High N2 Selectivity Research Articles

Highly selective electrochemical nitrate reduction using copper phosphide self-supported copper foam electrode: Performance, mechanism, and application

A highly active and selective electrode is essential in electrochemical denitrification. Although the emerging Cu-based electrode has attracted intensive attentions in electrochemical NO3− reduction, the issues such as restricted activity and selectivity are still unresolved. In our work, a binder-free composite electrode (Cu3P/CF) was first prepared by direct growth of copper phosphide on copper foam and then applied to electrochemical NO3− reduction. The resulting Cu3P/CF electrode showed enhanced electrochemical performance for NO3− reduction (84.3%) with high N2 selectivity (98.01%) under the initial conditions of 1500 mg L−1 Cl− and 50 mg N L−1 NO3−. The cyclic voltammetry (CV) and electrochemical impedance spectra (EIS) demonstrated that electrochemical NO3− reduction was achieved through electron transfer between NO3− and Cu0 originated from CF. The in-situ grown Cu3P served as the bifunctional catalyst, the electron mediator or bridge to facilitate the electron-transfer for NO3− reduction and the stable catalyst to produce atomic H* toward NO2− conversion. Meanwhile, the Cu3P/CF remained its electrocatalytic activity even after eight cyclic experiments. Finally, a 2-stage treatment strategy, pre-oxidation by Ir-Ru/Ti anode and post-reduction by Cu3P/CF cathode, was designed for electrochemical chemical oxygen demand (COD) and total nitrogen (TN) removal from real wastewater.

Electrochemical removal of nitrate from wastewater with a Ti cathode and Pt anode for high efficiency and N2 selectivity

In this work, electrochemical denitrification using a Ti cathode and Pt anode was studied with the objective of enhancing the removal efficiency of NO 3 − and the selectivity of NO 3 − to N 2 . We first determined the optimal working potential and initial pH value for the activity and selectivity of NO 3 − removal by constant-potential electrolysis experiments; in this case, a working potential of −1.26 V and an initial pH value of 6 were optimal. Then, the anodic oxidation of the ammonia byproduct was investigated by varying the cathode/anode surface area ratios, suggesting that anodic oxidation played an important role in electrochemical denitrification. Under optimal conditions, the NO 3 − removal efficiency could reach 82.1% with a N 2 selectivity of 81.3%; moreover, a current efficiency of 63.9% was achieved, surpassing most of the reported electrochemical denitrification processes. Additionally, in situ Fourier transform infrared (in situ FTIR) spectroscopy and cyclic voltammetry were used to determine the reduction mechanism. Results indicated that acidic conditions were suitable for direct and indirect nitrate reduction, while NO 3 − was mainly reduced via direct reduction under alkaline conditions; moreover, the reaction route of NO 3 − conversion was verified

Nitrogen selectivity upon catalytic ozonation of ammonia with CTAB-NiO catalyst

In this work, CTAB-NiO catalyst was prepared by solid-state method and employed for oxidizing ammonia (NH4+) in aqueous solution by catalytic ozonation. In order to obtain high N2 selectivity, the effects of operating parameters on catalytic ozonation of ammonia were investigated in detail. Experimental results revealed that initial pH played a crucial role both in single O3 process and CTAB-NiO/O3 process, especially in the decomposition of O3 and the pathway of ammonia being oxidized into final products. Meanwhile, CTAB-NiO catalyst exhibited good performance in treating low concentration NH4+-containing wastewater from rare earth smelting. The results of qualitative and quantitative analysis of the reaction product distribution showed that in the CTAB-NiO/O3 system, about 98 % ammonia mainly converted to N2 at 293 K and ambient atmospheric pressure, with a selectivity of 76 %. The mechanism of catalytic ozonation of ammonia in aqueous solution was investigated by adding tert-butanol to the CTAB-NiO/O3 system. The catalytic ozonation of ammonia in aqueous solution was primarily due to the synergistic effect between the active ingredient from CTAB-NiO catalyst and hydroxyl radicals (·OH) generated by ozonolysis.

Recent Progress of CeO2−TiO2 Based Catalysts for Selective Catalytic Reduction of NOx by NH3

AbstractSelective catalytic reduction of NOx with NH3 (NH3−SCR) is one of the widely used process to abate NOx emission from both stationary and mobile sources. Recently, CeO2−TiO2 based NH3−SCR catalysts due to their excellent medium and high temperature activities, high N2 selectivity and environmentally friendly, have attracted much attention as great candidate to replace the commercial VOx−TiO2 based NH3−SCR catalysts. During the past years, extensive works have been done to achieve the industrial commercialization of CeO2−TiO2 based NH3−SCR catalyst. In this review, we summarize the recent studies on the mechanism, deactivation, preparation and modification of CeO2−TiO2 catalyst. The focus of this review is the modification strategies on improving the catalytic performance of CeO2−TiO2 catalyst. By comparing the effect of different modification strategies on the catalytic performance of CeO2−TiO2 catalyst, the perspectives and challenges of CeO2−TiO2 based catalyst for NH3−SCR of NOx are discussed.

A novel strategy for sequential reduction of nitrate into nitrogen by CO2 anion radical: Experimental study and DFT calculation

In order to expand the application of CO2 anion radical (CO2−), as a novel green reductant in the control of environmental pollution, CO2− radical was induced into the reduction of nitrate. The reduction efficiency, products and mechanism of nitrate or nitrite by CO2− radical were investigated based on the results of batch experiments and theoretical calculation using density functional theory (DFT) methods, respectively. It was found that: (1) the efficiency of nitrate reduction by CO2− radical from the HCOOH/UV system was far lower than that of nitrite under the same reaction conditions, (2) the rate-control step of nitrate reduction by CO2− radical was the transformation process of nitrate into nitrite with an activation energy of 23.9 kcal/mol, (3) the final products of nitrate reduction were mainly composed of nitrogen (N2). On this basis, a novel strategy of rapid reduction of nitrate into N2 using CO2− radical was proposed. Specifically, nitrate was firstly reduced into nitrite with the assistance of Zn/Ag bimetal, and then nitrite was further reduced into N2 by CO2− radical. In this way, the removal efficiency of nitrate was all achieved nearly 100% in the initial nitrate concentration ranging from 25 to 100 mg (N)/L, while the highest N2 selectivity could reach 97.5%. This work provided a promising approach for the reduction of nitrate into nitrogen with high efficiency and high N2 selectivity by CO2− radical.

The synergy between manganese oxide and iron oxide in NO catalytic removal with MnFeOx/SiO2 catalyst

The catalytic NO removal efficiencies of MnFeOx/SiO2 catalysts with different Fe/Si were compared and studied. The reaction pathway analysis of NH3-SCR on the surface of MnFeOx/SiO2 catalyst was performed based on DFT calculations. The experimental results of catalytic activity show that the addition of an appropriate amount of iron oxide has significant improvement for the NO conversion from 240 °C to 330 °C and the N2 selectivity from 150 °C to 330 °C. The XRD test also shows that the addition of iron oxide can greatly improve the dispersion of MnO2. In addition, DFT calculations indicate that the main process of N2 formation is the NH2NO decomposition and N-NO reaction. The N-NO reaction to form N2 is a unique reaction pathway possessed by MnFeOx/SiO2, which is the main reason for the high NO conversion and good N2 selectivity of MnFeOx/SiO2 catalyst and shows good synergy between manganese oxide and iron oxide.

Cu+ based active sites of different oxides supported Pd-Cu catalysts and electrolytic in-situ H2 evolution for high-efficiency nitrate reduction reaction

Supported Pd-Cu NO3− reduction (NO3R) under H2 atmosphere is considered as a promising way to achieve NO3− removal directly in water through converting into N2, which is a harmless product in environment. However, desirable NO3R kinetics and N2 selectivity remain challenges. In this research, 2.5 wt% Cu and 10 wt% Pd are loaded on various oxides supports and combine with electrolytic in-situ H2 generation for NO3R. Pd10%Cu2.5%/TiO2 demonstrates a faster NO3R rate constant than Pd10%Cu2.5%/γ-Al2O3 and even greater than Pd10%Cu2.5%/CeO2. Pd10%Cu2.5%/γ-Al2O3 obtains better N2 selectivity than the other two. Crucially, the oxygen vacancies (VO) existing in TiO2 and CeO2 can reduce the nearby Cu2+ to Cu+, also Cu2+ can attract electrons from Pd0 to form Cu+ on the γ-Al2O3 surface. Verified by experiments and density functional (DFT) calculations, these Cu+ based active sites on the surface of substrates are vital for effective NO3− adsorption and high N2 selectivity.

Catalytic combustion of acetonitrile over CuCeOx-HZSM-5 composite catalysts with different mass ratios: The synergism between oxidation and hydrolysis reactions

A sequence of CuCeOx-HZSM-5 composite catalysts at different Cu-Ce loading synthesized by the citric acid complex impregnation method were evaluated for the catalytic oxidation of acetonitrile. Among which, the 2CuCeOx-HZSM-5 sample exhibited the best degradation efficiency. In the temperature range of 225–350 °C, its activity and mineralization rate were approximately 100%, and the N2 selectivity remained more than 93%. The characterization results revealed that all the samples showed an existence of isolated Cu2+ species. And more Cu-Ce mixed oxides covered on HZSM-5 at an elevated Cu-Ce content, leading to the enhanced reducibility. In situ DRIFTS results showed that both oxidation and hydrolysis reaction routes proceeded during the degradation of acetonitrile over the composite catalysts. Their synergism was crucial to guarantee both high activity and N2 selectivity. The highly dispersed CuOx species ensured the superior activity of the 2CuCeOx-HZSM-5 sample. And Cu2+ exchanged HZSM-5 zeolite would be beneficial to N2 selectivity owing to the improved internal SCR (Selective Catalytic Reduction) reaction to reduce NOx from oxidation routes. Additionally, the mineralization rate was lowered with the formation of carbonaceous products like CH4 and CO for the catalysts at low Cu-Ce loading due to the lack of redox capacity.

Unsaturated p-Metal-Based Metal–Organic Frameworks for Selective Nitrogen Reduction under Ambient Conditions

Electrochemical ammonia synthesis that utilizes renewable electricity in the nitrogen reduction reaction (NRR) has recently been remarkably considered. Of particular importance is to develop efficient electrocatalysts at low costs. Herein, highly selective nitrogen capture using porous aluminum-based metal-organic frameworks (MOFs) materials, MIL-100 (Al), is first designed for the electrochemical nitrogen fixation in alkaline media under ambient conditions. Owing to the unique structure, MIL-100 (Al) exhibits remarkable NRR properties (NH3 yield: 10.6 μg h-1 cm-2 mgcat.-1 and Faradaic efficiency: 22.6%) at a low overpotential (177 mV). Investigation indicates that the catalyst shows excellent N2-selective captures due to the unsaturated metal sites binding with N2. More specifically, as the Al 3p band can strongly interact with N 2p orbitals, Al as a main group metal presents a high and selective affinity to N2. The utilization of multifunctional MOF catalysts delivers both high N2 selectivity and abundant catalytic sites, resulting in remarkable efficiency for NH3 production.

Facile synthesis of cost-effective iron enhanced hetero-structure activated carbon/geopolymer composite catalyst for NH3-SCR: Insight into the role of iron species

A hetero-structure activated carbon/geopolymer composite catalyst enhanced with iron was fabricated via facile activated carbon embedded polymerization and controlled impregnation. Over the temperature window of 350-500 ℃, the as-synthesized catalyst exhibited NO conversion greater than 96.5%, N2 selectivity above 94% with stable durability, excellent SO2 and H2O resistance. The high NO conversion and N2 selectivity may be associated with synergistic effects of extra-framework iron species in the geopolymer rings and excessive iron species agglomerated to form FeOx clusters on the activated carbon surface with enhanced redox capability. These are attached to the composite catalyst’s unique hetero-structure, where the former provides active sites for lower temperature SCR while the latter provides reactivity at higher temperatures. The complex iron species in the catalyst are facile controllable through impregnation. This composite catalyst demonstrated a new approach for developing cost-effective NH3-SCR catalysts for practical implications.

Novel Nano-Fe2O3-Co3O4 Modified Dolomite and Its Use as Highly Efficient Catalyst in the Ozonation of Ammonium Solution

Catalytic ozonation is a new method used for removal of NH4OH solution. Therefore, high catalytic performance (activity and selectivity) should be achieved. In this work, we report the synthesis and catalytic performance of Fe2O3-Co3O4 modified dolomite in the catalytic ozonation of NH4OH solution. Dolomite was successfully activated and modified with Fe2O3 and Co3O4. Firstly, dolomite was activated by heating at 800°C for 3 h and followed by KOH treatment. Activated dolomite was modified with Fe2O3 by the atomic implantation method using FeCl3 as Fe source. Fe2O3 modified dolomite was further modified with Co3O4 by precipitation method. The obtained catalysts were characterized by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), energy-dispersive X-ray spectroscopy (EDS), scanning electron microscopy (SEM), N2 adsorption–desorption (BET), and temperature-programmed reduction (H2-TPR). From SEM image, it was revealed that nano-Fe2O3 and Co3O4 particles with the size of 80–120 nm. Catalytic performance of activated dolomite, Fe2O3 modified dolomite, and Fe2O3-Co3O4 modified dolomite in catalytic ozonation of NH4+ solution was investigated and evaluated. Among 3 tested catalysts, Fe2O3-Co3O4 modified dolomite has the highest NH4+ conversion (96%) and N2 selectivity (77.82%). Selectivity toward N2 over the catalyst was explained on the basis of bond strength M-O in oxides through the standard enthalpy ΔH°f of oxide. Catalyst with lower ΔH°f value has higher N2 selectivity and the order is the following: Co3O4 (ΔH°f of 60 kcal (mole O)) > Fe2O3 (ΔH°f of 70 kcal (mole O)) > MgO (ΔH°f of 170 kcal (mole O)). Moreover, high reduction ability of Fe2O3-Co3O4 modified dolomite could improve the N2 selectivity by the reduction of NO3- to N2 gas.

Unraveling the origin of extraordinary lean NOx reduction by CO over Ir-Ru bimetallic catalyst at low temperature

Ir-Ru/Al2O3 developed has shown an outstanding activity for reducing NOx by CO at low temperature in excess oxygen. However, it has remained elusive how the Ir-Ru catalyst derives this unique reactivity. Here, we tried to unveil the origin of the synergistic effect in the Ir-Ru catalyst on the lean deNOx by CO. Ir-Ru/Al2O3 showed superb NOx reduction activity along with high N2 selectivity compared to monometallic catalysts. Results of EXAFS and XRD studies indicated the formation of Ir-Ru alloy phases on the alumina. These alloy phases were likely to accelerate reaction steps required for the NOx reduction by CO, based on temperature programmed experiments together with DFT calculations. Ir-Ru/Al2O3 appeared to effectively dissociate NO on the bimetallic site, which could successively be reutilized by the facile CO-O reaction, believed to be the primary causes for the excellent deNOx activity of Ir-Ru/Al2O3 by CO under lean exhaust condition.

A plasma thermal slag-derived from hazardous waste has a born hydrothermal stability

Hydrothermal instability restricts performances of silica-based catalysts, which have wide applications in both industry and environment. For the first time, plasma-thermal slag was revealed to be a catalyst with a born hydrothermal stability in selective catalytic reduction of nitric oxide. The slag catalyst removed 98.5 % of NO with a high N2 selectivity (> 95 %) at 200 °C. After a hydrothermal treatment at 900 °C, the activity of the slag only decreased to 84.0 %. According to characterizations of XRD, HTREM, XPS, and EPR, active metals existed in coordination states in the slag at first. Under hydrothermal conditions, these species transformed to short-range single crystals, which were hindered from sintering by surrounded Si-O bands. At the same time, in-situ DRIFT indicated that more Brønsted and Lewis acid sites were formed. Hence, enough active sties were reserved for effective catalytic reduction of nitric oxide. The main result of this work helps us to understand hydrothermal stability of a catalyst. What’s more, the high-value-added utilization of plasma-thermal slag is in favor of the development of hazardous-waste treatment.

High Catalytic Activity and N2 Selectivity on Catalytic Denitrification by Fe0 and Bimetallic Catalyst

AbstractThis research focused on the improvement of catalytic activity and N2 selectivity in catalytic denitrification by zero-valent iron (Fe0) and bimetallic catalyst. Analysis of optimal operati...

Application of the UV/sulfoxylate/phenol process in the simultaneous removal of nitrate and pentachlorophenol from the aqueous solution

This study was aimed to evaluate the performance of hydrated electron (eaq−) and SO2− generated from reaction between UV/sulfoxylate/phenol ring (USP) for the simultaneous removal of nitrate and pentachlorophenol (PCP) from aqueous solutions. The results indicated, with adding PCP (50 mg L−1) in the photoreactor, 94% of NO3− reduction (50 mg L−1) (with N2, NO2− and NH4+ selectivity of 98.9%, 0.21% and 0.85%, respectively) was achieved; while in the backbite of PCP in solution, 91.6% of NO3− was reduced (with N2, NO2− and NH4+ selectivity of 80.15%, 19.6% and 0.19%, respectively). Therefore, it turned out that the hydrated electrons generated in UV/phenol process, has a significant role in the reduction of nitrate and resulted in the higher N2 selectivity and the lower nitrite selectivity. This point can be the great importance from the public health point of view. Also 96% of PCP degradation and 87% of PCP mineralization were obtained by SO2− generated from UV/sulfoxylate. The optimum conditions (the maximum degradation and mineralization of PCP and also the maximum nitrate reduction (with the higher N2 selectivity and the lower nitrite selectivity)), were obtained at sulfoxylate dosage, 100 mg L−1; reaction time, 180 min and pH, 7.0. The USP process indicated the higher performance of USP than the UV alone and sulfoxylate alone, as nitrate and PCP reduction rates by UV alone, sulfoxylate alone and USP processes were obtained (24% and 66%), (18% and 17%) and (94% and 96%), respectively. Also kinetic studies were proved the results mentioned above, as values of robs for USP in the nitrate reduction and degradation of PCP were (17 and 31 times) and (1.4 and 4.25 times) than that of the sulfoxylate alone and UV alone, respectively. Values of energy consumption for the removal of nitrate and PCP were 26 kWh m−3 and 22 kWh m−3, respectively. The several intermediate products including acetic acid, ethane-1,2-diol, acetic acid dihydroxyethene isomers, benzoquinone, 2-chlorobenzene-1,4-diol, adipic acid were identified by the LC/MS analysis. Therefore, it was found the USP process due to smaller total cost and energy consumption and also the higher robs, might be an efficient method for the simultaneous removal of nitrate and pentachlorophenol (PCP) form aqueous solution.

Progress on Selective Catalytic Ammonia Oxidation (NH3‐SCO) over Cu−Containing Zeolite‐Based Catalysts

AbstractThe selective catalytic oxidation of ammonia into nitrogen and water vapor (NH3‐SCO) has proven to be the most efficient technique for the removal of NH3 from the oxygen‐containing diesel exhausts. Until now, two reviews over investigated catalysts have been published in 2015–2016 (Jabłońska et al., RCS. Adv. 2015; Appl. Catal. B: Environ. 2016). Among various NH3‐SCO catalysts, Cu‐ and/or Fe‐containing zeolites are considered as promising candidates due to their benign nature, NH3 storage capacity, very high NH3 conversion and N2 selectivity. The present review focusses only on the Cu‐containing zeolites (mainly on chabazite (CHA): SSZ‐13, SAPO‐34) catalysts) applied in NH3‐SCO starting from 2015. The synthesis/preparation methods and the state of Cu in catalysts on the activity and selectivity are highlighted. The advantages of the understanding of the reaction mechanism are reviewed. Finally, an outlook is given together with expected inspirations for future research directions in developing zeolite‐based catalysts.

Features of Nb2O5 as a metal oxide support of Pt and Pd catalysts for selective catalytic oxidation of NH3 with high N2 selectivity

Selective catalytic oxidation of ammonia (NH3-SCO) to N2 and H2O was examined as one of the most efficient solutions for NH3 pollution because NH3 has potentially harmful effects on human health and the environment. The acidic metal oxide Nb2O5 that possesses both Brønsted and Lewis acid sites was chosen as the support of Pt and Pd catalysts for SCO of 50 ppm NH3. Both Pt/Nb2O5 and Pd/Nb2O5 showed extremely high levels of N2 selectivity (98% and 100%, respectively) at 100% NH3 conversion. The role of the acid sites of Pt/Nb2O5 and Pd/Nb2O5 in NH3-SCO was investigated by the NaOH treatment to neutralize the Brønsted acid sites. The selectivity to N2 decreased by the NaOH treatment of Pt/Nb2O5 and Pd/Nb2O5. These results suggested that the Brønsted acid sites were essentially important for improving N2 selectivity. This study provides a new concept for the design of a catalyst by using the acid sites of acidic metal oxide to improve the N2 selectivity of NH3-SCO.

Catalytic removal of NO and dioxins over W-Zr-Ox/Ti-Ce-Mn-Ox from flue gas: Performance and mechanism study

Co-catalytic removal of multiple pollutants was able to reduce operating costs of enterprises, which was the main development direction for the waste incineration industry. In this work, series W-Zr-Ox/Ti-Ce-Mn-Ox (WZ/TCM) catalysts were designed to investigate independent NH3-SCR, dioxins oxidation and co-catalytic removal of NO and chlorobenzene (CB, the substitute of dioxins). The W-Zr-Ox mainly provided solid super acids; CeO2 and MnO2 enhanced the redox performance; and TiO2 provided a large specific surface area. All these factors guaranteed the excellent performance of WZ/TCM catalyst. The NO conversion of WZ/TCM reached 100 %, and the oxidation activity of CB was also higher than 85 % at 350–500 ℃. Meanwhile, the WZ/TCM had high N2 selectivity and excellent resistances to sulfur and water. In situ infrared diffuse reflectance spectra confirmed that ammonia gas mainly adsorbed on the Lewis acidic sites of the WZ/TCM catalyst and participated in the SCR reaction at low temperature. The ammonia species (NH4+) at the Brønsted sites participated in the reaction at high temperature. Furthermore, the chlorine atom on the chlorobenzene molecule was mainly removed to reduce toxicity when the oxidation of CB was at low temperature, which was deeply oxidized and had a variety of intermediate products at high temperature.

Promotional role of Mo on Ce0.3FeOx catalyst towards enhanced NH3-SCR catalytic performance and SO2 resistance

The SO2 resistance of low temperature NH3-SCR in non-electric power industries has always been the bottleneck of this technology. Herein, a series of Mo-modified Ce0.3FeOx catalysts (MoaCe0.3FeOx) were synthesized by an easy to scale-up, environment-friendly two-step solid interface reaction and applied to the treatment of flue gas from the glass industry. Incorporation of Mo into Ce0.3FeOx catalyst could not only remarkably expand the operation temperature window in both low and high temperature regions, but also maintain high catalytic activity (>85% NOx conversion) under 65 h long stability test conditions even with the coexistence of H2O and SO2. The two-step interface reaction over MoaCe0.3FeOx provided an increased specific surface area and more amorphous structure, forming highly dispersed MoO3 species on the surface of the catalyst which serves as a sacrificial site to react with SO2. The process of redox reaction has been greatly improved due to the facilitated electron transfer between Fe2+ and Ce4+ as well as more oxygen vacancies and active oxygen. The enhanced presence of NH4+ could react with gaseous NO species via Eley–Rideal (E–R) mechanism due to the lack of nitrate species (greatly inhibited) while the NH4NO3 was not generated during the reaction which is responsible for excellent low temperature SCR performance as well as high N2 selectivity. Furthermore, less sulfate species and no bulk sulfate were formed, which indicated that the doping of Mo could effectively reduce the basic sites and delay the irreversible deactivation as well as reduce catalyst sulphation. The above features provide a strategy for design and development of non-vanadium-based catalysts with low temperature SO2 resistance in non-electric power industries with high NOx emission concentrations.

Catalytic reduction of nitrate in reverse osmosis concentrate by using Pd-Cu/activated carbon felt

The reverse osmosis concentrate generated during the water reuse process contains a high concentration of nitrate but a low amount of biodegradable organic carbon for heterotrophic denitrification. Catalytic reduction of nitrates using Pd-Cu is one of the most promising technologies to achieve complete removal of nitrate; however, the effect of a range of experimental factors on the nitrate removal rate and N2 selectivity is still an ongoing concern. Two kinds of supporting materials, alumina and activated carbon felt, were used to immobilize the Pd-Cu catalyst. The alumina-based catalyst was used to establish reference conditions for further experiments, and the effect of pH control was evaluated for both supporting materials. It was observed that pH has a direct influence on the nitrate reduction rate as well as the N2 selectivity. Nitrate reduction efficiency was low at acidic conditions while the highest N2 selectivity was obtained at the acidic conditions. The optimal pH condition for Pd-Cu/activated carbon felt was determined as pH 4, showing the highest total nitrogen removal as N2 gas. Finally, the feasibility of catalytic nitrate reduction for reverse osmosis concentrate was evaluated by investigating the effects of organic and inorganic components commonly present in reverse osmosis concentrate. The organic and inorganic components did not show a significant inhibitory effect on catalytic nitrate reduction, while a high concentration of salt significantly decreased the nitrate reduction rate as well as the N2 selectivity. The filter type morphology of the Pd-Cu/activated carbon felt would be beneficial for field application compared to the conventional catalyst with powder form.