Synthesis And Characterization Of Cassava Dregs Derivatives And Their Application As Retention And Drainage Aids

In order to alleviate the resources waste and pollution caused by a lack of way forcassava dregs(CD) comprehensive utilization, this study aims to use CD to synthesis newpaper wet end chemical agents to meet the demends of modern paper industry and to realizehigh added value transformation. CD is rich in crude fibre and starch, once pretreated byappropritate ways, the starch and cellulose in it could be well used for chemical modificationand applied as retention&filter aids.With SEM analysis, CD was mainly comprised of cellulose and starch with different sizeand density, and the cellulose existed in long crude fibre bundle,fiber fragments and reticularfibre, especially the starch was packaged by reticular fibre. With fiber coarse grinding andball-mill micronization pretreatment, fiber size was close to or even less than starch and theCD can realize homogenization. With sulfuric acid hydrolysis of CD and ion chromatographanalysis, four kinds of monosaccharides were detected and respectively with content of81.21%glucose,3.66%xylose,1.91%galactose,1.41%arabinose. After homogenization, therelative crystallinity of CD decreased to36.25%. On the based of homogenization, ultrasonicfurther pretreatment could promote relative crystallinity decrease to30.18%and improveWRV increase to414.5%. After series of pretreatment described as above, the pretreatedcassava dregs (PCD) could be used for chemical modification with good reaction uniformityand nice accessibility for chemical reagent.Cationic and anionic etherificatin modified product of PCD were synthesizedrespectively by reacting with3-chloro-2-hydroxypropyltrimethylammonium chloride(CHTAC) and chloroacetic acid. The optimization parameters of cationic etherificationmodified was describe as follow: concentration of isopropyl alcohol or ethanol (V/V) was70⁸0%, PCD10%, m_NaOH: m_CHTAC=0.3:1, m_CHTAC: m_PCD=0.5⁰.7:1, alkalization assistedwith ultrasonic-10min/power81w, reaction temperature55℃, reaction time is3.5h;Anionic etherification modified optimal conditions:80%ethanol, PCD15%, N_NaOH: N_chloroactic acid)=2.2:1; N_{chloroactic acid}: N_PCD=0.91:1; reaction temperature55℃, reactiontime4.5h. Meanwhile, the CPCD and CMPCD were used as substrate for graftting copolymerization with monomer of acrylamide and acrylamide&[2-(methacryloyloxy)ethyl]trimethylammonium chloride respectively, and CPCD-g-PAM, CMPCD-g-AD weresynthesised accordingly. The influence factors of the grafting copolymerization reaction, suchas the initiator concentration, monomers ratio and concentration, pH value, preoxidation time,reaction temperature, reaction time, substitution degree of etherification product, substrateconcentration were discussed in detail, and summarized the effect of these factors onmolecular weight and charge density of product. Then SEM, FT-IR,¹³C-NMR and TGanalysis technical were used for study on chemical structure and thermal stability propertiescharacterization of PCD modified products, and all of them had proved the correspondingproduct were synthesised successfully.A headspace gas chromatographic(HS-GC) technique for the determination of residualEpichlorohydrin (ECH) and generated1,3-Dichloro-2-Propanol (DCP) in synthesis processof CHTAC was set up. By a weight-based sampling method, coupled with significant dilutionin15.8%sodium sulfate and0.1%silver nitrate mixed solution rapidly, the sample forHS-GC analysis was prepared. Based on the reaction stoichiometry, the conversion ofCHTAC during the synthesis process could be calculated from sampling weight and GC peakarea. The results showed that the method has a good measurement precision (RSD <2.5%)and accuracy (Recovery=101～104%) for the quantification of both ECH and DCP inthe process samples. It was simple and accurate and used for the efficient determination of theCHTAC conversion in the synthesis research. With assistance of this method, the optimalsynthesis condition of CHTAC in aqueous phase was obtained—TMAC:2mol/kg; N_ECH: N_TMAC=1.1:1; initial pH value7; catalyst:2%ZnO; the process of reaction:12¹4℃,3.5hfollowed heating up to40℃,40min and then40℃,6.5h. On this condition, the conversionand concentration of CHTAC was95%,25.79%respectively, DCP0.23%, ECH0.04%. By aprocess of purification such as rotating evaporation, chloroform extraction and water vaporextraction, the purified product had good application.Series derivatives of PCD had good retention and filter aid performance on recycleddeinking pulp.0.4%addition of CMPCD-g-AD could increase first pass retention (FPR) offine components from78.69%to93.3%, and0.1%CPCD could increase the FPR to89.53%.With pre-addition of0.6%PAC,0.14%CMPCD-g-AD could increase FPR from88.37%to 93.71%, and0.1%CPCD could increase FPR to92.56%. But more addition of CPCD wouldcause retention and filter property decrease. The fuction of PCD derivatives hardly change aspH value varied from6.5⁸.5and showed good adaptability of quaternary ammonium saltcationic groups to pH. Meanwhile, CMPCD-g-AD showed good shearing resistance ability.Handsheet experiment showed that CMPCD-g-AD dramatically increase the paperquantitative. With0.2%addition of CMPCD-g-AD, the quantitative (compared with0.5%PAC) increased by10.36%, the FPR increased from69.58%to90.09%, meanwhile thephysical strength had little increase; When amount to1.2%, the quantitative increase14.06%,FPR increased to97.41%, the tensile index, brust index and tear index of handsheetrespectively increased by17.47%,25.56%and6.83%. With0.5%addition of CPCD (highDS), Even the physical strength have large increased, the performance of retention reduced.