Alkaline Hydrothermal Treatment Research Articles

Improving the adsorption of cloud concrete stone porous aggregate to phase change materials by alkali modification

In this paper, the pore structure of cloud concrete stone (CCS) was optimized by alkaline hydrothermal treatment to improve its adsorption capacity for phase change materials (PCMs), thus enhancing the heat storage effect of phase change composite aggregates. The results showed that the adsorption rate of CCS modified by alkaline solution for 36 h was 21.49%, which increased by 30.64% relative to that without modification. The macroscopic and microscopic morphology showed that the 24-hour modified CCS appeared small cracks in the surface and the internal pores became more numerous. The 48-hour modified CCS appeared exfoliated on the surface and the internal pores and cracks increased. Hydrothermal treatment changes the pore structure of CCS, making it more conducive to the adsorption of PCM.

Effects of Preheating and Alkaline Roasting on Gangue Removal During the Alkaline Hydrothermal Treatment of Low-Grade Iron Ores

Effects of Preheating and Alkaline Roasting on Gangue Removal During the Alkaline Hydrothermal Treatment of Low-Grade Iron Ores

HUMIC ACIDS: PROPERTIES, STRUCTURE, AND APPLICATION

Humic substances (HSs) are a diverse class of natural compounds with no fixed chemical composition, formed from plant and microbial residues through the action of environmental factors and living organisms over many years. Despite extensive research spanning two centuries, the complex and variable nature of HSs' structure remains a subject of scientific inquiry. These substances, notably humic acids, fulvic acids, and humin, play crucial roles in ecological and environmental processes due to their abundant functional groups and resilience to biodegradation. This review explores the intricate structure and properties of HSs, their classification, and their occurrence in nature. It highlights the different models proposed to describe the structural fragments of humic acids, emphasizing their aromatic cores and diverse functional groups. The variability in the molecular weight distribution of HSs, attributed to their polydisperse nature, is also discussed, along with methods used for their determination, such as exclusion chromatography. Furthermore, the elemental and functional compositions of humic acids are examined, detailing their acid-base properties and capacity for heavy metal complexation. The synthesis of HSs from natural sources, such as soil, peat, coal, and artificial processes, is covered, showcasing methods like alkaline extraction and hydrothermal treatment. Recent advancements in artificial humification, including oxidative ammonolysis and Fenton reagent-based oxidation, are reviewed for their potential in producing environmentally friendly humic materials from lignin and waste biomass. The study concludes by underscoring the environmental significance and practical applications of HSs, particularly in agriculture, soil conditioning, and environmental remediation. The diverse properties and synthesis methods of HSs make them promising candidates for sustainable material production and environmental management. Humic acids are versatile compounds beneficial for human health due to their potent antioxidant properties, immune-modulating effects, and support for gastrointestinal health and detoxification. Structurally diverse, they feature groups like carboxyl, phenolic hydroxyl, quinones, ketonic carbonyls, amino, and sulfhydryl, contributing to their stability and amphiphilic nature. In pharmaceutical applications, they show promise for drug delivery, antioxidant therapies, wound healing, antimicrobial actions, and biofilm disruption, underlining their biocompatibility and safety. Key words:

Kinetics and Mechanism of SiO2 Extraction from Acid-Leached Coal Gangue Residue by Alkaline Hydrothermal Treatment.

Acid-leached gangue residue is produced after the gangue extraction of metal ions; the main component is silicon, which can be used to extract silica. To ascertain the kinetics and mechanism of silica extraction from acid-leached coal gangue residue, this study explored the effects of the NaOH concentration, solid-to-liquid ratio, reaction temperature, and reaction time on the extraction process. The optimized conditions, determined through this investigation, involved a NaOH concentration of 4 mol/L, a reaction time of 4 h, a solid-to-liquid ratio of 1:4, and a reaction temperature of 180 °C, yielding a SiO2 extraction ratio of 90.16%. Additionally, the leaching kinetics of silica in a NaOH solution were examined using three kinetic equations from the "unreacted shrinking core model". The results revealed that the control type of the leaching process was the "mixing control", and the apparent activation energy was determined to be 52.36 kJ/mol.

Optimizing alkaline hydrothermal treatment for biomimetic smart metallic orthopedic and dental implants

Orthopedic and dental implant failure continues to be a significant concern due to localized bacterial infections. Previous studies have attempted to improve implant surfaces by modifying their texture and roughness or coating them with antibiotics to enhance antibacterial properties for implant longevity. However, these approaches have demonstrated limited effectiveness. In this study, we attempted to engineer the titanium (Ti) alloy surface biomimetically at the nanometer scale, inspired by the cicada wing nanostructure using alkaline hydrothermal treatment (AHT) to simultaneously confer antibacterial properties and support the adhesion and proliferation of mammalian cells. The two modified Ti surfaces were developed using a 4 h and 8 h AHT process in 1 N NaOH at 230 °C, followed by a 2-hour post-calcination at 600 °C. We found that the control plates showed a relatively smooth surface, while the treatment groups (4 h & 8 h AHT) displayed nanoflower structures containing randomly distributed nano-spikes. The results demonstrated a statistically significant decrease in the contact angle of the treatment groups, which increased wettability characteristics. The 8 h AHT group exhibited the highest wettability and significant increase in roughness 0.72 ± 0.08 µm (P < 0.05), leading to more osteoblast cell attachment, reduced cytotoxicity effects, and enhanced relative survivability. The alkaline phosphatase activity measured in all different groups indicated that the 8 h AHT group exhibited the highest activity, suggesting that the surface roughness and wettability of the treatment groups may have facilitated cell adhesion and attachment and subsequently increased secretion of extracellular matrix. Overall, the findings indicate that biomimetic nanotextured surfaces created by the AHT process have the potential to be translated as implant coatings to enhance bone regeneration and implant integration.Graphical

Enhanced Fenton-like catalysis via interfacial regulation of g-C3N4 for efficient aromatic organic pollutant degradation

For the efficient degradation of organic pollutants with the goal of reducing the water environment pollution, we employed an alkaline hydrothermal treatment on primeval g-C3N4 to synthesize a hydroxyl-grafted g-C3N4 (CN-0.5) material, from which we engineered a novel Fenton-like catalyst, known as Cu–CN-0.5. The introduction of numerous hydroxyl functional groups allowed the CN-0.5 substrate to stably fix active copper oxide particles through surface complexation, resulting in a low Cu leaching rate during a Cu–CN-0.5 Fenton-like process. A sequence of characterization techniques and theoretical calculations uncovered that interfacial complexation induced charge redistribution on the Cu–CN-0.5 surface. Specifically, some of the π electrons in the tris-s-triazine units were transferred to the copper oxide particles along the newly formed chemical bonds (C(π)-O-Cu), forming a π-deficient area on the tris-s-triazine plane near the complexation site. In a typical Cu–CN-0.5 Fenton-like process, a stable π-π interaction was established due to the favorable positive-negative match of electrostatic potential between the aromatic pollutants and π-deficient areas, leading to a significant improvement in Cu–CN-0.5's adsorption capacity for aromatic pollutants. Furthermore, pollutants also delivered electrons to the Cu–CN-0.5 Fenton-like system via a “through-space” approach, which suppressed the futile oxidation of H2O2 in reducing the high-valent Cu2+ and significantly improved the generation efficiency of •OH with high oxidative capacity. As expected, Cu–CN-0.5 not only exhibited an efficient Fenton degradation for several typical aromatic organic pollutants, but also demonstrated both a low metal leaching rate (0.12 mg/L) and a H2O2 utilization rate exceeding 80%. The distinctive Fenton degradation mechanism substantiated the potential of the as-prepared material for effective wastewater treatment applications.

Alkaline hydrothermal treatment of gentamycin mycelial residues: characteristics of disintegration, solid-state fermentation, and antibiotic resistance genes reduction

Alkaline hydrothermal treatment of gentamycin mycelial residues: characteristics of disintegration, solid-state fermentation, and antibiotic resistance genes reduction

Study on the Synthesis and Photocatalytic Performance of Modified TiO2 Supported by G‐C3N4 in the Degradation of 2,4‐Dichlorophenoxyacetic Acid

AbstractThe impact of alkaline hydrothermal treatment on the structure and morphology of Degussa P25 was evaluated. The modification results in a larger surface area, which improves 2,4‐dichlorophenoxyacetic acid (2,4‐D) adsorption capacity and has a remarkable effect on the 2,4‐D photocatalytic degradation. The 30 % mod. TiO2/g‐C3N4 and 50 % mod.TiO2/g‐C3N4 composites were made by combining the treated Degussa P25 with g‐C3N4 at mass ratios of 30 % and 50 %. Using XRD, SEM, EDX, BET, UV‐vis DRS, and PL, the synthesized materials were physically characterized. When compared to their pure components, the composites show a longer “lifetime” of charge carriers and a reduced energy band gap. The 2,4‐D degradation under visible light irradiation (λ&gt;400 nm) was used to assess their photocatalytic activity. The influence of pH and 2,4‐D initial concentration were investigated. The enhanced 2,4‐D degradation efficiency of more than 80 % is ascribed to the cooperative photocatalytic action of mod.TiO2 and g‐C3N4. Both ⋅OH, O2⋅− radicals and h+ were the ROS dominating the degradation of 2,4‐D under investigated experimental circumstances. The 2,4‐D photocatalytic degradation follows pseudo‐first order kinetics. The findings of this work indicate that Degussa P25/g‐C3N4‐based photocatalysts may be employed, depending on the pH conditions, in the wastewater treatment.

Optimization of alkaline hydrothermal treatment for humic acids production from corn straw digestate using the response surface methodology

Anaerobic digestion (AD) technology was widely used for treating waste biomass, during which a large amount of lignin-rich digestate would be produced, needing further treatment. In this study, corn straw digestate (CSD) was used as raw material for hydrothermal humic acids (HHA) producing through alkaline hydrothermal treatment (AHT). According to the response surface analysis, the optimal reaction conditions were determined to be 156°C, 2 hours, and 5% KOH (% of the dry digestate), resulting in a HHA yield of 40.3 wt%. Structural characterization analysis showed the produced HHA had abundant oxygen-containing functional groups (e.g., C-O and CO) in HHA and aromatic structures, which also showed good thermal stability. By AHT with hemicellulose and lignin, the HHA yields reached 79.2%. Hemicellulose and lignin proved to be important components for HHA formation. In addition, the protein content in the EPS extraction solution of HC was significantly reduced compared to CSD, indicating that the dewaterability of the digestate were improved after AHT. This technique provides a feasible approach for the further utilization of residual lignocellulosic materials after anaerobic digestion.

Exceptional levofloxacin adsorption/photo-regeneration cycles using nanosheets-like hollow TiO2 adsorbent: Adsorption performance and mechanism

Exploring efficient adsorbents still remains an important challenge due to the poor efficiency of the reported adsorbents for the adsorption of antibiotics. Herein, we design and prepare a novel nanosheets-like hollow TiO2 (NHT) adsorbent by using hollow TiO2 as a precursor through alkaline hydrothermal treatment. Adsorption results show that NHT exhibits a high adsorption percentage (98.05%) within 20 min and a maximum adsorption uptake of 24.51 mg/g for Levofloxacin (LVOF) pollutant (10 mg/L, 50 mL), which is 17 times higher than that (1.4 mg/g) of pristine hollow TiO2 (HT). Notably, NHT realizes >91% of the adsorption percentage for LVOF pollutant after the tenth run only through photo-regeneration without extra post-treatments, effectively overcoming the disadvantages of harsh regeneration procedures for most of the existed adsorbents. Adsorption data and the performance characterizations present deep insights into adsorption mechanism, which reveals that pore filling effect, hydrogen-bond interactions, and electrostatic attraction are the key parameters for the excellent adsorption of LVOF by NHT. Therefore, the present study can provide a promising direction for the fabrication of efficient adsorptive photocatalyst by using low-cost TiO2 as a precursor.

Enhancing the immunomodulatory osteogenic properties of Ti-Mg alloy by Mg2+-containing nanostructures.

Facilitating an appropriate immune response is crucial for promoting bone tissue regeneration upon biomaterial implantation. In this study, the Mg2+-containing nanostructures on the surface of Ti-1.25Mg alloy were prepared by a one-step hydrothermal reaction method via regulating pH value to enhance the immunomodulatory osteogenic properties of Ti-Mg alloys. In neutral (HT7) or alkaline (HT9) hydrothermal treatment (HT) solution, the size of MgTiO3 nanostructures formed on the surface of Ti-1.25Mg alloy is smaller than that in acidic HT solution (HT5), and lamellar Mg(OH)2 nanostructures are found in HT7 and HT9. In addition, the sample surface has a lower roughness and higher wettability with increasing pH value. The Mg2+-containing nanostructures on the Ti-1.25Mg alloy inhibited inflammatory response by promoting the polarization of M2 macrophages, thereby promoting osteogenesis in vitro. The micro-CT and histological assessment proved that the regeneration of bone defect was faster in HT7 than the Ti-1.25Mg in vivo. Mechanically, Mg2+-containing nanostructures can mediate the immune response of macrophages via upregulating integrins α5β1 and inhibiting Toll-like receptors (TLR-4), subsequently inhibiting the NF-κB signaling pathway. Overall, osteoimmunity-regulating Mg2+-containing nanostructures on Ti-1.25Mg present a promising biomaterial for bone repair.

Facet-dependent adsorption of safranin dye and phosphate ions by synthesized hematite nanorods derived from natural lateritic iron ore: steric and energetic investigations

Natural lateritic iron was subjected to a morphological transformation process based on a simple alkaline hydrothermal treatment process, producing well-developed hematite nanorods (HM24).

Alkaline Hydrothermal Treatment of Chabazite to Enhance Its Ammonium Removal and Recovery Capabilities through Recrystallization

The treatment of chabazite (CHA), a natural zeolite, with the alkaline hydrothermal method to improve its ion-exchange capacity is a widely adopted route by environmental scientists for the purpose of better ammonium (NH4+) removal from wastewater. This work addresses a noteworthy trend in environmental science, where researchers, impressed by the increased ion-exchange capacity achieved through alkaline hydrothermal treatment, often bypass the thorough material characterization of treated CHA. The prevalent misconception attributes the improved features solely to the parent zeolitic framework, neglecting the fact that corrosive treatments like this can induce significant alterations in the framework and those must be identified with correct nomenclature. In this work, alkaline-mediated hydrothermally treated CHA has been characterized through X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), solid-state magic-angle spinning nuclear magnetic resonance (MAS-NMR), high-resolution transmission electron microscopy (HRTEM), and energy-dispersive X-ray spectroscopy (EDS) and it is concluded that the treated samples have been transformed into a desilicated, aluminum (Al)-dense framework of analcime (ANA) with a low silica–alumina ratio and with a strikingly different crystal shape than that of parent CHA. This treated sample is further examined for its NH4+ removal capacity from synthetic wastewater in a fixed-bed column arrangement. It achieved a maximum NH4+ removal efficiency of 4.19 meq/g (75.6 mg/g of NH4+), twice that of the parent CHA. Moreover, the regeneration of the exhausted column yielded a regenerant solution, with 94% reclaimed NH4+ in it, which could be used independently as a nitrogenous fertilizer. In this work, the meticulous compositional study of zeolitic materials, a well-established practice in the field of material science, is advocated for adoption by environmental chemists. By embracing this approach, environmental scientists can enhance their comprehension of the intricate changes induced by corrosive treatments, thereby contributing to a more nuanced understanding of zeolitic behavior in environmental contexts.

Titanium-based substrate modified with nanoenzyme for accelerating the repair of bone defect

Titanium (Ti) and titanium alloy are the most common metal materials in clinical orthopedic surgery. However, in the initial stage of surgery and implantation, the production of excessive reactive oxygen species (ROS) can induce oxidative stress (OS) microenvironment. OS will further inhibit the growth of new bone, resulting in surgical failure. In this study, based on the fact that nanoscale manganese dioxide (MnO2) can show H2O2-like enzyme activity, a MnO2 nanocoating was prepared on mciro-nano structured surface of Ti substrate via a two-step method of alkaline thermal and hydrothermal treatment. The results of scanning electron microscopy (SEM), X-ray diffractometer (XRD) and X-ray photoelectron spectroscopy (XPS) showed that the nano-MnO2 coating was successfully fabricated on the surface of Ti substrate. The results of measurement of H2O2, dissolved O2 and intracellular ROS in vitro showed that the treated Ti substrate could efficiently eliminate H2O2 and reduce ROS. Furthermore, the modified Ti substrate could promote the early adhesion, proliferation and osteogenic differentiation of MSCs, which was demonstrated by experimental results of cell morphology, cell viability, alkaline phosphatase, collagen, and mineralization deposition. The results of quantitative real-time polymerase chain reaction (qRT-PCR) of MSCs adhered the modified Ti substrate showed that the expression of genes related to osteogenic differentiation significantly increased. More importantly, the modified Ti implant could eliminate ROS at the injury site, reduce OS and promote the regeneration of bone tissue, which was demonstrated via hematoxylin/eosin, Masson's trichrome and immunohistochemical staining. In conclusion, the modified Ti implant presented here had the effect of reducing OS and promoting osseointegration. Relevant research ideas and results provide new methods for the research and development of functional implants, which have potential application value in the field of orthopedics.

Morphological evolution and biocorrosion response of a hierarchical micro- nano-structured Ti alloy: Physico-chemical characterization and electrochemical studies

In the present study, hierarchically architectured micro/nano-scale surface topography inspired from the leaves of Euphorbia myrsinites was fabricated on Ti-6Al-4V ELI alloy through laser micro-texturing (LT) followed by alkaline hydrothermal treatment (HT). The hybrid (LT + HT) surface revealed distinct multi-scaled morphological features differing from individually treated LT and HT surfaces. Alongside topographical cues, the evolved elemental and phase constitution also influenced the wettability, mechanical and corrosion properties. The (LT + HT) surface exhibited improved hydrophilicity and reduced surface stiffness of ~14.82 GPa (closely mimicking human bone-tissue), attributing to a hydrothermally-induced porous titania-layer extending up to a few microns depth. Corrosion tests in Hank's solution revealed that HT alone couldn't substantially improve the corrosion resistance as compared to polished surface (control). Integrating LT with HT not only altered the surface topography, but also introduced a relatively denser barrier-oxide layer (laser-induced oxidation) that transformed into a stable anatase-rich phase structure upon hydrothermal etching and subsequent annealing. Both LT and (LT + HT) recorded reduced corrosion current densities and suppressed corrosion rates, but (LT + HT) performed substantially better in the anodic polarization regime (till 2 V), with passivation current densities reduced by at least two orders of magnitude. AC impedance studies affirmed the role of an adsorptive nanostructured outer-layer in (LT + HT) towards accelerating the passivation kinetics, while the inner barrier layer imposed higher charge transfer resistance. Also, better biomineralization ability was observed in (LT + HT) after 30 days immersion in Hank's solution, with Ca: P (at. ratio) ~1.4, thereby indicating higher propensity of apatite nucleation.

Effects of various factors on gangue removal in alkaline hydrothermal treatment of iron ores

The upgrading technology of low-grade iron ores by alkaline treatment was investigated in this study. The basic experiments (evaluation of the effects of solvent types, treatment temperature, holding time, solvent concentration, particle size, and solid–liquid ratio) were carried out with the alkaline hydrothermal treatment in a small batch-type reactor. The gangue removal rate in the 5 M NaOH hydrothermal treatment increased with the increase in treatment temperature, and about 90% of Si, Al, and P could be removed below 250 °C. The gangue removal rate tended to increase with the increase in NaOH concentration, the decrease in particle size, and the decrease in solid–liquid ratio. The order of the removal rate was P < Al < Si. The optimum conditions for alkaline hydrothermal treatment were found to be as follows: particle size, <500 μm; solvent, NaOH; solvent concentration, >0.1 M; solid–liquid ratio, ≤1.2; heating temperature, ≥150 °C; and holding time, 30 min. According to the results of XRD and N2 adsorption measurements of the treated ores, the gangue removal from low-grade iron ores, the improvement of Fe quality (higher Fe content), and densification were possible by alkaline hydrothermal treatment.

Unlocking the potential of humic acid production through oxygen-assisted hydrothermal humification of hydrochar

The utilization of biomass as a raw material and production of hydrothermal humic acid (HHA) through hydrothermal method using hydrochar as an intermediate product is a sustainable approach for the preparation of humic acid. In this study, hydrochar was prepared through acid hydrothermal treatment of corn straw and then oxygen was introduced to alkaline hydrothermal treatment of hydrochar to improve the yield of humic acid. It was discovered that an oxygen pressure of 5 bar could significantly enhance the yield of HHA from 41.9 wt% to 49.2 wt% at a hydrothermal temperature of 180 °C, while oxygen pressures of 10 bar and 20 bar led to a decrease in HHA yield (41.5 wt% to 28.2 wt%). Oxygen addition could also reduce the energy input and the economic cost required for hydrothermal reactions. Further study revealed that the increase in HHA yield was the oxidation of aliphatic carbon in the solid residue derived from hydrochar by oxygen, which became part of the HHA and resulted in weaker fluorescence intensity of the HHA. However, excessive oxygen could increase the oxygen-containing functional groups of the HHA while also causing further cleavage of macromolecular components with high carbon numbers, generating smaller molecules that partially dissolve in the liquid phase. The HHA synthesized at an oxygen pressure of 5 bar showed good performance in promoting Chinese cabbage seedlings growth and was superior to the HHA synthesized in the absence of oxygen in terms of cadmium adsorption. This study proved an improved hydrothermal humification method and provided technical support for industrial applications.

Efficient enrichment of platinum group metals from spent automotive catalysts by alkaline hydrothermal treatment and the subsequent acid leaching method

Spent automotive catalysts (SAC) is the most important secondary resource for the recovery of platinum group metals (PGMs). This paper demonstrates that the acid-resistant and alkali-resistant cordierite carrier can be transformed into hydroxysodalite by a alkaline hydrothermal treatment (AHT), which can then be dissolved by subsequent acid leaching (AL) to enrich PGMs. Experiments were conducted to assess the influencing factors and the optimal conditions were determined as follows: holding temperature of 150 °C; NaOH to raw material mass ratio 10:10; holding time of 60 min; liquid to solid ratio of 3:1, and stirring speed of 400 rpm. The residue ratio in the AHT process was 132.57% under optimized conditions. The total residue ratio was 18.68% under fixed acid leaching experimental conditions of holding temperature of 60 °C, liquid to solid ratio of 15:1, holding time of 60 min, stirring speed of 400 rpm, and hydrochloric acid concentration of 2.5 mol·L-1. The contents of Pt, Pd, and Rh in the enriched residue reached 650.50, 2131.54, and 405.28 g·t−1, respectively, and the corresponding enrichment times were 7.13, 7.25, and 7.07. The additions of sodium formate before the AHT and aluminum powder during the AL were found to effectively inhibit PGMs leaching. The losses of Pt, Pd, and Rh throughout the entire process were only 2.77%, 1.89%, and 4.28%, respectively.

Alkaline hydrothermal activation of molybdenum tailings to prepare one-part geopolymer: Activation mechanism and strength

Molybdenum tailings (MT) are solid waste from molybdenum ore beneficiation, which can cause environmental pollution when stored in tailings ponds for a long time. The use of alkaline hydrothermal activation to improve the low reactivity of MT as an active precursor to one-part geopolymers is a novel way to resource MT. This paper evaluates the feasibility of alkaline hydrothermal activation of MT and investigates the mechanical properties of the activated MT base polymer prepared by a one-part method. The results showed that alkaline hydrothermal activation greatly promoted the dissolution of silicon in MT, weakened the crystal properties of quartz phase in MT and destroyed the original structure of MT. The amorphous sodium aluminosilicate on the surface of activated MT dissolves in water and provides an alkaline environment for the geological polymerization reaction. Combined with the analytical results of XRD and FTIR, the alkaline hydrothermal activation of MT was controlled by the optimal sodium hydroxide solution concentration, activation temperature and activation time of 5 M NaOH, 200 °C and 4 h, respectively. Based on this, the one-part geopolymer was prepared directly by adding water to activated MT 5-4-200 and slag, and the compressive strength can be improved. SEM and EDS results show that alkaline hydrothermal activation treatment renders inert MT reactive and the reaction product of activated MT and slag forming a one-part geopolymer is an amorphous C(N)A-S-H gel.

Mild Nitric Acid Treatments to Produce Nitrocellulose from Kapok Fiber (Ceiba Pentandra)

Kapok (Ceiba pentandra) is one of the natural fibrous sources with a high content of cellulose. The natural kapok used contains 54.3% of cellulose, 11.3% of hemicellulose, and 19.11% of lignin. Kapok is a potential material to be explored by isolating the fiber, then converting into nitrocellulose. The effect of nitric acid concentration on the nitration process and characterization of material were investigated. Kapok fiber was isolated by delignification and bleaching process. Delignification was done in the presence of 5% (w/v) of NaOH and 30% (v/v) of H2O2 for alkaline and acid hydrothermal treatment, respectively. Kapok was washed until neutral pH and dried in an oven at 100 oC for 4 h to get kapok fiber (CK). For the nitration process, CK 5% (w/w) was added to a solution of 15% (v/v) phosphoric acid and variation of 15%, 20%, and 25% of nitric acid. The mixture was stirred at 10 oC, 300 rpm, for 30 min. The solid CK was separated and poured into hot water for 5 min and continuously washed with demineralized (DI) water and sodium hydrogen carbonate until neutral pH. The nitrocellulose (KN) was produced after the material dried. The smooth surface of fiber and diameter around 14.5-19.1 µm was changed into a plat fiber of 13.3-21.2 µm after hydrothermal treatment. The crystallinity index (CrI) of CK was increased up to 58.17% based on X-Ray Diffraction (XRD) observation. The degree of substitution (DS) was calculated by data spectra of Fourier Transform-Infra Red (FT-IR) analysis of a specific functional group for N-O and C-O stretching vibrations. The DS optimum value was achieved at about 0.885 at concentration of 20% nitric acid (NK20). The synthesis of nitrocellulose kapok fiber-based has potential as a functional material.