Microbial Electrolysis Desalination And Chemical-production Cell Research Articles

Improved microbial electrolysis desalination and chemical-production cell for a high-value product: Hydrogen peroxide

A high-value product of microbial electrolysis desalination and chemical-production cell (MEDCC) is a promising method for reducing costs and broadening the cell’s application. This study proposed a modified MEDCC in terms of hydrogen peroxide (H2O2) production, electrochemical performance, desalination, energy consumption by comparing it with conventional MEDCC. At the optimal voltage (1.0 V), the improved system achieved the H2O2 concentration of 1183 ± 32 mg/L, the energy consumption of 8.42 ± 1.39 kWh/kg H2O2, the desalination efficiency of 60.36 ± 9.24% within 12 h. Although the MEDCC-H2O2 system had a lower transfer rate of electrons, the system had analogous performances on current density, desalination, and acid and alkali productions with the conventional system. These results meant that the ideal voltage for achieving bipolar membrane and electrochemically active bacteria (EAB) synergism was 1.0 V in the improved MEDCC. In terms of chemical production in the cathode chamber of the MEDCC, the application of H2O2 production increased the rate of return by four times when compared to conventional alkali production. Only about 55% of total consumption was attributed to bioenergy in the substrate, suggesting the system was energy-saving. Therefore, the revised MEDCC had great potential in the field of energy-efficient and green H2O2 generation and desalination whilst maintaining acid and alkali productions.

High current density with spatial distribution of Geobacter in anodic biofilm of the microbial electrolysis desalination and chemical-production cell with enlarged volumetric anode

The aim of this study was to establish the relationship between spatial distribution of Geobacter and electric intensity in the microbial electrolysis desalination and chemical-production cell (MEDCC) and to investigate the effect of enlarged volumetric anode on the performance of MEDCC. The MEDCC was constructed with nine carbon brush anodes (length × diameter = 11 cm × 3 cm) as enlarged volumetric anode, and operated by feeding with 1 g/L acetate as substrate and 35 g/L NaCl as artificial seawater under the applied voltages of 1.2–4.5 V. Spatial distribution of Geobacter in the anodic biofilm was determined according to the bacterial community analysis on 27 biofilm samples from the top, middle and bottom layers of anodes (i.e., with distance of 4.5, 10, and 15.5 cm to the cathode, respectively). Results showed that the enlarged volumetric anode significantly improved the performance of MEDCC. The maximum desalination rate and current density reached 338.5 ± 21.8 mg/L∙h and 55.7 ± 3.7 A/m2 in the MEDCC, respectively. The electric intensity values decreased with the distance from the anode to the cathode and formed an uneven distribution in the anode chamber. The samples in the top layer of anodes had the highest average 16S rRNA gene copy number of Geobacter of 1.55 × 107 copies/μL, which was 18 times higher than that in the bottom layer of anodes. A linear relation was established between the spatial distribution of Geobacter and electric intensity (R2 = 0.994–0.999). The electric intensity gradient created the uneven spatial distribution of Geobacter in the biofilms of volumetric anode. Results from this study could be useful to enrich Geobacter in the anodic biofilm thus to improve the performance of MEDCC.

Seawater desalination using the microbial electrolysis desalination and chemical-production cell with monovalent selective cation exchange membrane

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 H2SO4) 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.

Simultaneous desalination and ammonia recovery using microbial electrolysis desalination and chemical-production cell: A feasibility study of alkaline soil washing wastewater

The high concentrations of ions and ammonia nitrogen (NH3−N) in soil washing wastewater can remarkably affect ecosystem balance. This study aims to prove the feasibility of using alkaline soil washing wastewater as inlet water of microbial electrolysis desalination and chemical-production cell (MEDCC) to desalinate and recover NH3-N, from the views of performance and mechanism. The system could obtain desalination, and NH3-N removal efficiencies of 73 ± 7% and 85 ± 3%, respectively, within 12 h at the maximum current density of 9.8 ± 0.1 A/m2. Importantly, 82.5% of the removed NH3-N could be recovered in the form of NH3·H2O. The addition of electrochemically active bacteria in the anode chamber of MEDCC improved desalination and NH3-N recovery efficiencies by strengthing electric field. Bioenergy provided 58% of the total energy consumption, forming an energy-saving method for soil washing wastewater treatment. Alkalization pretreatment and acid immersion could reduce precipitation from membranes to improve desalination performance and reduce energy consumption. From the standpoint of the mechanism of desalination and NH3-N recovery, the MEDCC is expected to have the potential to simultaneously complete desalination and NH3-N recovery in alkaline wastewater with low energy consumption.

Pesticide wastewater treatment using the combination of the microbial electrolysis desalination and chemical-production cell and Fenton process

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.

Combined microbial desalination and chemical-production cell with Fenton process for treatment of electroplating wastewater nanofiltration concentrate

With high concentrations of salinity, heavy metals, and refractory organics, the nanofiltration (NF) concentrate in electroplating wastewater is difficult to be treated using the traditional methods. The aim of this study was to investigate the feasibility to treat the NF concentrate using the microbial electrolysis desalination and chemical production cell (MEDCC) combined with the Fenton process. Results showed that heavy metals of nickel and zinc were efficiently removed using the proposed method. The maximum current density reached 9.4 A/m2 in the MEDCC fed with the pretreated NF concentrate. Within 20 h, 94%, 82%, and 91% of nickel, zinc, and calcium were removed in the desalination chamber of MEDCC. The dilute acid with pH = 0.9 and alkali with pH = 12.9 were recovered in the MEDCC. The Fenton oxidation process with and without the MEDCC removed COD 79% and 30%, respectively. In the MEDCC and Fenton combined system, refractory organics were transformed to linear alkanes and efficiently degraded. With high removal of COD and heavy metals, acid and alkali recovery, and low energy consumption, our combined MEDCC and Fenton process should provide a promising method to efficiently treat the NF concentrate in electroplating wastewater.

A review of microbial desalination cell technology: Configurations, optimization and applications

Abstract Seawater could be a potential source of freshwater to manage the intensified demand of drinking water for new generations. The recent techniques for desalination and wastewater treatment are energy intensive and unsustainable. Therefore, an integrated and sustainable approach is essential to achieve cost-effective desalination through wastewater treatment. Microbial desalination cell (MDC) has been proven to be one of the emerging technologies capable of simultaneous wastewater treatment, seawater desalination and eco-energy production. This technique generates electricity through the bio-electrochemical oxidation of organics present in wastewater. The produced electricity is utilized to drive the migration of ions in MDC system. This ionic migration will result in desalination as well as formation of value-added by-products. The review summarizes the recently investigated MDC configurations along with their critical evolution of designs and operational parameters on the desalination and power generation capabilities. The review also acknowledges the emerging applications of MDC for microbial electrochemical desalination, bio-remediation, nutrients recovery, water softening, and value-added chemical production. The key findings included that the MDC system achieved a remarkable desalination without any external power input, and treatment of wastewater, and recovery of power without intermediate steps. The technical challenges associated with their practical applications were maintaining the pH in cathodic and anodic fluids, higher internal resistance, usage of catalysts on electrodes, and membrane fouling and durability. However, for certain configurations especially for microbial electrolysis and desalination cell (MEDC)/microbial electrolysis desalination and chemical production cell (MEDCC), the integration with electrodialysis module can significantly increase their performances. The installation of ED module will establish the pH neutrality and increased water recovery through recirculation of electrolytes between chambers of ED module and these MDC configurations. However, the sustainable development of MDC technology and its scale-up requires future investigations related to prevention of membrane fouling, materials feasibility, electron transfer kinetics, microbial growth and durability of catalyst. The feasibility studies are also needed to be conducted for determining the suitability of MDC operation in terms of reactor performance and stability.

Tetramethyl ammonium hydroxide production using the microbial electrolysis desalination and chemical-production cell with long anode

The aim of this study was to investigate the feasibility to improve the tetramethyl ammonium hydroxide (TMAH) production in the microbial electrolysis desalination and chemical-production cell (MEDCC) with long anode of 48 cm. Different concentrations of tetramethylammonium chloride (0.3–0.7 M) and applied voltages (1.5–3.5 V) were tested in the MEDCC. With 0.6 M of tetramethylammonium chloride as the raw material and under the applied voltage of 3.5 V, the maximum TMAH production rate in the MEDCC reached 1.13 ± 0.12 mmol/h, which was 9.4 times higher than those previously reported in the MEDCCs. The maximum current density of 41.0 ± 4.0 A/m2 in the MEDCC was obtained, which was the highest value in the bioelectrochemical systems using the carbon cloth or carbon brush as the anode so far. Our results should provide a promising method to improve the TMAH production and boost the MEDCC application.

Improved performance of the microbial electrolysis desalination and chemical-production cell with enlarged anode and high applied voltages

The aim of this study was to improve performance of the microbial electrolysis desalination and chemical-production cell (MEDCC) using enlarged anode and high applied voltages. MEDCCs with anode lengths of 9 and 48cm (i.e., the 9cm-anode MEDCC and 48cm-anode MEDCC, respectively) were tested under different voltages (1.2–3.0V). Our results demonstrated for the first time that the MEDCC could maintain high performance even under the applied voltage higher than that for water dissociation (i.e., 1.8V). Under the applied voltage of 2.5V, the maximum current density in the 48cm-anode MEDCC reached 32.8±2.6A/m2, which is one of the highest current densities reported so far in the bioelectrochemical system (BES). The relative abundance of Geobacter was changed along the anode length. Our results show the great potential of the BES with enlarged anode and high applied voltages.

Formic acid production using a microbial electrolysis desalination and chemical-production cell

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 72cm of the anode fiber length (72-MEDCC) reached 24.0±2.0A/m2, 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 24cm of the anode fiber length (37.00±1.15vs. 7.00±0.25mg/h). High performance in the 72-MEDCC was attributed to small membrane spacing (1mm), high flow rate (1500μL/min) on the membrane surface and high anode biomass. The minimum electricity consumption of 0.34±0.04kWh/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.

Treatment of reverse osmosis concentrate using microbial electrolysis desalination and chemical production cell

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 1g/L NaCl. Within 18h 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±0.23kWh/m3, 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.

Citric acid production using a biological electrodialysis with bipolar membrane

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 0.1M Na3Cit, the maximum current density was 7.7±0.3, 9.2±0.6, and 11.1±0.5A/m2 in the batch, recirculation, and packed IER modes, respectively. The maximum CA production of 0.443±0.096M was achieved within 96h operation using 0.5M Na3Cit with the recirculation mode. The lowest internal resistance of 48.5Ω was observed with the packed IER mode. The lowest electric consumption of 0.81±0.03kWh/kg in the MEDCC was achieved with 0.5M Na3Cit 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.

A comparative evaluation of different types of microbial electrolysis desalination cells for malic acid production

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±0.6mmol/Lh) and the lowest energy consumption (0.35±0.14kWh/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.

Tetramethylammonium hydroxide production using the microbial electrolysis desalination and chemical-production cell

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.

Microbial electrolysis desalination and chemical-production cell for CO2 sequestration

Mineral carbonation can be used for CO2 sequestration, but the reaction rate is slow. In order to accelerate mineral carbonation, acid generated in a microbial electrolysis desalination and chemical-production cell (MEDCC) was examined to dissolve natural minerals rich in magnesium/calcium silicates (serpentine), and the alkali generated by the same process was used to absorb CO2 and precipitate magnesium/calcium carbonates. The concentrations of Mg(2+) and Ca(2+) dissolved from serpentine increased 20 and 145 times by using the acid solution. Under optimal conditions, 24 mg of CO2 was absorbed into the alkaline solution and 13 mg of CO2 was precipitated as magnesium/calcium carbonates over a fed-batch cycle (24h). Additionally, the MEDCC removed 94% of the COD (initially 822 mg/L) and achieved 22% desalination (initially 35 g/L NaCl). These results demonstrate the viability of this process for effective CO2 sequestration using renewable organic matter and natural minerals.

Integrated utilization of seawater using a five-chamber bioelectrochemical system

To reduce membrane scaling, effectively desalinate seawater, and recover magnesium, acid and alkali from the desalination process, a novel five-chamber bioelectrochemical system (BES) was developed in this study. This development was based on a four-chamber BES proposed recently, called microbial electrolysis desalination and chemical-production cell (MEDCC). Results showed that the desalination efficiency of seawater in the five-chamber BES was two times of that in the MEDCC. Removal efficiencies of Na+, Mg2+, and Ca2+ within 18h using the system were 65±2%, 100±0%, and 80±2%, respectively, which were 20%, 66%, and 36% higher than those in the MEDCC. With the form of Mg(OH)2 precipitation, 73% of the total magnesium in solutions was recovered from the cathodic surface. Although the removal efficiencies of Mg2+ and Ca2+ in the five-chamber BES were higher, the Mg2+ and Ca2+ scaling found on the membrane surface was only 38.5% and 18.5% of that in MEDCC, respectively. With the different removal mechanism of Mg2+/Ca2+ ions, the membrane scaling problem was better resolved in the five-chamber BES than the other desalination BESs. With reduction of membrane scaling, the production of alkali, acid, and magnesium, the five-chamber BES should be a promising way to realize an integrated utilization of seawater.

Improved performance of the microbial electrolysis desalination and chemical-production cell using the stack structure

The microbial electrolysis desalination and chemical-production cell (MEDCC) is a device to desalinate seawater, and produce acid and alkali. The objective of this study was to enhance the desalination and chemical-production performance of the MEDCC using two types of stack structure. Experiments were conducted with different membrane spacings, numbers of desalination chambers and applied voltages. Results showed that the stack construction in the MEDCC enhanced the desalination and chemical-production rates. The maximal desalination rate of 0.58±0.02mmol/h, which was 43% higher than that in the MEDCC, was achieved in the four-desalination-chamber MEDCC with the AEM–CEM stack structure and the membrane spacing of 1.5mm. The maximal acid- and alkali-production rates of 0.079±0.006 and 0.13±0.02mmol/h, which were 46% and 8% higher than that in the MEDCC, respectively, were achieved in the two-desalination-chamber MEDCC with the BPM–AEM–CEM stack structure and the membrane spacing of 3mm.

Development of the Microbial Electrolysis Desalination and Chemical-Production Cell for Desalination as Well as Acid and Alkali Productions

By combining the microbial electrolysis cell and the microbial desalination cell, the microbial electrolysis desalination cell (MEDC) becomes a novel device to desalinate salty water. However, several factors, such as sharp pH decrease and Cl(-) accumulation in the anode chamber, limit the MEDC development. In this study, a microbial electrolysis desalination and chemical-production cell (MEDCC) was developed with four chambers using a bipolar membrane. Results showed that the pH in the anode chamber of the MEDCC always remained near 7.0, which greatly enhanced the microbial activities in the cell. With applied voltages of 0.3-1.0 V, 62%-97% of Coulombic efficiencies were achieved from the MEDCC, which were 1.5-2.0 times of those from the MEDC. With 10 mL of 10 g/L NaCl in the desalination chamber, desalination rates of the MEDCC reached 46%-86% within 18 h. Another unique feature of the MEDCC was the simultaneous production of HCl and NaOH in the cell. With 1.0 V applied voltage, the pH values at 18 h in the acid-production chamber and cathode chamber were 0.68 and 12.9, respectively. With the MEDCC, the problem with large pH changes in the anode chamber was resolved, and products of the acid and alkali were obtained.