Research On Preparation And Performance Of Silanized Flexible Balsa Wood Oil/Water Separation Materials

Oil plays a very important role in social life,but the frequent occurrence of oil leaks during storage and transportation,as well as the reckless discharge of large amounts of oily wastewater from industrial production,have not only caused a waste of resources but also caused great damage to the ecological environment on which people rely for survival.Therefore,the development of oil-water separation materials has gradually become the focus of attention.Adsorption-type three-dimensional porous oil-water separation materials have been a hot research due to the advantages of high pore size,low density and ease to use.However,traditional three-dimensional porous oil-water separation materials have the disadvantages of complicated preparation process,expensive materials,non-biodegradable and non-recyclable.As a purely natural green biomass composite material,wood has the advantages of being widely sourced,inexpensive,renewable and biodegradable,etc.Due to its unique three-dimensional hierarchical porous network structure,wood has the structural basis to become an adsorption-type three-dimensional porous oil-water separation material.However,the hydrophilic/oleophilic properties of wood surface hinder its functionalization in the field of oil-water separation.This study uses balsa wood,a natural wood with relatively high porosity,as the raw material and uses a two-step modification method to functionally modify balsa wood,and finally successfully prepares silanized flexible balsa wood with superhydrophobic/superoleophilic properties.Specifically,the balsa wood was firstly subjected to alkali heat modification treatment,and the effects of alkali heat treatment time on the surface micromorphology,chemical composition,porous structure（porosity and specific surface area）,compression properties,fatigue resistance and thermal properties of the balsa wood were investigated to determine the optimal alkali heat treatment time for the preparation of flexible balsa wood;then the flexible balsa wood was silanized by a solution impregnation method using dodecyltrimethoxysilane（DTMS）.The effects of different impregnation times on the surface micromorphology,chemical composition and hydrophobic properties of the flexible balsa wood were investigated to determine the optimal impregnation time to prepare the silanized flexible balsa wood.The oil-water separation selectivity,adsorption kinetic behavior,oil absorption performance and recycling performance of silanized flexible balsa were also investigated and analyzed.The results of the study are as follows:1.After alkali heat treatment,the honeycomb porous structure of balsa wood in cross-section was damaged to some extent,and voids appeared between cell wall fibers,and the size of these voids gradually became larger with the increase of alkali heat treatment time.With the increase of alkali heat treatment time,the relative content of lignin and hemicellulose in balsa wood and gradually decreased,the relative content of cellulose gradually increased,the true porosity and specific surface area increased,and the average pore size became smaller.2.The compressive strength and compressive modulus of balsawood in both the R and T directions decreased gradually with increasing alkali heat treatment time,and were lower in the R direction.When the alkali heat treatment time reached 5 h,the balsa wood exhibited compression resilience in the R direction and showed good compression resilience as well as fatigue resistance in a 50-cycle compression test.After alkali heat treatment,the thermal stability of balsa was improved due to the removal of hemicellulose and other small molecules,and the thermal conductivity of balsa was reduced in both the L and R directions,with a significant reduction in the thermal conductivity in the R direction from 0.145 W/mk to 0.039W/mk.The optimum time for the modification of balsa by alkali heat treatment was 5 h.3.After DTMS modification,a polysiloxane coated film formed by self-polymerization after DTMS hydrolysis appeared on the surface of the flexible balsa.The modified flexible balsa surface exhibited hydrophobic properties,and the water contact angle increased from 0°to a maximum of 151.2°.When the impregnation time reached 2 h,the hydrophobic angle was not greatly enhanced by further extending the impregnation time,and 2 h can be considered as the optimal impregnation time for the silanization modification of flexible balsa.4.The silanized flexible balsa exhibits superhydrophobic/superoleophilic properties and can selectively adsorb oil or organic reagents from oil-water mixed solutions into the pore structure inside the material,thus achieving oil-water separation.The kinetic behavior of the adsorption of dimethyl silicone oil by silanized flexible balsa was more in line with the quasi first-order kinetic model,with a fitted correlation coefficient R² of 0.99626 and a faster adsorption rate constant K₁ of 0.14631.After the silanized flexible balsa absorbed oil or organic reagents,the oil or organic reagents could be discharged and recovered by extrusion to achieve secondary use.In the ten cycles of oil adsorption test,the saturation adsorption amount of silanized flexible balsa to various types of oil or organic reagents basically did not change much,and the water contact angle was still maintained at 143.2°after ten cycles of oil adsorption test.