| The development and utilization of lignocellulosic biomass is conducive to the transformation of world energy system core from fossil resource to renewable resource,alleviating the impact of environmental pollution and fossil energy depletion on human lives.In this paper,the environmental friendly and low-toxic deep eutectic solvent(DES)system was used to treat Phyllostachys pubescens(moso bamboo),a lignocellulosic biomass which were widely cultivated in our country.The change of components during the process and the relevant mechanism were also investigated.According to the chemical properties(dispersion and oxidation)of DES systems based on different components,this study prepared functionalized nanocellusic-composites as electrical material and adsorbent,respectively.Effects of reaction conditions on the properties of composites were systematically discussed,and the reaction mechanism between DES system and components of composite were also studied.The main findings of this study were summarized as follows:The DES system consisted of choline chloride and lactic acid with mole ratio of 1:9 had an excellent separation effect on moso bamboo components.The analysis results indicated that temperature is the predominant factor which influences the delignification efficiency a lot,followed by solid-to-liquid ratio and reaction time.However,long-term and high-temperature reaction could result in aggregation of lignin and remain in the product.After pretreatment,the crystallinity,content of carboxy groups(0.30±0.04mmol·g-1)and thermal stability of materials were increased,and the length of molecular chain for cellulose was remained.Furthermore,cellulose nanofibril(CNF)with excellent mechanical properties was successfully prepared from the pretreated-materials.The obtained CNF could be used to fabricate self-standing films(40 g·m-2)featuring a high tensile strength of 163-213 MPa and elastic modulus of9.0-11.0 GPa.The mixture of ethanol and water could effectively recover 80.68%of high purity(95.32%)ligin product(DESL)with a low weight-average molecular weight of 2.06×103 g·mol-1 from the liquid waste of pretreatment.Lactic acid-DES could effectively cut off the bond in lignin carbohydrate complex,and?-O-4 and C-C(?-?and?-5)linkages between lignin moleculars.It also showed a high selectivity of phenylcoumaran and tricin groups in moso bamboo.Impurities in recovered-DES were attributed to esterification and oligomerization of DES components,low-molecule-weight lignin and esterification of lignin with lactic acid.This study presents a one-step synthesis strategy based on urea-choline chloride(with a mole ratio of 1:1)DES as a media for preparation of CNF/reduced graphene oxide(rGO)hybrid film with high electrical conductivity.The electrical conductivity of composite film was increased with the increasing rGO dosage,and reached the maximum(square resistance of 11.85?·sq-1,electrical conductivity of 26.47S·cm-1)when the mass ratio of rGO and CNF was 2:1.The CNF plays a role of support and separation to reduce?-?conjugation thus to decrease agglomeration of rGO sheets.The cooperative action of graphene materials and CNF made the tensile strength of composite films(40 MPa)nearly twice of pure CNF film.As-obtained composite film(rGO:CNF=1:1)featured the maximum electrochemical properties of the areal capacitance was 98.90 m F·cm-2(the current density of 1 m A·cm-2)and the equivalent series resistance of 2.09?.The influence of DES concentration,temperature,time and reducing agent dosage on the electrical properties of rGO/CNF composite film were also evaluated.The results indicated that temperature was the most important factor influence the properties of rGO/CNF composite film(rGO:CNF=1:1).The electrical conductivity of composite film increased with the increasing temperature,and film prepared at100°C had a minimum square resistance of 12.89?·sq-1 which decreased 11.93 times of samples which prepared at 60°C.The electrochemical performance of the composite film was ascend in first and descend at last,and the maximum areal specific capacitance of 168.48 m F·cm-2(the current density of 1 m A·cm-2)was belong to the 60°C-sample.In addition,a little amount of nitrogen atoms were introduced in the composite film during the process,which was benefit to the electrochemical properties of composite films.Alkaline environment provided by urea-based DES system could result in the deprotonation of anionic groups on composite surface to enhance electrostatic repulsion and bond with choline cations,thus improving dispersion of fibers and graphene sheets in reaction system.Malonic acid-choline chloride(1:1)DES system with strong oxidation effect was used to functionalize CNF/graphene oxide composite aerogels for efficient adsorption of cationic dye——methylene blue(MB).The specific surface area of composite aerogel was 65.80 m2·g-1 and average pore size was 3.06 nm.According to the plot of pseudo second-order model,the aerogel exhibited a maximum theoretical adsorption capacity of 256.41 mg·g-1.The adsorption of MB dye on the surface of composite aerogel fitted to Langmuir isotherm,indicating the adsorption process was mainly chemical,single-layer and exothermic reaction.When p H was 11,the adsoption capacity of composite aerogel was 396.85 mg·g-1 and removal percentage reached 99.52%.Hydrogen bondings,?-?interaction and electrostatic attraction played a main role during the adsoption process. |
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