Oil Spill Adsorbent Prepared By Straw Modification

People have to enhance deepwater oilfield exploitation to keep the balance of oil supply and demand, while facing the dwindling onshore oil fields. Oil is more easily spilt into the ocean and other waters in the process of mining, transportation, and refining, thus causing a series of ecological and economic loss. It has important practical significance to exploit the oil absorption material which is suitable for floating oil on water surface. In this article we take the agricultural waste straw as raw material, and get different oil absorption material for floating oil on water surface through pretreatment, esterification and surface modification. The quantitative changes before and after pretreatment and composition modified were determined by chemical method. The channel structure, the chemical construction, the crystallinity and the morphology of the materials were characterized by BET, FT-IR, XRD and SEM. Details in the following aspects:We separate a series of straw particle size by mechanical crushing after cleaning, drying, standard sieve of raw straw. Measuring oil absorption capacity by weight method, the results showed that the oil absorption capacity is related to oil viscosity and density. It has good oil absorption effect for those smaller than 80 mesh particle straw, not only have high oil absorption capacity(oil absorption capacity of 100 mesh or smaller particles of straw at 15 ℃ can reach 7.16 g·g-1) but also can be stable floating on the calm water surface for a long time after oil absorption; 20-60 mesh large particle straw has lower oil absorption capacity(oil absorption capacity of 20-40 mesh straw at 25 ℃ for 0 # diesel is only 1.18 g·g-1) and poor floatability; Oil keeping ratio of the straw is also associated with the particle size of straw, the straw in the particle range 0f 60-100 mesh have high oil keeping ratio, and oil keeping ratio of the straw are positively correlated to surface tension of the oil; Under the condition of wind and waves, most of the raw material straw will sink into the bottom and lost oil absorption ability. So the straw can be used to deal with the floating oil on calm water surface, and the smaller the particle size it is, the higher oil absorption rate it has.After treated with 10% ammonia water in a certain mass ratio of the raw material whose particle size is less than 40 mesh at room temperature, we got active preprocessed straw. Using acetic anhydride as esterification agent, ice acetic acid as diluent, concentrated sulfuric acid as catalyst for esterification of the active preprocessed straw. According to the result analysis of 0# diesel oil absorption, floating oil on water surface absorption experiment and oil keeping ratio, optimum reaction conditions of esterification are as follows: reaction temperature 110℃, the mass ratio of the straw and ice acetic acid and acetic anhydride mixture is 1:15, reaction time 5 h, 4.5wt% H2SO4 as catalyst(based on straw quality). Under this condition the maximum absorption capacity to 0 # diesel oil reached 9.03 g·g-1, while the raw straw to 0 # diesel oil absorption capacity is only 1.90 g·g-1, the pretreated straw is 4.61 g·g-1.We characterize the straw before and after pretreatment, before and after esterification by BET, FT- IR, XRD, SEM, the results showed that the raw corn straw exhibited hierarchical pores while the structure of the pretreated corn straw was micropore and the esterified corn straw belonged to the mesoporous material; The characteristic peak attributed to acetyl group was observed in FT-IR spectrogram. XRD results revealed the amorphous state of the esterified corn straw sample which evidenced the occurrence of esterification reaction. Furthermore, the rough morphology of the esterified corn straw as shown in SEM analysis was helpful to improve the hydrophobicity of the obtained esterified material. The components of raw corn straw and pretreated corn straw were determined by modified Van-Soest method, suggesting that ammonia pretreatment might efficiently eliminate the small molecules such as accharides, proteins etc while preserved cellulose, hemicellulose and so on. Reference the determination method of degree of substitution(DS) of the esterified cellulose, quantify the equivalent ester group content of the straw before and after the pretreatment and after esterification.After treated with sodium hydroxide, ball milling process with water and the freeze drying process, we gained spongy straw material,this material presents a three-dimensional structure crosslinked micropore,mespore and macropore, and it is mircrofibrillated celluose. This kind of material can achieve rapid oil absorption, the oil absorption capacity to soybean oil can be 41.08 g·g-1, XRD analysis show that the ball milling can reduce the crystallinity of cellulose fiber and change it into mircrofibrillated celluose.Using straw as raw material, we got biodegradable oil absorption materials through mild pretreatment and modification, it not only achieve full use of the of agriculture and forestry waste,also it has good economic value and ecological significance, and it can partially replace the traditional chemical synthetic oil absorption materials.