Synergistic Treatment of Low-concentration Organic Waste Gas by Micro-nano Bubble Coordinated with Peroxymonosulfate

Continuous dynamic experiment was conducted for the treatment of low-concentration organic waste gas with xylene as a representative, using micro-nano bubble and peroxymonosulfate working in synergy. The degradation rule of xylene under different conditions such as the ORP value of the spray liquid, pH value of the spray liquid, liquid-gas ratio of the spray liquid, residence time of xylene, and initial concentration of xylene was investigated. The results showed that at a low concentration, the pH value of the spray liquid had little effect on the degradation rate of xylene. The degradation rate of xylene rose with the increase of the ORP value of the spray liquid, the liquid-gas ratio of the spray liquid, the residence time of xylene, and the initial concentration of xylene.

Molecular Simulations of Water Transport Resistance in Polyamide RO Membranes: Interfacial and Interior Contributions

Understanding the transport resistance of water molecules in polyamide(PA)reverse osmosis(RO)membranes at the molecular level is of great importance in guiding the design,preparation,and applications of these membranes.In this work,we use molecular simulation to calculate the total transport resistance by dividing it into two contributions:the interior part and the interfacial part.The interior resistance is dependent on the thickness of the PA layer,while the interfacial resistance is not.Simulation based on the 5 nm PA layer reveals that interfacial resistance is the dominating contribution(>62%)to the total resistance.However,for real-world RO membranes with a 200 nm PA layer,interfacial resistance plays a minor role,with a contribution below 10%.This implies that there is a risk of inaccuracy when using the typical method to estimate the transport resistance of RO membranes,as this method involves simply multiplying the total transport resistance of the simulated value based on a membrane with a 5 nm PA layer.Furthermore,both the interfacial resistance and the interior resistance are dependent on the chemistry of the PA layer.Our simulation reveals that decreasing the number of residual carboxyl groups in the PA layer leads to decreased interior resistance;therefore,the water permeability can be improved at no cost of ion rejection,which is in excellent agreement with the experimental results.

Structure and dynamics of water in TiO_(2) nano slits:The influence of interfacial interactions and pore sizes

The interaction of water with TiO_(2) surfaces is of enduring interest because of wide applications of the TiO_(2) materials in aqueous environments.The structure and dynamic properties of water molecules in TiO_(2) nanopores are crucial as increasingly TiO_(2) materials are synthesized into nanoporous structures.In this work,the structural and dynamic properties of water molecules in nanoscale slit pores of TiO_(2) are investigated,by using three sets of force field models for the water-TiO_(2) interaction,as well as four TiO_(2) slit pore widths.It is concluded that the water-TiO_(2) interaction dominates the interfacial structure of water molecules,while the dynamic properties of water molecules are primarily influenced by the slit width in both interfacial and central regions.These findings indicate that both of the fluid properties and the interactions of fluids with pore wall will determine the transport properties of fluid in nanopores.If the pore size is large enough,e.g.1.0 nm or larger in this work,the transport properties will be determined most by the fluids themselves.For the cases of pores whose sizes are in the range of interfacial region,the influences of pore size and interfacial interaction will interfere each other.

Heat transfer of nanofluidics in hydrophilic pores: Insights from molecular dynamics simulations

Nanofluidics in hydrophilic nanopores is a common issue in many natural and industrial processes. Among all,the mass transport of nanofluidics is most concerned. Besides that, the heat transfer of a fluid flow in nano or micro channels is always considered with adding nanoparticles into the flow, so as to enhance the heat transfer by convection between the fluid and the surface. However, for some applications with around 1 nm channels such as nano filtration or erosion of rocks, there should be no nanoparticles included. Hence, it is necessary to figure out the heat transfer mechanism in the single phase nanofluidics. Via non-equilibrium molecular dynamics simulations, we revealed the heat transfer inside nanofluidics and the one between fluid and walls by setting simulation into extremely harsh condition. It was found that the heat was conducted by molecular motion without temperature gradient in the area of low viscous heat, while it was transferred to the walls by increasing the temperature of fluids. If the condition back to normal, it was found that the viscous heat of nanofluidics could be easily removed by the fluid-wall temperature drop of less than 1 K.

Scenario analysis of water pollution control in the typical peri-urban river using a coupled hydrodynamic-water quality model

The water quality pollution and ecological deterioration in peri-urban rivers are usually serious under rapid urbanization and economic growth.In the study,a typical peri-urban river,Nansha River,was selected as a case study to discuss the scheme of peri-urban river rehabilitation.Located in the north part of the Beijing central region,the Nansha River watershed has been designated as an ecologically friendly garden-style area with high-tech industry parks and upscale residential zones.However,the Nansha River is currently seriously contaminated by urban and rural pollutants from both nonpoint sources(NPS)and point sources(PS).In this study,the pollutant loads from point sources and nonpoint sources in the Nansha River watershed were first assessed.A coupled model,derived from the Environmental Fluid Dynamics Code and Water Quality Analysis Simulation Program,was developed to simulate the hydrodynamics and water quality in the Nansha River.According to the characteristics of the typical peri-urban river,three different PS and NPS control scenarios were designed and examined by modeling analyses.Based on the results of the scenario analysis,a river rehabilitation scheme was recommended for implementation.

How Pore Hydrophilicity Influences Water Permeability?

Membrane separation is playing increasingly important role in providing clean water.Simulations predict that membrane pores with strong hydrophobicity produce ultrahigh water permeability as a result of low friction.However,experiments demonstrate that hydrophilic pores favor higher permeability.Herein we simulate water molecules transporting through interlayers of twodimensional nanosheets with various hydrophilicities using nonequilibrium molecular dynamics.We reveal that there is a threshold pressure drop(ΔPT),exceeding which stable water permeability appears.Strongly hydrophobic pores exhibit extremely highΔPT,prohibiting the achievement of ultrahigh water permeability under the experimentally accessible pressures.Under pressures<ΔPT,water fows in hydrophobic pores in a running-stop mode because of alternative wetting and nonwetting,thus leading to signifcantly reduced permeability.We discover that hydrophilic modifcation to one surface of the nanosheet can remarkably reduceΔPT by>99%,indicating a promising strategy to experimentally realize ultrafast membranes.