Significant accrual of soil organic carbon through long-term rice cultivation in paddy fields in China.

Paddy fields serve as significant reservoirs of soil organic carbon (SOC) and their potential for terrestrial carbon (C) sequestration is closely associated with changes in SOC pools. However, there has been a dearth of comprehensive studies quantifying changes in SOC pools following extended periods of rice cultivation across a broad geographical scale. Using 104 rice paddy sampling sites that have been in continuous cultivation since the 1980s across China, we studied the changes in topsoil (0-20 cm) labile organic C (LOC I), semi-labile organic C (LOC II), recalcitrant organic C (ROC), and total SOC. We found a substantial increase in both the content (48%) and density (39%) of total SOC within China's paddy fields between the 1980s to the 2010s. Intriguingly, the rate of increase in content and density of ROC exceeded that of LOC (I and II). Using a structural equation model, we revealed that changes in the content and density of total SOC were mainly driven by corresponding shifts in ROC, which are influenced both directly and indirectly by climatic and soil physicochemical factors; in particular temperature, precipitation, phosphorous (P) and clay content. We also showed that the δ13 CLOC were greater than δ13 CROC , independent of the rice cropping region, and that there was a significant positive correlation between δ13 CSOC and δ13 Cstraw . The δ13 CLOC and δ13 CSOC showed significantly negative correlation with soil total Si, suggesting that soil Si plays a part in the allocation of C into different SOC pools, and its turnover or stabilization. Our study underscores that the global C sequestration of the paddy fields mainly stems from the substantial increase in ROC pool.

Facile extraction and characterization of cellulose nanocrystals from agricultural waste sugarcane straw.

BACKGROUND: Sugarcane straw is an available but largely ignored lignocellulosic biomass to obtain cellulose nanocrystals (CNCs) with highly crystalline, tunable surface chemistries and a wide-ranging adaptability. Herein, we utilized sugarcane straw to obtain pure cellulose via purification processes, followed by subsequent preparation of CNCs via sulfuric acid hydrolysis. The properties of the purified fibers and obtained CNCs were assessed by their composition, morphology, chemical structure, crystallinity and thermal stability. RESULTS: After the purification process, alkali-treated fibers (ATFs) contained 886.33 ± 1.25 g kg-1 cellulose, and its morphological analysis revealed a smooth and slender fibrous structure. The CNCs obtained by treatment with 64 wt% sulfuric acid at 45 °C for 60 min were isolated in a yield of 21.8%, with a diameter and length of 6 to 10 nm and 160 to 200 nm, respectively. Moreover, crystallinity index of these CNCs reached 62.66%, and thermal stability underwent a two-step degradation. Short-term ultrasonication after hydrolysis was employed to enhance isolation of the CNC particles and improve the anionic charge with higher value -38.00 mV. CONCLUSION: Overall, isolation and characterization results indicated the potential for CNCs preparation using sugarcane straw, in addition to offering a fundamental understanding of this material and indicating potential applications. © 2021 Society of Chemical Industry.

Comparative hydrolysis analysis of cellulose samples and aspects of its application in conservation science.

Knowledge about the carbohydrate composition of pulp and paper samples is essential for their characterization, further processing, and understanding the properties. In this study, we compare sulfuric acid hydrolysis and acidic methanolysis, followed by GC-MS analysis of the corresponding products, by means of 42 cellulose and polysaccharide samples. Results are discussed and compared to solid-state NMR (crystallinity) and gel permeation chromatography (weight-averaged molecular mass) data. The use of the hydrolysis methods in the context of cellulose conservation science is evaluated, using e-beam treated and artificially aged cellulose samples. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s10570-021-04048-6.

Cellulose Nanocrystal Isolation from Hardwood Pulp using Various Hydrolysis Conditions.

To expand the application field of the pulping industry, this study conducted a series of sample preparations for processing cellulose nanocrystals (CNCs) from a dry hardwood pulp to achieve optimal sulfuric acid hydrolysis. The properties of laboratory-prepared pulp CNCs (P-CNCs) were investigated with different preparation conditions including sulfuric acid concentrations, hydrolysis temperatures, and hydrolysis durations. Results showed a gradient of color changes observed with the increase of hydrolysis duration and temperature. Under certain conditions, the derived P-CNCs exhibited nanoscale dimensions, detected by transmission electron microscopy, and a crystallinity index similar to commercial products. In addition, the surface sulfate groups were assumed to be contributed by sulfuric acid hydrolysis. However, a high acid concentration and long hydrolysis processing duration introduced more sulfate groups on the derived P-CNCs, which may have acted as flame retardants and, thus, increased the amount of char residue.

Centrifuge fractionation during purification of cellulose nanocrystals after acid hydrolysis and consequences on their chiral self-assembly.

The inherent colloidal dispersity (due to length, aspect ratio, surface charge heterogeneity) of CNCs, when produced using the typical traditional sulfuric acid hydrolysis route, presents a great challenge when interpreting colloidal properties and linking the CNC film nanostructure to the helicoidal self-assembly mechanism during drying. Indeed, further improvement of this CNC preparation route is required to yield films with better control over the CNC pitch and optical properties. Here we present a modified CNC-preparation protocol, by fractionating and harvesting CNCs with different average surface charges, rod lengths, aspect ratios, already during the centrifugation steps after hydrolysis. This enables faster CNC fractionation, because it is performed in a high ionic strength aqueous medium. By comparing dry films from the three CNC fractions, discrepancies in the CNC self-assembly and structural colors were clearly observed. Conclusively, we demonstrate a fast protocol to harvest different populations of CNCs, that enable tailored refinement of structural colors in CNC films.

Formation mechanism of starch nanocrystals from waxy rice starch and their separation by differential centrifugation.

Starch nanocrystals (SNCs) were prepared from waxy rice starch via sulfuric acid hydrolysis. The objective focused on the following: i) the hydrolysis kinetics and structural properties of SNCs; ii) the effects of differential centrifugation on the yield and size distribution of SNCs. The hydrolysis was divided into a rapid hydrolysis stage in the initial two days and a slow hydrolysis stage after two days. During the two-day hydrolysis, the average diameter of SNCs reached 244 nm. After two days of hydrolysis, the degree of crystallinity, crystallite size, and melting temperature and enthalpy increased. The proportion of A-branched chains decreased, whereas the proportion of B1-branched chains and molecular weight did not change considerably. Thus, the reaction in the slow hydrolysis stage could be considered as the surface modification and gradual release of SNCs. Furthermore, SNCs with a small size and high charge density could be used for differential centrifugation.

Microfibrillated Cellulose with a Lower Degree of Polymerization; Synthesis via Sulfuric Acid Hydrolysis under Ultrasonic Treatment.

A new approach is being considered for obtaining microfibrillated cellulose with a low degree of polymerization by sulfuric acid hydrolysis with simultaneous ultrasonic treatment under mild conditions (temperature 25 °C, 80% power control). Samples of initial cellulose, MCC, and MFC were characterized by FTIR, XRF, SEM, DLS, and TGA. It was found that a high yield of MFC (86.4 wt.%) and a low SP (94) are observed during hydrolysis with ultrasonic treatment for 90 min. It was shown that the resulting microfibrillated cellulose retains the structure of cellulose I and has an IC of 0.74. It was found that MFC particles are a network of fibrils with an average size of 91.2 nm. ζ-potential of an aqueous suspension of MFC equal to -23.3 mV indicates its high stability. It is noted that MFC has high thermal stability, the maximum decomposition temperature is 333.9 °C. Simultaneous hydrolysis process with ultrasonic treatment to isolate MFC from cellulose obtained by oxidative delignification of spruce wood allows to reduce the number of stages, reduce energy costs, and expand the scope.

Controlling the nanocellulose morphology by preparation conditions.

Nanocellulose (NC) is the desired building block for novel biomaterials. The morphology of NC is one of the core parameters impacting the functionality and property of engineered functional materials. This work aims to reveal the relationship between the product morphology and sulfuric acid hydrolysis conditions (including acid concentration, temperature and time), and to realize morphological regulation of obtained NC. Three representative products were obtained from microcrystalline cellulose via sulfuric acid hydrolysis, which are cellulose nanocrystals with broad size distribution (W-CNC, 383.9 ± 131.7 nm in length, 6 ± 2.1 nm in height) obtained by 61 % H2SO4, 55 °C and 90 min, cellulose nanospheres (CNS, 61.3 ± 15.9 nm in diameter) obtained by 64 % H2SO4, 35 °C and 75 min, and CNC with narrow size distribution (N-CNC, 276.1 ± 28.7 nm in length, 4.1 ± 0.6 nm in height), obtained by 64 % H2SO4, 45 °C and 45 min. The results showed that the crystallographic form of W-CNC and N-CNC are cellulose I, while cellulose I and II coexist in CNS. Only W-CNC and N-CNC can form chiral nematic structures through evaporation-induced self-assembly strategy and reflected light with specific wavelengths. In addition, the formation mechanism of CNS with cellulose I/II was proposed, which provided a better understanding of NC morphology regulation.

Producing bacterial cellulose from industrial recycling paper waste sludge.

This study aimed to produce bacterial cellulose from paper waste sludge (PWS) as a method of utilizing the cellulose source from the remaining pulp in the material. Initially, PWS was hydrolyzed by sulfuric acid to create an enriched-reducing sugar hydrolysate. One-factor experiments were conducted with a fixed amount of PWS (5 g) to investigate the influence of hydrolysis conditions, including water, sulfuric acid addition, temperature, and retention time, on the production yield of reducing sugars. Based on these results, the Box-Behnken model was designed to optimize the hydrolysis reaction. The optimal hydrolysis conditions were 10 ml/g of the sulfuric acid solution (30.9%) at 105.5 °C for 90 min of retention time 0.81 (gGE/g PWS), corresponding to a conversion yield of 40.5%). Subsequently, 100 ml of the filtered and neutralized PWS hydrolysate was used as the culture to produce the bacterial cellulose (BC) using Acetobacter xylinum, which produced 12 g/L of bacterial cellulose. The conversion yield of bacterial cellulose calculated as the ratio of the weight of produced bacterial cellulose to that of cellulose in PWS reached 33.3%. The structure of the obtained BC was analyzed using scanning electron microscopy (SEM) and X-ray diffraction (XRD) to indicate the formation of nano-cellulose fiber networks. This research proposed a combined method to convert paper waste sludge into bacterial cellulose, demonstrating the potential for waste utilization and sustainable production of paper industries for added-value products.

Fermentable sugars production from wheat bran and rye bran: response surface model optimization of dilute sulfuric acid hydrolysis.

ABSTRACTOptimization of hydrolysis conditions of lignocellulosic biomass is crucial to able to produce value-added products by fermentation. This study not only determines optimal dilute sulfuric acid (H2SO4) hydrolysis conditions of wheat bran (WB) and rye bran (RB) by using one-factor-at-a-time method and subsequently Box-Behnken design but also elucidates chemical composition of hydrolysates yielded under optimal hydrolysis conditions. Based on the results, optimal hydrolysis conditions of WB and RB were 121 and 130°C of temperature, 1/8 and 1/8 w/v of solid to liquid ratio, 2.66 and 1.58% v/v of dilute H2SO4 ratio, and 30 and 16 min of implementation time, respectively. Hydrolysates obtained from WB and RB at these conditions contained 72.7 (0.58 g sugar/g biomass) and 89.4 g/L (0.72 g sugar/g biomass) of reducing sugar concentration, respectively. Hydrolysis rates of WB and RB were 87.79 and 91.33%, respectively. Main reducing sugar in RB hydrolysate was glucose with 31.17 g/L (0.25 g glucose/g biomass) while glucose and xylose were the main monosaccharides with 20.90 (0.17 g glucose/g biomass) and 18.69 g/L (0.15 g xylose/g biomass) in WB hydrolysate, respectively. With acidic hydrolysis of WB and RB, inhibitors such as phenolics, 5-Hydroxymethylfurfural, 2-Furaldehyde (not for RB), acetic acid, and formic acid (not for WB) formed. Catalytic efficiency values of H2SO4 for WB and RB were 15.2 and 24.4 g /g, respectively, indicating that inhibitor concentration in WB hydrolysate was higher than that of RB. These results indicated that WB and RB have a high potential in production of value-added products by fermentation.

Fabrication of silk fibroin film enhanced by acid hydrolyzed silk fibroin nanowhiskers to improve bacterial inhibition and biocompatibility efficacy.

In this study, silk fibroin nanowhiskers (SNWs) were extracted from natural silk fiber by sulfuric acid hydrolysis with the assistance of ultrasonic wave treatment. The obtained SNWs were mixed with regenerated silk fibroin (RSF) solution to fabricate the SNWs/RSF films. The fabricating SNWs were systematically characterized by using SEM, FTIR, and the SNWs/RSF films were observed by digital camera, PM, etc. The results show that the monodisperse SNWs are evenly distributed in the RSF film. The presence of SNWs in RSF film significantly improves the performances of the film, including the swelling ability, mechanical properties, hydrophilicity, antibacterial efficacy, cytocompatibility. Meanwhile, the SNWs/RSF film can endorse the wound healing efficiency in vivo mice wound site. The proposed techniques for extracting SNWs and fabricating silk fibroin composite film may provide a valuable method for creating an ideal silk-based material for biomedical applications.

Preparation of nanocellulose in high yield via chemi-mechanical synergy.

Nanocellulose has gained increasing attention due to its excellent properties and wide application prospect. However, fast and low-waste preparation of nanocellulose is still challenging. Here, a time-saving and low-cost chemi-mechanical method was proposed to prepare cellulose nanocrystals (D-CNCs) and cellulose nanofibers (D-CNFs) by dilute sulfuric acid hydrolysis and the homogenization of the un-hydrolyzed cellulose residues, respectively. After hydrolyzed by 0.3 wt% sulfuric acid at 160 °C for 2 h, the diameter and length distribution of the obtained D-CNCs were 16 ∼ 45 nm and 150 ∼ 600 nm, respectively. The yield of D-CNCs and D-CNFs reached to 15.78 % and 69.11 %. The thermostability of D-CNCs was more superior to CNCs manufactured by 64 wt% sulfuric acid. In conclusion, this approach offers a promising strategy for high yield of nanocellulose due to its easy operation and low pollution.

Transition of cellulose supramolecular structure during concentrated acid treatment and its implication for cellulose nanocrystal yield.

Cellulose nanocrystals with cellulose I and II allomorphs (CNC-I and CNC-II) were prepared from eucalyptus cellulose I substrate by controlling the sulfuric acid hydrolysis conditions, including acid concentration (56-64 wt%), reaction temperature (45 or 60 °C) and time (10-120 min). The crystalline structures were verified by XRD and 13C-NMR. CNC-II only appeared at very restricted reaction conditions. The rapid cellulose supramolecular structure transition under sulfuric acid concentration of around 60 wt% resulted in an abrupt change in CNC yield. A maximal CNC yield of 66.7% was obtained at acid concentration of 58 wt% and reaction temperature of 60 °C. CNC-I exhibited spindle-shape, while CNC-II showed a twisted strip structure. The state of order in cellulose during the acid hydrolysis process has been studied using a coagulation method. A tentative model of CNC-I and CNC-II formation was then proposed. This work provided significant knowledge for the production of CNCs with high yield and controllable allomorph.

Preparation and characterization of cellulose nanocrystal extracted from ramie fibers by sulfuric acid hydrolysis.

Cellulose nanocrystals (CNCs) were isolated from ramie fibers through chemical pretreatments accompanied by sulfuric acid hydrolysis. The influences of both temperature and hydrolysis time on the properties of CNCs were discussed in the present study. The characterization of CNCs was conducted using FT-IR, XRD, TEM, and TGA. The results showed the characteristics of obtained CNCs were influenced significantly by both temperature and time of hydrolysis. The crystallinity, dimensions, and thermal stability of CNCs were found to reduce by increasing both temperature and reaction time of hydrolysis. The optimal hydrolysis parameters were achieved at 45 °C for 30 min with 58% sulfuric acid to produce CNCs, rod-like particles with a high crystallinity (90.77%), diameter (6.67 nm), length (145.61 nm), and best thermal stability among all CNCs. The obtained CNCs had a higher potential for application of alternative reinforcing fillers in the nanocomposites.

Structure characterization of a heavily fucosylated chondroitin sulfate from sea cucumber (H. leucospilota) with bottom-up strategies.

Two bottom-up strategies, disaccharide and oligosaccharide analyses, were applied to elucidate the structure of a fucosylated chondroitin sulfate (FCS). The FCS was hydrolyzed with mild acid. The remained part was digested with CS lyase for disaccharide analysis. The products from each step were analyzed and the results revealed that mild sulfuric acid mainly released sulfated fucose branches, but also affected some residues and sulfo-groups on the backbone. Over 140 oligosaccharide fragments were generated by catalytic oxidation and identified by HPSEC-MS, including sulfated fucose oligosaccharides exclusively from branches, sulfated backbone fragments, and junctional fragments. Based on the results provided by these two methods, the proposed backbone of the FCS is mainly composed of GlcA→GalNAc4S6S and GlcA→GalNAc6S, and the branch is mainly located at GalNAc. The longest branch observed is nonasaccharide, and most of the fucose on the branches are mono and/or di-sulfated. NMR results supported the conclusion.

Obtainment and characterization of nanocellulose from an unwoven industrial textile cotton waste: Effect of acid hydrolysis conditions.

Cellulose nanocrystals (CNCs) have a promising application in many advanced products, such as biomedical applications and hydrogels. In this research, industrial cotton waste was treated using alkali and bleaching to eliminate hemicellulose, lignin, and other amorphous contents. The efficiency of these treatments was proven by chemical compositions analysis, which showed an increase in cellulose percentage with the progression of treatments. Fibers were analyzed by X-ray diffraction, thermogravimetric, and Scanning Electron Microscopy (SEM). CNCs were then prepared by acid hydrolysis using different sulfuric acid concentrations (50 wt%, 60 wt% and 64 wt%) and two reactions time (60 min. and 75 min.) resulting in six CNCs suspensions. CNCs were analyzed by X-ray diffraction, thermogravimetric, zeta potential, and Transmission Electron Microscopy (TEM). CNCs obtained exhibited a good crystallinity index varying from 75 to 81% and thermal stability between 146 °C and 200 °C. TEM analysis showed that sulfuric acid concentration influenced in CNCs length (105 nm-5880 nm). By analyzing all results, the optimal parameters for acid hydrolysis were 64% (w/w) of acid concentration combined with 60 min. of reaction time. The preparation of CNCs in this work showed some prospects of using untraditional industrial cotton waste as an advanced material.

Isolation and Characterization of Nanocellulose with a Novel Shape from Walnut (Juglans Regia L.) Shell Agricultural Waste.

Herein, walnut shell (WS) was utilized as the raw material for the production of purified cellulose. The production technique involves multiple treatments, including alkaline treatment and bleaching. Furthermore, two nanocellulose materials were derived from WS by 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO) oxidation and sulfuric acid hydrolysis, demonstrating the broad applicability and value of walnuts. The micromorphologies, crystalline structures, chemical functional groups, and thermal stabilities of the nanocellulose obtained via TEMPO oxidation and sulfuric acid hydrolysis (TNC and SNC, respectively) were comprehensively characterized. The TNC exhibited an irregular block structure, whereas the SNC was rectangular in shape, with a length of 55-82 nm and a width of 49-81 nm. These observations are expected to provide insight into the potential of utilizing WSs as the raw material for preparing nanocellulose, which could address the problems of the low-valued utilization of walnuts and pollution because of unused WSs.

A comparative study on the preparation and characterization of cellulose nanocrystals with various polymorphs.

Polymorphic changes of cellulose nanocrystals (CNCs) are strongly associated with its properties and applications. In this study, CNCs with different polymorphs were produced by a simple polymorphic transformation treatment. Cellulose I nanocrystals were produced by typical sulfuric acid hydrolysis (CNC-I). Cellulose II nanocrystals were prepared by two different methods: (1) sulfuric acid hydrolysis of cellulose previously mercerized with 18.5 wt% NaOH (CNC-II), (2) mercerization of CNC-I with 18.5 wt% NaOH (MCNC-II). Cellulose III nanocrystals were prepared by ethylenediamine treatment of CNC-I (ECNC-III). The polymorphic changes of CNCs, and their properties including morphology, crystallinity, thermal stability, and re-dispersion ability were systematically investigated. The results showed that the other properties of CNC-II and MCNC-II were quite different from each other except for the morphology. The morphology of polymorphic transformed CNCs were strongly relate to the fashion of cellulose chains arrangement. Both CNC-II and MCNC-II exhibited a rod-like shape with short lengths, whereas the ECNC-III showed relatively long length, like CNC-I.

Cellulose I and II nanocrystals produced by sulfuric acid hydrolysis of Tetra pak cellulose I.

Polymorphism is an important factor associated with the cellulose nanomaterial properties. In this study, cellulose fibers (CFs) were efficiently isolated from waste Tetra pak packages, and cellulose I and II nanocrystals were produced by treatment of CFs with 64% sulfuric acid and controlling the reaction time from 15 to 30 min. Cellulose I (CI) was partially converted to cellulose II (CII) within 15 min and the resulting cellulose nanocrystal product (i.e. CNC15) contained 93.2% CII. Further extending the hydrolysis time decreased the CII content of CNC20 to 25.5% and CNC30 was completely CI without CII. CNC15 (285.1 ±â€¯120.7 nm long, 50.6 ±â€¯16.5 nm wide, 0.64 at% sulfur) was much thicker, slightly longer, less thermal stable and contained more sulfate groups than CNC30 (207.2 ±â€¯77.8 nm long, 23.2 ±â€¯7.8 nm wide, 0.34 at% sulfur). CNCs with controllable allomorph may have potentially diverse applications.

Enhanced sorption of hexavalent chromium [Cr(VI)] from aqueous solutions by diluted sulfuric acid-assisted MgO-coated biochar composite.

Metal oxide-Carbon composites have aroused great interesting towards specific anionic contaminants removal from the polluted environment. In this study, aiming at removing toxic chromate ion [Cr(VI)] from aqueous solutions, a novel approach was developed to produce surface-enhanced MgO-coated biochar adsorbent from sugarcane harvest residue (SHR). It was found that sulfuric acid hydrolysis and MgO-coating both facilitated the removal of Cr(VI) by biochars, and the maximum sorption capacities for the pristine biochar (SHR550), MgO-coated biochar (MgSHR550), and acid-assisted MgO-coated biochar (MgASHR550) that derived from the Langmuir isotherm model were 20.79, 54.64, and 62.89 mg g-1, respectively. Additionally, the Cr(VI) removal was a pseudo-second-order kinetic model controlled process with equilibrium reached within 24 h. The mechanism investigation revealed that Cr(VI) ions was directly sorbed by the MgO-coated biochars via the chemical interaction between MgO and Cr(VI), whereas the sorption-coupled reduction of Cr(VI) to Cr(III) governed the sorption of Cr(VI) on the SHR550. Although the increases of solution pH (>2.0) and KNO3 concentration (>0.05 mol L-1) reduced the Cr(VI) removal by biochars, while there were lower secondary pollution risks in MgO-coated biochar treatments due to the suppressed release of Cr(III) in solutions. This work could provide guidance for the production of efficient biochar for the removal of Cr(VI) from wastewater.