The Study On The Preparation Of Efficient Oil Spill Adsorbent Based On Wheat Straw

With increasing energy consumption,petroleum products and their derivatives play a crucial role in the production of human.However,Refining,extraction,transfer,and storage of crude oil,especially with ocean transportation,can cause leakages and other issues,which seriously affect ocean ecology and natural environment.Amongst lager numbers of oil-spill treatments,adsorption method is one of the most economical and effective treatment methods.Firstly,the classification,advantages,and disadvantages of oil absorbing materials are simply discussed.Wheat straw（RWS）was selected as raw material to prepare the oil-spill adsorbent by acetyl chemical modification.The prepared oil-spill adsorbent,the acetylation wheat straw（AWS）,have many advantages of low cost,high-adsorption efficiency,high buoyancy,no toxicity and biodegradability.Chemical composition and morphologic structure of RWS before and after acetylation were investigated and compared using Fourier transform infrared（FT-IR）spectroscopy,X-ray diffraction（XRD）and contact angle analysis.Oil-absorption capacity,oil-retention ability,recyclability,selectivity,adsorption kinetics,and buoyancy of acetylated wheat straw were discussed.1.RWS was pretreated with 1.3% NaClO2 and 10% NaOH,respectively and the components of RWS before and after pretreatment were analyzed.The main component of RWS and pretreated wheat straw（PWS）as follows: RWS: cellulose 39.73%,hemicellulose 35.01%,lignin 13.46%;PWS: cellulose 81.35%,hemicellulose 7.84%,lignin 4.19%.In comparison with RWS,pretreatment is very effective in the removal of hemicellulose and lignin.The characterizations of RWS and PWS were performed by FT-IR,and XRD.FT-IR spectroscopy showed that cellulose fiber was extracted from RWS by pretreatment.XRD analysis demonstrated that the crystallinity of PWS is larger than RWS.2.In this study,natural fiber,wheat straw,were selected as the source of cellulose,N-bromosuccinimide（NBS）as the catalyst,acetic anhydride as the acetylating reagent,and dimethylacetamide（DMAC）as the reaction solvent to prepare the oil-spill adsorbent.The following optimum conditions were confirmed by single factor experiments and orthogonal experiments: reaction temperature 100 °C,reaction time 1.5 h,NBS concentration 55 mM,acetic anhydride content 5 m L.The oil absorbencies of AWS for diesel fuel is 24.37 g/g,which is higher than that of PWS（15.56 g/g）.The adsorption curve,oil retention curve,repeated utilization ratio and selectivity of AWS showed that AWS has many advantages of high adsorption efficiency,good effect of oil retention,good performance of recycling.Newly emerging absorption peaks in FT-IR spectra of AWS indicated that hydrophobic groups had been grafted to the surface of pretreatment straw.XRD analysis showed that the crystallinity of AWS is smaller than AWS.Wheat straw modified by acetylation could achieve a water contact angle of about 129.5° and an oil contact angle of 0°,demonstrating hydrophobic and lipophilic properties in the usual sense.3.Acetylation of cellulose extracted from RWS,using acetic anhydride as acetylating reagent without additional catalysts in dimethyl sulfoxide/ Nmethylimidazole（DMSO/NMI）at room temperature to prepare the cellulosic adsorbent.The optimum conditions were confirmed by single factor experiments: reaction time 10 min,acetic anhydride content 5 mL.Compared with the traditional method of acetylation,the method of acetylation in this manuscript has many superiorities of simple preparation process,low temperature,short time,and no catalysts.The adsorption curves of RWS,PWS and AWS* were in accord with the pseudo-two-stage adsorption kinetics curves through the analysis of the adsorption curves of RWS,PWS and AWS*.Moreover,chemical composition and morphologic structure of AWS* was investigated and compared using FT-IR spectroscopy,XRD,contact angle analysis,and solid-state ¹³C NMR.