Qingxi Hou

Production of cationic xylan-METAC copolymer as a flocculant for textile industry.

Xylan is a part of hemicelluloses of woody materials and can be converted to value-added products such as flocculants for the textile industry. To assess the production of flocculants from hemicelluloses of woody materials, xylan was selected as a model and rendered cationic via copolymerization. In this study, the copolymerization reaction of xylan and [2-(methacryloyloxy) ethyl] trimethylammonium chloride (METAC) was optimized. The optimum parameters were 3mol/mol METAC/xylose, 3h reaction time, 80°C reaction temperature, pH 7 and 25g/L xylan concentration. The copolymer was characterized by a charge density analyzer, viscometer, gel permeation chromatography (GPC), light scattering instrument, Fourier transform infrared spectroscopy (FTIR) and an elemental analyzer. The application of the cationic xylan copolymer as a flocculant to decolorize the simulated reactive orange 16 azo-dye wastewater was evaluated. The results confirmed that, by having 160mg/L xylan-METAC concentration in the dye solution with the concentration of 100mg/L, 97.8% of dye could be removed.

Cationic xylan–METAC copolymer as a flocculant for clay suspensions

The work presented herein focused on the flocculation of kaolin and bentonite clay suspensions using cationic copolymerized xylan under controlled conditions. Cationic xylan-2-(methacryloyloxy)ethyl]trimethyl ammonium chloride (METAC) copolymers were produced under the conditions of pH 7, 3 h reaction time, 80 °C and 2 or 3 mol mol−1 METAC/xylan ratio. The charge densities of the produced cationic xylan copolymers, CMX1, and CMX2 were +1.8 and +2.4 meq. g−1 while their molecular weights were 88 986 and 102 545 g mol−1, respectively. The attachment of METAC to xylan was confirmed by elemental and gel permeation chromatography analyses. CMX2 was a more efficient flocculant than CMX1 as it adsorbed and removed more clay particles from the clay suspensions. CMX2 also changed the zeta potential and turbidity of the clay suspensions more remarkably than CMX1, which was attributed to its higher charge density and molecular weight. CMX2 was more efficient in flocculating bentonite than kaolin suspensions. The presence of CMX on the clay particles was confirmed by Fourier Transform Infrared Spectroscopy (FTIR) analysis. The size of kaolin particles increased from 3.2 to 9.8 and 11.7 μm, and that of bentonite particles from 5.8 to 13.8 and 15.5 μm by having 16 mg L−1 of CMX1 and CMX2 copolymers in the clay suspensions, respectively. The reversibility of the flocculation process was assessed with a photometric dispersion analyzer. Furthermore, unmodified xylan was ineffective in flocculating clay particles.

Stability and efficiency improvement of ASA in internal sizing of cellulosic paper by using cationically modified cellulose nanocrystals

Alkenyl succinic anhydride (ASA) is a reactive sizing agent that can impart good water repellence to paper by decreasing the wettability of the cellulose fibers. However, ASA can undergo hydrolysis, which is detrimental to the ASA sizing efficiency. In order to improve the ASA emulsion stability and ASA sizing efficiency, we used cationically modified cellulose nanocrystals (CNCs) to stabilize the cationic starch-emulsified ASA. Transmission electron microscope observation revealed that ASA droplets were well shielded by both the cationic CNCs and cationic starch, which may be responsible for the improved stabilization of ASA. The Hercules size test sizing degree, contact angle and particle size measurements demonstrated that cationic CNCs–ASA sized paper exhibited improved results in comparison with the control (without cationic CNCs under otherwise the same conditions). Furthermore, the resulting cationic CNCs–ASA system can improve the tensile index and burst index of the sized paper.

Hemicelluloses prior to aspen chemithermomechanical pulping: Pre-extraction, separation, and characterization

A portion of hemicelluloses and acetic acid can be pre-extracted with dilute sulfuric acid prior to the aspen chemithermomechanical pulp process. The streams collected from the second press-impregnation stage after acid pre-extraction contain a significant amount of acid pre-extracted hemicelluloses. Most of the total sugars obtained from the pressate were xylan, in which xylan was further hydrolyzed to sugar monomers under the acid pre-extraction condition. To fully understand the characteristics of hemicelluloses yielded prior to pulping, the pre-extracted hemicelluloses were separated and characterized by FT-IR, (1)H NMR, and thermogravimetric analysis in this study. Most of the FT-IR bonds from the hemicelluloses agreed well with the other two spectra of birch xylan and CA0050 xylan, except a new absorption at 1734 cm(-1) contributed to acetyl groups. The hemicelluloses obtained from acid pre-extraction began to decompose significantly at about 225 °C, slightly lower in comparison with organosolv and alkaline hemicelluloses reported in the literature.

Structural Properties of the Purified Lignins of Cornstalk in the Cooking Process with a Solid Alkali

To avoid undesired polymerization and maximize the selectivity of alkyl levulinate from the acid-catalyzed conversion of biomass-derived furfuryl alcohol, the effects of catalyst and reaction parameters on the formations of humin and alkyl levulinate were investigated. The results show that Amberlyst 15, of moderate acidic strength, was more favorable for the selective conversion of furfuryl alcohol to alkyl levulinate, and heteropolyacids of strong acidic strength tended to promote furfuryl alcohol polymerization. Compared with water as a reaction medium, alcohol significantly lowered humin formation and enhanced the yield of the resulting products. The formations of humin and alkyl levulinate were both favored at high catalyst loadings and reaction temperatures. An augmentation in initial furfuryl alcohol concentration caused an increase in humin formation and a decrease in alkyl levulinate yield. A high alkyl levulinate yield of up to 94% (100% furfuryl alcohol conversion) was achieved at 110 °C for 4 h with 5 g/L Amberlyst 15 catalyst and an initial furfuryl alcohol concentration of 0.1 mol/L. At this point, about 5% furfuryl alcohol was polymerized to form the humin, and its polymerization occurred mainly during the initial reaction stage.

Effects of combined pretreatment of dilute acid pre-extraction and chemical-assisted mechanical refining on enzymatic hydrolysis of lignocellulosic biomass

An efficient enzymatic hydrolysis of lignocellulosic biomass into fermentable sugars depends greatly on the pretreatment of raw materials. In this study, a combination of dilute acid pre-extraction and chemical-assisted mechanical refining was used to pretreat wood lignocellulosic biomass for subsequent enzymatic hydrolysis. This work analyzed the surface lignin concentration, specific surface area, crystallinity, fines content, fiber length, and kink index of the resultant pulp substrates and their effects on the enzymatic hydrolysis. The results showed that the combined pretreatment significantly enhanced the enzymatic hydrolysis efficiency, and the maximum glucose conversion yield and glucose concentration were 93.32% and 21.41 g L−1, respectively. It is found that the surface lignin concentration, specific surface area, and fines content significantly affected the enzymatic hydrolysis.

Improving the efficiency of enzymatic hydrolysis of Eucalyptus residues with a modified aqueous ammonia soaking method

Abstract Eucalyptus residues from pulp mill were pretreated with aqueous ammonia soaking (AAS) method to improve the efficiency of enzymatic hydrolysis. The optimized condition of AAS was obtained by response surface methodology. Meanwhile, hydrogen peroxide was introduced into the AAS system to modify the AAS pretreatment (AASP). The results showed that a fermentable sugar yield of 64.96 % was obtained when the eucalypt fibers were pretreated at the optimal conditions, with 80 % of ammonia (w/w) for 11 h and keeping the temperature at 90 °C. In further research it was found that the addition of H2O2 to the AAS could improve the pretreatment efficiency. The delignification rate and enzymatic digestibility were increased to 64.49 % and 73.85 %, respectively, with 5 % of hydrogen peroxide being used. FTIR analysis indicated that most syringyl and guaiacyl lignin and a trace amount of xylan were degraded and dissolved during the AAS and AASP pretreatments. The CrI of the raw material was increased after AAS and AASP pretreatments, which was attributed to the removal of amorphous portion. SEM images showed that microfibers were separated and explored from the initial fiber structure after AAS pretreatment, and the AASP method could improve the destructiveness of the fiber surface.

Cationic High Molecular Weight Lignin Polymer: A Flocculant for the Removal of Anionic Azo-Dyes from Simulated Wastewater

The presence of dyes in wastewater effluents made from the textile industry is a major environmental problem due to their complex structure and poor biodegradability. In this study, a cationic lignin polymer was synthesized via the free radical polymerization of lignin with [2-(methacryloyloxy) ethyl] trimethyl ammonium chloride (METAC) and used to remove anionic azo-dyes (reactive black 5, RB5, and reactive orange 16, RO16) from simulated wastewater. The effects of pH, salt, and concentration of dyes, as well as the charge density and molecular weight of lignin-METAC polymer on dye removal were examined. Results demonstrated that lignin-METAC was an effective flocculant for the removal of dye via charge neutralization and bridging mechanisms. The dye removal efficiency of lignin-METAC polymer was independent of pH. The dosage of the lignin polymer required for reaching the maximum removal had a linear relationship with the dye concentration. The presence of inorganic salts including NaCl, NaNO3, and Na2SO4 had a marginal effect on the dye removal. Under the optimized conditions, greater than 98% of RB5 and 94% of RO16 were removed at lignin-METAC concentrations of 120 mg/L and 105 mg/L in the dye solutions, respectively.