The Study On Preparation And Properties Of Corn Straw Pith Laccase-modified Oil Spill Adsorbent

Oil spills could cause water environment pollution and seriously affect biological survival and human economic activities.Therefore,the preparation of green and efficient oil-absorbing materials has important practical significance.Biomass waste had the advantages of biodegradability and economy,and had good application prospects,but its adsorption capacity and selective adsorption capacity were the main obstacles to its development.Based on this,this thesis selects corn straw pith with large quantity and low cost as raw material,and proposes that the laccase-TEMPO system was grafted with octadecylamine to prepare selective oil-absorbing material;-at the same time,scanning electron microscope(SEM),contact angle(CA),fourier infrared spectroscopy(FTIR)and other means were used to characterize the oil absorbing agent;combined with the adsorption kinetics,isotherms,and thermodynamics of the material,the mechanism of the modified corn straw pith oil absorption was preliminarily discussed.The main findings are as follows:1.The content of cellulose,hemicellulose,and lignin in natural corn straw pith were 40.51%,22.09%,and 3.72%respectively.Its contact angles with engine oil and deionized water were 52.8° and 58.8°,respectively.The saturated adsorption capacity of natural straw fiber to soybean oil and diesel was only 16.36 g/g and 13.81 g/g.Natural straw pith had a high oil absorption rate,and the adsorption process conforms to the Lagergren pseudo-second-order kinetic equation.2.Using corn straw pith as the raw material,a high roughness,low surface energy oil absorbing agent(LCSP)with high roughness and low surface energy(LCSP)was successfully prepared by the method of laccase-TEMPO oxidation and grafting of stearylamine,and the optimal preparation conditions were discussed.Its oil adsorption capacity was 40.82 g/g,which was much higher than the raw material(13.24 g/g)and 3.08 times that of the raw material.The adsorption capacity of soybean oil and diesel was also greatly improved.The water adsorption capacity of the raw material was 13.76 g/g,and the water adsorption capacity after operation was reduced to 3.83 g/g.After 4 cycles of use,the maximum oil absorption was still maintained at 35.05 g/g and the adsorption capacity was still 85.9%.Considering factors such as raw material and production costs,oil absorption and hydrophobic effect,environmental friendliness,etc.,laccase-TEMPO-octadecylamine modified corn straw pith was a promising environmentally friendly oil-absorbing material.3.SEM results show that the modification increases the surface roughness.The BET results show that the total pore volume of the modified material has increased by 541%,and the average pore diameter was 7.5 times that of the raw material,providing oil storage space,XRD confirmed that the modification reduced the crystallinity of the material and improved oil accessibility.The results of FTIR,XPS,etc.showed that hydroxyl groups decreased,aldehyde groups,and other oxygen-containing functional groups increased,and carbon-nitrogen double bonds appeared.It was confirmed that the primary hydroxyl groups on cellulose molecules could be selectively oxidized to aldehyde groups by using the laccase-TEMPO catalytic system.The amine group in the hydrophobic octadecylamine molecule undergoes a graft reaction.The contact angle test showed that the oil droplets were instantly absorbed by the modified material,the water contact angle increased to 142.5°,and the hydrophobicity was enhanced.4.For two modified oil absorbents prepared by laccase-TEMPO grafted stearylamine(LCSP)and laccase-guaiacol grafted stearyl ester(GCSP),the oil removal rate under neutral conditions can reach 98%.Chloride ions had little effect on both,which proved that the oil absorbing agent also had good applicability in seawater.When the thickness of the oil slick on the water surface was small,the adsorption capacity of LCSP and GCSP was similar,and the GCSP effect was better when the thickness was large.The adsorption process of LCSP and GCSP on suspended diesel was in accordance with the Lagergren pseudo-second-order kinetic model,which was suitable for the Freundlich isotherm,proving that the adsorption of diesel was a heterogeneous multi-layer adsorption dominated by chemical adsorption.Temkin and thermodynamic analysis could find that the adsorption process had exothermic properties.Figure 29 table 13 reference 93...