Study On The Preparation Of Polymer Adsorbents And Pickering Emulsion By OSA Hydrophobic Modified Sweet Potato Residue Cellulose

Cellulose is the most abundant resource in nature,and has a wide range of sources.In recent years,high value-added use of cellulose has been the focus of research in the fields of macromolecules and foods.Since cellulose contains a large amount of active hydroxyl groups,it has a certain degree of emulsification and adsorptivity,but the effect is not good,it can use its characteristics,access to modified groups,and organic acid or inorganic acid esterification reaction,giving cellulose stronger properties.This study to the raw material of sweet potato residue cellulose,through the homogeneous modification in the DMAc/LiCl system,has a long-chain alkenyl group attached to the cellulose chain to make it amphiphilic,and the presence of the carboxyl group gives the cellulose modification product pair the strong binding capacity of heavy metal ions.Then the degree of substitution as the response value,The CCD test design was used to optimize the synthesis of octenyl succinic anhydride cellulose ester,and the potato was compared and analyzed.The structural characteristics of saccharose cellulose and octenylsuccinic anhydride cellulose esters with different degrees of substitution were studied to investigate the influence of three different substitution degrees on the properties of pickering emulsions and the adsorption mechanism of heavy metals.The main findings are as follows:?1?Utilizing four important factors:m_DMAP/m_cellulose,temperature,time,n_OSA/n_cellulose for single factor test,using CCD test design combined with response surface analysis to establish a quadratic regression model,and optimizing the model The optimum combination of the four main factors was determined to obtain the optimum conditions for the preparation of octenyl succinic anhydride cellulose ester:m_DMAP/m_cellulose was 0.48,temperature was 78.64°C,time was 186.52 min,n_OSA/n_celluloseellulose was 1.93.The verification test results showed that under the optimal modified process conditions,the predicted replacement value was 0.3650±0.0350 and the prediction accuracy was as high as 94.81%,which proved the accuracy of the regression model.?2?The properties of C,RC and OSA-C were studied by means of FTIR,XRD,SEM,DSC,TG-DTG,etc.The results showed that:the FTIR shows that new characteristic absorption peaks appeared at 2926,2850,1724,and 1572 cm^-1 in OSA-C,and these characteristic peaks also proved that they passed through octenyl succinic anhydride.Esterified cellulose had been successfully introduced into-CH₂,C=O,RCOO-and other groups after DMAc/LiCl derivation;C was a cellulose I type crystal,RC was a mixture of cellulose I and II structure crystals,and the crystallinity had decreased.It showed that after the DMAc/LiCl solvent dissolves at high temperature,the crystallinity of cellulose decreased significantly,and the amorphous area increased,making the esterification reaction easier.SEM observation showed that the homogeneous derivatization reaction increased.The amorphous state of cellulose,the change of OSA-C structure,and the appearance of a continuous layered hollow state on the surface of the particles,the exposure of more small molecules of cellulose facilitates the esterification reaction,and was also favorable for the adsorption and emulsification.DSC focused on 200-400°C.It was found that the results were consistent with the trends of maximum weightlessness temperature and weight loss rate of TG and DTG.It was concluded that the stability of OSA-C is between C and RC;After modification,the thermal resistance of the modified product was significantly increased,probably due to the change of the crystal structure and the introduction of long chain groups.?3?The properties of three different octenyl succinic anhydride cellulose esters were studied by infrared spectroscopy,FTIR,XRD,SEM,DSC,TG-DTG,ect.The succinic anhydride-esterified cellulose has been successfully introduced with-CH₂,C=O,RCOO-and other groups,and the strength of the peak type had a positive correlation with the degree of substitution;In the homogeneous modification,cellulose type II structure was contained in H-OSA-C,the crystal form was completely changed,and the crystallographic orientation was the conversion of amorphous and amorphous species reaches a saturated state.The state of H-OSA-C particles was loose,and there were a large number of small particles between the particles,and the layers appeared hollow on the surface of the particles.As the degree of substitution increased,the state of voids was obvious.More crystalline cellulose was converted to amorphous or amorphous cellulose;the higher the degree of substitution of octenyl succinic anhydride cellulose ester,the lower the degree of polymerization of cellulose,the lower the degree of crystallinity,the change in crystal form,More-OH exposure leaded to an early exotherm,The degree of substitution had a great influence on the degree of crystallinity,and it was found that the stability in H-OSA-C was the lowest;generally,the larger the degree of substitution,the lower the thermal stability.After reaction,the conformation of the cellulose molecule chain was irreversibly caused.The change caused rearrangement within the cellulose molecule,and the steric hindrance effect of the substituent group will also affect the thermal stability?4?Emulsion stability analysis of octenylsuccinic anhydride cellulose esters with different degrees of substitution at high,medium and low temperatures using contact angle measuring instruments,digital cameras,particle size analyzers,electron microscopes,and rheometers,contact angles.The measurement results showed that the?of H-OSA-C was closest to 90°,indicating that H-OSA-C had higher amphipathicity;the emulsion observed that at 15 days,H-OSA-C emulsion was stable and L-OSA-C is more stratified than M-OSA-C.The higher the degree of substitution,the more substitution groups in the molecule maked the emulsion have a stronger ability to reduce the interfacial tension,and can be densely arranged at the O/W interface to form a higher interface.The viscoelastic interfacial film can stabilize the emulsion formation.The emulsification index measurement found that when 1.75%was stored,H-OSA-C remained stable at 7,15 days,while M/L-OSA-C were at 15 days.Compared with 1,7days,,the emulsification index decreased significantly,indicating the formation of a three-dimensional network structure;particle size analysis found that the Pickering emulsion can be prepared with a low concentration of OSA-C and have a larger particle size and larger particle gaps at the oil-water interface.Collisional coalescence occured,increasing the droplet area and stabilizing the larger particle size of the emulsion,while H-OSA-C can be Long time stable emulsion;Emulsion microscope observation,when the concentration of 1.75%,H-OSA-C particle size was significantly smaller than M/L-OSA-C,storage 1,7,15d;In terms of apparent viscosity,the H-OSA-C viscous coefficient was significantly higher than that of M/L-OSA-C;The storage modulus,loss modulus,and tan?were that,the three-dimensional network structure and the interfacial film together play a decisive role in the stability of the emulsion.When the concentration reaches 1.75%.Combining the apparent viscosity,the emulsion observation chart and the rheological data,it was found that the H-OSA-C emulsion had the best stability and can be form a stable pickering emulsion.?5?The adsorption behavior of cellulose esters of octenyl succinic anhydride with three different substitution degrees for Pb?II?and Cu?II?was studied.The results showed that when the pH was at 7 or 5,different degrees of substitution were observed.Adsorption capacity of Pb?II?and Cu?II?adsorbed by octenyl succinic anhydride cellulose ester can reach the maximum;adsorption of Pb?II?and Cu?II?to cellulose esters with different substitution degree.The fitting was carried out to analyze the relationship between adsorption time and Q_t over time.The results were all applicable to the pseudo-second-order kinetic equation.The adsorption isotherm indicated that Langmuir was more suitable for the adsorption of Pb?II?and Cu?II?than the Freudlich adsorption isotherm model.The impact of the process,the correlation coefficient R² was around 0.99.The theoretical maximum adsorption capacities of L-OSA-C,M-OSA-C and H-OSA-C were 77.041,125.787,140.647 mg/g and 56.433,67.295,and 75.415mg/g,respectively.