Preparation Of Lignin/cellulose Porous Material And Its Application In Oil-water Separation Field

At present,the oil pollution problem has become increasingly serious and how to efficiently separate oil-water mixtures has become an urgent problem in oil-water separation field.Cellulose-based porous materials have been widely studied in oil-water separation field due to their environmental friendliness and biodegradability.However,the existing cellulose-based porous materials have many disadvantages such as high raw material costs,poor mechanical properties,and low absorption capacity,making them difficult to produce and use on a large scale.Therefore,reducing the preparation cost of cellulose-based porous materials and improving their mechanical properties are the key to expanding their applications in oil-water separation field.In recent years,researchers combined cellulose and other biopolymers to successfully prepare a series of oil-water separation materials,but there are few reports on incorporating lignin into cellulose-based porous materials.Lignin has a wide range of sources and low cost.It has a rigid three-dimensional network structure and a large number of active groups in the molecule are also conducive to adsorption.It has huge application potential in oil-water separation field.Firstly,this work used industrial alkali lignin(without purification and modification)and hydroxyethyl cellulose as raw materials,epichlorohydrin as the cross-linking agent,using chemical cross-linking and freeze-drying to prepare low density(0.0204 g/cm³?0.0838 g/cm³),hydrophilic(water contact angle distribution in 32.68°?45.52°)lignin/cellulose porous material,and the effects of different epichlorohydrin content and different industrial alkali lignin content on the properties of porous materials were studied.It was shown that the content of epichlorohydrin and the content of industrial alkali lignin can significantly affect the network structure and water absorption performance of porous materials.When the epichlorohydrin content was 0.6 m L and the industrial alkali lignin content was 73%,the prepared porous material(LCB-0.4-aerogel)had good honeycomb network pore structure,hydrophilic properties and saturated water absorption.It also had a good oil-water separation effect for three oil-water mixtures and three O/W emulsions(separation efficiency is higher than 90%),and it can still maintain good separation performance after five cycles of use.In order to expand the application field of the porous material,a hydrophobic lignin/cellulose porous material was prepared by using n-dodecyl mercaptan through impregnation method,the effects of different dosages of n-dodecyl mercaptan on the hydrophobic properties and oil-water separation properties of porous materials were studied.It was shown that with the increase in the amount of n-dodecyl mercaptan,the water contact angle of the porous material increased from 86.42°to 111.18°,and the oil-water separation performance enhanced.When the dosage of n-dodecyl mercaptan was 0.4 m L,the prepared porous material(HLC-0.4-aerogel)has excellent performance:the saturated absorption capacity of different oil products was 9.76 g/g?37.46 g/g,the oil absorption rate was 12.20 mg/s.Furthermore,in order to enable the porous material to be quickly recovered from the oil-water mixture,the hydrophobic magnetic lignin/cellulose porous material was prepared by using n-dodecyl mercaptan and nano-Fe₃O₄ particles through impregnation method,the effects of different dipping time on the magnetic properties,hydrophobic properties and oil-water separation properties of porous materials were studied.It was shown that the increase of the dipping time can significantly increase the loading of nano-Fe₃O₄ particles in the porous material,making the magnetic properties of the porous material(saturation magnetization increased from 1.73 emu/g to 7.77 emu/g),hydrophobicity(water contact angle increased from92.15°to 131.98°)and the oil-water separation capability enhanced.When the dipping time was 30 min,the prepared porous material(HFLC-30-aerogel)has excellent performance:the saturated absorption capacity of different oil products was 8.71 g/g?28.07 g/g,the oil absorption rate was 2.03 mg/s.In addition,HLC-0.4-aerogel and HFLC-30-aerogel had good separation capabilities for oil-water mixtures in seawater environments and O/W emulsions,and it can still maintain good separation performance after three cycles of use.In this work,unpurified and modified industrial alkali lignin was successfully incorporated into cellulose-based materials to prepare lignin/cellulose porous materials,and the content of alkali lignin was as high as 73%.The introduction of alkali lignin can significantly improve the network structure and mechanical properties of cellulose-based materials,and greatly reduce the production cost of cellulose-based materials,providing a new idea for the preparation of cellulose-based materials used in oil-water separation field.