Lignin Impurities Research Articles

Discard the dross and select the essence: Purified orange peel with coupled alkali-acid hydrolysis as potential Cd(II)-capturing adsorbent

Turning agricultural wastes into green adsorbents is a compatible and cost-effective strategy for solid waste disposal and environmental pollution control. Herein, the discarded orange peel (OP) sample was purified via coupled alkali-acid hydrolysis and the obtained adsorbents were applied for eliminating toxic cadmium (Cd(II)) from the liquid phase. Based on the single factor experiments, the optimal Cd(II)-capturing adsorbent (i.e., OP-OH-H-25) was generated under the purification condition of soaking raw OP in 2.0 M NaOH solution at 25 °C followed by an acid hydrolysis treatment with 2.5 M HCl solution at 25 °C. Spectral analyses reflected the efficient elution of hemicellulose/pectin and lignin impurities, the transformation of cellulose type I to cellulose type II, and the exposure of sulfhydryl functional groups. The kinetics removal process of Cd(II) by OP-OH-H-25 reached equilibrium after 0.5 h with a removal efficiency of ∼88%. The maximum Cd(II) sorption capacity of OP-OH-H-25 (i.e., 124.90 mg/g) was higher than a series of previously reported adsorbents. The sorption behavior of Cd(II) onto the prepared OP-OH-H-25 material was mostly interfered with by the coexisting Mg2+, Ca2+, and heavy metals. The desorption data and spectroscopic analysis jointly pointed to the inner-sphere binding of Cd(II) with OP-OH-H-25 functional groups. Overall, the extracted OP-OH-H-25 sample could act as a promising decontaminant for the remediation of Cd(II)-polluted water environment.

Session IX:

Turning agricultural wastes into green adsorbents is a compatible and cost-effective strategy for solid waste disposal and environmental pollution control. Herein, the discarded orange peel (OP) sample was purified via coupled alkali-acid hydrolysis and the obtained adsorbents were applied for eliminating toxic cadmium (Cd(II)) from the liquid phase. Based on the single factor experiments, the optimal Cd(II)-capturing adsorbent (i.e., OP-OH-H-25) was generated under the purification condition of soaking raw OP in 2.0 M NaOH solution at 25 °C followed by an acid hydrolysis treatment with 2.5 M HCl solution at 25 °C. Spectral analyses reflected the efficient elution of hemicellulose/pectin and lignin impurities, the transformation of cellulose type I to cellulose type II, and the exposure of sulfhydryl functional groups. The kinetics removal process of Cd(II) by OP-OH-H-25 reached equilibrium after 0.5 h with a removal efficiency of ∼88%. The maximum Cd(II) sorption capacity of OP-OH-H-25 (i.e., 124.90 mg/g) was higher than a series of previously reported adsorbents. The sorption behavior of Cd(II) onto the prepared OP-OH-H-25 material was mostly interfered with by the coexisting Mg2+, Ca2+, and heavy metals. The desorption data and spectroscopic analysis jointly pointed to the inner-sphere binding of Cd(II) with OP-OH-H-25 functional groups. Overall, the extracted OP-OH-H-25 sample could act as a promising decontaminant for the remediation of Cd(II)-polluted water environment.

Eco-friendly bleaching of sugarcane bagasse with crude xylanase and pectinase enzymes to reduce the bleaching effluent toxicity.

Bio-bleaching effect on bagasse pulp using xylano-pectinolytic enzymes produced by a bacterial species was studied in order to evaluate the potential of these enzymes in paper industry. In this study, action of enzymes was maximum with xylanase/pectinase dose 7/1.75 IU/g, pulp consistency 1:12.5 g/L, pH 8.5, temperature 50° C and 180 min of treatment time. Under the optimized bio-bleaching conditions, removal of reducing sugars (6.15±0.05 mg/L), brightness (16.08%), whiteness (25.54%) and release of chromophores (hydrophobic and phenolic compounds and lignin impurities) were maximum, along with decrease in kappa number (26.28%), and yellowness (27.88%) values were obtained. Improvement in the various physical properties like breaking length (10.28%), burst index (29.55%), tear index (5.02%), double fold (14.89%), Gurley porosity (15%) and viscosity (8.6%), along with the reduction of chlorine dioxide dose by 27%, was also observed. There is also reduction in COD and BOD values of bio-bleached effluents by 27.62% and 20.52%, respectively. This is the first report on bio-bleaching of bagasse pulp using xylano-pectinolytic enzymes.

Sonication-Assisted Pine Cone Flower Cellulose Hydrolysis Using Formic Acid

Nanocellulose has many applications in industrial sectors, such as in pulp and papermaking, production of synthetic textile fibers, dye, ink, and coating materials. The cellulose itself can be isolated from the waste of pine cone flower. This paper reports formic acid in the different concentrations (10%, 30%, and 60%) for hydrolyzing of cellulose using sonication technique (48 kHz) at 45 °C for 60 mins. The hydrolyzed cellulose was analyzed using FTIR and XRD spectrometry. It was found that the hydrolyzed-cellulose isolated was 92.4%, 94.6%, and 89.6%, respectively. The FTIR spectra provided the band for O-H (3435 cm−1) and C-O-C (1180-1060 cm−1) functional groups. However, the spectra also showed the C=C band for lignin impurities at 1661 cm−1. Furthermore, The XRD data gave similar 2-theta values for all hydrolyzed cellulose at 16°, 22°, and 34° respectively. The crystallite size was 18.34, 15.09, and 15.07 nm. Meanwhile, the crystallinity index was 50.50, 52.70, and 51.60% respectively.

The Effect of Mechanical Activation and Lignin Impurities on the Hydrolysis-Dehydration of Cellulose in the Presence of Sibunit-4 Solid Acidic Carbon Catalysts

In the presence of acidic catalysts based on the Sibunit-4 material the effects of mechanical activation and a lignin impurities on both the reactivity of cellulose and yields of products (monosaccharides and furfurals) being achieved during the hydrolysis of the polysaccharide isolated by hydrotropic cooking of miscanthus, wheat straw, and fruit shells of oats were studied. Activation was shown to significantly increase the reactivity of all substrates and the yields of the target products. Impurities of lignin led to decreasing product yields

Impact of Lignin Content on the Properties of Hemicellulose Hydrogels.

Hemicellulose is a promising renewable raw material for the production of hydrogels. This polysaccharide exists in large amounts in various waste streams, in which they are usually impure and heavily diluted. Several downstream processing methods can be combined to concentrate and purify the hemicellulose. However, such an approach can be costly; hence, the effect of impurities on the formation and properties of hydrogels must be determined. Lignin usually exists in these waste streams as a major impurity that is also difficult to separate. This compound can darken hydrogels and decrease their swellability and reactivity, as shown in many studies. Other properties and effects of lignin impurities are equally important for the end application of hydrogels and the overall process economy. In this work, we examined the feasibility of producing hydrogels from hemicelluloses that originated from sodium-based spent sulfite liquor. A combination of membrane filtration and anti-solvent precipitation was used to extract and purify various components. The influence of the purity of hemicellulose and the addition of lignosulfonates (emulated impurities in the downstream processing) to the crosslinking reaction mixture on the mechanical, thermal, and chemical properties of hydrogels was determined.

Antisolvent precipitation of water-soluble hemicelluloses from TMP process water

During the thermomechanical pulping (TMP) of spruce, hemicelluloses (mainly galactoglucomannans, GGMs) are released into the process water at relatively low concentrations that are currently impossible to efficiently recover. This paper examines the recovery of hemicelluloses precipitated from TMP process water via solubility reduction by adding antisolvents such as methanol, ethanol, and acetone. The phase separation was monitored by turbidity measurements. Gravimetric analysis, FTIR, GC–MS, UV spectroscopy, and ICP-OES were used to determine the yield, purity, and composition of the precipitates. Gel permeation chromatography and pulsed field-gradient self-diffusion NMR were used to measure the molecular mass distribution of the precipitates. Acetone was found to be the most efficient antisolvent, giving the highest yield at the lowest addition. The contents of lipophilic extractives and lignin impurities were below 0.5% and 1.6%, respectively, and the metal content was approximately 2% in the precipitates obtained with acetone.

Investigation on molar mass, solubility and enzymatic fragmentation of xylans by multi-detected SEC chromatography

Four xylan samples from different origin were investigated, using a multi-detector, size exclusion, chromatographic system with two chromatographic column sets and mobile phases differing in the DMSO:water ratio. Molar mass distribution could be analysed best using a mobile phase of DMSO:water (90:10) with addition of 0.05 M LiBr, a system offering good solubilisation of the polymers and a proper chromatographic separation. SEC analysis in aqueous systems provided information on solubility and aggregation of xylans. A comparison of UV- and RI-signals in different systems gave further information on lignin impurities, which in some cases were involved in aggregation phenomena. Both analytical systems were applied to study the enzymatic fragmentation of xylans. Combining the information derived from the two systems can differentiate between the enzymatic degradation of the well-dissolved and the associated polymer fractions.