Electrocatalytic reduction of nitrate using Pd-Cu modified carbon nanotube membranes

Excessive nitrate in water is harmful to the ecological environment and human health.Electrocatalytic reduction is a promising technology for nitrate removal.Herein,a Pd-Cu modified carbon nanotube membrane was fabricated with an electrodeposition method and used to reduce nitrate in a flowthrough electrochemical reactor.The optimal potential and duration for codeposition of Pd and Cu were-0.7 V and 5 min,respectively,according to linear scan voltammetry results.The membrane obtained with a Pd:Cu ratio of 1:1 exhibited a relatively high nitrate removal efficiency and N_(2)selectivity.Nitrate was almost completely reduced(~99%)by the membrane at potentials lower than-1.2 V.However,-0.8 V was the optimal potential for nitrate reduction in terms of both nitrate removal efficiency and product selectivity.The nitrate removal efficiency was 56.2%,and the N_(2)selectivity was 23.8%for the Pd:Cu=1:1 membrane operated at-0.8 V.Nitrate removal was enhanced under acidic conditions,while N_(2)selectivity was decreased.The concentrations of Cl-ions and dissolved oxygen showed little effect on nitrate reduction.The mass transfer rate constant was greatly improved by 6.6 times from 1.14×10^(-3)m/h at a membrane flux of 1 L/(m^(2)·h)to 8.71×10^(-3)m/h at a membrane flux of 15 L/(m^(2)·h),which resulted in a significant increase in the nitrate removal rate from 13.6 to 133.5 mg/(m^(2)·h).These findings show that the Pd-Cu modified CNT membrane is an efficient material for nitrate reduction.

Nanofiltration for drinking water treatment: a review

In recent decades,nanofiltration(NF)is considered as a promising separation technique to produce drinking water from different types of water source.In this paper,we comprehensively reviewed the progress of NFbased drinking water treatment,through summarizing the development of materials/fabrication and applications of NF membranes in various scenarios including surface water treatment,groundwater treatment,water reuse,brackish water treatment,and point of use applications.We not only summarized the removal of target major pollutants(e.g.,hardness,pathogen,and natural organic matter),but also paid attention to the removal of micropollutants of major concern(e.g.,disinfection byproducts,per-and polyfluoroalkyl substances,and arsenic).We highlighted that,for different applications,fit-for-purpose design is needed to improve the separation capability for target compounds of NF membranes in addition to their removal of salts.Outlook and perspectives on membrane fouling control,chlorine resistance,integrity,and selectivity are also discussed to provide potential insights for future development of high-efficiency NF membranes for stable and reliable drinking water treatment.