Preparing porous Cu/Pd electrode on nickel foam using hydrogen bubbles dynamic template for high-efficiency and high-stability removal of nitrate from water.

Electrochemical reduction is a promising technology to remove nitrate from water. The metallic composition and geometry of electrodes usually dominate the nitrate removal property. Based on nickel foam (NF), we prepared Cu/Pd bimetallic electrode using hydrogen bubbles dynamic template according to a two-step electrodeposition method (Pd after Cu). The micromorphology, crystal structure, and metallic composition were analyzed by using the field emission scanning electron microscope with energy dispersive spectroscopy (FESEM-EDS), powder X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) instruments, respectively. 4.4 mg of Cu and 1.4 mg of Pd were detected on the prepared Cu/Pd electrode. The micromorphology of prepared Cu/Pd electrode showed a grape-bunch look with porous structure of two stage sizes (100-500 nm and 200-300 µm). 98% of the initial NO3--N (100 mg/L) was removed under the potential of - 1.6 V vs. Ag/AgCl saturated KCl after 24 h of reaction when using 0.05 mol/L of Na2SO4 or NaCl as electrolyte. But the concentration of produced NH4+-N was higher than 80 mg/L when using Na2SO4 as electrolyte, which was close to 0 mg/L when using NaCl as electrolyte. The cyclic voltammetry curves of 1000 cycles and the long-term continuous flow test of about 200 h suggested that the prepared Cu/Pd electrode showed high stability for nitrate removal from water.

Variation trends and principal component analysis of nitrogen oxide emissions from motor vehicles in Wuhan City from 2012 to 2017.

In addition to fine particulate matter and oxysulfides, nitrogen oxides (NOx) emitted by motor vehicles are among the most important pollutants affecting air quality and public health in those urban areas where centralized heating and chemical industry absent. We utilized correlation analysis (pearson correlation coefficient and spearman correlation coefficient) and principal component analysis (PCA) to identify the variation trends and main causes of NOx emissions from motor vehicles in Wuhan City. We considered the total number of motor vehicles (TN), ratios of motor vehicles of different emission standards (RE), rations of labeled motor vehicles (RL), and rations of motor vehicles' fuel types (RF). The results show that: 1) with an increase in the total amount of motor vehicles, the NOx emissions of motor vehicles have been decreasing since 2015; 2) three sub-categories (the ratio of the State III emission standard, the ration of yellow label diesel vehicles, and the ration of diesel vehicles) were recognized as key indexes of PE, PL and PF, respectively, in the PCA; 3) a new parameter, the ESindex is proposed as an index to represent the variation trend of the NOx emissions of motor vehicles in Wuhan City.

An empirical study on waste generation rates at different stages of construction projects in China.

Estimation of construction waste generation is critical to construction waste management decisions. However, current construction waste estimation methods have various limitations (e.g. small samples). To address those limitations, this research conducts an empirical study to evaluate the waste generation rate of different types of waste at different construction stages. In this study, construction waste from 148 new-built residential construction sites in China were sorted and weighted on site and their waste generation rates were estimated separately. The results indicated that the amount of inorganic nonmetallic waste with a generation rate of 16.59 kg m-2 was the highest among the five types of waste (i.e. inorganic nonmetallic waste, organic waste, metallic waste, composite waste, hazardous waste), while the waste generation rate for the underground construction stage, which was 27.57 kg m-2, was the highest among the three stages (i.e. underground stage, superstructure stage, finishing stage). Compared with previous data, the new waste generation rate proposed in this research can better estimate the actual waste generation situation in construction sites, which provides reliable information for proper decision-making. Furthermore, based on the result of the empirical study, some recommendations for construction waste reduction are proposed.

Simultaneous removal of nitrate/phosphate with bimetallic nanoparticles of Fe coupled with copper or nickel supported on chelating resin.

Given the prevalence of nitrate and phosphate in surface and groundwater, it is important to develop technology for the simultaneous removal of nitrate and phosphate. In this study, we prepared the bimetallic nanoparticles of Fe coupled with copper or nickel supported on chelating resin DOW 3N (D-Fe/Ni and D-Fe/Cu) for removing nitrate and phosphate simultaneously. XPS profiles revealed that Cu has better ability than Ni to increase the stability of Fe nanoparticles and prevent nZVI from oxidation. The results showed that nitrate removal efficiencies by D-Fe/Ni and D-Fe/Cu were 98.7% and 95.5%, respectively and the phosphate removal efficiencies of D-Fe/Cu and D-Fe/Ni were 99.0% and 93.0%, respectively. Besides adsorption and coprecipitation as reported in previous studies, the mechanism of phosphate removal also includes the adsorption of the newly formed polymeric ligand exchanger (PLE). Moreover, in previous studies, the presence of phosphate had significant negative effects on the reduction of nitrate. However, in this study, the removal efficiency of nitrate was less affected with the increasing concentration of phosphate for D-Fe/Cu. This was mainly because D-Fe/Cu had higher adsorption capacity of phosphate due to the newly formed PLE according to the XPS depth profile analysis.

Variation Trends of Fine Particulate Matter Concentration in Wuhan City from 2013 to 2017.

Fine particulate matter (PM2.5) is directly associated with smog and has become the primary factor that threatens air quality in China. In order to investigate the variation patterns of PM2.5 concentrations in various regions of Wuhan city across different time spans, we analyzed continuous monitoring data from six monitoring sites in Wuhan city from 2013 to 2017. The results showed that the PM2.5 concentration from the various monitoring sites in the five-year period showed a decreasing trend. January, October, and December are the three months with relatively high mean monthly PM2.5 concentrations in the year, while June, July, and August are the three months with relatively low mean monthly PM2.5 concentrations in the year. The number of days with a daily mean concentration of 35⁻75 µg/m³ was the highest, while the number of days with a daily mean concentration of more than 250 µg/m³ was the lowest. PM2.5 accounted for a large proportion of the major pollutants and is the main source of air pollution in Wuhan city, with an average proportion of over 46%.