The desalination treatment of shale gas fracturing flowback wastewater can be used for the wastewater reuse and reasonable discharge. The modeling and energy efficiency analysis of desalination treatment process can guide the process optimization and efficient operation. The membrane-based desalination process of shale gas fracturing flowback wastewater includes the pretreatment process (electrocoagulation and ultrafiltration) and reverse osmosis. For the membrane module of reverse osmosis unit, the solution-diffusion model is adopted to describe the mass transfer process. Furthermore, the water permeability constant and the mass transfer coefficient of salt were calculated based on the experimental data. Finally, the energy efficiency and economic evaluation model is established, and the influence of the energy recovery system on the economy and energy efficiency of the desalination process is considered. The results show that the total energy consumption is reduced by 20.45%, and the annual operation cost of the pump is reduced by 15.29% with the help of energy recovery system.

Efficient separation of CH₄ and C₂H₆ remains a critical challenge in the recovery of light hydrocarbons from natural gas. So we developed a zeolite imidazolate framework-8 (ZIF-8)/iso-hexadecane slurry for CH₄/C₂H₆ separation, and conducted solubility measurements for pure components and equilibrium separation experiments for gas mixtures. A rigorous absorption-adsorption coupled phase equilibrium model and a single equilibrium stage mathematical model were established to describe the phase equilibrium performance of gas-slurry system. The results indicated that the model exhibits high predictive accuracy for the solubility of CH₄ and C₂H₆ in the slurry, with an average relative error of less than 3.053%. Furthermore, the whole process of absorption-adsorption-desorption was designed, and the mathematical model and multi-objective optimization framework were established. The effects of operating pressure and gas-slurry ratio on product purity, recovery ratio, and total unit energy consumption were investigated. The results showed that the C₂H₆ purity in the feed gas is enriched from 22 mol/mol to 94.69 mol/mol, the C₂H₆ recovery ratio reaches 95.21%, and the total unit energy consumption is 0.4558 kW·h·Nm⁻³ (feed gas). In addition, the effects of pressure, temperature, and ZIF-8 solid content on slurry separation performance were analyzed using the established equilibrium-stage model. The results showed that the introduction of ZIF-8 enhances the separation performance of the iso-hexadecane solvent for mixed gases. Compared to the pure solvent, the separation factor increased by an average of 72.5%, which theoretically proved the advantages of slurry separation process.

Non-methane hydrocarbons (NMHCs) are a common type of volatile organic compounds (VOCs) pollutant in the petrochemical industry and have attracted widespread attention because of their adverse health effects and environmental impacts. In this paper, we report a new porous slurry formed with zeolitic imidazolate framework-8 (ZIF-8) and iso-hexadecane to capture the low-concentration and multi-component NMHCs (mainly ethane (C₂H₆), propane (C₃H₈), and n-butane (n-C₄H₁₀)) from the oil field exhaust. The sorption capacity of C₂H₆ in the slurry is significantly higher than that of nitrogen (N₂) and methane (CH₄). Moreover, the slurry demonstrated a clear advantage for C₂H₆ over N₂ and CH₄ in competitive adsorption through the pressure-drop curves. In the NMHCs capture experiments, the C₃H₈ and n-C₄H₁₀ concentrations after purification can be reduced to below 100 ppm, while the C₂H₆ concentration can reach approximately 180 ppm. More encouragingly, in the breakthrough tests, the slurry exhibits a perfect kinetic separation selectivity for multi-component NMHCs. Furthermore, to avoid structural collapse of ZIF-8 material during long-term use in acidic and wet environments, a certain amount of 2-methylimidazole was retained in the slurry as a protective agent in the material synthesis process. In this way, the ZIF-8 materials in the slurry can retain the stable characteristic structure in an aqueous and acidic environment and keep the capture capacity for NMHCs without degradation. We believe the porous ZIF-8/iso-hexadecane slurry is a promising capture agent for low-concentration and multi-component NMHCs with strong purification capacity and stability.