Nitrogen-doped porous carbons with BET surface area of 1068.2–3314.5 m 2 /g and nitrogen contents of 3.2–6.5% were prepared with solid waste grape-seed as raw material, NaNH 2 as activator and nitrogen source at low activation temperature. Super The activation mechanism of NaNH 2 on hydrothermal carbon precursors was first explored by thermodynamic analysis and TG-IR, which provided theoretical support for pore forming of carbon materials. Maximum CO 2 and CH 4 adsorption capacity at 273 K and pressure of 101 kPa was 5.42 and 1.76 mmol g −1 respectively, which are higher than those of majority of carbon derived from most solid wastes reported in literature. IAST selectivities of GS-3-450 with the largest BET surface area for CO 2 /CH 4 (40v/60v), CO 2 /N 2 (15v/85v), CH 4 /N 2 (50v/50v) were found to be 20.3, 71.4, 6.0 under 101 kPa and 298 K respectively. The competitive adsorption of GS-3-450 for CO 2 /CH 4 (40v/60v), CO 2 /N 2 (15v/85v), CH 4 /N 2 (50v/50v) gases mixture were examined through breakthrough experiments, and the results showed that the breakthrough time of CO 2 was longer than that of CH 4 and N 2 , which was beneficial to the separation of CO 2 from gases mixture. Eight cycles of CH 4 adsorption–desorption studies revealed that the material exhibited excellent recycling stability. Low temperature preparation method, excellent BET specific surface area and total pore volume, as well as excellent adsorption ability of CO 2 and CH 4 make it have a very great potential for the capture of CO 2 and CH 4 .

Supersaturation of total dissolved gas (TDG) is a common occurrence in high dams during the spill process, which can lead to fish bubble disease and threaten aquatic organisms. As a result, many scholars have taken a keen interest in this issue. Research into the gas-liquid mass transfer mechanism has improved the accuracy of TDG prediction models. This article investigates the factors affecting TDG dissipation through laboratory experiments. Especially, the mass transfer coefficient across the bubble interface based on the slip penetration model was calibrated, and the coaxial bubble coalescence added to the coefficient was studied. The results show that the aeration rate has the most significant impact, followed by water depth, and then the aeration aperture. The TDG dissipation rate increases with the parameter beta, and the parameter of 0.35 shows the highest correlation with the experimental data. Furthermore, the concentration change rate after coalescence is lower than before, suggesting that aggregation negatively impacts mass transfer. This study improves TDG concentration prediction accuracy and proposes measures for mitigating supersaturation to avoid fish bubble disease.

N-doped microporous carbons have attracted much attention for micromolecule gas separation and accumulation owning to their superior adsorption potential and surface polarizability. However, to prepare N-doped microporous carbon usually acquire excess corrosive KOH as activator, which limits its application in industry. Here, we propose a non-corrosion method for the manufacture of narrow N-doped microporous carbons using potassium citrate acts as activating agent, and urea acts as both a nitrogen doping agent and coactivator without any solvent. The BET surface area, micropore volume, pore size distribution and N content can be easily adjusted by changing the potassium citrate/urea ratio and activating temperature. The influence of porous structure and N content on CH4 uptake and separation was investigated, and ultra-micropore volume (<1nm) plays a dominate role in CH4 selectivity adsorption. ACK2N1 had the largest CH4 adsorption capacity of 3.00 mmol/g and CH4/N2 selectivity of 7.11 at 273.15 K and 100 KPa due to its largest ultra-micropore volume and N content. The adsorption breakthrough, regeneration experiments and adsorption thermodynamics showed that the prepared well-developed N-doped microporous carbons have very good potential for CH4 separation and enrichment from low coal bed methane. Furthermore, the pore formation mechanism of the well microporous carbon materials is proposed.

Although carbon material are widely used for gas separation and adsorption due to its well-developed pore structure, their prevalent wide pore size distribution and scarcity of active adsorption sites limit its gas adsorption capacity. Therefore, in this paper, a series of N-doped microporous carbon adsorbent materials were prepared via utilizing cheap starch as the carbon source and the synthesized melamine resin as the N-doped modifier with the assistance of hydrothermal conversion and high temperature activation by KOH.BET test showed that MF@Cs was a typical microporous carbon material with a pore size distribution of 0.3–2 nm, and its most accessible pore size was about 0.6 nm,which benefits the adsorption of CO2 and CH4. MF@C–1–750 porous carbon material present prominent pore structure parameters, with a maximum specific surface area of 2415.9 cm2/g, a total pore volume of 1.36 cm2/g, and a maximum ultramicro pore volume of 0.42 cm2/g at 0.3 ~ 1.0 nm. MF@Cs porous carbon materials show high static adsorption capacity for CO2 and CH4, the adsorption capacity of CO2 of MF@C–1–750 is as high as 6.54 mmol/g at 273 K and 100 kPa, which is attributed to the excellent ultramicro pore volume of carbon materials. MF@Cs porous carbon material is expected to play a huge application potential in the separation and enrichment of CO2 in the future, due to its simple preparation and low cost, excellent specific surface area, outstanding ultrafine pore capacity and high adsorption capacity of CO2 gas.

An Interconnected River System Network (IRSN) project could change the drainage pattern and influence the river's ecological health. However, the relevant research is still in a preliminary stage and needs to have a supplement. Considering environmental and ecological characteristics of the karst area, this paper analyzed the relationship between IRSN projects and environmental indicators, and proposed a multi-layer indicator system that has three first-class indicators (water environment, river–lake organism, connectivity) and 15 second-class indicators for assessment of the ecosystem. The weight of each level of indicators' can be determined using the analytic hierarchy process (AHP), and the change rate of indicators critical value is normalized, then five threshold levels are established within the range of 0–1. Refer to the established response mechanism and threshold level of the karst basin, The Wangerhe River project taken as an example can well reflect the IRSN status through this method. These results can provide scientific support for constructing an evaluation index in other karst areas.

The total dissolved gas (TDG) supersaturation observed in a spillway that flows downstream various hydraulic structures has long been recognized as having a negative environmental effect on fish and aquatic organisms. This paper focuses on learning the mass transfer of supersaturation total dissolved gas downstream and the rule of mass transfer between air-water interfaces. Besides, the three main coefficients of mass transfer are concluded: the surface mass transfer coefficient, the bubble interface mass transfer coefficient, and the dissipation coefficient and relevant transport process model. These can provide a foundation to analyze the supersaturation of high dam in near future.