Hydrophobic Modification Of Melamine Sponge And Its Oil-Water Separation Performance

Offshore oil spills not only cause great harm to the ecological environment,but also endanger human life,health and property.Adsorption method is one of the most potential solutions to oil leakage,with high adsorption capacity,high efficiency and other advantages,the selection of adsorption materials is very important.In this paper,melamine sponges with low cost,wide source,elasticity and three-dimensional porous structure were selected as the base,which were chemically modified,and three kinds of super hydrophobic oil-philic sponges were prepared as adsorption materials,and their oil-water separation performance was tested and evaluated.Superhydrophobic melamine sponge TA-MS was prepared from melamine sponge（MS）by soaking the sponge in the mixed solution of octadecylamine（ODA）and tannic acid（TA）.The results showed that the spongy skeleton changed from smooth to rough,and the amine group of ODA reacted with the phenolic hydroxyl group of TA successfully on the surface of the sponge.The hydrophobic Angle of sponge can reach 152.6±1.38°,realizing the transformation from hydrophilic state to hydrophobic state.This superhydrophobicity enables the sponge to have oil-water selectivity,and the oil-water separation efficiency for a variety of oil-water mixing systems is greater than 98%.The sponge has high oil adsorption(100～140g.g^-1)and excellent recycling（25 sorption-press cycles）.It also maintains hydrophobicity in harsh chemical environments（high salt and acid-base solutions）.The nano Fe₃O₄ was dispersed on the surface of melamine sponge,and the adhesive coating was formed by the reaction of catecholol（CT）and diethylenetriamine（DETA）on the surface of sponge.The nano Fe₃O₄ was fixed on the sponge skeleton,and finally modified with dodecyl trimethoxysilane（DTMS）.Magnetic superhydrophobic melamine sponges CT-MS were prepared.The results showed that nano Fe₃O₄ constructed rough structures on the sponge skeleton,CT and DETA were able to cross-link to form coating on the sponge surface,and DTMS were successfully grafted on the coating.The sponge is superhydrophobic,with a hydrophobic Angle of 154±1.2°.Sponges have excellent oil adsorption performance and recyclable performance,can adsorb 50～60g.g^-1 oil and organic solvent,recycling efficiency can be maintained at more than 80%after 25 times of use.Sponges can also effectively separate a variety of oil-water mixtures,have excellent salt resistance and acid and alkaline resistance,and can be quickly recycled due to the presence of nano Fe₃O₄.In order to further improve the durability of melamine sponge,nano Fe₃O₄ and nano WS₂ were attached to the melamine sponge skeleton by polydopamine（PDA）,and the sponge was modified with n-octachymeric alcohol（OTD）.Finally,magnetic composite super hydrophobic melamine sponge PDA-MS was obtained,and the hydrophobic Angle could reach 156.8±1.18°.The results showed that nano Fe₃O₄ and nano WS₂ modified the spongy skeleton to have a rough structure.At the same time,PDA/OTD hydrophobic coating is formed on the surface of the sponge.The oil adsorption capacity of various oils and organic solvents can reach 40～100g.g^-1,the separation efficiency of oil and water is greater than 98%,and the separation of oil-in-water emulsion can also be very good.After25 cycles of use,the oil absorption is still greater than 40g.g^-1.The magnetic response of Fe₃O₄ nanoparticles enables sponges to be effectively recycled.WS₂ nanoparticles increase the durability of sponges and maintain good superhydrophobicity after soaking in a variety of complex environments,such as strong light,high temperature,high salt,strong acid,and strong alkali.