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The development of efficient energy storage systems is critical in the transition towards sustainable energy solutions. In this context, the present work investigates the viability of using orange juice, as a promising and sustainable precursor, for the synthesis of activated carbon electrodes for supercapacitor technologies. Through the carbonization-activation process and controlling the preparation parameters (KOH ratio and activation time), we have tailored the specific surface area (SSA) and pore size distribution (PSD) of the resulting carbon materials—crucial parameters that support supercapacitive performance. Several spectroscopic, morphological, and electrochemical techniques are used to characterize the obtained carbon materials. In particular, our optimization efforts revealed that a 5:1 KOH ratio with an activation time up to 120 min produced the highest SSA of about 2203 m2/g. Employing these optimal conditions, we fabricated symmetric coin cell supercapacitors using Na2SO4 as the electrolyte, which exhibited interesting specific capacitance (~56 F/g). Durability testing over 5000 cycles sustained the durability of the as-made activated carbon electrodes, suggesting an excellent retention of specific capacitance. This study not only advances the field of energy storage by introducing a renewable material for electrode fabrication but also contributes to the broader goal of waste reduction through the repurposing of food byproducts. [ABSTRACT FROM AUTHOR]

In this study, the electrocoagulation (EC) treatment was used to minimize and separate pollutants from textile industrial wastewater (TIWW), including high color, chemical oxygen demand (COD), total organic carbon (TOC), and total dissolved solids (TDS). To enhance the EC treatment efficiency, a novel strategy has been followed in the study that involves thin‐film coating on 316 stainless steel (SS) electrodes with banana peel‐derived activated carbon (BPAC) by dip coating, spin coating, or spray coating. Among the different types of coating, thickness and contact angle measurements have elucidated that the spray coating of BPAC on SS electrode is the best tool with minimum thickness and contact angle. In this study, a bare SS electrode was used as the anode and a thin‐film spray‐coated BPAC on the SS electrode was used as the cathode. Moreover, optimization plays a key role in EC treatment process, where operating conditions such as a current density of 10 mA/cm2, contact time of 15 min, and a pH of 7 were fixed. As a result, the findings indicate comparatively high color removal of 98%, COD removal of 91%, TOC removal of 89.6%, and TDS removal of 68% are achieved with ease. Accordingly, in comparison with plain SS electrodes or dip‐ or spin‐coated BPAC on SS electrodes, spray‐coated BPAC on SS electrodes in EC treatment outperforms in removing high color, TOC, COD, and TDS. Overall, the study highlights the potential of EC treatment integrated with adsorption procedures for TIWW treatment. Particularly, the use of thin‐film spray‐coated BPAC on SS electrodes in the EC treatment process led to an effective and sustainable tool for treating and reuse of TIWW. It is due to its low operation and maintenance cost and studied in a short interval of time. Finally, the ultimate goal was firmly achieved in pilot‐scale studies by the safe discharge into the environment or reuse of treated textile wastewater. Thus, it is a promising alternative with an environmentally friendly footprint that could be easily implemented in any textile industry premises. Practitioner Points: Heavy metals, oils, facts, suspended solids, and other pollutants can be removed from industrial effluent by using electrocoagulation.The process is both cost‐effective and energy‐efficient, and it is easily integrated with other water treatment technologies.According to the findings of this study, minimum current density should be applied to BPAC–SS‐coated electrodes by DC power supplies to treat textile industry effluents at low operating costs.When compared with a plain SS electrode, the spray‐coated BPAC on SS electrode provides better performance in effluent treatment. [ABSTRACT FROM AUTHOR]

Capacitive deionization (CDI) is a promising and cost-effective technology that is currently being widely explored for removing dissolved ions from saline water. This research developed materials based on activated carbon (AC) materials modified with zinc oxide (ZnO) nanorods and used them as high-performance CDI electrodes for water desalination. The as-prepared electrodes were characterized by cyclic voltammetry, and their physical properties were studied through SEM and XRD. ZnO-coated AC electrodes revealed a better specific absorption capacity (SAC) and an average salt adsorption rate (ASAR) compared to pristine AC, specifically with values of 123.66 mg/g and 5.06 mg/g/min, respectively. The desalination process was conducted using a 0.4 M sodium chloride (NaCl) solution with flow rates from 45 mL/min to 105 mL/min under an applied potential of 1.2 V. Furthermore, the energy efficiency of the desalination process, the specific energy consumption (SEC), and the maximum and minimum of the effluent solution concentration were quantified using thermodynamic energy efficiency (TEE). Finally, this work suggested that AC/ZnO material has the potential to be utilized as a CDI electrode for the desalination of saline water. [ABSTRACT FROM AUTHOR]

Magnetic activated carbon particles (Fe3O4/active carbon composites) as auxiliary electrodes (AEs) were fixed on the surface of Ti/Sb-SnO2 foil by a NdFeB magnet to form a new magnetically assembled electrode (MAE). Characterizations including cyclic voltammetry, Tafel analysis, and electrochemical impedance spectroscopy were carried out. The electrochemical oxidation performances of the new MAE towards different simulated wastewaters (azo dye acid red G, phenol, and lignosulfonate) were also studied. Series of the electrochemical properties of MAE were found to be varied with the loading amounts of AEs. The electrochemical area as well as the number of active sites increased significantly with the AEs loading, and the charge transfer was also facilitated by these AEs. Target pollutants' removal of all simulated wastewaters were found to be enhanced when loading appropriate amounts of AEs. The accumulation of intermediate products was also determined by the AEs loading amount. This new MAE may provide a landscape of a more cost-effective and flexible electrochemical oxidation wastewater treatment (EOWT). [ABSTRACT FROM AUTHOR]

Water pollution by metals is increasing. An electrode material, copper hexacyanoferrate (CuHCF), for capacitive deionization (CDI) to remove Co2+ from wastewater was developed. The asymmetric electrode structure of the CDI overcomes the limitations of traditional activated carbon electrodes (low ion removal capacity, ion removal rate, and charge efficiency). The specific capacitance of the CuHCF electrode (216.7 F g−1) at 1 mV s−1 was higher than that of a traditional electrode (92.0 F g−1), and its deionization capacity was 156.85 mg g−1 in 50 mg L−1 aqueous Co2+ (charge efficiency = 68.4%). CuHCF is a high-performance electrode material for wastewater remediation. [ABSTRACT FROM AUTHOR]

• Activated carbon derived from agriculture by-products obtain high surface area, high porosity, and low density. • Deionization efficiency of CDI, MCDI, and FCDI reached 80–90 % and water recovery rate 90 %. • The roller, spray coating, and mill ball grinding are useful to fabricate electrodes for industry applications. • The adsorption capacities of AC and AC-modified electrodes were 25–40 mg/g. • Life span and deionization efficiency of the flow electrode are higher than electrode plate. Capacitive deionization (CDI), membrane capacitive deionization (MCDI), and flow capacitive deionization (FCDI) are emerging technologies applied to remove ions from brackish water or saline wastewater based on electrode double layer (EDL) mechanisms. The electrode itself can be seen as the most important factor that determines the deionization efficiency of the CDI system. Electrode fabrication using activated carbon derived from agriculture byproducts is a useful solution to decrease cost, restrict environmental pollution, and enable agriculture waste recovery. In this review, the primary parameter's impact on activated carbon (AC) and the electrode fabrication process from the agriculture byproducts is detailed in a discussion to find the most optimal conditions. With excellent characteristics for the activated carbon such as a surface area of up to 2500 m2/g, it can be used to fabricate electrodes that have a high adsorption capacity of approximately 25 mg/g, able to be advanced to 40 mg/g with a modified AC. It can achieve a cycle performance of 95–97 %. The deionization efficiency of the CDI, MCDI, and FCDI systems can be up to 90 % with an input salt concentration from 2000 to 3000 mg/L where the water recovery ratio achieved is 50–90 %, alongside a salt rejection rate of about 7–75 %. AC can be modified to increase its special properties such as surface area, conductivity, and ion selectivity using different methods. The drawbacks and challenges of the CDI technology are also mentioned along with useful solutions such as electrode coating techniques using an anilox roller and a spray, for use in industry applications. [Display omitted] [ABSTRACT FROM AUTHOR]

The capacitive deionization of water (CDW) was investigated with the purpose to obtain pure water. To this end, mosaic cation–anion-exchange membranes and activated carbon electrodes were used. The mosaic membranes contained cation- and anion-exchange components embedded in a synthetic-fiber-based matrix. The means of preparation for the pressed mosaic membranes included pressing the cation- and anion-exchange membranes into each other. Another method was via the subsequent formation of cation- and anion-exchange bands in the fibrous matrix (in a banded membrane). The activated carbon electrodes and mosaic membranes possessed sufficient specific ion surface conductivities even in clean water. The specific energy consumption was 31.9 and 111.7 W mol–1 for the CDW devices containing banded and pressed membranes, respectively. Therefore, the banded membrane was preferable for obtaining pure drinking water. It was found that the CDW with the banded mosaic membrane exhibited the best performance at a voltage of 2 V and a solution flow rate of 15 cm3/min. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Microporous activated carbon pellets have been prepared from date stone without the use of binder. • Binderless activated carbon was used as supercapacitor in water treatment: capacitive deionization. • The capacitive deionisation electrosorptive performance of the activated carbons was evaluated. Abstract Microporous activated carbon pellets have been prepared from date stone without the use of a binder. These pellets were tested as electrodes for capacitive deionization. The activation process involved two steps. First, a pyrolysis of the date stone was conducted to a temperature of 1000 °C under nitrogen flow. Then, the obtained carbon monoliths were physically activated at 900 °C under CO 2 flow. Elemental analysis, BET, SEM, mercury porosimetry, conductivity measurement and electrochemical performance testing carried out to characterize the structure and the properties of activated carbon pellets. The activated carbon exhibited predominant microporosity with a specific surface area of 896 m2 g−1 which leads to the highest specific capacitance 270.90 F/g. The performance of activated carbon electrode at 900 °C in capacitive deionization (CDI) test was also examined. [ABSTRACT FROM AUTHOR]

A high quality of activated-carbon electrode materials is of great importance for improving the electrochemical performance of desalination in membrane capacitive deionization. In this study, porous activated carbon was prepared by pyrolytic carbonization and chemical activation of lignocellulosic loofa sponge ( Luffa cylindrica , LS) to act as a carbonaceous electrode. After activation, a hierarchically porous structure formed, characterized by the generation of micro-/mesopores on the channel walls. The total specific surface area and pore volume of the activated carbon material rose as the alkali/char ratio increased. The LS-based carbon electrode LSCK14, referring to the activation product produced with a KOH/char ratio of 4, displayed excellent electrochemical behavior, characterized by a remarkable specific capacitance of 93.0 F g −1 at 5 mV s −1 in 1 M NaCl solution, as well as extraordinary reversibility for capacitive charge storage. Moreover, the electrosorption capacity was investigated in batch-mode membrane capacitive deionization at 1.0 V while treating a 10 mM NaCl electrolyte. As demonstrated, the LSCK14 activated carbon electrode presented a superior electrosorption capacity of 22.5 mg g −1 . The improved capacitor characteristics and high electrosorptive performance of this material can be attributed to its unique porous characteristics (high surface area, micrometer-scale channels and both meso- and micropores). Consequently, activated carbons derived from resource-recovered LS, which combine a multi-channeled structure, mesopores and micropores, were demonstrated to be a promising electrode material for electrochemical water desalination. [ABSTRACT FROM AUTHOR]

In an attempt to improve the capacitive deionization (CDI) performance and develop an efficient CDI electrode material, the effect of carbon characteristics on CDI was investigated. Activated carbon (AC) and ordered mesoporous carbon (OMC) materials synthesized by template method were used for the electrode manufacture. The capacitive deionization performance of AC and OMC based electrodes was investigated and compared. We found that when the specific surface areas of AC materials increased from 712 to 1347 m 2 /g, the electrosorption capacities of AC electrodes increased slightly from 9.43 to 10.14 mg/g. The characteristics of OMC materials can be optimized by the adjustment of the mesoporous silica beads template proportion, resulting in a maximum average pore size of 11.35 nm and total pore volume of 2.101 cm 3 /g. The optimum electrosorption capacity obtained with OMC4 electrode was 10.83 mg/g, which was not only higher than that of AC electrodes, but obviously higher than the values of most carbon-based electrodes in other studies. In conclusion, these results provide important insights into the effect of carbon characteristics on capacitive deionization and suggest that OMC synthesized by template method could be a promising carbon material for the CDI electrode manufacture. [ABSTRACT FROM AUTHOR]

A feasibility study for water recycling and reuse of a reverse osmosis (RO) brackish wastewater by capacitive deionization (CDI) was carried out in the present work. Palm-shell wastes enriched in carbon was recycled to yield valuable activated carbon (AC) that has advantages of high surface area, high specific capacitance, and low electrical resistance as the CDI electrodes. The GAC prepared by dispersion of AC in the graphene (rGO) layers has a high surface area and electrical conductivity for CDI. The GAC electrodes have increasing electrosorption efficiencies from 1.6 to 3.0% during the repeated electrosorption-regeneration cycles under +1.2 → 0 → +1.2 V while the efficiencies the AC electrodes decrease from 2.7 to 1.6%. It is clear that the GAC-based electrodes have a better electrosorption efficiency and stability in, for example, the three repeated electrosoption-regeneration cycles for CDI of the wastewater. This work also exemplifies that the AC recycled from biomass such as palm-shell wastes can be used in CDI electrodes for recycling and reuse of wastewater. [ABSTRACT FROM AUTHOR]

Flow-electrode capacitive deionization (FCDI) has been studied for its ability to perform continuous deionization; however, there are no reports on the degradation of the desalting performance of FCDI under short-circuited closed cycle operation (SCC) mode. In this study, we observed a gradual decrease in FCDI desalting performance and weight increase of the flow-electrode under SCC mode, which mixes the cathode and anode flow-electrodes. Through an analysis of NaCl and water accumulation rates obtained from the weight variation of the flow-electrode, the gradual decline in the desalting performance was caused by a decrease in the content of activated carbon (AC) with ion adsorption sites in the flow-electrodes. This was driven by water transfer from the feed stream to the flow-electrodes through the ion exchange membrane attributed to hydrated ions and osmosis. We calculated the salt adsorption capacity (SAC) and salt adsorption rate (SAR) based on the variable weight of the flow-electrode. The maximum SAC (mSAC) and average SAR (ASAR) values of the FCDI were higher and lower than those of conventional capacitive deionization systems, respectively. This was likely due to the repetitive use of the flow-electrode and long ion transport pathways in the flow-electrode, respectively. [ABSTRACT FROM AUTHOR]

Capacitive deionization (CDI) is an energy efficient desalination technology. In this study, we conducted CDI experiments under different conditions and observed severe performance degradation from 7.3 to 0.5 mg/g after 70 cycles in symmetric 1.2/0 V operation because of anode oxidation under polarization. To eliminate the degradation, different charging and discharging voltages were tested in an asymmetric cell and 0.8/−0.4 V was selected as the optimized voltage window. Under the optimized voltage window, a capacity of 6.3 mg/g was obtained, only somewhat lower than that of the 1.2/0 V experiment, and the stability and charge efficiency were much higher by greatly mitigating the electrode corrosion. In addition, the process had a lower energy consumption. The stable performance in air- and oxygen-saturated conditions indicates that the optimized CDI has superior capacity and better performance than conventional CDI. [ABSTRACT FROM AUTHOR]

[Display omitted] • Survey on biowaste material derived activated carbon (BMDAC) electrodes in CDI. • Applications of BMDAC electrodes for removal of pollutant ions are explained. • Systematic tabulation on BMDAC electrodes performance and parameters is presented. Capacitive deionization (CDI) is water desalination process used to remove pollutant ions and water purification. In present review contains current status biowaste material derived activated carbon (BMDAC) electrodes for pollutant ion removal using CDI. This review systematically present the fundamental about CDI, application of CDI, discusses the numerous BMDAC material, comparative tabulation on current status removal of pollutants ion using BMDAC electrodes by CDI and a future scope in present area. [ABSTRACT FROM AUTHOR]

Activated carbon cloth is a promising electrode material for capacitive deionization to accomplish energy efficient desalination of water. The most attractive feature is the combination of high porosity and the ability to shape binder-free electrodes by simple cutting. The macroporous inter-fiber space also assists facile flow of the aqueous medium. Our work presents a thorough benchmarking of activated carbon cloth materials with different pore structures which show different potentials at zero charge. The studied activated carbon cloth textiles possess a large microporosity with an average pore size of 0.7–1.3 nm and stable electrochemical performance in aqueous media with specific capacitance of up to 125 F/g. In aqueous 5 mM NaCl, the electrodes achieve up to 16 mg/g salt adsorption capacity with charge efficiency of 80% at cell voltage of 1.2 V. Further on, we investigated cell voltages between 0.6 V and 1.2 V and applied our predictive salt adsorption tool that is based on the pore structure to the entire voltage window range. Our work also shows that activated carbon cloth can even be operated without a current collector. [ABSTRACT FROM AUTHOR]

In the electro-Fenton process, there still suffers concern of low H 2 O 2 generation caused by inadequate mass transfer of oxygen and low selectivity of oxygen reduction reaction (ORR). To solve it, in this study, various particle sizes (850 μm, 150 μm, and 75 μm) of granular activated carbon filled in a microporous titanium-foam substate was used to develop a gas diffusion electrode (AC@Ti–F GDE). This facile-prepared cathode has seen a 176.15% improvement in H 2 O 2 formation compared to the conventional one. Aside from a much higher oxygen mass transfer by creating gas-liquid-solid three-phase interfaces coupled with much high dissolved oxygen, the filled AC played a significant role in H 2 O 2 accumulation. Among these particle sizes of AC, the one in 850 μm has observed the highest H 2 O 2 accumulation, reaching 1487 μM in 2 h electrolysis. Because there is a balance between chemical nature for H 2 O 2 formation and micropore-dominant porous structure for H 2 O 2 decomposition, resulting in an electron transfer of 2.12 and H 2 O 2 selectivity of 96.79% during ORR. In a word, the facial AC@Ti–F GDE configuration is promising for H 2 O 2 accumulation. [Display omitted] • Titanium-based air diffusion cathode was designed by filling in activated carbon. • This facile-prepared cathode has seen a 176.15% improvement in H 2 O 2 formation. • H 2 O 2 accumulation was a balance between porous structure and chemical nature. • Filled activated carbon with 850 μm has an electron transfer of 2.12 during ORR. [ABSTRACT FROM AUTHOR]

Currently, efficient and cost-effective recycling of waste capacitors is a pressing issue. In this study, the recovery of electrode powder from waste supercapacitors and enabling the reuse of the prepared samples are reported. The recovered powder is directly activated by mixing it with KOH using chemical activation to regenerate the waste-activated carbon. The regenerated activated carbon's specific surface area could be restored to a level similar to that of the original commercial powder, reaching 1803.15 m2/g. The regenerated activated carbon has a high proportion of microporous, which played a crucial role in its electrochemical performance. The samples' capacity in the organic system reached 125.96 F/g at 0.2 A/g and 111.77 F/g at 20 A/g, with a retention rate of 88.74%. Furthermore, the capacitance was maintained at 91.18% after 10,000 cycles, showing good cycling performance. Additionally, the supercapacitor assembled from the regenerated activated carbon delivered a high energy density of 31.83 Wh/kg and a power density of 269.76 W/kg, indicating great application potential. Overall, this study offers a useful and low-cost approach for recycling activated carbon from waste electrodes, which would be possible for supercapacitors recycling. [Display omitted] • The waste electrode carbon powder is regenerated into activated carbon. • The electrochemical properties of 21RAC-3 are superior than 21KSN. • 21RAC-3 organic supercapacitor exhibits an energy density of 31.83 Wh/kg. [ABSTRACT FROM AUTHOR]

Flow electrode capacitive deionization (FCDI) has great advantages in high salinity wastewater desalination. However, due to the limited adsorption capacity of electrode material, membrane concentration polarization would form and increase energy consumption, and affect the continuity of desalination. In this work, milling technology was used to modify original activated carbon (AC), the obtained ball milled activated carbon (BAC) was used as FCDI electrode material. The milling process modified multiple physical and electrochemical characteristics of original AC. The highest average salt removal rate (ASRR) of BAC was 2.2 times of that of AC, which was attributed to the modified surface properties including more oxygenated functional group, larger electrostatic gravitation characteristics and better hydrophilicity. The reduced concentration polarization during the desalination was responsible for the increased adsorption capacity, which was due to larger electrolyte contact area, enhanced ions capacity by more suitable pore structures, and 5 times higher energy normalized removal salt (ENRS) of BAC flow electrode than that of AC. Because of its simple operation and remarkable modification effect, ball milling technology shows great potential in large scale modification of electrode materials. [ABSTRACT FROM AUTHOR]

Capacitive deionization is an alternative approach for desalination using nanomaterial modified porous electrodes. The review presents the current progress of capacitive deionization electrodes prepared from nanoparticle oxides, carbon nanotubes, graphene, carbon nanofibers, and nonporous carbon cloth. The synthesis and benefits of nanomaterial electrodes for capacitive deionization electrode are discussed. The application of these nanomaterials for capacitive deionization has been shown to improve electrosorption and efficiency for salt removal compared to activated carbon electrodes. [ABSTRACT FROM PUBLISHER]

Commercially available activated carbon cloth electrodes are treated using nitric acid and ethylenediamine solutions, resulting in chemical surface charge enhanced carbon electrodes for capacitive deionization (CDI) applications. Surface charge enhanced electrodes are then configured in a CDI cell to examine their salt removal at a fixed charging voltage and both reduced and opposite polarity discharge voltages, and subsequently compared to the salt removal of untreated electrodes. Substantially improved salt removal due to chemical surface charge and the use of a discharge voltage of opposite sign to the charging voltage is clearly demonstrated in these CDI cycling tests, an observation which for the first time validates both enhanced CDI and extended-voltage CDI effects predicted by the Donnan model [Biesheuvel et al., Colloids Interf. Sci. Comm., 10.1016/j.colcom.2015.12.001 (2016)]. Our experimental and theoretical results demonstrate that the use of carbon electrodes with optimized chemical surface charge can extend the CDI working voltage window through discharge voltages of opposite sign to the charging voltage, which can significantly enhance the salt adsorption capacity of CDI electrodes. Thus, in addition to carbon pore size distribution, chemical surface charge in carbon micropores is considered foundational for salt removal in CDI cells. [ABSTRACT FROM AUTHOR]

The unequal distribution of the water resources warrants a search for more energy efficient water treatment technologies. In this regard, capacitive deionization (CDI) could play a leading role particularly in the case of brackish water desalination. In this work, inexpensive materials that are commercially available were investigated for being used as electrodes in CDI. After physical and electrochemical evaluation, activated carbon (AC) demonstrated superior performance compared to the different fabrics tested. Hereafter, a factorial design of experiments was used to investigate the effect of cell potential, mass of AC ( m AC ), carbon black, and interparticle porosity on ion removal, charge efficiency and energy consumption. The results showed that neither carbon black nor macroporosity had a single effect on electrode performance. An interaction effect of macroporosity and m AC was found to be beneficial in terms of ion electrosorption for thick electrodes. An additional evaluation concerning the role of electrode thickness revealed that an increase in thickness translated into an increase in the total salt removed and a reduction in ion removal per mass of electrode. In addition, while electrosorption kinetics were found to be independent of the AC thickness, slow desorption kinetics were detected for the thicker electrodes. [ABSTRACT FROM AUTHOR]

[Display omitted] • Fungal hypha activated carbon pad (FhACPad) is a promising electrode for desalination. • FhACPad is a freestanding electrode readily prepared from the fungus suspension for CDI. • The continuous and porous structure of FhACPad facilitates both electron and ion transfer. • FhACPad with hierarchical pores exhibits a high desalination capacity of 35.6 mg NaCl /g. Capacitive deionization (CDI) is an emerging technology for water desalination, especially low-salinity water. Freestanding porous carbon-based electrodes with rapid electron transfer rate and effective ion diffusion features are desired to achieve high desalination performance. Here, a porous carbon pad derived from the fungal hyphae of Aspergillus niger was prepared as a precursor of the electrode. After carbonization and activation, the intertwined and hierarchical porous structure of the fungal hypha pad was well-preserved, producing a freestanding fungal hypha activated carbon pad (FhACPad) electrode for MCDI. The interconnected carbon fibers and open pore structure of the FhACPad yielded an electrode with high electrical conductivity and rapid ion transport properties. The novel FhACPad exhibited a gravimetric salt adsorption capacity of 35.6 ± 2.3 mg NaCl /g with an average desalination rate of 1.2 mg NaCl /g electrode /min from a 585 mg/L NaCl aqueous solution at a cell voltage of 1.2 V and a flow rate of 1 mL/min. As a result, the FhACPad outperformed conventional powdered activated carbon (PAC) electrodes and the most recently reported porous carbon electrodes under similar desalination conditions. This work also provides insights into the structure-performance relationships of CDI electrodes and shows a great potential of fungal biomass-derived porous carbon electrodes for high-performance MCDI applications. [ABSTRACT FROM AUTHOR]

Owing to fresh-water shortage, developing highly efficient capacitive deionization (CDI) system equipped with low-cost electrodes is urgently required to process saline water to freshwater. On the other hand, Enteromorpha prolifera (EP for short, a typical bio-waste in global oceans) induced marine ecological crisis has become a serious threat to the global marine ecosystem. Aiming to kill two birds with one stone, we report the design of an EP-derived MnO 2 -decorated activated carbon composite (ep-AC@MnO 2) as low-cost electrodes for high-performance dual-mode capacitive deionization. The as-fabricated ep-AC@MnO 2 displays a high specific capacitance of 335.6 F g−1 with dual-mode sodium storage behavior. Benefiting from this unique dual-mode capacitance feature, the ep-AC@MnO 2 -based dual-mode CDI system exhibits highly efficient desalination performance (desalination capacity/rate: 25.7 mg g−1/2.95 mg g−1 min−1) with excellent desalination recyclability (11.3% declination after 30 cycles). This work could be of broad interest since it not only exemplifies the simple fabrication of low-cost yet high-efficiency CDI electrode material with dual-mode capacitance for capacitive desalination, but also offers a sustainable strategy to turn marine biowaste into treasure for possible relieving of the EP-induced marine ecological crisis. Highly-efficient dual-mode capacitive deionization system is developed based on utilizing freestanding MnO 2 decorated Enteromorpha prolifera -derived carbon as the low-cost flow-through electrode. Unlabelled Image • MnO 2 decorated porous carbon (ep-AC@MnO 2) was fabricated from Enteromorpha prolifera. • ep-AC@MnO 2 were used as flow-through electrode for novel dual-mode capacitive deionization (DCDI). • The ep-AC@MnO 2 -based DCDI exhibits excellent desalination capacity and rate. • Our strategy offers a feasible strategy to process bio-waste into sustainable DCDI electrodes. [ABSTRACT FROM AUTHOR]

The fouling of capacitive deionization (CDI) electrodes can adversely affect the CDI performance. One major foulant during water treatment relies on natural organic matter (NOM). A better understanding of the electroadsorption and electrochemical behavior of different groups NOM could clarify their relative contributions in electrode fouling. In this study, commercial sodium alginate (SA), humic acid (HA), and bovine serum albumin (BSA) were selected as representative model substances of NOM. During CDI process Salt ions were removed from brackish water during CDI and porous electrodes surfaces were covered by NOM to block the surface sites and micropores. After 50 CDI cycles, the salt adsorption capacity decreased by 78.2%, 47.6% and 66.0%, while the energy consumption increased by 213.6%, 63.3% and 129.1% for SA, HA and BSA, respectively. The charge efficiency diminished to 20.0%, 44.9% and 27.8% for SA, HA and BSA. The presence of NOM degraded the practical performances of porous activated carbons in terms of salt storage capacity, ion diffusion, and electron transport. Both SA and HA showed the worst impacts on the cathode, and BSA aggravated the oxidation process of the anode. The valuable information might be useful for future studies and applications. • The presence of NOM degraded the practical electrosorption performances of porous activated carbons. • This capacity loss was primarily attributed to a decline in salt storage, ion diffusion, and electron transport. • SA and HA showed the worst impacts on the cathode, BSA aggravated the oxidation process of the anode. [ABSTRACT FROM AUTHOR]

We developed a continuous-flow three-dimensional electrode reactor (3DER) to remove ibuprofen (IBP) from water. The effects of the operating parameters on the 3DER performance were investigated. The 3DER was constructed by filling a conventional two-dimensional electrode reactor with granular activated carbon, which acted as particle electrodes. The IBP removal efficiency of the 3DER was 98% in 4 h, which was 2.5 times higher than the removal efficiency for the two-dimensional electrode reactor. IBP removal kinetics tests indicated that the current density (1–20 mA/cm2) correlated better than the other operating parameters with the first-order rate constant (k). The flow rate affected the IBP removal kinetics to a small degree. Chloride and sulfate supporting electrolyte concentrations between 17 and 100 mM affected the IBP removal kinetics in opposite ways. Increasing the chloride concentration increased k, but increasing the sulfate concentration decreased k. Radical quenching experiments indicated that much more IBP degradation occurred through both indirect and direct oxidation mechanisms in the 3DER than in the two-dimensional electrode reactor. The particle electrodes caused hydroxyl radicals to form when the 3DER treatment was started, but the particle electrodes later acted as third electrodes and favored direct oxidation of IBP. Image 1 • A continuous-flow 3DER was developed for treating ibuprofen (IBP). • Current density had the greatest influence on the IBP removal rate. • 3DER enhanced both indirect and direct oxidation of IBP compared to 2DER. • Direct oxidation of IBP became dominant as 3DER operation proceeded. [ABSTRACT FROM AUTHOR]

Capacitive deionization (CDI) is an emerging technology as a sustainable low energy process for desalination of brackish water. Activated carbon electrodes are often used in the CDI devices. Electrosorption capacity was found to be improved on asymmetric electrode configuration using activated carbon cloth doped with fluorine due to redistribution of electric potential. This led to improvement in desalination performance up to 12.4 mg/g for a desalination cycle of 6 min employing an asymmetric fluorinated electrode as cathode (ACC//F-ACC). A relatively high charge efficiency of 77 % was obtained representing 92 % charge efficiency neglecting the leakage currents. Furthermore, the ion adsorption rate was found to improve substantially due to an increased surface conductivity of the fluorinated electrode confirmed by Mott-Schottky analysis. Energy consumption during desalination of 1000 ppm sodium chloride solution of 0.71kWh/m3 for symmetric electrode configuration was found to reduce by 36 % upon employing asymmetric configuration. This study shows some of the benefits of asymmetric configuration to achieve an optimal operation of CDI device, as well as improvements related to energy consumption. Image, graphical abstract [ABSTRACT FROM AUTHOR]

• Highly porous carbons were prepared from pyrolysis of dry loofah sponge using ZnCl 2. • MnO 2 /AC electrode was synthesized through KMnO 4 reduction. • Electrochemical mineralization of oxalic acid were performed over MnO 2 /AC electrode. • Phase transformation via calcination strongly improved effectiveness of MnO 2 redox. Manganese dioxide incorporated activated carbon (MnO 2 /AC) was synthesized and used to electrochemically degrade oxalic acid in aqueous solutions. The highly porous carbon provided reactive sites for the electro-sorption of oxalic acid and MnO 2 , with a specific polymorphism efficiently mediating the electron transfer between the electrode and organic pollutants. The activated carbon, made from the pyrolysis of dry loofah sponge using ZnCl 2 as activating agent, exhibited a high double-layer capacitance dependent upon the heating temperature (100 F/g at 800 °C). The γ -MnO 2 was in-situ deposited over the microporous structure of activated carbon through the redox reaction between KMnO 4 and carbon. Simple further calcination converted γ -MnO 2 to α -MnO 2 nano-whisker at temperatures above 500 °C. Cyclic voltammetry showed that oxalic acid significantly improved the anodic current of the Mn(III)/Mn(IV) redox couple on the MnO 2 /AC electrode at an electrode potential around + 0.6 V (vs. Ag/AgCl). About 95% of oxalic acid degradation was achieved at pH < 4; meanwhile, 80% of the mineralization (total organic carbon removal) was attained independent of pH. Calcination converted γ -MnO 2 to α -MnO 2 which had higher electrochemical stability and inhibited the dissolution of Mn(II) from the electrode. [ABSTRACT FROM AUTHOR]