Pd/Cu bimetallic nano-catalyst supported on anion exchange resin (A520E) for nitrate removal from water: High property and stability

The collaborative removal of copper/nitrate via catalytic hydrogenation processes over Pd/TiO2 catalyst

Nitrate (NO3-) and Cu2+ are common water pollutants that were frequently detected in varied waters such as metallurgical wastewater, electronic wastewater, etc. It is challenging to achieve simultaneous removal of NO3- and Cu2+. Herein, we prepared varied Pd/TiO2 catalysts for the catalytic hydrogenation reduction of Cu2+ and NO3-, and found that single Cu2+ could be effectively reduced (100 %) within 15 min, while the removal of NO3- was ignorant. Interestingly, the catalytic reduction of NO3- was triggered rapidly with the presence of Cu2+, where Cu2+ was still efficiently removed. The detected NO3- reduction intermediate products were NO2-, NH4+ and N2, and the selectivity for N2 and NH4+ in the final products were 27 % and 73 %, respectively, reflecting a synergistic treatment of multiple pollutants with clean products. The active H generated on the Pd active sites and newly formed Cu species played vital roles for the reduction of Cu2+ and NO3-, respectively. The low valence Cu was regenerated by the appearance of active H and cyclically joined NO3- reduction. Conventional technologies for NO3- removal are often inhibited or compromised in the presence of Cu2+, whereas this study circumvents these limitations and achieves efficient simultaneous removal of both Cu2+ and NO3-, with negligible generation of the byproduct NO2-. This study provided a new pathway to simultaneously catalytic eliminate heavy metal and NO3- and insights into the promote effect of coexisted Cu2+ for NO3- elimination.

Removal of hexavalent chromium from wastewater by chelating resin supported Fe/Cu bimetallic nanoparticles: Characterization, performance and mechanisms

In this work, Bimetallic Fe/Cu nanoparticles were successfully stabilized by chelating resin, which was specifically employed for the remediation of hexavalent chromium contaminated wastewater. Based on the characterization results, it was observed that the Fe/Cu bimetallic nanoparticles were uniformly and well distributed on the surface of the resin DOW M4195. The results demonstrated that the supported bimetallic Fe/Cu nanoparticles exhibited an excellent performance for Cr(VI) removal efficiency, reaching up to 99.4%. A series of factors, including initial pH, initial concentration of Cr(VI), co-exciting ions and humic acid were systematically evaluated to ascertain their respective impacts on Cr(VI) removal. The kinetics study followed intra-particle diffusion model demonstrated that both the adsorption and diffusion processes of Cr(VI) by the DOW M4195 resin played an important role in the overall removal of Cr(VI). The analytical results derived from XPS spectra at specific reaction times revealed the underlying removal mechanism of Cr(VI): Cr(VI) was adsorbed onto M-Fe/Cu due to the rich porous structure of the chelating resin DOW M4195. Additionally, the presence of the second metal, Cu, was found to significantly enhance the reduction performance of Fe0 and Fe(II) during the Cr(VI) removal process. The Cr(VI) removal mechanism was determined to involve a combination of physical adsorption, redox reactions and co-precipitation.

Structure properties and industrial applications of anion exchange resins for the removal of electroactive nitrate ions from contaminated water

The presence of nitrates in lakes, rivers, and groundwater is common. Anion exchange resins (AER) are polymeric structures that contain functional groups as well as a variety of particle sizes that are used for removing nitrate ions from solutions. This article provides a concise review of the types and properties of AER, synthesis methods, characterization, and environmental applications of AER. It discusses how different factors affect the adsorption process, isotherm and kinetic parameters, the adsorption mechanism, and the maximum adsorption capacities. Additionally, the present review addresses AER's regeneration and practical stability. It emphasizes the progress and proposes future strategies for addressing nitrate pollution using AER to overcome the challenges. This review aims to act as a reference for researchers working in the advancement of ion exchange resins and presents a clear and concise scientific analysis of the use of AER in nitrate adsorption. It is evident from the literature survey that AER is highly effective at removing nitrate ions from wastewater effluents.

Performance and microbial response to nitrate nitrogen removal from simulated groundwater by electrode biofilm reactor with Ti/CNT/Cu5-Pd5 catalytic cathode

To enhance the removal of nitrate nitrogen (NO3 - -N) in groundwater with a low C/N ratio, electrocatalytic reduction of NO3 - -N has received extensive attention since its electrons can be directly produced in situ while simultaneously providing a clean electronic donor of hydrogen for denitrifying bacteria. In this study, Ti/CNT/CuPd bimetallic catalytic electrodes with different copper-palladium (CuPd) ratios were prepared by electrodeposition onto carbon nanotube (CNT) using titanium (Ti) plates. The results showed that the NO3 - -N conversion rate by Ti/CNT/Cu5-Pd5 electrode was the highest (53.60%) compared with other CuPd electrode ratios because of the combined role of the copper's high NO3 - -N catalytic activity and the palladium's high N2 selectivity. A new type of electrode biofilm reactor (EBR) with Ti/CNT/Cu5-Pd5 cathode, biochar substrate was constructed to explore the removal ability of NO3 - -N in simulated low C/N groundwater. When the influent NO3 - -N concentration was 30 mg/L, under the condition of a 30 mA electronic current and hydraulic retention time (HRT) of 12 h, the removal rate of NO3 - -N could reach as high as 78.1 ± 1.2%, and the N2 conversion rate was 99.7%. The horizontal distribution of microbial communities in EBR showed that the denitrification capacity was significantly improved through the electrochemical catalytic reduction of the Ti/CNT/Cu5-Pd5 cathode and the supply of the hydrogen electron donor to autotrophic denitrogenerating microbes such as Anaerobacillus, Thauera, and Hydrophaga. This study provides a new bimetallic catalytic cathode to enhance the removal of NO3 - -N in groundwater with a low C/N ratio. PRACTITIONER POINTS: The Cu5Pd5/CNTs/Ti electrode is beneficial to the adsorption and reduction of NO3 - -N to N2 . The production of hydrogen electron donors by cathode promoted nitrogen degradation. Activated electrodes together with denitrifying microorganisms contributed to the improved N removal rate.