Preparation And Performance Of Oil Sorbents From Typical Aquatic Plants

Water pollution caused by oil spills has become one of the most serious disasters due to its severe threat to the marine ecosystem and human health.Thus,it is vital to choose appropriate strategies for collecting oil completely from water in time.Oil sorbent is generally considered as an effective and promising method used for oil recovery and cleaning,thus the research of efficient oil sorbent has vital significance.An ideal oil sorbent for practical applications should possess high oil sorption capacity,high oil-water selectivity,good flotability,superior recyclability,good biodegradation as well as low cost.Eutrophicated aquatic plants are a kind of waste with fast growth,high biomass and high processing cost.In this work,four typical eutrophic aquatic plants were used to prepare diffenrent types of oil sobents for realizing the effective utilization of waste aquatic plants.Recycling of four eutrophicated aquatic plants including Eichhornia crassipes,Herba Lysimachiae,Alternanthera philoxeroides and Potamogeton crispus as spilled oil sorbents were firstly researched.Then above four eutrophicated aquatic plants were modified with acetic anhydride.Three kinds of Cellulose-based aerogels?CBAs?were prepared form Eichhornia crassipes based on the NaOH/PEG solution,PAE and PVA as crosslinking agent,respectively.Moreover,oil sorption performance and mechanism of several oil sorbents were preliminary investigated.Main conclusions were as follows:?1?The surface wettability and oil sorption tests show that the leaf and stalk of Eichhornia crassipes,Herba Lysimachiae and Alternanthera philoxeroides?ES and EL,HS and HL,AS and AL?and the entirety of Potamogeton crispus?PE?had a very low water absorption and high oil absorption rate in oil and water system,which primarily is related to the hydrophobic surface and high capillarity of the plant materials.The saturated sorption capacities of ES,EL,HS,HL,AS,AL and PE for crude oil,diesel oil,soybean oil,lubricating oil and silicone oil were between2.62-18.86 g g^-1.Especially,the stalk of Eichhornia crassipes?ES?exhibited the highest sorption capacity and the corresponding sorption capacities for above oils were 9.29,11.90,13.71,17.46 and 18.86 g g^-1.The results also showed that the oil sorption capacity was significantly affected by particle size,but was hardly influenced by temperature.Furthermore,the four aquatic plants had good reusability and could be recycled more than 10 cycles,and the loss of sorption capacity of ES,EL,HS,HL,AS,AL and PE for diesel oil was only between 7⁴3%.?2?The leaf and stalk of Eichhornia crassipes,Herba Lysimachiae and Alternanthera philoxeroides and the entirety of Potamogeton crispus were modified using acetic anhydride?AES,AEL,AHS,AHL,AAS,AAL and APE?.The C=O,C-H and-CO-groups were observed by FT-IR.The greatly enhanced hydrophobicity of acetylated sorbents was also verified by surface wettability tests,and the corresponding water contact-angles?CA?were more than 100°.The oil sorption capacity of AES,AEL,AHS,AHL,AAS,AAL and APE for crude oil,diesel oil and lubricating was 1.5-3 times of raw material.Among them,the oil sorption capacity of AES was the highest,the corresponding oil sorption capacities were 16.23,18.33,and25.16 g g^-1,respectively.?3?Cellulose-based aerogels?CBAs?were prepared via freezing,freeze-drying and subsequent hydrophobic modificated process based on Eichhornia crassipes and NaOH/PEG solution.The optimal CBAs was prepared with 1 wt%cellulose,3 wt%NaOH and 10 wt%PEG.The CBA demonstrated good sorption capacity for five experimental oils and five solvents(12.95-29.21 g g^-1)which was attributed to the low density(0.0375 g cm^-3)and the high porosity?93.33%?.?4?Cellulose-based aerogels?CBAs?were prepared based on Eichhornia crassipes as a raw material and a paper wet-strengthening agent?PAE?as a cross-linker via freezing,freeze-drying and subsequent hydrophobic modificated process.The effect of cellulose content and PAE concentration on the recyclability and oil absorbency of CBA was also studied,and the superior CBA with both superior oil absorbency and good recyclability was obtained at 0.35 wt%cellulose and 40 wt%PAE(i.e.,_0.35CBA40).The prepared _0.35CBA40 had excellent properties,including low density(0.0055 g cm^-3),high porosity?99.6%?,excellent oil/solvent sorption capacities(58.06-101.14 g g^-1 for five experimental oils and five solvents)and superhydrophobicity?water contact angle as high as 154.8°?.Furthermore,the absorbed oil could be quickly recovered by squeezing,and the oil sorption capacity of_0.35CBA40 was still as high as 58.61 g g^-1 after 16 cycles.?5?Using Eichhornia crassipes as cellulose source and polyvinyl alcohol directly as cross-linker,the superhydrophobic?water contact angle as high as 154.8°?cellulose-based aerogels?CBAs?with highly porous?99.56%?and low-density(0.0065 g cm^-1)were prepared via a combination of freezing,freeze-drying and subsequent hydrophobic modification.The optimal PVA content for preparing CBA was studied,and the corresponding prepared CBA was low density(0.0065 g cm^-1),high porosity?99.56%?,superhydrophobic?water contact angle as high as 156.7°?and excellent sorption capacities(58.06-101.14 g g^-1 for five experimental oils and five solvents).Moreover,the absorbed oil of CBA was still as high as 60.91 g g^-1 after 16cycles.?6?Based on cost estimating obtained,the four aquatic plants could be used as low-cost sorbents for spilled oil removal.The excellent oil sorption performance of CBA prepared with PAE or PVA crosslinking makes CBA a very promising material for oil spillage cleaning.