mode of exposition, even with lower current densities. After 5 h of electrocoagulation, sulfate could be removed from MIW with a mean efficiency of 70.95% (in continuous mode of exposition and 65 A m⁻² current density), and this sulfate removal follows probable third-order decay kinetics in accordance with the quick drop in sulfate concentration until 3 h of exposure time, remaining virtually constant at longer times. Graphical abstract

The oily wastewater was treated by electrocoagulation with Fe₇₈Si₉B₁₃ amorphous ribbons as anode and graphite plates as cathode under such processing parameters as different pH values and current density, respectively. The degradation effect on the oily wastewater was characterized by chemical demand oxygen (COD), while the ribbons before and after using were analyzed by X-ray diffraction (XRD) and scanning electron microscope (SEM). The results indicate that under the conditions of pH = 3 and current density being 3.125 A/cm², the optimal COD removal efficiency was obtained to be 73.22%. Compared with the ordinary crystalline iron plate, the COD removal efficiency of resultant wastewater degraded by the amorphous ribbons is more than doubled. Simultaneously, the Fe₇₈Si₉B₁₃ amorphous ribbons exhibit good structural stability even after four cycles of using.

In this work, removal of antipyrine was studied through two-dimensional (2D) and three-dimensional (3D) electrolysis. 2D electrolysis was firstly studied with the Ti/SnO₂-Ta₂O₅-IrO₂ anode as working electrode. Operating parameters affecting antipyrine removal, such as current density, electrode distance, and initial concentration of antipyrine, were investigated and optimized. As the limited antipyrine removal efficiency of 48.0% was not satisfying, 3D electrolysis with γ-Al₂O₃ as particle electrodes was introduced in the purpose of improving the antipyrine removal. An obviously enhanced removal efficiency of 78.3% was obtained, which seemingly validated the effect of particle electrodes in improving antipyrine removal. Hence, an effort to further enhance the antipyrine removal efficiency was made through improving the electrochemical characteristics of γ-Al₂O₃ as particle electrodes. Modified Sn-Sb-Bi/γ-Al₂O₃ particles were thus prepared through impregnation method. And a desirable antipyrine removal efficiency of 94.4% and energy consumption of 0.18 kWh/g antipyrine were achieved in the 3D electrolysis with Sn-Sb-Bi/γ-Al₂O₃ as particle electrodes. Furthermore, possible mechanism and pathway of antipyrine degradation in 3D electrolysis were explored through detection of ·OH using terephthalic acid fluorescent probe method and detection of antipyrine degradation intermediates using LC-MS.

Phosphorus removal from wastewater is very important in order to prevent water eutrophication. Although there are many ways to remove phosphorus, electrocoagulation (EC) is a promising method. However, the efficiency of conventional EC processes needs to be further improved. In this study, magnetized iron particle anodes used for EC were fabricated and batch experiments were conducted. The results showed that magnetized anode configuration (iron powder, iron filings, iron sheet), current density (i), as well as electrolysis time had significant effects on phosphorus removal. Particle electrodes (e.g., iron powder) with both large specific surface area and high current density were beneficial for phosphorus removal. Simultaneously, anode magnetization could also enhance the phosphorus removal to some extent based on the effect of magnetic field (MF) on water characteristics (e.g., conductivity). Combining the advantages of particle electrode and MF, magnetized particle anode was superior to other electrodes in phosphorus removal and cell voltage maintenance. Compared with the conventional plate anode, the magnetized iron particle anode was more economical and could reduce operating cost by more than 50%. The results are useful for the practical application of phosphorus removal by EC.