Nitric Acid Concentration Research Articles

Kinetics of nitric acid leaching of bornite and chalcopyrite

The paper presents a study of the process of nitric acid dissolution of the natural minerals chalcopyrite and bornite. The influence of various parameters, including temperature, nitric acid concentration and particle sizes, on this process was examined. Based on the data obtained, the values of apparent activation energy (57.41 and 42.98 kJ/mol for chalcopyrite and bornite, respectively), empirical orders with respect to nitric acid (1.62 and 1.57 for chalcopyrite and bornite, respectively) and with respect to particle size (–1.16 and –2.53 for chalcopyrite and bornite, respectively) were calculated using the shrinking core model. Generalized kinetic equations for the dissolution process of both minerals were derived. Based on the calculations performed, it was suggested that the dissolution processes of chalcopyrite and bornite under these conditions are limited by internal diffusion.

Colloid-chemical properties of surfactant–nitric acid–water systems

The behavior of the surfactants Tween 80, SaS and alkyl betaine in aqueous and nitric acid environments as promising additives for nitrate leaching of hard-to-process ore concentrates of non-ferrous metals was studied. The influence of surfactant concentration (0.04–1.28 g/dm3), nitric acid concentration (0.1–10 g/dm3) and temperature (295–343 K) on the surface tension, critical micelle concentration (CMC), pH and optical density of aqueous surfactant solutions and surfactant–HNO3–H2O systems was found. The critical micelle concentration of the surfactants used was estimated. A positive effect of nitric acid on the surface activity of surfactants was discovered, which manifests itself in a decrease in both the CMC and the surface tension at the liquid–gas interface. The values of surface activity and Gibbs energy of surfactant micelle formation in aqueous and nitric acid media were calculated. Associative processes in the solutions and compositions were confirmed by measuring the optical density of the systems under study.

Efficient Adsorption of Ammonia by Surface-Modified Activated Carbon Fiber Mesh.

In view of the characteristics and risks of ammonia, its removal is important for industrial production and environmental safety. In this study, viscose-based activated carbon fiber (ACF) was used as a substrate and chemically modified by nitric acid impregnation to enhance the adsorption capacity of the adsorbent for ammonia. A series of modified ACF-based adsorbents were prepared and characterized using BET, FTIR, XPS, and Boehm titration. Isotherm tests (293.15 K, 303.15 K, 313.15 K) and dynamic adsorption experiments were performed. The characterization results showed that impregnation with low concentrations of nitric acid not only increased the surface acidic functional group content but also increased the specific surface area, while impregnation with high concentrations of nitric acid could be able to decrease the specific surface area. ACF-N-6 significantly increased the surface functional group content without destroying the physical structure of the activated carbon fibers. The experimental results showed that the highest adsorption of ammonia by ACFs was 14.08 mmol-L-1 (ACF-N-6) at 293 K, and the adsorption capacity was increased by 165% compared with that of ACF-raw; by fitting the adsorption isotherm and calculating the equivalent heat of adsorption and thermodynamic parameters using the Langmuir-Freundlich model, the adsorption process could be found to exist simultaneously. Regarding physical adsorption and chemical adsorption, the results of the correlation analysis showed that the ammonia adsorption performance was strongly correlated with the carboxyl group content and positively correlated with the relative humidity (RH) of the inlet gas. This study contributes to the development of an efficient ammonia adsorption system with important applications in industrial production and environmental safety.

Targeted production of aromatics from corn stover and high-density polyethylene composite pyrolysis over nitric acid modified biochar catalyst

The pore structure and active functional groups of biochar play a critical role in determining its catalytic performance. In this study, coconut shell-derived biochar underwent modification with nitric acid to serve as a catalyst in the pyrolysis of a corn stover/high-density polyethylene composite (CHC) in a fixed bed reactor. The effects of nitric acid concentration, treatment time, and temperature on the catalytic performance of biochar were investigated, specifically targeting the production of aromatics during the CHC pyrolysis process. The results revealed that a higher modification temperature, a longer treatment time, and a lower concentration of nitric acid effectively enhanced the catalytic performance of biochar in producing aromatics, while simultaneously reducing the formation of aliphatics and oxygenates. The highest yield of aromatic hydrocarbons (56.1 %) was obtained under the conditions of a modification temperature of 90 °C, a modification time of 10 h, and a nitric acid concentration of 1.0 mol/L. Furthermore, the nitric acid-modified biochar catalyst promoted the production of CO and CH4 during the CHC pyrolysis process, indicating that the decarbonylation and end-chain breaking reactions were enhanced due to the presence of abundant oxygen-containing functional groups introduced by nitric acid oxidation.

Insight into the novel low cost green air pollution monitoring and control systems: A technological solution from concept to market

Nitrogen oxide emissions, also referred to as NOx including NO and NO2 are hazardous to human life and have negative effects on the environment. Wet and dry treatments have both been explored as methods to significantly minimize these emissions. The wet process offers several benefits, the most notable of which are the flue gas adaptability, low operating temperatures, and the lack of poisoning and catalyst inactivation. In the research work, a NOX filter is being developed, with composite material for better transparency and non-reactive nature. Mechanical and electronic components have been employed to develop a stable and rigid experimental setup that effectively handles environmental challenges. Different tests are performed during performance analysis with known quantities of NOX through cylinders and varied the flow rate of ambient air. The concentration of NOX, H2O2, nitric acid, and other parameters were captured to get the optimum configuration that will provide maximum efficiency. The envisaged cost of implementing a solar tree-based air pollution monitoring and control system is estimated at $2796. This cost projection serves to exemplify the techno-economic analysis of the system, showcasing its potential to contribute to a cleaner environment and facilitate renewable energy utilization. The different financial model payback periods of the system are from 3.12 to 5.21 years. The developed system benefits people with respiratory health issues, elderly people, children, and infants, sports enthusiasts, traffic police persons, street hawkers or vendors, and people living in areas where the pollution level is high.

Mixed nitrate and metal contamination influences operational speciation of toxic and essential elements

Environmental contamination constrains microbial communities impacting diversity and total metabolic activity. The former S-3 Ponds contamination site at Oak Ridge Reservation (ORR), TN, has elevated concentrations of nitric acid and multiple metals from decades of processing nuclear material. To determine the nature of the metal contamination in the sediment, a three-step sequential chemical extraction (BCR) was performed on sediment segments from a core located upgradient (EB271, non-contaminated) and one downgradient (EB106, contaminated) of the S-3 Ponds. The resulting exchangeable, reducing, and oxidizing fractions were analyzed for 18 different elements. Comparison of the two cores revealed changes in operational speciation for several elements caused by the contamination. Those present from the S-3 Ponds, including Al, U, Co, Cu, Ni, and Cd, were not only elevated in concentration in the EB106 core but were also operationally more available with increased mobility in the acidic environment. Other elements, including Mg, Ca, P, V, As, and Mo, were less operationally available in EB106 having decreased concentrations in the exchangeable fraction. The bioavailability of essential macro nutrients Mg, Ca, and P from the two types of sediment was determined using three metal-tolerant bacteria previously isolated from ORR. Mg and Ca were available from both sediments for all three strains; however, P was not bioavailable from either sediment for any strain. The decreased operational speciation of P in contaminated ORR sediment may increase the dependence of the microbial community on other pools of P or select for microorganisms with increased P scavenging capabilities. Hence, the microbial community at the former S-3 Ponds contamination site may be constrained not only by increased toxic metal concentrations but also by the availability of essential elements, including P.

Wet removal of elemental mercury by acid-assisted electrochemical oxidation method

As a global pollutant, mercury emission is increasingly restricted in recent years. It is urgent to explore a new and efficient mercury removal technology for coal-fired power plants. A new acid-assisted electrochemical oxidation (AEO) technique for mercury removal was proposed using platinum plate as cathode and fluorine-doped tin dioxide (FTO) glass as anode. The effects of acid type, acid concentration, applied direct current (DC) voltage, electrolyte type, SO2, NO and O2 on the Hg0 removal efficiency were carried out. The results indicated that the mercury removal efficiency increased with the increase of DC voltage and nitric acid concentration. When the concentration of nitric acid increased to 0.15 mol/L, the mercury removal efficiency remained unchanged. SO2 and NO inhibited the removal of Hg0 in AEO system, but the inhibition was reversible. Compared with the mercury removal efficiency under single experimental conditions, the mercury removal efficiency of electrochemical oxidation can reach 96% under the experimental conditions of 0.1 mol/L nitric acid and 4V DC voltage, suggesting that the synergistic effect of nitric acid and DC voltage plays a key role. According to the experimental results, the mechanism of Hg0 removal in AEO system was analyzed. At the anode, Hg0 was oxidized by hydroxyl radical (.OH) generated by the oxidation reaction on the anode surface. At the cathode, dissolved oxygen or O2 adsorbed on the surface of Pt is reduced to form anionic superoxide radicals (.O−2). Moreover, parts of .O−2 would produce .OH with the aid of electron at acidic condition. Free radicals capture experiments showed that .O−2 and .OH were the main active substances for the removal of Hg0 by acid-assisted electrochemical method. The research is helpful for the development of effective electrochemical techniques for industrial mercury removal and recycling of industrial acid waste.

Unrevealing the role of the sulfonitric media composition on the design and properties of potato starch-based nitrogen-rich biopolymer

In research of crafting high-energy materials from sustainable sources, this study undertook the synthesis of energetic nitrostarches employing diverse sulfonitric mediums to better assess how they influence the characteristics and performance of potato starch nitrate. Accordingly, a deep exploration of the physicochemical properties, morphology, heat behavior, mechanical sensitivities, and combustion energy of starch nitrate was carried out. The experimental results highlighted that an increase in the nitric acid concentration from 70% to 100% enhanced the density (≥1.71 g/cm3) and the crystallinity of potato starch nitrate, whereas the nitrogen content does not exhibit any evident correlation. Moreover, its short-term stability remains unaffected as a function of nitric acid content, in contrast to the long-term stability together with mechanical sensitivities (Impact Sensitivity ≥ 4 J; Friction Sensitivity ≥ 252 N) that decrease with nitrogen content. The investigation of the thermolysis kinetics of starch nitrate demonstrated a decrease in the activation barrier (Ea) with the increase in nitrogen content. The Ea of high nitrogen content potato starch nitrate is inferior to that of cellulose nitrate, proving the enhanced reactivity of starch nitrate. These findings demonstrated that the elaborated nitrogen-rich potato starch biopolymers display promising features that support their use in high-performance propellant or explosive formulations.

Modification of the Method for the Determination of Zinc Content in Insulins by Atomic Absorption Spectrometry

Scientific relevance. Zinc quantification in insulin active substances and preparations by atomic absorption spectrometry requires a sample preparation procedure using hydrochloric acid, a narcotic and psychotropic precursor. The exclusion of precursors from laboratory practice significantly reduces labour costs during analysis.Aim. This study aimed to modify the pharmacopoeial method for quantifying zinc in insulins with a view to eliminating drug precursors and to evaluate the applicability of the modified method across different insulin preparations.Materials and methods. The study considered insulin active substances and preparations of various types, dosage forms, and strengths. Zinc content determination involved using an Agilent 240FS atomic absorption spectrometer at a characteristic wavelength of 213.86 nm.Results. The authors selected the conditions for elemental analysis (nitric acid concentration, monochromator slit width, and flame stabilisation time) corresponding to the pharmacopoeial requirements for quantifying zinc in insulins (RSD ≤1.4%, standard zinc solution with a concentration of 0.8 mg/dm3, and calibration curve correlation coefficient ≥0.99). The study compared zinc content measurements in the studied insulin samples with hydrochloric acid or nitric acid as a solvent; it did not reveal any significant differences between the results obtained by the pharmacopoeial method and the modified method.Conclusions. The modified method enables analysts to quantify zinc in insulin preparations in various dosage forms without drug precursors.

Comparison of Raman and mid-infrared spectroscopy for quantification of nitric acid in PUREX-relevant mixtures

During the plutonium uranium reduction extraction (PUREX) process, nitric acid facilitates the extraction of actinides from the aqueous phase into the organic phase by forming neutral, organic soluble complexes with tri-n-butyl phosphate (TBP). The concentration of nitric acid is generally measured by titration; however, titration is a time-consuming method that generates significant volumes of additional waste. Optical spectroscopic techniques can be used to perform fast, automated measurements off-line or on-line, without generating any waste. In this work, the effectiveness of Raman and mid-infrared (MIR) spectroscopy has been compared for the first time as an alternative to titration for the quantification of nitric acid in PUREX-relevant mixtures. Samples of 0–12 M nitric acid in the aqueous phase and 0–1.10 M nitric acid in the organic phase (TBP/odourless kerosene (OK)–H2O–HNO3 model system) were analysed and partial least squares (PLS) regression models were built to predict nitric acid concentration. MIR spectra required less pre-processing than Raman spectra and more accurate predictions of nitric acid concentration were obtained for MIR spectroscopy than for Raman spectroscopy, with root mean square error of prediction (RMSEP) values of 0.099 M versus 0.148 M obtained for the aqueous phase and root mean square error of cross validation (RMSECV) values of 0.006 M versus 0.013 M obtained for the organic phase. To investigate the ability to predict nitric acid concentration in the presence of uranyl nitrate, samples containing uranium (0–100 g/L) and nitric acid (0.15–0.64 M) in the organic phase (U-TBP/OK-H2O–HNO3 model system) were analysed by Raman and MIR spectroscopy. The RMSECV was 0.027 M and 0.066 M for MIR and Raman spectroscopy, respectively; these values are higher than those obtained in the absence of uranyl nitrate owing to differences in the experimental approaches employed. Therefore, the results obtained demonstrate that MIR or Raman spectroscopy could be used to measure the concentration of nitric acid in the organic and aqueous phases in the PUREX process.

Impact of Air Refreshing and Cloud Ice Uptake Limitations on Vertical Profiles and Wet Depositions of Nitrate, Ammonium, and Sulfate

AbstractThe impacts of cloud mixing and uptake on wet scavenging are not adequately resolved in global models which can lead to an overestimation of the removal of water‐soluble gases and aerosols from the atmosphere. To address this issue, we develop and implement novel parameterizations to consider the impacts of these processes. Our analysis of vertical profiles of nitric acid, inorganic nitrate, ammonium, and sulfate concentrations during the Atmospheric Tomography Mission periods indicates that air refreshing limitation has a significant impact above 800 hPa, while cloud ice uptake limitation plays an important role above 500 hPa. Incorporating these two processes resulted in a reduction of wet depositions of these species across source regions and a slight increase in their downwind regions. Wet depositions of nitrate, ammonium, and sulfate were reduced in source regions by 22.7%, 8.4%, and 8.3%, respectively and increased in downwind regions by 10.1%, 7.0%, and 4.3%, respectively.

An Integrated Model Combining Mass Transfer and Chemical Reaction for Co-Decontamination Extraction Step of PUREX Process in a Pulsed Extraction Column

ABSTRACT The accurate prediction of the extraction behaviors of various solutes in PUREX reprocessing process is crucial for the operation and implementation of the actual process. In this paper, an integrated model is developed to predict the extraction behaviors of U, Np, Pu, and HNO3 in the co-decontamination step (1A extraction step) in a pulsed extraction column. The model couples several physical and chemical processes, such as countercurrent flow, mass transfer, and chemical reaction. The mass transfer coefficients and the distribution ratios of U(VI), Pu(IV), Np(IV), Np(V), Np(VI), HNO3 and HNO2 can be obtained using this model. In particular, the redox and disproportion reactions of Np are considered in the model, and the flow direction of Np can be judged under various process conditions and the corresponding influential factors can be analyzed. The judgment is based on the yield calculated from the relative concentration profiles of Np(VI), Np(V), and Np(IV) in the two phases. For neptunium to inter 1AP step, it is necessary to select high nitric acid concentration, low nitrite concentration and especially high flow ratio. For neptunium to inter 1AW step, low nitric acid concentration, high nitrite concentration and low flow ratio are needed. Compared with the experimental data, the relative errors of the distribution ratios of various solutes are less than 30%, and the relative errors of the concentrations of U(VI) and Pu(IV) at the outlet of the organic phase are less than 10%, and our model is indicated to be reliable and applicable for co-decontamination step in the PUREX reprocessing process.

Controlled double perovskites for the efficient catalytic combustion of Cl containing VOCs

For catalytic combustion of chlorobenzene (CB), a series of cobalt-based double perovskites La2BCoO6 (BCu, Fe, Ni, Al) were synthesized by sol-gel method. These double perovskites were controllably etched by nitric acid to remove part of surface A-site and improve their catalytic activity for catalytic combustion of CB, toluene and benzene. Crystalline structure, micromorphology, surface composition, redox properties, oxidation state of the catalysts were investigated in detail by various methods. Concentration of nitric acid and the etching time were used to tune the surficial active sites of B and B′ (Cu, Co) whilst maintaining the structure. Among these double perovskites, La2CuCoO6 had the strongest oxidation ability and acidity and showed the best catalytic performance. Temperature for 90% conversion of CB (T90) on La2CuCoO6 etched by 5% nitric acid was 260 °C lower than that of as-prepared La2CuCoO6. T90 for combustion of toluene and benzene is only 240 and 290 °C, respectively. The nitric acid etching also resulted in a change in the surface charge of the Cu, Co sites, provided an oxidation cycle of Cu2++Co2+↔Cu++Co3+, which facilitated the production of surficial active oxygen, accelerated the oxygen mobility and enhanced the catalytic performance. La2CuCoO6 etched by 5% nitric acid showed good catalytic stability over 100 h testing. This work shows a novel, facile approach to prepare efficient and stable catalysts for chloride containing VOCs catalytic combustion.

Triflimide Effect in Solvent Extraction of Rare-Earth Elements from Nitric Acid Solutions by TODGA

ABSTRACT Outer-sphere interactions play an important role in the liquid-liquid extraction and separation of metal ions and they could be used to tune the efficiency and selectivity of recovery. Here, we report the extraction behaviour and separation of trivalent rare-earth elements from aqueous nitric acid solutions with N,N,N’,N’-tetra-n-octyl diglycolamide (TODGA), which was preliminarily contacted with an aqueous solution of N-H acid bis[(trifluoromethyl)sulfonyl]imide (triflimide, HTf2N; Tf = CF3SO2) resulting in an adduct TODGA⋅HTf2N. We examined in detail the extraction system composed of TODGA acidified with HTf2N and 1,2-dichloroethane as diluent. The effect of various experimental conditions such as the nature of diluent, aqueous nitric acid concentration, and TODGA⋅HTf2N concentration in the organic phase was studied. It has been found that the distribution coefficient values for metal ions are much greater, especially at low aqueous acidity in the extraction systems with the acidified organic solvent phase. Furthermore, the heavier lanthanides were effectively extracted and the intergroup lanthanide selectivity was greatly improved (separation factors for the Lu/La pair increased by 40 and 2 times for the two systems under study, respectively).

Simulation of technetium rejection in an advanced PUREX flowsheet

Controlling the routing of technetium to keep it away from the uranium product streams is essential in order to deliver efficient and safe recycling of spent nuclear fuel in future processes such as Advanced PUREX. In this paper, a flowsheet simulation code is developed for the simulation of technetium and zirconium routing in an Advanced PUREX flowsheet. The essence of this code is its consideration of the slow conversion of inextractable forms of zirconium to extractable forms in the modelling of mass transfer rates. The code is applied to model a flowsheet tested experimentally and is validated by experimental results. Sensitivity of the flowsheet to operating parameters, including temperature, organic-to-aqueous (O/A) flow ratio, and scrub nitric acid concentration is investigated; an optimized set of operating conditions is suggested that could result in lower amounts of technetium being routed to the uranium product.

Synthesis and formation mechanism of pitch-based carbon foam for three-dimensional structural applications

Carbon foam is a three-dimensional porous, rigid, and permeable material with applications in many fields owing to its excellent electrical and thermal properties. Pitch is a promising carbon source for carbon foam production, and its modification with nitric and sulfuric acids has been widely investigated. However, the foaming phenomenon resulting from the acid treatment of pitch and the resultant formation of porous structures remain poorly understood. Herein, we clarified the mechanism by which the porous structure of pitch-derived carbon foam is formed by analyzing the components of pitch modified by nitric acid treatment and identifying essential conditions for foam production. Carbon foam was obtained by pitch modification at a high concentration of nitric acid (60 wt%), whereas no carbon foam was formed at low nitric acid concentrations (<60 wt%). Furthermore, at high nitric acid concentrations, carbon foam formation proceeded at a relatively low temperature (280 °C). The formation of carbon foam from modified pitch was attributed to the synergistic effect of the functional groups introduced onto pitch and the low-molecular-weight components resulting from cracking. This work provides new insights into pitch as a precursor and provides a straightforward method for producing carbon foam.

Establishment and Verification of the Kinetics Model of Uranium Continuous Dissolution by Using Discrete Element Method

Continuous dissolution of spent fuel is indeed one of the key technologies that can significantly improve the efficiency and stability of spent fuel reprocessing. The China Institute of Atomic Energy designed a prototype rotary drum dissolver, and the dissolution behavior of UO2 pellets in the dissolver was calculated using the Discrete Element Method. A kinetic equation was established to model the dissolution behavior, considering variables such as temperature, nitric acid concentration, and stirring intensity. The calculations showed that complete pellet dissolution took about 10 h in the continuous reaction, compared to 6 h in the batch dissolution experiment due to the gradual decrease in nitric acid concentration. A 16 h continuous dissolution experiment confirmed the calculated results, with a deviation of 10.8% between the simulation and experiment in terms of the mass of dissolved pellets. It was also found that it takes approximately 30 h to reach equilibrium in the continuous rotary dissolver, with a nitric acid concentration of 2.8 mol/L and a uranium concentration of 243 g/L at equilibrium.

Understanding the fast formation mechanism of hard nanoporous alumina films on aluminum in acidic solutions containing nitric acid

Nanoporous alumina films formed on aluminum via anodization are widely used for scientific and technical purposes owing to their various advantageous properties, including excellent corrosion and wear resistance, good thermal and electrical insulation, and facile producibility at low cost. Herein, we report a novel approach to fabricate hard porous anodic alumina (PAA) films by adding an appropriate amount of nitric acid to sulfuric-, oxalic-, and phosphoric-acid solutions at critical high current densities. The effects of the nitric additives on the anodizing behavior, film growth mechanism, microstructure, chemical composition, film thickness, microhardness, and appearance of the PAA films formed from various solutions were systematically investigated. The addition of nitric acid enhanced the formation of alumina and resulted in fast growth rates of 196 μm/h and 166 μm/h for sulfuric- and oxalic-based solutions, respectively, while maintaining high hardness of approximately 380 and 430 HV0.1, respectively. The surface hardness of the films decreased to some extent with the increase in nitric acid concentration and/or film thickness owing to the strong corrosive nature of nitric acid during prolonged anodization, although nitrogen inclusion in anodic alumina films was not detected through X-ray photo-electron spectroscopy, which differs from the other acidic anions. In particular, the barrier layer thickness and pore intervals of PAA films increased with the nitric concentration in the aforementioned solutions, leading to a fast growth rate and high hardness inside the films.

Synthesis and Optimization Study of Microcrystalline Cellulose (MCC) through Acid Hydrolysis from Confiscated Cigarette

Tobacco is a type of plant which is used to make some products such as cigarettes and cigarettes are known to have a lot of harmful effects. There are few factors which causes the Royal Malaysian Custom Department to confiscate cigarettes which are white smuggled cigarette, contraband and false while storing the confiscated cigarettes for long time does not give any benefits. Therefore, cigarette butts which are chosen for this research study come from these confiscated cigarettes to utilize the waste. The tobacco was first undergoing alkaline pretreatment followed by bleaching process. Finally, hydrolysis process was done to synthesize microcrystalline cellulose (MCC). In this research, various acids (hydrochloric acid, sulphuric acid, and nitric acid) were used for the hydrolysis process. It was found that the best acid to synthesize MCC was nitric acid where the highest percentage of MCC yield was 76.83%. Scanning electron microscopy (SEM) shows the surface morphology of MCC which is observed to be like rod-like structure, while X-ray diffraction (XRD) results indicate that the crystalline and crystalline size of MCC was 74.28% and 4.61nm, respectively. FTIR spectra shows a successful removal of lignin structure from raw cigarette butts after hydrolysis process. Besides that, optimization of acid hydrolysis using Design of Expert software (DOE) were conducted where three independent variables were chosen which are hydrolysis time, hydrolysis temperature and acid concentration (nitric acid). Through this study, the highest yield of MCC obtained was 78% and the optimum conditions of parameters are 60 minutes, 60°C and 1.25M of nitric acid. The results of this study can be used to eliminate the hazards of the cigarette butts scattered in the environment and create the added value for the overall process.&#x0D;

Isotropic coal tar pitch-based carbon fibers: Effect of nitric acid towards elimination of air-stabilization step

The remarkable properties exhibited by carbon fibers have generated considerable interest in seeking alternative approaches to replace time-consuming, energy-intensive, and multi-step procedures for their synthesis. Among the various stages involved in carbon fiber synthesis, the stabilization step plays a crucial role as it necessitates an extended duration to transform thermoplastic pitch-fibers into thermosetting fibers, thus preventing them from melting during high-temperature treatments. In this study, isotropic coal tar pitch (ICTP) was transformed into pitch fibers through melt-spinning process and subsequently subjected to chemical treatment for stabilization using varying concentrations (ranging from 5% to 50% v/v) of aqueous nitric acid (HNO3) solutions. The objective was to determine the optimal concentration for effective stabilization. Consequently, this research eliminates the conventional, time-consuming air-stabilization process by treating the pitch fibers with nitric acid prior to carbonization. To produce carbon fibers, all chemically stabilized pitch fibers were directly carbonized at 1000 °C. Comprehensive characterizations including Rheology, Elemental analysis, FTIR, TGA, FE-SEM, XRD, Raman, and XPS were conducted to investigate the chemical and structural transformations occurring during the fiber processing. It was observed that aqueous nitric acid solutions ranging from 15% to 30% (v/v) exhibited superior structural, morphological, and mechanical properties compared to other concentrations of HNO3.