Effect of Hydrogen on Corrosion Behavior of 321 Stainless Steel in NH4Cl Solution

For a hydrogenation heat exchanger operating under severe working conditions such as high temperature, high pressure and a hydrogen environment, perforation accidents caused by NH4Cl corrosion occur frequently. However, few reports on the effect of hydrogen on the corrosion behavior of metal materials in NH4Cl aqueous solution have been published. In this paper, X-ray photoelectron spectroscopy (XPS), electrochemical dynamic potential polarization, electrochemical impedance spectroscopy (EIS), Mott–Schottky (M-S) curves and scanning electron microscopy (SEM) were used to study the effect of electrochemical hydrogen charging (EHC) on the corrosion behavior of 321 stainless steel in an NH4Cl solution environment. The results show that: (1) hydrogen can change the structure and chemical composition of 321 stainless steel passive film and promote the conversion of metal oxide to hydroxide. At the same time, it can reduce the stability of the passive film. (2) Hydrogen can increase the thermodynamic and kinetic tendency of corrosion reaction and cooperate with Cl− to promote the occurrence of pitting corrosion

Preparation of Magnetic Hyper-Cross-Linked Polymers for the Efficient Removal of Antibiotics from Water

A novel method for fabricating magnetic hyper-cross-linked polymers (MHCPs) with high Brunauer–Emmett–Teller (BET) specific surface area, large pore volume, and good magnetic properties was developed. The synthesis process of MHCPs included two steps: the preparation of HCPs by external cross-linker and the in situ oxidation of the iron source in the structure of HCPs. On the basis of the systematic investigation of the influences of oxidation time and amount of hydrogen peroxide added, a series of MHCPs with different specific surface area, pore volume, and magnetic responsiveness was controllably prepared with the highest BET specific surface area and maximum saturation magnetization of 729.93 m²/g and 12.4 emu/g, respectively. Furthermore, the adsorption performance of MHCPs with antibiotics was studied by using chloramphenicol (CAP) and tetracycline hydrochloride (TC) as model adsorbates. The kinetics isotherms of CAP and TC followed a pseudo-second-order model, and the adsorption isotherms of them were proved to fit the Langmuir adsorption model. The maximum adsorption capacity of CAP and TC at the temperature of 20 °C could reach 114.94 and 212.77 mg/g, respectively. The above results showed that the MHCPs would be one of the most promising candidates for application in the adsorption of antibiotics

Evaluation of the Performance of Low-Cost Air Quality Sensors at a High Mountain Station with Complex Meteorological Conditions

Low-cost sensors have become an increasingly important supplement to air quality monitoring networks at the ground level, yet their performances have not been evaluated at high-elevation areas, where the weather conditions are complex and characterized by low air pressure, low temperatures, and high wind speed. To address this research gap, a seven-month-long inter-comparison campaign was carried out at Mt. Tai (1534 m a.s.l.) from 20 April to 30 November 2018, covering a wide range of air temperatures, relative humidities (RHs), and wind speeds. The performance of three commonly used sensors for carbon monoxide (CO), ozone (O3), and particulate matter (PM2.5) was evaluated against the reference instruments. Strong positive linear relationships between sensors and the reference data were found for CO (r = 0.83) and O3 (r = 0.79), while the PM2.5 sensor tended to overestimate PM2.5 under high RH conditions. When the data at RH >95% were removed, a strong non-linear relationship could be well fitted for PM2.5 between the sensor and reference data (r = 0.91). The impacts of temperature, RH, wind speed, and pressure on the sensor measurements were comprehensively assessed. Temperature showed a positive effect on the CO and O3 sensors, RH showed a positive effect on the PM sensor, and the influence of wind speed and air pressure on all three sensors was relatively minor. Two methods, namely a multiple linear regression model and a random forest model, were adopted to minimize the influence of meteorological factors on the sensor data. The multi-linear regression (MLR) model showed a better performance than the random forest (RF) model in correcting the sensors’ data, especially for O3 and PM2.5. Our results demonstrate the capability and potential of the low-cost sensors for the measurement of trace gases and aerosols at high mountain sites with complex weather conditions