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The aim of this study was to investigate different microbial electrolysis desalination cells for malic acid production. The systems included microbial electrolysis desalination and chemical-production cell (MEDCC), microbial electrolysis desalination cell (MEDC) with bipolar membrane and anion exchange membrane (BP-A MEDC), MEDC with bipolar membrane and cation exchange membrane (BP-C MEDC), and modified microbial desalination cell (M-MDC). The microbial electrolysis desalination cells performed differently in terms of malic acid production and energy consumption. The MEDCC performed best with the highest malic acid production rate (18.4 ± 0.6 mmol/L h) and the lowest energy consumption (0.35 ± 0.14 kW h/kg). The best performance of MEDCC was attributable to the neutral pH condition in the anode chamber, the lowest internal resistance, and the highest Geobacter percentage of the anode biofilm population among all the reactors. [ABSTRACT FROM AUTHOR]

The aim of this study was to investigate the feasibility of tetramethylammonium hydroxide (TMAH) production using the microbial electrolysis desalination and chemical-production cell (MEDCC). With 1.0 g/L acetate in the anode chamber and tetramethylammonium chloride solutions with different concentrations in the desalination chamber, TMAH could be efficiently produced in the cathode chamber of MEDCC. With an applied voltage of 1.0 V, the concentration of TMAH reached 0.087 M within 17.5 h, with current efficiency of 52–58%. The electrical energy consumed for the TMAH production using the MEDCC was 0.76 kWh/kg, which was only 5–12% of that for the electrolysis and electrodialysis process. With the high value of TMAH produced in a friendly environment with low energy consumption, the MEDCC should be a potentially valuable method for the chemical production in practice. [ABSTRACT FROM AUTHOR]

Malic acid is a valuable organic acid and important acidulant in food and pharmaceutical industries and can be produced using electrodialysis with bipolar membrane (EDBM). The aim of this study was to investigate the possibility of malic acid production using a system integrating EDBM and biochemical process, i.e., the microbial electrodialysis and chemical-production cell (MEDCC). With an applied voltage of 1.0 V, the MEDCC successfully conversed 0.3 M malate into 0.23 M malic acid, which was about four times as that produced in the EDBM (0.06 M). The maximum current density in the MEDCC was five times higher than that in the EDBM (10 vs. 1.9 A/m 2 ). The specific electric consumption for the malic acid production in the MEDCC was 0.34 kWh/kg, which was only 10–30% of that in the reported EDBMs. In the MEDCC, the energy from the anode biodegradation provided about 50% of the total energy demand (0.68 kWh/kg) during the malic acid production. Our results show that the MEDCC should be a promising method for organic acid production with advantages of lower electrical consumption and diverse substrates utilized by exoelectrogens. [ABSTRACT FROM AUTHOR]

The combination of the microbial electrolysis desalination and chemical-production cell (MEDCC) and Fenton process for the pesticide wastewater treatment was investigate in this study. Real wastewater with several toxic pesticides, 1633 mg/L COD, and 200 in chromaticity was used for the investigation. Results showed that desalination in the desalination chamber of MEDCC reached 78%. Organics with low molecular weights in the desalination chamber could be removed from the desalination chamber, resulting in 28% and 23% of the total COD in the acid-production and cathode chambers, respectively. The desalination in the desalination chamber and organic transfer contributed to removal of pesticides (e.g., triadimefon), which could not be removed with other methods, and of the organics with low molecular weights. The COD in the effluent of the MEDCC combined the Fenton process was much lower than that in the perixo-coagulaiton process (< 150 vs. 555 mg/L). The combined method consumed much less energy and acid for the pH adjustment than that the Fenton. [ABSTRACT FROM AUTHOR]

The membrane concentrate from landfill leachate has great potential risks of the environmental pollution. The aim of this study was to investigate the structure effect of stacked electro-Fenton (EF) reactor on the nanofiltration (NF) concentrate treatment from landfill leachate. The stacked EF reactor was constructed with a carbon-PTFE gas diffusion cathode and an IrO 2 -Ta 2 O 5 anode with different electrode spacings (i.e., 2, 5, 10, and 40 mm) and electrode pairs (i.e., 1, 3, 6, and 9). Results showed that smaller electrode spacing and more electrode pairs in the stacked EF reactor improved the COD removal in the NF concentrate treatment. The specific energy consumption decreased with smaller electrode spacing but increased with more electrode pairs. Under the current density of 15 mA cm −2 , Fe 2+ dosage of 560 mg L −1 , the stacked EF reactor with 9 electrode pairs and the electrode spacing of 2 mm removed 71 ± 6% of the total COD in the NF concentrate within 6 h and the specific energy consumption was 207 ± 20 kWh∙kg COD −1 . The COD removal was kept stable in the stacked EF reactor within 3 cycles of operation. Three-dimensional fluorescence spectroscopic and gas chromatographic mass spectrometric analysis showed that humic acids and aromatic proteins were efficiently degraded in the EF process and large amount of aromatic hydrocarbons was detected in the treated NF concentrate. Our stacked EF reactor could be used to treat leachate concentrates with effectively degradation of the refractory organic pollutants. [ABSTRACT FROM AUTHOR]

The aim of this study was to investigate the feasibility of citric acid (CA) production using a biological electrodialysis with bipolar membrane, i.e., the microbial electrolysis desalination and chemical-production cell (MEDCC). To optimize the performance, batch, recirculation, and packed ion-exchange resin (IER) modes were carried out in the MEDCC. With 0.1 M Na 3 Cit, the maximum current density was 7.7±0.3, 9.2±0.6, and 11.1±0.5 A/m 2 in the batch, recirculation, and packed IER modes, respectively. The maximum CA production of 0.443±0.096 M was achieved within 96 h operation using 0.5 M Na 3 Cit with the recirculation mode. The lowest internal resistance of 48.5 Ω was observed with the packed IER mode. The lowest electric consumption of 0.81±0.03 kW h/kg in the MEDCC was achieved with 0.5 M Na 3 Cit and the recirculation mode, which was only 10–40% of the electrical energy consumed in other electrodialysis processes. The MEDCC with the recirculation mode had higher abundance of Geobacter and higher biomass in the anode biofim than that with the batch mode, resulting in better performance in terms of higher current density and CA production. The MEDCC should be a potential valuable method for CA production with low energy consumption. [ABSTRACT FROM AUTHOR]

[Display omitted] • FeS 2 and Fe 2 (SO 4) 3 are artfully employed in synergy in spent LIBs recovery firstly. • About ∼ 99.9 % of valuable metal ions were extracted into solution. • The reaction mechanism was studied in depth by DFT calculations. • Valuable elements were separated and realizing regeneration of cathode materials. With the concepts of carbon peaking and carbon neutrality taking hold, the demand for recycling of spent lithium-ion batteries (LIBs) is increasing rapidly. However, current recycling methods are mostly faced with the dilemma of high cost and low efficiency and unable to meet the demand for energy conservation and consumption reduction. Here, inspired by the formation of acid mine drainage (AMD), we propose a Fe(III)-driven recovery approach, in which the leaching of valuable metals is enhanced by the addition of solid reagents Fe 2 (SO 4) 3 and pyrite (FeS 2) to create an acidic reducing atmosphere. Under optimal conditions, the leaching efficiency of Ni/Co/Mn/Li reached 99.9%. In addition, NH 3 ·H 2 O-NaOH was employed to adjust the pH of the leachate for stepwise precipitation of Fe and Ni/Co/Mn. Li was finally collected as Li 2 CO 3 and Fe(III) could be recycled. We have also made attempts on Ni/Co/Mn co-precipitation and Li 2 CO 3 resynthesis of regenerated LiNi x Co y Mn z O 2 (NCM). It is predicted that this process can provide a green, efficient and economical closed-loop approach for cathode recovery of LIBs, with far-reaching implications for the entire battery recycling industry. [ABSTRACT FROM AUTHOR]

The aim of this study is to explore the feasibility of applying bipolar membrane electrodialysis (BMED) to treat coal chemical waste salt with different pretreatments of organic pollutants. The organic content in the real waste salt reached 0.6 ± 0.1 % with a weight averaged molecular weight of 641 g/mol. Only 26.5 % of the total COD in a 250 g/L waste salt solution could be removed by the coagulation pretreatment, resulting in no apparent improvement in BMED performance. Thermal pretreatment at 850 °C for 180 min completely removed organics from the waste salt, resulting in efficient control of membrane fouling in the BMED. At the current density of 50 mA/cm2 and 250 g/L waste salt solution, the base concentration in the BMED with 850 °C pretreatment of waste salt was higher than that with 550 °C pretreatment and without any pretreatment (58.2 ± 1.0 vs. 56.0 ± 2.4 and 53.6 ± 2.0 g/L) within 180 min, respectively. The average current efficiency based on base productions with 850 °C pretreatment of the waste salt reached 91 ± 5 % in the BMED within 180 min. Our results should be useful for the resource utilization of coal chemical waste salt. [Display omitted] • Resource utilization of coal chemical waste salt was realized in this study. • Organics in the waste salt caused AEM fouling in BMED without any pretreatment. • Thermal pretreatment at 850 °C completely removed the organics in the waste salt. • Thermal pretreatment of waste salt resulted in low energy consumption of BMED. [ABSTRACT FROM AUTHOR]

The aim of this study was to investigate the feasibility and optimization of formic acid production in the microbial electrolysis desalination and chemical-production cell (MEDCC). The maximum current density in the MEDCC with 72 cm of the anode fiber length (72-MEDCC) reached 24.0 ± 2.0 A/m 2 , which was much higher than previously reported. The maximum average formic acid production rate in the 72-MEDCC was 5.28 times higher than that in the MEDCC with 24 cm of the anode fiber length (37.00 ± 1.15 vs. 7.00 ± 0.25 mg/h). High performance in the 72-MEDCC was attributed to small membrane spacing (1 mm), high flow rate (1500 μL/min) on the membrane surface and high anode biomass. The minimum electricity consumption of 0.34 ± 0.04 kWh/kg in the 72-MEDCC was only 3.1–18.8% of those in the EDBMs. The MEDCC should be a promising technology for the formic acid production. [ABSTRACT FROM AUTHOR]

Containing high salinity and biotoxic organic compounds, reverse osmosis (RO) concentrate from municipal wastewater treatment plants has high environmental risks. The aim of this study was to investigate the feasibility of RO concentrate treatment using the microbial electrolysis desalination and chemical production cell (MEDCC). RO concentrate was put into the desalination chamber. Both acid production and cathode chambers contained with 1 g/L NaCl. Within 18 h operation, the maximum desalination rate of 86 ± 7% and no significant COD removal in the RO concentrate were achieved in the MEDCC, although the humic-like and fulvic acid-like organic compoundscould transfer from the desalination chamber into the acid-production chamber. The minimum and maximum pH in the acid-production and cathode chambers reached 1.08 ± 0.06 and 12.2 ± 0.10, respectively. The average total energy consumption was 6.51 ± 0.17–9.81 ± 0.23 kWh/m 3 , among which 37%–61% was provided by the bioenergy from substrate utilization. The acid and alkali recovery, COD rejection in the treated RO concentrate and low electricity consumption in the MEDCC indicate that MEDCC may be a novel method for RO concentrate treatment in practical applications. [ABSTRACT FROM AUTHOR]

The aim of this study was to investigate the feasibility of sulfate removal from seawater using the bioelectrochemical system (BES). A single-chamber BES was constructed with graphite felt as the anode and carbon brush as the cathode. The BES was inoculated with sea mud and tested with seawater containing 2200 ± 200 mg/L SO 4 2− and 2 g/L sodium acetate as the substrate under an applied voltage of 0.8 V. Results showed that 98.5 ± 5.0 % of SO 4 2− in the seawater was efficiently removed in the BES within 132 h. The maximum current density in the BES reached 3.4 ± 0.1 A/m3 with ~100 % acetate utilization. Most of SO 4 2− was reduced to S2− and the final S2− concentration reached 498 ± 25 mg/L in the BES. Organic sulfur compounds were detected in the SO 4 2− reduction. According to bacterial community and reconstruction of unobserved state analyses, the SO 4 2− removal was mainly attributed to the reaction in the cathodic biofilm. The electricity consumption for the SO 4 2− removal was much lower in the BES than in the membrane technology. Our results can provide a promising method to enhance the seawater utilization in the industry. [Display omitted] • The SO 4 2− removal from the seawater was realized in the single-chamber BES. • 98.5 ± 5.0 % of 2200 ± 200 mg/L SO 4 2− was removed in the BES within 132 h. • The maximum current density in the BES reached 3.4 ± 0.1 A/m3. • The SO 4 2− removal was mainly attributed to the cathodic reduction. [ABSTRACT FROM AUTHOR]

The aim of this study was to develop a microbial electrolysis cell (MEC) constructed with spiral wound electrode and to evaluate its effectiveness for wastewater treatment and methane (CH 4 ) production. The spiral wound design can provide more than 60 m 2 /m 3 of specific surface area of the electrode and low internal resistance. With acetate as the substrate and increasing applied voltages from 0.7 to 1.3 V, the average current density and CH 4 production rate increased from 46 to 132 A/m 3 and from 0.08 to 0.17 m 3 /m 3 d, respectively. With the increasing applied voltages, the energy efficiencies decreased from 157% to 69%, while the COD removal rates increased from 0.31 to 0.69 kg COD/m 3 d. The optimal applied voltage of the spiral-wound-electrode MEC was about 0.95 V. Fed with dairy wastewater, the MEC also showed good performance with the average current density of 24 A/m 3 , CH 4 production rate of 0.03 m 3 /m 3 d, energy efficiency of 66%, and COD removal rate of 0.20 kg COD/m 3 d. [ABSTRACT FROM AUTHOR]

The objective of this study was to investigate the feasibility of seawater desalination using the microbial electrolysis desalination and chemical-production cell (MEDCC) with monovalent selective cation exchange membrane (MSCEM) (MEDCC-MSCEM). With dissolved aquarium sea salts as artificial seawater, the maximum current density in the MEDCC-MSCEM reached 19.6 ± 0.3 A/m2, which was 43.1% higher than that in the MEDCC with cation exchange membrane (i.e., the traditional MEDCC as the control). The desalination efficiency within 24 h was 76 ± 7% in the MEDCC-MSCEM. The harvested acids (mainly HCl and H 2 SO 4) and alkali (NaOH with 96% purity) concentrations reached 0.28 ± 0.02 and 0.26 ± 0.02 M, respectively. The total energy consumption within 24 h was much lower in the MEDCC-MSCEM than in the control (3.46 ± 0.41 vs. 4.99 ± 0.46 kWh/kg·TDS). The separation efficiency of Na+:Ca2+ and Na+:Mg2+ in the MSCEM was in the range of 42% - 72% and 53% - 87%, respectively. Effective limitation of Ca2+ and Mg2+ by MSCEM resulted in low precipitation of Ca (OH) 2 and Mg(OH) 2 in the membrane and cathode, which significantly improved the performance of MEDCC. The MEDCC-MSCEM has great potential in seawater desalination with resource recovery. [Display omitted] • MEDCC-MSCEM was constructed and tested for seawater desalination. • Desalination efficiency (DE) in the MEDCC- MSCEM was 76 ± 7% within 24 h. • DE in the MEDCC-MSCEM was 61.7% higher than that in the control. • Effective rejection of Ca2+ and Mg2+ by MSCEM improved the performance of MEDCC. [ABSTRACT FROM AUTHOR]