Preparation And Properties Of Polymer-assisted Shaped Calotropis Gigantea Fiber Oil Absorbents

Petroleum is not only the most dependent energy substance for the development of the world economy,but also the raw material for the production of many chemical products,playing a very important role in many areas of our daily life.However,the large-scale exploitation and use of petroleum has also brought many serious problems.The frequency of oil spill is getting higher and higher,and the pollution situation is becoming more and more serious,causing not only waste of oil resources,but also serious pollution of the aquatic environment,even ecology damage.Nowadays,it has become one of the main pollution factors of water pollution,and accordingly,the control and treatment of oil pollution is very urgent and important.Compared with other treatments such as in-situ combustion,chemical dispersion,catalytic degradation and biodegradation,absorbing oil pollutants by oil-absorbents shows the advantages of high efficiency,low cost and no secondary pollution,and then is considered to be a treatment method with great potential.In this thesis,Calotropis gigantea fiber(CGF)was used as the raw material,and three polymers including polyether sulfone(PES),polyvinylidene fluoride(PVDF)and polylactic acid(PLA)with good mechanical property and hydrophobic property were applied to assist in shaping the CGF.Using a simple solvent replacement method,three oil-absorbents with typical sandwich structure were prepared,i.e.PES-s-CGF,PVDF-s-CGF,and PLA-s-CGF.Subsequently,an improved freezing-solvent replacement method was used for obtaining a novel oil absorbent,i.e.PLA-CGF foam(PCF).After that,relevant experiments were designed to analyze the oil-absorption capacity,structural characteristics,hydrophobic property,absorption selectivity and reusability of the oil absorbents.This thesis includes the following four parts:(1)A simple solvent replacement method was used for achieving an oil absorbent PES-s-CGF,in which PES was applied to assist in shaping the CGF.Inaddition to the characterization of morphology,oil-absorption capacity,hydrophobic property,absorption selectivity and reusability of PES-s-CGF were also measured and analyzed.The results revealed that PES-s-CGF showed a typical sandwich structure,and the mechanical property was greatly improved compared to natural CGF.PES-s-CGF had a good absorption capacity for different model oils,with the oil-absorption capacity of 4.26~9.24 g/g.PES-s-CGF was able to absorb the oils quickly,and could reach the absorption equilibrium within 30 s.PES-s-CGF had the water contact angle of 117.5° and then showed good hydrophobic property and high absorption selectivity for the model oils on the surface and bottom of water.PES-s-CGF was an oil absorbent with good reusability,maintaining a high re-absorption percentage after ten absorption-desorption cycles.(2)Similarly,a simple solvent replacement method was used to prepare a CGF-based oil-absorbent PVDF-s-CGF,in which PVDF was applied to assist in shaping the CGF.Subsequently,a series of experiments were conducted to explore the shaping effect,oil-absorption capacity,hydrophobic property,and reusability of PVDF-s-CGF.The results showed that when the weight ratio of PVDF and CGF was3:2,PVDF-s-CGF exhibited not only good mechanical property but also excellent oil-absorption capacity.The oil-absorption capacity was higher than PES-assisted shaped PES-s-CGF,with the maximum capacity of up to 18.81 g/g.Meanwhile,PVDF-s-CGF also exhibited good hydrophobic property and absorption selectivity,and then it could absorb the model oils in n-hexane/water and methylene chloride/water mixtures but without absorbing the water.After repeating oil-absorption experiment for 10 cycles,the re-absorption percentage was still as high as 84.11%,suggesting that PVDF-s-CGF had excellent reusability.(3)A biodegradable polymer PLA was used to assist in shaping the CGF,by which PLA-s-CGF was successfully prepared from a simple solvent replacement method.The structural characteristic,hydrophobic property,oil-absorption property and reusability were measured and discussed.The experimental results indicated that compared with PES-s-CGF and PVDF-s-CGF,the resulting PLA-s-CGF was a more efficient oil-absorbent,showing an oil-absorption capacity of up to 29.69 g/g.Meanwhile,PLA-s-CGF also showed excellent hydrophobic-lipophilic property,absorption selectivity and reusability.In addition,compared to PES and PVDF,PLA was a biodegradable polymer,and thus PLA-s-CGF was also a sustainable oil-absorbent.(4)By replacing the solvent to dissolve PLA and improving the shaping method,a biodegradable foam-like oil-absorbent PCF was successfully prepared when PLA was applied to assist in shaping the CGF.Prior to solvent replacement,a freezing process was used to improve the preparation method.The foam-like PCF had greater porosity and better mechanical property,and was able to be compressed to 30% of the initial volume without fracture.Compared to sandwich structured PES-s-CGF,PVDF-s-CGF and PLA-s-CGF,the foam-like PCF showed higher oil-absorption capacity,with the value of up to 48.29 g/g,even higher than natural CGF.In addition,PCF had the advantages of low density,high temperature resistance,good hydrophobic property and high absorption selectivity,and accordingly,PCF was suitable for the practical application to treat the oily wastewaters.After 10 cycles,the re-absorption percentage of PCF was still up to 88.06% for kerosene,an indication of its excellent reusability.