HNO3 Acid Research Articles

Process optimization and economic estimation of nitric acid dissolution for recycling waste wind blades

With the widespread retirement of wind turbines, many discarded waste wind blades have been generated, and how to handle them efficiently has become a critical issue. This study investigated the dissolution of discarded waste wind blades with nitric acid (HNO3) by varying acid concentration, reaction time, temperature, and HNO3 volume. Based on a series of single-factor experiments, the optimal conditions for low energy and acid consumption were determined, and the separation rate of resin reached 95%. As the cost-benefit analysis results suggested, an economic method to recycle a variety of high-value products was achieved. Furthermore, the implementation of a continuous chemical decomposition strategy for multi-batch processing significantly minimized acid consumption, resulting in a further reduction in recycling costs. This work provided an economically and technologically feasible way for recycling materials from decommissioned wind turbines, in order to answer the challenge of emerging solid waste management.

Do Wettability Measurements Define Corrosion Inhibition of Etched Surfaces? A Study on Acid‐Etched 316L Stainless Steel

Special wetting surfaces have attracted attention owing to their potential applications in the automotive, engineering, environmental, and biomedical industries. Specifically, nature‐inspired superhydrophobic surfaces are more effective in blocking moisture, thus limiting corrosion. Hence, surface wettability analysis remains the primary method for demonstrating the corrosion mitigation characteristics of rough‐engineered surfaces. Herein, the influence of wettability measurements on the corrosion inhibition of 316L stainless steel surfaces etched in HCl: HNO3 acid is systematically investigated. Interestingly, etched hydrophobic surfaces with a contact angle of ≈125° significantly improve the corrosion resistance by 50%, resulting in suppressed corrosion rates. Furthermore, the surface chemical states of the etched 316L steel are analyzed and discussed in detail.

Photocatalytic activity of self-heterojunctioned intermediate phases in HCl protonated and HNO3 deconjugated g-C3N4 nanostructures

This research involved the different acid-treatment conditions of graphitic carbon nitride and its modified nanostructures through thermal polycondensation of urea at various temperatures. X-ray diffraction patterns revealed that processing at a lower temperature than 500 °C resulted in melem and its derivatives, indicating incomplete transformation of urea to g-C3N4. However, treatment at higher temperatures and the HCl acid treatment led to the formation and expansion of g-C3N4 networks, as evidenced by notable differences in peak intensities observed in their Fourier-transform infrared and Raman spectra. Scanning electron microscopy analysis illustrated a transition from the granular morphology of melamine to the layered structure characteristic of g-C3N4. The nanoparticle morphology observed in the HNO3 acid treatment sample was attributed to the deconjugation of nanosheets through the highly oxidative acid medium. The most suitable photocatalytic activity for Methylene Blue (MB) degradation under UV and visible light illumination was observed for the samples prepared at 550 °C and HCl post-processed nanostructures. It is proposed that the enhanced photocatalytic activity observed in these samples is most likely attributed to the reduced recombination of photogenerated charge carriers facilitated by heterojunctions formed between different intermediate phases. These findings highlight the potential of modified g-C3N4 and its derivatives as promising photocatalytic materials for water purification applications.

Microwave digestion method for sulfide analysis of Çanakkale region coal

ABSTRACT Quantitative analysis of sulfide content in coal is a necessary step for complete analysis. Conventional analysis methods take several days, whereas it takes a few hours in microwave digestion method. In the present study, a new wet chemical analysis technique was developed and applied to quantify the sulfide content in Turkish coal samples. In the initial step, 5 M HCl solution is employed to dissolve the sulfate phases present in the coal. Subsequently, pyrite is separated from the residue obtained in stage 1 through the utilization of 2 M HNO3 solution. The final stage involves the determination of organic sulfur, wherein concentrated HNO3, HCl, HF, and boric acid are utilized to completely decompose the remaining residue from stage 2. The extracted solutions from each stage are promptly analyzed for sulfur content using ICP-OES. The cumulative values of the three sulfur forms consistently correspond with certified total sulfur data for the majority of the examined coals. Among several advantages, the analysis duration is the most distinctive feature. Chemical analysis of sulfide in coal with microwave analysis method completed three times rapid than with conventional analysis.

Utilizing acid-etched Fe-waste for sustainable synthesis of conductive perovskite-type materials from automotive industrial residue

A common method for reducing waste and environmental problems brought on by landfills is to reuse waste, especially heavy metals such as iron. Automotive industrial waste containing Fe-rich metal is successfully transformed into a highly pure structure of Fe2O3 using an etching method with HNO3 acid. This resulting structure serves as a precursor for synthesizing LaNi1-xFexO3±δ perovskite conducting materials. The desired perovskite conductive phase can be produced by substituting Fe2O3-treated waste at the B-site (Ni position) before calcination at 1200 °C. However, LaNiO3±δ and LaNi0.6Fe0.4O3±δ could not be synthesized under ideal conditions, as indicated by XRD analysis using TOPAS software, which revealed the presence of undesirable phases. Both compounds, LaNiO3±δ and LaNi0.6Fe0.4O3±δ demonstrated electrical conductivity with values of 362 S/cm and 42 S/cm at 550 °C, respectively. Nonetheless, electrical conductivity of both compounds decreased due to unintended phase contamination during the synthesis process. The Fe2O3-substituted compounds at the Ni position, in an exact amount of 1 mol, exhibited minimal electrical conductivity. Although the synthesis conditions to produce a single phase of LaFeO3±δ were identified, LaFeO3±δ, despite its low electrical conductivity, is frequently used in electrical devices as a gas detection sensor. The thermal expansion coefficient of all synthesized waste samples is represented in the range of 12–13 × 10−6 °C−1, which is comparable to IT-SOFC electrolyte materials. Furthermore, microstructural investigation revealed that the introduction of Fe into LaNiO3±δ reduced particle size and porosity, ultimately resulting in higher densities. These findings were confirmed through synchrotron radiation x-ray tomographic microscopy (SR-XTM) analysis. The research suggests that converting Fe-waste into a pure phase of Fe2O3 using a strong acid etching technique can serve as a viable precursor for synthesizing conductive materials. This approach enhances the value of industrial waste while also reducing its volume.

Sulphur/functionalized graphene composite as cathode for improved performance and life cycle of lithium-sulphur batteries

Over the past years, significant advantages have been introduced to upgrade the performance of lithium-sulfur battery (Li-S) batteries since their prototype in the 1960s. Due to high theoretical energy density and cost efficiency, Li-S batteries have obtained great attention and have made great progress in the last few years. In this work, we developed the sulfur-attached few-layer graphene composite (S/FLG), sulfur-attached functionalized few-layer graphene using acetic acid (S/FLG-COOH) and sulfur-attached functionalized few-layer graphene using strong acid H2SO4 and HNO3 (S/FLG-OH) as a cathode material with high sulfur loading. The material’s structure is confirmed through XRD. The surface morphology is confirmed through SEM and elemental composition has been obtained through EDAX. The functional groups are confirmed through FTIR. The defect level and number of layers are confirmed through Raman characterization with an excitation laser wavelength of 532 nm. The electrochemical performance of three cathodes is also identified through EIS, CV, and GCD characterization. Meanwhile, highly developed defects and edges found in the functionalization of few-layer graphene using the strong acid (H2SO4 and HNO3) which consists of a hydroxyl functional group (FLG-OH) serve as polysulfide reservoirs to mitigate the shuttle effect. Among these cathodes, S/FLG-OH shows a high specific capacitance of 157.4 F g−1 and when applied as a cathode host on a coin cell it obtained a voltage of about 2.6 V. Well-performed S/FLG-OH cathode was used to fabricate the Coin Cell. The fabricated Coin Cell with S/FLG-OH as the cathode shows a stable potential over 50 cycles.

Application of functionalized carbon nanofibers as a modifying additive to motor oil

Due to the widespread of lubricants, improving their tribological characteristics remains an important practical task. Among the promising modifying additives, carbon nanomaterials attract special attention. Such materials are found to improve the antifriction characteristics of lubricants and oils. In the present research, carbon nanofibers were synthesized via catalytic pyrolysis of a mixture of light hydrocarbons (C2-C4) over the NiCu catalyst. In order to form functional groups on the surface of carbon nanofibers, they were treated with diluted acids HCl, HNO3, and H2SO4 as well as with concentrated HNO3. The functionalized samples were comprehensively characterized by a set of physicochemical methods including atomic absorption spectroscopy, scanning and transmission electron microscopies, low-temperature nitrogen adsorption, X-ray photoelectron spectroscopy, temperature-programmed desorption/oxidation, and Raman spectroscopy. As defined, the surface oxygen concentration in the samples varies from 3.5 to 16.3 at.%. It was shown that the addition of modified carbon nanofibers to a motor oil leads to an improvement in its tribological characteristics. In particular, the most effective additive was the sample treated with diluted HNO3. The motor oil with this modifying additive exhibited the heating temperature decreased by 10 °C and the contact spot area on the stationary body decreased by 20 %.

Optimizing a radiochemical separation of 26Al from an acidic V-rich matrix

Sorption and desorption of Al(III) on a series of different extraction resins (LN, LN2, LN3, TK100, TK101, TK201) in acidic HNO3 media containing high concentrations of V(IV,V) was investigated. Static batch studies were conducted as a way of obtaining preliminary distribution coefficient (Kd) values that were further used to develop dynamic tests on real samples. It was shown that a complete separation and recovery of Al(III) from V(V) under acidic conditions (pH = 2) is possible by utilizing LN resin. Active “hot” dynamic studies with 26Al (≈10 Bq) as a radiotracer and real waste samples were conducted to further investigate and confirm the results of the inactive “cold” experiments. Utilizing this separation procedure, we have successfully removed all traces of 26Al (∼10−9 g) radiotracer from the bulk vanadium matrix.

Enhancing adsorption capacity of a kaolinite mineral through acid activation and manual blending with a 2:1 clay

The efficiencies of raw and modified kaolinite mineral in removing selected heavy metal ions from their respective aqueous solutions were investigated. The mineral was modified through two different methods; i) activation with HNO3, H2SO4, H3PO4, CH3COOH and C2H2O4 acids to form NK, SK, PK, AK and OK acid activated clays respectively and ii) preparations of 3:1 and 1:1 Kaolinite: Bentonite blends to form UBK and EBK composites respectively through manual blending. The adsorbents were characterized by X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Fourier Transform Infra-Red Spectroscopy (FTIR) and Brunauer Emmett Teller (BET) analysis for surface area determination. The surface area increased in some of the modified clays from 114.9457 m2/g (RK) to 288.685 m2/g (EBK), 205.92 m2/g (UBK), 162.227 m2/g (NK), 151.335 m2/g (SK), and 115.837 m2/g (OK) but reduced to 113.872 m2/g (PK) and 112.865 m2/g (AK) after modification. Adsorption studies were subsequently conducted out to remove Pb2+, Cd2+ and Ni2+ ions from synthetic solutions. Pb2+ was found to be most removed (383.5 mg g-1 (RK), 591.13 mg g-1 (EBK), 576.61 mg g-1 (UBK), 475 mg g-1 (NK), 450 mg g-1 (SK), and 425 mg g-1 (PK), 375 mg g-1 (OK) and 375 mg g-1 (AK)) with highest removals on the composites.

Investigation of the Effects of Different H2SO4, HCI, HNO3 and HCIO4 Liquid Acid Media on the Synthesis of CdTe Semiconductor Thin Films for Solar Cells

The main target of the present paper is to investigate the effect of different acidic aqueous media(DAAM) on the synthesis of cadmium telluride thin films(CdTeTFm). The synthesis of CdTeTFm was carried out by the electrochemical deposition method(EDM) in DAAM. The chronoamperometry method of electrodeposition(ED) was used for the production of CdTeTFm. Furthermore, the electrochemical behaviors of the solutions were studied using cyclic voltammetry. The experiments were carried out with 3 electrodes (a working electrode (WE), a reference electrode(CE), and a counter electrode(RE)) using the electrochemical cell potentiostatic method. The experimental conditions of the acidic aqueous CdTe solution have been determined to be pH 3.56-3.57, the temperature of the solution is 85°C, the concentration of CdTe 2.45x10-1 M, and the reaction time is 25 minutes. The physical properties of CdTeTFm were determined by XRD, SEM/EDX, FT-IR, and UV-VIS analysis methods. According to the results of the analysis, it was observed that acidic aqueous media have an important role in the synthesis of CdTeTFm. The bandgap ranges and Cd/Te ratios of the synthesized thin films were obtained as 1.42, 1.48, 1.50, 1.58 eV, 0.65, 0.587, 0.79 and 0.738, respectively.

Enhancement of dielectric properties of the La2NiO4-CuO terpolymer nanocomposites by modified SiC nanofiller

This work investigates the enhancement of dielectric properties of La2NiO4-CuO terpolymer nanocomposites using surface modified SiC nanoparticles as fillers. SiC nanoparticles were subjected to acid treatment and annealing at 1000 °C to tailor the surface chemistry. Acid treatment involved immersing the SiC powder in a mixture of H2SO4 and HNO3 acids and sonicating for 30 min, followed by stirring at 60 °C for 6 h. Annealing was carried out at 1000 °C for 2 h in an inert argon atmosphere. La2NiO4 and CuO nanoparticles were synthesized by sol-gel and precipitation techniques respectively, with average particle sizes of 20–40 nm and 10–15 nm confirmed by XRD and FESEM. Nanocomposites were fabricated by dispersing 2–10 wt% of untreated, acid treated and annealed SiC nanoparticles in a La2NiO4-CuO mixture solution, using PVDF as the polymer matrix. Impedance spectroscopy revealed that addition of 5 wt% acid treated SiC resulted in the highest dielectric constant of 42 at 1 kHz, in comparison to 25 for the unfilled polymer. This was attributed to increased interfacial polarization arising from uniform dispersion of nanoparticles and abundant charge trapping sites introduced by the SiC filler.

Titanium Dioxide/Graphene Oxide Composite Coatings for 316 Stainless Steel Dental Implants.

Stainless steel has been used in orthopedics and orthodontic fields. However, it cannot be used for fabrication of dental implants due to its inertness, low biocompatibility and weak resistance to corrosion. A composite coating of titanium oxide /graphene oxide has been prepared for stainless steel to improve its biological properties. Stainless steel discs were polished, cleaned and pre-treated with a mixture of HNO3 and HF acid for 15 min. The composite coating composed of TiO2 produced by sol-gel technique and doped with 0.75 wt% graphene oxide. XRD, SEM-EDX and AFM were employed to characterize the composite coating. The anti-bacterial action of the composite coating was investigated against S. aureus and E. coli. The corrosion resistance of coated and noncoated samples was assessed in SBF using electrochemical technique. Cytotoxicity was assessed using osteoblast-like cells. The wettability was determined by contact angle, and bioactivity assessed by immersion in SBF. The results revealed that the composite coating was dense with few micro-cracks, and was not cytotoxic to osteoblast-like cells. The composite coating reduced bacterial colonies and the corrosion rate of the steel was improved. The wettability of the sample was increased with the composite coating and apatite formation appeared after 21 days.

Mechanochemically induced hydrometallurgical method for recycling d-elements from Li-ion battery cathodes

The exponential growth of the Li-ion battery (LIB) market necessitates the development of environmentally friendly and economically viable recycling technologies. One of the approaches for recycling and selective recovery of critical battery components is the hydrometallurgical method. Despite its effectiveness, this technology has notable drawbacks, including environmental pollution caused by corrosive waste, high energy consumption, and complexity. Herein we present a highly efficient mechanochemically (MC) induced acid leaching process that enables the extraction of transition metals as water-soluble salts from cathode materials of different and mainly used chemistries such as LiCoO2, LiMn2O4, and Li(CoNiMn)O2. The described method utilizes HNO3, H2SO4, and HCl mineral acids to leach transition metal composites obtained by MC reduction and delithiation processes. The presented technology achieves a significant material dissolution efficiency of more than 95 % at low acid concentrations at room temperature. Furthermore, it was concluded that the mechanochemical pretreatment step plays a crucial role in reducing particle sizes as well as for the chemical reduction of d-elements in the cathode materials to lower electrochemical charging states which greatly enhances the effectiveness of the leaching process. This advancement brings us closer to achieving ecological and economic feasibility in recycling Li-ion batteries.

Fabrication of InGaN/GaN multiple quantum well embedded on nanoporous GaN mirror under different acid electrolytes

Large-size (2 inch) InGaN/GaN multiple quantum wells (MQW) embedded on nanoporous (NP)-GaN distributed Bragg reflectors (DBR) were fabricated by electrochemical (EC) etching at different acid electrolytes (e.g. HF, oxalic, and HNO3 acids). The sample obtained in HNO3 electrolyte presents the highest reflectance and the strongest photoluminescence (PL) intensity, whereas the sample fabricated by the HF etching has uneven surface, leading to very low reflectance. Compared with the as-deposited sample, the HNO3 etching leads to a 5-fold enhancement of PL intensity of etched sample, probably resulting from two factors which reflection of NP-GaN DBR mirror enhanced the light output, and amplify spontaneous emission (ASE) via a resonant cavity increased PL performance.

Rapid adsorption of benzotriazole onto oxidized carbon cloth as an easily separable adsorbent

A commercial carbon cloth (CC) was oxidized by HNO3 acid and the features of the plain and oxidized CC were evaluated. The results of characterization illustrated that HNO3 oxidization duplicated the oxygen-containing functional groups and the surface area of the CC. The adsorption performance of the plain and oxidized CC (Oxi-CC) toward benzotriazole (BTR) was compared. The results disclosed that the uptake of BTR by oxidized CC was greater than the plain CC. Thence, the affinity of oxidized CC toward BTR was assessed at different conditions. It was found that the adsorption was quick, occurred at pH 9 and improved by adding NaCl or CaCl2 to the BTR solution. The kinetic and isotherm studies revealed that the surface of Oxi-CC is heterogeneous and the adsorption of BTR follows a physical process and forms multilayer over the Oxi-CC surface. The regenerability and reusability study illustrated that only deionized water can completely regenerate the Oxi-CC and that the Oxi-CC can be reused for five cycles without any loss of performance. The high maximum adsorption capacity of Dubinin–Radushkevich isotherm model (252 mg/g), ease of separation and regeneration, and maintaining the adsorption capacity for several cycles revealed the high efficiency and economical and environmental feasibility of Oxi-CC as an adsorbent for BTR.

Study on Effect of Toluene-Acid Treatments of Recycled Carbon Black from Waste Tyres: Physico-Chemical Analyses and Adsorption Performance

Recycled carbon black (rCB) produced by pyrolysis has a low value because it contains high levels of impurities, such as sulfur, nitrogen, and oxygen. Various treatments have been proposed using chemicals to purify and improve the properties of rCB. In this study, rCB was treated with toluene (rCB-T), followed by subsequent treatment using acids HCl (rCB-T-HCl), HNO3 (rCB-T-HNO3), and HCl-HNO3 (rCB-T-HCl-HNO3). The treated rCB samples were characterized using CHNS analyser, scanning electron microscope, BET analyser, zeta potential, Fourier transform infrared spectroscopy, and Raman spectroscopy. The adsorption of methylene blue dye onto the rCB samples was also investigated to study the effectiveness of the treatments. Treatment with toluene alone was insufficient to increase the carbon content and surface area of the rCB. Subsequent treatment of rCB with acids, especially HNO3, significantly increases the carbon content, surface area, surface functional groups, and surface charge of the rCB. This results in an increased adsorption capacity of the rCB, from 6.04 mg/g to 46.51 mg/g for the rCB-HNO3 and 54.80 mg/g for the rCB-T-HCl-HNO3.

ANALYSIS OF ACID MIXTURE COMPARISON ON THE PROCESS OF DESTRUCTION OF LEAD METAL (Pb) ON SAMPLE OF CARPET SHELL’S MEAT (Ruditapes variegatus)

ABSTRACT
 
 Analysis of the acid mixture ratio in the lead (Pb) metal deconstruction process in carpet shell’s meat samples (Ruditapes variegatus). In the deconstruction agent HNO3 : HCl (1:3), the average lead metal concentration contained in sweet clam meat is 4.6305 ± 1.066 mg/kg and for the HNO3 : H2SO4 (3:1), the average lead metal concentration contained in the same sweet clam meat was 5.6516 ± 2.556 mg/kg. Statistical test results showed no significant difference in the dissolving power of the acid mixture HNO3 : HCl (1:3) and HNO3 acid mixture: H2SO4 (3:1) as seen from the p>0.005 value, so both the HNO3 acid mixture: HCl (1:3) and HNO3 acid mixture: H2SO4 (3:1) can be used to deconstruct Pb metal in sweet clam meat (Ruditapes variegatus) because there is no significant difference in the two acid mixtures.

Multi-hollow Surface Dielectric Barrier Discharge: Production of Gaseous Species Under Various Air Flow Rates and Relative Humidities

An evaluation of the gaseous species production by the discharge, i.e., discharge chemical activity, is very important for determining its potential for practical applications. In this work, production of gaseous species by the multi-hollow surface dielectric barrier discharge generated in a perforated ceramic substrate with the air-exposed electrode is investigated under conditions of various discharge powers (1–5 W), air flow rates (0.25–2.4 L/min) and air relative humidities (0–80%). Production of ozone O3, nitrous oxide N2O, nitric oxide NO, nitrogen dioxide NO2, dinitrogen pentoxide N2O5 and nitric acid HNO3 is evaluated in terms of concentration (ppm), production yield (g/kWh) and production rate (mg/h). The work demonstrates a critical impact of both air flow rate and relative humidity on prevailing discharge mode (“O3 mode” vs. “NOx mode”) and, thus, on overall composition and concentration of produced gaseous species. For low discharge power, the discharge operates in the “O3 mode”, when O3, N2O, N2O5 and HNO3 are dominant gaseous products. With the increasing power, the discharge transfers into the “NOx mode”, when N2O and HNO3 along with NO and NO2 are mostly produced. In dry air, transition from “O3 mode” to “NOx mode” is found for the specific input energy of 1000–1100 J/L. With an increase of air relative humidity from 20 to 80%, the transition gradually decreases from approximately 600 to 450 J/L, respectively.

Synthesis and Properties of Sol-gel Coatings Deposited on Hybrid Materials

ZrO2-Al2O3 and ZrO2-Y2O3 coatings were synthesized using sol-gel technology with a complexing agent and HNO3 acid catalyst. The resulting coatings were deposited on Nb/Al, Ti/Al substrates. The synthesized coatings were studied by X-ray photoelectron spectroscopy (XPS analysis), Atomic Force Microscopy (AFM) and XRD (X-ray phase analysis). The obtained data indicate that XPS analysis is very suitable for studying the deposited coatings. Interesting data on the phase composition and surface morphology were obtained from the XRD analysis and the AFM method.

Effect of Nb Addition on Corrosion Resistance of U-6Zr Alloys

The fuel element plates in a research reactor can be exposed to an acidic, neutral, or alkaline environment based on its surroundings. This study aimed to investigate the effect of Nb addition on the corrosion properties of U-6Zr alloys in various environments. U-6Zr-xNb alloys (U-6Zr-2Nb, U-6Zr-5Nb, and U-6Zr-8Nb) with different Nb compositions of 2, 5, and 8 wt%, respectively, were prepared and cut into smaller pieces. The pieces were then mounted with chemical resin equipped with copper wire cables and metallography prepared by grinding using sandpaper with grit sizes ranging from 320 to 1200. The electrochemical corrosion tests used in this work were the polarization test and Tafel extrapolation method. In the first step of corrosion testing, the corrosion potential and polarization resistance were measured using standard settings from a voltage range of −0.02 to 0.02 V with a scanning rate of 0.05 mV/s. In the next step, a destructive method, called the Tafel extrapolation method, was used. Corrosion tests were carried out on U-6Zr-xNb alloys (x = 2, 5, 8) under various environmental conditions using electrochemical methods. Polarization resistance test and Tafel extrapolation methods revealed that the U-6Zr-2Nb alloy exhibited good corrosion resistance in an acidic HNO3 environment with a pH of 1.18. The best corrosion resistance of the U-6Zr-5Nb alloy was observed in demineralized water. Meanwhile, the U-6Zr-8Nb alloy showed the best corrosion resistance in an alkaline NaOH environment with a pH of 11.02. It can be concluded that the higher Nb composition added to U-6Zr alloys, the better their corrosion resistance in higher pH environments.