Application Of Porous Materials In CO₂ Separation Membranes Preparation And Low Concentration Wastewater Treatment

Porous materials are widely used in the fields of CO₂adsorption and separation,the adsorption and removal of pollutants in water and gas because of their various types,high specific surface area,adjustable pore structure,and easy functional modification.Based on the two application research goals of CO₂separation and the removal of low-concentration pollutants in water,we prepared a variety of functional porous materials（ZIF-8,nitrogen-doped rubber seed shell biomass activated carbon and nitrogen-rich polyacetal）,and intruduce them into the polymer membrane to prepare a series of mixed matrix membranes（MMMs）with high CO₂permeation flux and separation selectivity.The type of polymer,the type of porous filler,and the amount of addition have been studied on the effect of the mixed matrix membrane.And CO₂separation performance and transmission mechanism.The adsorption and removal performance of the prepared nitrogen-doped activated carbon material in the actual chemical wastewater containing heavy metal ions and phenolic organic matter was further studied.The main research contents of this thesis are as follows:（1）In view of the trade-off between the gas permeation flux and separation selectivity of the polymer membrane,the excellent dispersibility of ZIF-8 nanoparticles in the solution is used,and ZIF-8 is added with the strategy of first dispersion and then crosslinking into the polymer network of polytrifluoropropyl methylsiloxane（PTFPMS）,a series of ZIF-8/PTFPMS mixed matrix membranes were prepared.Studies have shown that the CO₂permeation flux of the 3 wt%ZIF-8/PTFPMS membrane reaches 1668 Barrer,and the CO₂/N₂selectivity is 20.0.Compared with the pure PTFPMS membrane,the CO₂permeation flux of the mixed matrix membrane is increased by 76.6%,The selectivity of CO₂/N₂is increased by 50.7%.（2）For the high value-added utilization of biomass resources,biomass rubber seed shells are used as carbon source,melamine is used as nitrogen source,KOH is used as activator,and a series of specific surface areas are obtained by optimizing preparation conditions by using one-step calcination measures.Nitrogen-doped biomass activated carbon material with adjustable pore structure and surface functional groups.Studies have shown that under the conditions of a rubber seed hull/KOH/melamine addition ratio of 1/2/0.8and an activation temperature of 600°C,the prepared nitrogen-doped activated carbon（RSS-5-600°C）has a CO₂adsorption capacity of 5.81 mmol/g（273 K/1 bar）,the adsorption selectivity of CO₂/N₂and CO₂/CH₄reached 35.81 and9.67,respectively.In order to further improve the separation selectivity of the mixed matrix membrane for CO₂,a cross-linked PEO membrane with higher affinity for CO₂is selected,RSS-5-600°C is used as a porous filler,and RSS-5-600°C is introduced into the polymer membrane through thermal cross-linking measures.A series of mixed matrix membranes with different addition amounts of RSS-5-600°C were prepared.The CO₂/N₂and CO₂/CH₄selectivities of the 1.5 wt%RSS-5-600°C/PEO membrane were as high as48.6 and 19.0,respectively,and the CO₂permeation flux was 821 Barrer.Compared with pure PEO membrane（390 Barrer）,the CO₂permeation flux of nitrogen-doped activated carbon-based mixed matrix membrane was increased by 110.5%,the selectivity of CO₂/N₂and CO₂/CH₄were increased by 49.5%and 50.8%,respectively.（3）Aiming at the problem of low nitrogen content in biomass nitrogen-doped activated carbon,a nitrogen-rich ultra-microporous polyaminal PAN-NH₂was prepared.Its rich nitrogen-containing groups（primary amines,secondary amines and triazines）lead to high CO₂/N₂selectivity and form hydrogen bonds with polymer PEO segments to further improve the CO₂separation performance of the membrane.A series of PAN-NH₂/PEO mixed matrix membranes were prepared by thermal cross-linking reaction.When the PAN-NH₂filling amount is 2 wt%,the permeation flux of CO₂reaches 1030Barrer,which is 164.1%higher than that of pure PEO.The ideal selectivity of CO₂/N₂and CO₂/CH₄reached 72 and 19.8,respectively,and the relative pure PEO was increased by 121.5%and 57.1%,respectively,the separation performance of CO₂/N₂exceeded the upper bound（2019）.In the separation of binary gas mixtures,the CO₂/N₂and CO₂/CH₄separation factors of 2 wt%PAN-NH₂/PEO MMMs are 73 and 19.7,and the CO₂/N₂separation factor in the actual flue gas is 65.（4）For the treatment of low-concentration pollutants in wastewater,the prepared nitrogen-doped rubber seed shell activated carbon is used for the adsorption and separation of low-concentration wastewater containing heavy metal ions and phenolic organic produced in actual chemical production.Among them,the Hg²⁺adsorption capacity of RSS-5-700°C is as high as 2711mg/g.When there is a competitive adsorption of various metal ions(Hg²⁺,Cu²⁺,Cd²⁺,Pb²⁺,Zn²⁺and Mg²⁺),the removal rates of Hg²⁺,Cu²⁺,Cd²⁺,and Pb²⁺were 81.9%,94.8%,85.7%and 75.1%,respectively.RSS-5-800°C activated carbon has an adsorption capacity of 89 mg/g for phenolic organic wastewater with an initial COD concentration of 228 mg/L.Within 4 cycles of use,the COD removal rate for phenol wastewater of RSS-5-800°C is maintained above 70%when the raw material concentration is 228 mg/L.