Preparation And Oil/water Separation Performance Of Porous Cellulose Acetate-based Monoliths

In recent years,the frequent occurrences of marine oil spillage,organic chemicals leakage and industrial oily wastewater discharging have brought grave damages to ecosystem and human health severely.Therefore,it is an urgent issue to deal with oily wastewater rapidly and efficiently,which attracts more and more attention in both academic and industrial worlds.Currently,the treatment methods of oily wastewater include gravity deposition,adsorption,flotation,in-situ burning dispersion,bioremediation,etc.However,these methods have some shortcomings in practical application,such as time-consuming process,high cost,secondary pollution,etc.Adsorbing materials with special wettability gradually become research hotspot due to environmental friendliness,efficient separation,simplicity of operator,low energy consumption etc.The polymer-based porous materials as adsorbing material exhibit many excellent oil/water separation performances such as good separation selectivity,high saturation adsorption capacity and fast adsorption rate by virtue of its low density,high porosity,large specific surface area,3D interconnected pore structure,hydrophobic and lipophilic,which stand out from various oil/water separator materials and exhibit extensive application prospect.In this work,CA monolith with novel hierarchical micro/nano-porous structure was fabricated successfully via a simple and green thermally impacted nonsolvent induced phase separation（TINIPS）.The microstructure and oil/water separation performances of porous CA monoliths were characterized by scanning electron microscope（SEM）,specific surface area and pore size analyzer,mercury porosimetry and contact angle measuring instrument,etc.The results show that:（1）the CA-20%monolith exhibits a novel hierarchical micro/nano-porous structure.The micrometer-scale microstructure is composed of coralloid skeleton with granule size between 4 to 20μm and micron-sized pores with diameter between 3 to 25μm.The coralloid skeleton presents a nanometer-scale nest-like structure consisting of interconnecting different-sized nanofibers.（2）The water and oil contact angles of porous CA monolith are respectively 147^o and 0^o,which show outstanding hydrophobicity and super-oleophilicity.Then the CA monolith can selectively separate oils and organic solvents from water,and the saturation adsorption capacities（Q_m）of the CA monolith for various oils and organic solvents are in the range of6.59-15.03 g g^-1.（3）The CA monolith still maintains excellent adsorption capacity after ten cycle experiments.（4）The CA monolith still maintains outstanding hydrophobicity and oil adsorption ability in different p H（1-14）,temperature（0-70 ^oC）and turbulent environments,which demonstrates superior environmental suitability.In order to improve the performance of CA porous monolith,the OMWNTs as filler was added into the process during preparation to adjust the microstructure of the porous monolith.The superhydrophobic porous CA/OMWNTs monolith was successfully prepared by TINIPS.And the structure and performances of the monolith were researched.The results are as follows:（1）Compared with porous CA monolith,the microstructure of porous CA/OMWNTs monolith has a vast change,which exhibit 3D interconnected network structure with nanofiber clusters.（2）The addition of OMWNTs（0.5-2 wt%）can improve the hydrophobicity and oil adsorption ability of monolith evidently.And the CA/OMWNTs monolith possesses best performances when the content of OMWNTs is 1.5 wt%.The CA/OMWNTs-1.5%monolith shows best hydrophobicity（water contact angle of 155^o）and adsorption capacity with the Q_m of 7.39-19.84 g g^-1.（3）The CA/OMWNTs monolith possesses superior separation selectivity and environmental suitability in different p H and temperature environments.（4）The CA/OMWNTs monolith can continuously and selectively separate oil/water mixture by a pump-assisted continuous adsorption device with the separation efficiency of 99.2%.