NaOH Pretreatment Research Articles

Alkaline-washed phosphogypsum-based cemented paste backfill prepared using steel slag and blast furnace slag: mechanical properties, fluoride immobilization, and hydration mechanism

Phosphogypsum (PG)-based cemented paste backfill (PCPB) is an effective way to deal with the problem of PG storage, but the low strength, high cost, and serious fluoride pollution of PCPB limit the popularization of this technology. Alkaline washing has been proven to be an effective means to decrease fluoride from PG. Steel slag (SS) and ground granulated blast furnace slag (GGBFS) are common materials possessing pozzolanic activity. SS and GGBFS can be employed as cement substitutes under alkaline conditions. This paper proposes the combined heuristic effect of NaOH pretreatment, SS, and GGBFS to improve the strength of alkaline-washed PCPB (APCPB) and the ability of fluoride immobilization. The study results show that alkali washing stimulates the secondary hydration activity of solid waste materials and promotes the formation of hydration products such as AFt and C-S-H so that the UCS value of APCPB increases greatly in the later stages of hydration increases by 309.8% (7.06MPa), and the leaching concentration of fluoride decreases by 21.5% (0.85mg/L). Through microscopic characterization experiments on the APCPB, it was discovered that in the alkaline hydration system, the transformation of C-S-H and AFt into C-A-S-H, F-C-S-H, and F-AFm, coupled with the physical encapsulation of hydration products, are the main factors immobilizing fluoride. This work provides a much-needed supplement to the in-situ cement-free repair technology of PG in mines to develop more lower-carbon and environmentally friendly mixture formulations.

Microcrystalline Cellulose Extracted from Tissue Paper and its Comparison to Commercial Microcrystalline Cellulose

Introduction: Tissue paper has been utilized to extract Microcrystalline Cellulose (MCC) using sulphuric acid. The two approaches used for MCC extraction were with NaOH pretreatment (NaOH-EMC) and without NaOH (EMC). Method: The extracted MCC was characterized by FTIR, SEM, TGA, XRD, zeta potential, particle size, and degree of polymerization and then subsequently compared with the commercially available MCC(CMC). The particle size of the NaOH-EMC was lesser than the CMC, while the EMC had a larger size. The values recorded were respectively 1.322, 6.750, and 8.521 μm. The SEM images also supported the values reported by the particle size analyzer. Result: The distribution, however, was staggered for the prepared samples, as against the CMC. The prepared MCC suspensions were found to be more stable than the CMC based on the recorded zeta potential. The crystallinity for NaOH-EMC, EMC, and CMC was recorded to be 69.91, 68.59, and 70.89 percent, respectively, and the observations were not significantly different. Conclusion: The degree of polymerization of NaOH-EMC and EMC was 129 and 94, which was 189 lower than that of CMC, having the value of 178. The study successfully reports the extraction of MCC from the tissue paper as an alternative source.

Effects of NaOH and Na2CO3 pretreatment on the saccharification of sweet sorghum bagasse

In this work, the chemical composition, chemical structures, and sugar release were evaluated for sweet sorghum bagasse (SSB) biomass in response to alkaline pretreatments and enzymatic hydrolysis. Five different ratios of 2 M sodium hydroxide (NaOH) and sodium carbonate (Na2CO3) solutions were used for biomass fractionation along with two heat treatment conditions, 85°C and 150°C for 1 h. Sugar yields from enzymatic hydrolysis were measured at different durations up to 72 h. SSB samples pretreated at high temperature using alkaline solutions containing equal amounts of Na2CO3 and NaOH favored retaining cellulose content (up to 90%) while effectively removing hemicellulose (65%) and lignin (92%). The high-temperature pretreatment conditions resulted in improved delignification, higher sugar concentrations, and sugar yields. Pretreatment solutions consisting of 50% or more NaOH produced higher glucose yields (85%–90%) and total sugar concentrations. Moreover, pretreatment solutions containing Na2CO3 improved the hydrolysis rates allowing SSB samples reach maximum yields faster than those without it, 48 versus 72 h. Results showed pretreatment methods combining NaOH and Na2CO3 were effective at promoting SSB biomass conversion, increasing sugar recovery after hydrolysis, and reducing the hydrolysis duration, all of which are desirable and cost beneficial.

A method of pretreating incineration ashes containing metallic aluminium using NaOH to mitigate volume expansion under highly alkaline conditions

Globally, millions of tonnes of incineration ashes are produced with a substantial portion remaining underutilized in low-value applications or disposed in landfills. Many types of fly ashes and bottom ashes contain metallic aluminium (Al0), which causes volume expansion when the ashes are used in alkali-activated materials and as a supplementary cementitious material due to the generation of hydrogen gas at high-pH conditions. This phenomenon significantly restricts the potential applications of these ashes. To address this issue, ashes can be pretreated with NaOH to oxidize the metallic aluminium (Al0) before their utilization. This study focuses on investigating the effect of the NaOH pre-treatment duration on fly ashes from the co-combustion of recovered solid fuel, peat, and wood. A pre-treatment process was conducted using 8 mol/L aqueous NaOH solution to treat the fly ash for up to 60 minutes. The formed slurry was subsequently used to prepare alkali-activated material by mixing it with bottom ash and employing either sodium silicate or sodium carbonate as an alkali activator. The NaOH pre-treatment demonstrated a 100 % metallic aluminium conversion into oxidized form resulting enhancement in mechanical performance, microstructure, and water absorption properties. The proposed method offers a highly efficient and rapid solution for eliminating the drawbacks caused by the presence of metallic aluminium and it can be conveniently implemented on construction sites. Concurrently, this study also explores the leaching behaviour of heavy metals during alkali-activation. Significant reductions in the leaching of Ba, Cr, Cu, Mo, and Pb were observed, highlighting the environmental remediation potential of alkali-activation methods.

Oil palm frond leaves (OPFLs), a high recalcitrant biomass as an alternative cellulose source for glucose conversion

Among the oil palm biomass, oil palm frond leaves (OPFLs) are under-valued since they can be classified as a high recalcitrance feedstock due to the high lignin and hemicellulose content. This work proposes a new way of using OPFLs as alternative cellulose sources for glucose conversion by an application of various pre-treatments at varying parameters. From green pre-treatment, steam explosion (SE) is much more effective in disrupting the OPFLs structure in contrast to hydrothermal (HT) pre-treatment, by a vast dissolution of hemicellulose and depolymerization of lignin. The pre-impregnation with H2SO4 prior to steam explosion was beneficial to enhance the hemicellulose removal up to 89.94 %. The 2D-HSQC NMR analysis divulged the reduction of ß-O-4 linkage and S/G value after the SE and HT pre-treatment, verifying the degradation of lignin-carbohydrate linkage in OPFLs. Meanwhile, the dilute NaOH pre-treatment enhanced the delignification by 87.14 %. SEM analysis revealed a well-disrupted structure of pre-treated OPFLs exposing a higher cellulosic fraction, whereas SEC analysis divulged a decreasing pattern of degree of polymerization of cellulose. The enzymatic analysis revealed that pre-treated OPFLs yielded higher glucose ranging from 29.81 % to 49.98 % w/w, which was ∼3-fold higher than raw OPFLs (14.31 % w/w). A maximum cellulose digestibility (100 %) was achieved by steam-exploded OPFLs after 72 h of enzymatic hydrolysis. This suggests the potency of various pre-treatments to enhance enzymatic saccharification of OPFLs producing a higher glucose yield.

Alkali pretreatment-assisted catalytic pyrolysis of waste cellulose acetate for selective preparation of levoglucosenone

With the increasing demand for cellulose acetate (CA) in industrial and daily applications, the disposal of its waste has emerged as an environmental concern. In this study, a novel and sustainable method for value-added utilization of waste CA was proposed, which involved NaOH pretreatment and subsequent catalytic pyrolysis using phosphoric acid-activated carbon (PAC) to prepare levoglucosone (LGO). The effects of pretreatment temperatures and NaOH concentrations on the physicochemical characteristics of CA were thoroughly investigated. Furthermore, the pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) experiments were conducted to methodically assess the impacts of both pretreatment and pyrolysis conditions on the production of LGO. The results indicated that NaOH pretreatment could effectively hydrolyze the ester bonds in CA, leading to the removal of acetyl groups and a decrease in thermal stability. At a pretreatment temperature of 40 °C, a NaOH concentration of 0.5 mol/L, a catalyst/sample ratio of 1/3, and a pyrolysis temperature of 400 °C, the LGO yield could reach 11.52 wt%, much higher than that obtained from catalytic pyrolysis of CA (2.70 wt%). This study provides an efficient method for treating waste CA and demonstrates its potential for conversion into high-value chemicals, laying a solid foundation for the green recycling of waste plastics.

Co-pyrolysis of pretreated cotton stalk and low-density polyethylene: Evolved products and pyrolysis mechanism analysis

The preparation of bio-oil from cotton stalks and agricultural residue films using co-pyrolysis technology can achieve resource recovery and energy conversion, which has important research value and significance. In this study, cotton stalks were subjected to different chemical pretreatments using NaOH, HCl, and H2O solutions to understand their structural changes and pyrolysis characteristics. In addition, the lower H/C ratio of cotton stalks resulted in higher oxygen content in the pyrolysis oil, which limited its efficient and clean utilization. Therefore, the characteristics and pyrolysis kinetics of the pyrolysis products of pretreated cotton stalks and LDPE (low-density polyethylene) were studied. The results showed that the ash content of alkali pretreatment cotton stalks decreased by 1.24 %, and the dense structure of cotton stalks significantly relaxed. NaOH pretreatment effectively removed hemicellulose sugars and cracked them. During the co-pyrolysis process, when the ratio of NaOH-CS/LDPE was 50/50, the synergistic effect was more pronounced, and the oil yield increased by 2 % compared to the theoretical value. The oxygen content of CO and CO2 in the pyrolysis gas was higher than the theoretical value, at 10.4 % and 14.1 % respectively. The synergistic effect of bio-oil on hydrocarbons was the most significant, reaching 18.9 %. More hydrogen and less oxygen migrated into the co-pyrolysis oil, resulting in an increase in hydrocarbons and a decrease in oxygen-containing compounds, and improving the quality of bio-oil. Results from electron paramagnetic resonance (EPR) indicated that adding LDPE might raise the quantity of stable free radicals. The evolution mechanism of functional groups of NaOH-CS and LDPE co-pyrolysis behavior was analyzed by Fourier in-situ infrared spectrometry (FTIR), and it was found that C–O–C, C=O, and O–H decreased due to dehydroxylation, decarboxylation, decarbonylation, and demethoxy reactions with the increase of temperature, indicating that there was a synergistic effect between NaOH-CS and LDPE co-pyrolysis. The pyrolysis kinetics of NaOH-CS, LDPE and their blends were determined by the model-free method. The introduction of LDPE can reduce the activation energy of NaOH -CS pyrolysis alone, and the 3D diffusion (D3) model is suitable for their blends.

Alkaline pretreatment of Durio sp. residual biomass enhances cellulose accessibility for efficient bioethanol production

The reliance on fossil fuels for energy generation has led to significant environmental, social, and economic challenges, necessitating the exploration of sustainable alternatives. Bioethanol, derived from renewable sources such as agricultural waste, presents a promising substitute. This study investigates the potential of durian skin, an abundant agricultural byproduct, as a raw material for bioethanol production. Alkaline pretreatment using NaOH significantly altered the chemical composition and structural properties of durian skin, increasing cellulose content and removing lignin. The cellulose content of the outer durian skin (ODS) and deep durian skin (DDS) increased by 57.53% and 59.28%, respectively, after pretreatment. The X-ray diffraction and Fourier transform infrared spectroscopy of cellulose and lignin provide significant information. Using 30 FPU enzymes to load the substrate results in DDS producing 126 g/L of glucose and 42.8 g/L of ethanol. The optimal conditions are 15% NaOH pretreatment, 150 °C, 4 bars pressure, and 90 min. The study demonstrates the economic viability and environmental benefits of utilising durian skin for bioethanol production, offering insights into sustainable energy sources and waste valorisation. These findings contribute to the global shift towards renewable energy and highlight the importance of pretreatment in enhancing bioethanol production efficiency from agricultural biomass waste.

Tailoring mesoporous and macroporous structures in activated carbon from NaOH-pretreated oak for superior supercapacitors

The growing need for sustainable and efficient energy storage solutions has intensified research efforts into eco-friendly materials such as activated carbon (AC) derived from lignocellulosic biomass. Herein, we present a method to enhance the physical characteristics of AC from oak via NaOH pretreatment. The NaOH-pretreated oak was converted into AC through carbonization and chemical activation using KOH as the activating agent. The AC tended to develop mesopores (2–50 nm) and macropores (> 50 nm) as the pretreatment ratio increased (0 %, 1 %, 2 %, and 8 %), achieving a specific surface area of up to 2706 m2 g−1 and a pore volume of up to 1.97 cm3 g−1. This result is due to the transformation of the structure of lignocellulosic biomass into a more advantageous structure for pore development through the reactions of delignification and deacetylation that occur during NaOH pretreatment. The mesoporous and macroporous structures offer efficient ion diffusion pathways and reduce resistance, which leads to superior rate capability, capacity retention, and a gravimetric specific capacitance of 44.5 F g−1 at a current density of 1 mA cm−2 in supercapacitors. The maximum energy and power densities achieved were 45.1 Wh kg−1 and 16.4 kW kg−1, respectively. These results underscore the potential of NaOH-pretreated oak as a sustainable and effective precursor for high-performance AC in energy storage applications, offering new insights into the optimization of the material properties for supercapacitors.

Optimizing the Conditions of Pretreatment and Enzymatic Hydrolysis of Sugarcane Bagasse for Bioethanol Production.

The agricultural waste sugarcane bagasse (SCB) is a kind of plentiful biomass resource. In this study, different pretreatment methods (NaOH, H2SO4, and sodium percarbonate/glycerol) were utilized and compared. Among the three pretreatment methods, NaOH pretreatment was the most optimal method. Response surface methodology (RSM) was utilized to optimize NaOH pretreatment conditions. After optimization by RSM, the solid yield and lignin removal were 54.60 and 82.30% under the treatment of 1% NaOH, a time of 60 min, and a solid-to-liquid ratio of 1:15, respectively. Then, the enzymolysis conditions of cellulase for NaOH-treated SCB were optimized by RSM. Under the optimal enzymatic hydrolysis conditions (an enzyme dose of 18 FPU/g, a time of 64 h, and a solid-to-liquid ratio of 1:30), the actual yield of reducing sugar in the enzyme-treated hydrolysate was 443.52 mg/g SCB with a cellulose conversion rate of 85.33%. A bacterium, namely, Bacillus sp. EtOH, which produced ethanol and Baijiu aroma substances, was isolated from the high-temperature Daqu of Danquan Baijiu in our previous study. At last, when the strain EtOH was cultured for 36 h in a fermentation medium (reducing sugar from cellulase-treated SCB hydrolysate, yeast extract, and peptone), ethanol concentration reached 2.769 g/L (0.353%, v/v). The sugar-to-ethanol and SCB-to-ethanol yields were 13.85 and 11.81% in this study, respectively. In brief, after NaOH pretreatment, 1 g of original SCB produced 0.5460 g of NaOH-treated SCB. Then, after the enzymatic hydrolysis, reducing sugar yield (443.52 mg/g SCB) was obtained. Our study provided a suitable method for bioethanol production from SCB, which achieved efficient resource utilization of agricultural waste SCB.

Extraction yield and properties of biogenic silica from palm oil fuel ash: effect of re-ashing pretreatment and solvent concentration

Abstract Pretreatments and extraction conditions can affect the yield and characteristics of biogenic silica (biosilica) from palm oil fuel ash (POFA). This study aimed to examine how reashing pretreatment and varying NaOH concentrations influence the yield and properties of biosilica extracted from POFA by a simple sol-gel method. Re-ashing pretreatment was conducted using a furnace at a temperature of 600°C for 2h. All samples were leached using a citric acid solution. Extraction process was carried out using NaOH solutions with concentrations of 6%, 8%, and 10%). The results showed that re-ashing pretreatment and concentrations of NaOH significantly influenced (p<0.05) the extraction yield, color, crystallinity, and specific surface area of POFA-derived biosilica. Re-ashing pretreatment in combination with a 10% NaOH solution produced the highest extraction yield of biosilica (17.25% w/w) with a bright white color (L=91.83; WI=91.32), SiO2 concentration of 94.68%, crystallinity of 50.10%, and specific BET surface area of 390.80m2/g. XRD patterns confirmed the amorphous nature of POFA-derived biosilica. FTIR spectra revealed the presence of silica functional groups in all samples. This study demonstrated the important roles of re-ashing pretreatment and NaOH concentration in producing POFA-derived biosilica with better yield and properties that could broaden its potential applications.

Optimization of biogas production from thermal-alkali pre-treated sludge using response surface methodology and random forest regressor model

BackgroundUnderstanding the intricate relationships between input variables and methane potential is crucial for optimizing anaerobic digestion process after thermal-alkali pre-treatment. This study aimed to optimize low-temperature thermal alkali pre-treatment, focusing on dosage based on the total solids (TS) content of raw sludge. A comparative analysis was conducted to optimize input parameters related to biogas generation potential as the primary response. MethodsBiomethane potential data were collected following the pre-treatment of sludge within the temperature range of 40–70 °C, using various doses of NaOH, KOH, Mg(OH)2, and Ca(OH)2 ranging from 40 mg alkali/g TS to 120 mg alkali/g TS. The optimization of biogas and methane production was conducted through Response Surface Methodology (RSM) and the Random Forest Regressor (RFR) model considering dosage and temperature as input variables. Additionally, sensitivity analysis was performed using the permutation feature importance function to gain insights into the influence of alkali types on biogas and methane production. FindingsThe results obtained from the RFR model showcased a notably high accuracy in predicting optimal solutions. NaOH addition was the most effective pre-treatment with an optimal dose of 65 mg/g TS and at a temperature of 56 °C. NaOH pre-treatment increased methane yield to 414.40 mL/g VS, compared to 117.08 mL/g VS for the untreated sludge. The sensitivity analysis results indicated that the temperature had a more significant effect on biogas potential than the alkali dosage.

Evaluation of free and immobilized cellulase on chitosan-modified magnetic nanoparticles for saccharification of sorghum residue.

Enzymatic hydrolysis plays a pivotal role in transforming lignocellulosic biomass. Addressing alternate techniques to optimize the utilization of cellulolytic enzymes is one strategy to improve its efficiency and lower process costs. Cellulases are highly specific and environmentally benign biocatalysts that break down intricate polysaccharides intosimple formsofsugars. In contrast to the most difficult and time-consuming enzyme immobilization processes, in this research, we studied simple, mild, and successful techniques for immobilization of pure cellulase on magnetic nanocomposites using glutaraldehyde as a linker and used in the application of sorghum residue biomass. Fe3O4 nanoparticles were coated with chitosan from the co-precipitation method, which served as an enzyme carrier. The nanoparticles were observed under XRD, Zeta Potential, FESEM, VSM, and FTIR. The size morphology results presented that the Cs@Fe3O4 have 42.2nm, while bare nanoparticles (Fe3O4) have 31.2nm in size. The pure cellulase reaches to 98.07% of loading efficiency and 71.67% of recovery activity at optimal conditions. Moreover, immobilized enzyme's pH stability, thermostability, and temperature tolerance were investigated at suitable conditions. The kinetic parameters of free and immobilized enzyme were estimated as Vmax; 29 ± 1.51 and 27.03 ± 2.02µmolmin-1mg-1, Km; 4.7 ± 0.49mM and 2.569 ± 0.522mM and Kcat; 0.13s-1, and 0.89s-1. Sorghum residue was subjected to 2% NaOH pre-treatment at 50℃. Pre-treated biomass contains cellulose of 64.8%, used as a raw material to evaluate the efficiency of reducing sugar during hydrolysis and saccharification of free and immobilized cellulase, which found maximum concentration of glucose 5.42g/L and 5.12g/L on 72h. Thus, our study verifies the use of immobilized pure cellulase to successfully hydrolyze raw material, which is a significant advancement in lignocellulosic biorefineries and the reusability of enzymes.

Study on the dyeing properties of Chinese fir with Cinnamomum camphor pigment by premordant dyeing

ABSTRACT Wood staining can improve the quality of Chinese fir. In this study, Cinnamomum camphora natural plant pigment was used as a substitute for synthetic dyes to stain Chinese fir, and the staining performance was enhanced through pre-mordanting with alum. The dyeing effects of direct dyeing and mordant dyeing were compared, and the factors and levels influencing color difference, wash fastness, and light fastness were investigated through an orthogonal experimental design. The results showed that mordanting time had the greatest influence on color difference and lightfastness, while mordanting temperature had the greatest influence on washfastness. After pre-mordanting, the washfastness of Chinese fir improved to a level of 2–3, while the improvement in lightfastness was not significant. Pre-mordanting increased the dye uptake rate by 6.67%. Scanning electron microscopy revealed that NaOH pretreatment opened the wood pores and increased the flow channels for dye liquor. Infrared analysis indicated that O-H in wood fibers formed complexes with Al3+ in the mordant, resulting in a decrease in the characteristic peak intensity of O-H. X-ray diffraction analysis showed that the attractive effect of Al3+ vacant orbitals on O-H partially influenced the ordered arrangement structure in the crystalline region.

Effects of alkali pretreatment on the flotation of spodumene and feldspar

The surface chemistry and morphology of minerals produced by alkali pretreatment affects their flotation behaviors. This study systematically investigated the impact on the mineral surface dissolution using NaOH as a modifier, which could modify the surface properties of minerals and improve the floatability difference between spodumene and feldspar. Various characterizations including flotation experiments, flotation kinetics analysis, SEM analysis, microcalorimetry analysis, zeta potential measurements, XPS analysis and ICP-MS analysis were conducted. Single minerals and actual ore flotation experiment results were in good agreement, and the flotation grade and recovery of Li2O in spodumene concentrates increased by 1.11 % and 6.99 %, respectively, after NaOH pretreatment. The flotation kinetics results demonstrated the cumulative recoveries of spodumene exhibited the best agreement with the first-order kinetic model and the flotation kinetic constant was improved after alkali pretreatment. Microcalorimetric results indicated the absolute values of the reaction heat for spodumene were higher than that of feldspar reacted with collectors after the alkali pretreatment. XPS and ICP results demonstrated the amounts of Al active sites on the spodumene surface was significantly increased after alkali pretreatment compared to that on the feldspar surface, improving the selective adsorption of NaOL.

Fabrication of 3D-printed scaffolds loaded with gallium acetylacetonate for potential application in osteoclastic bone resorption

We recently reported the potential of a new gallium compound, gallium acetylacetonate (GaAcAc) in combating osteoclastic bone resorption through inhibition of osteoclast differentiation and function. Herein, we focused on 3D-printed polylactic acid scaffolds that were loaded with GaAcAc and investigated the impact of scaffold pretreatment with polydopamine (PDA) or sodium hydroxide (NaOH). We observed a remarkable increase in scaffold hydrophilicity with PDA or NaOH pretreatment while biocompatibility and in vitro degradation were not affected. NaOH-pretreated scaffolds showed the highest amount of GaAcAc loading when compared to other scaffolds (p < 0.05). NaOH-pretreated scaffolds with GaAcAc loading showed effective reduction of osteoclast counts and size. The trend was supported by suppression of key osteoclast differentiation markers such as NFAT2, c-Fos, TRAF6, & TRAP. All GaAcAc-loaded scaffolds, regardless of surface pretreatment, were effective in inhibiting osteoclast function as evidenced by reduction in the number of resorptive pits in bovine cortical bone slices (p < 0.01). The suppression of osteoclast function according to the type of scaffold followed the ranking: GaAcAc loading without surface pretreatment > GaAcAc loading with NaOH pretreatment > GaAcAc loading with PDA pretreatment. Additional studies will be needed to fully elucidate the impact of surface pretreatment on the efficacy and safety of GaAcAc-loaded 3D-printed scaffolds.

Enhancing biomass conservation and enzymatic hydrolysis of sweet sorghum bagasse by combining pretreatment with ensiling and NaOH.

Lignocellulosic pretreatment is an important stage in biomass utilization, which usually requires high input. In this study, a low-cost method using combined ensiling and NaOH was developed for lignocellulosic pretreatment. Sweet sorghum bagasse (SSB) was ensiled for 21 days and then treated with diluted NaOH (0%, 1%, and 2%) for fermentation. The results showed that the application of Lactobacillus plantarum (L) reduced fermentation losses of the silages, mainly low water-soluble carbohydrate (WSC) and ammonia nitrogen loss. Meanwhile, the application of Lactobacillus plantarum and ensiling enzyme (LE) promoted lignocellulosic degradation, as evidenced by low neutral detergent fiber (NDF), acid detergent fiber (ADF), lignin (ADL), and hemicellulosic (HC) contents. The dominant bacterial genera were Lactobacillus, uncultured_bacterium_f_Enterobacteriaceae, and Pantoea after silage, which corresponded to the higher lactic acid and acetic contents and lower pH. The reducing sugar yields of SSB increased after combined pretreatment of silage and NaOH and were further enhanced by the 2% NaOH application, as evidenced by the high reducing sugar yield and microstructure damage, especially in the L-2% NaOH group and the LE-2% NaOH group, in which the reducing sugar yields were 87.99 and 94.45%, respectively, compared with those of the no additive control (CK)-0 NaOH group. Therefore, this study provides an effective method for SSB pretreatment to enhance biomass conservation.

Enhancing Enzymatic Hydrolysis and Delignification of Sugarcane Bagasse Using Different Concentrations of Sodium Alkaline Pretreatment

Lignin, being highly resistant, needs to be eliminated in the process of extraction of soluble reducing sugar and bioethanol production from lignocellulosic biomass. In the present work, pretreatment of sugarcane bagasse (SCB) was performed using NaOH of various concentrations (1-5%) to facilitate delignification. The hydrolysis efficiency of pretreated SCB was evaluated at different reaction times by the production of reducing sugar using the Cellic CTec2 enzyme. The maximum cellulose content of 57.6% and lignin removal of 62.04% were observed with 2% sodium hydroxide at 121°C autoclaved for 60 min. The hemicellulose content decreased with increasing NaOH concentration with the maximum decrease of 13.6% from native bagasse having 26.5% xylan content. The microstructure, morphology, and chemical composition of SCB were analyzed using Field Emission Scanning Electron Microscopy (FESEM), Fourier Transform InfraRed (FTIR), and XRD. The hydrolysis with 10 FPU.g-1 of enzyme at 48 h of reaction time shows a maximum yield of 12.34 g.L-1 corresponding to 55.53 ± 0.45% at 2% NaOH pretreated SCB. This study claims that lignin components exhibited the highest susceptibility to NaOH pretreatment, which directly affects enzymatic hydrolysis.

Monocyclic aromatic hydrocarbons production from NaOH pretreatment metallized food plastic packaging waste through microwave pyrolysis coupled with ex-situ catalytic reforming

Metallized food plastic packaging waste (MFPPW), as found in packaging bags like potato chips and coffee, presents an intricate structural and compositional complexity, rendering its recycling considerably more challenging in comparison to pure plastic packaging. In this work, a process route to produce monocyclic aromatic hydrocarbons (MAHs) from caustic (NaOH) treatment MFPPW through microwave pyrolysis coupled with ex-situ catalytic reforming was proposed. NaOH pretreatment disrupted the chemical bonds between the plastic layers and aluminum layer, reducing the complexity of the subsequent pyrolysis reaction. The removal of the aluminum layer diminished its shielding effect on the microwave, and enhanced the efficient conversion of the microwave energy into heat energy, thus accelerating the pyrolysis of the remaining plastic. After pretreatment, the activation energy for the pyrolysis reaction decreased from 250.55 kJ/mol to 189.70 kJ/mol, and the MAHs content of the liquid oil increased. The highest MAHs content of 80.50% was achieved with an HZSM-5 (Si/Al = 50) zeolite catalyst, pyrolysis temperature of 550°C, and catalysis temperature of 550°C. The unique characteristics of the MFPPW demonstrate its suitability for MAHs production. MFPPW is predominantly composed of PP and PET polymers. PP, as a hydrogen-rich plastic, provides abundant hydrogen-rich free radicals to the PET and promotes hydrogen transfer reactions, thus facilitating the formation of MAHs. Following pretreatment, these two polymers come into closer contact, further enhancing their synergy. This study provides valuable insight into waste management and recovery for metallized food plastic packaging waste.

Effect of alkaline pretreatment on the characteristics of barley straw and modeling of methane production via codigestion of pretreated straw with sewage sludge

Straw pretreatment enhances the cellulose accessibility and increases the methane yield from anaerobic digestion. This study investigated the effects of alkali pretreatments with different chemical agents (NaOH, KOH, and Na2CO3) on the physicochemical and thermal characteristics of barley straw, as well as methane production from codigestion with sewage sludge. Artificial neural network modeling with a feedforward neural network (FFNN) and slime mold optimization (SMO) techniques were used to predict methane production. NaOH pretreatment was shown to be the best pretreatment for removing hemicellulose and lignin and for increasing the cellulose accessibility. Moreover, there was a 2.57-fold higher level of methane production compared to that from codigestion with untreated straw. The removal ratios for the total solids, volatile solids, and chemical oxygen demand reached 59.3, 67.2, and 73.4%, respectively. The modeling results showed that the FFNN-SMO method can be an effective tool for simulating the methane generation process, since training, validating, and testing produced very high correlation coefficients. The FFNN-SMO accurately predicted the amount of methane produced, with an R2 of 0.998 and a 3.1×10-5 root mean square error (RMSE).