Integrated experimental and theoretical analysis of Millettia pinnata (Karanja) Leaf extract as an eco-friendly inhibitor for zinc in hydrochloric acid

The development of sustainable corrosion mitigation strategies is essential for protecting metallic materials in aggressive environments. In this study, Desmodium adscendens (Sw.) DC. extract (DAPE) was investigated as a bio-based corrosion inhibitor for carbon steel in hydrochloric acid. A central composite design integrated with response surface methodology (CCD–RSM) was employed to quantify and optimize the combined effects of acid concentration, temperature, inhibitor concentration, and immersion time on weight loss (WL), corrosion rate (CR), and inhibition efficiency (IE). The resulting quadratic models exhibited high statistical reliability and predictive accuracy (R² = 0.9881 for WL, 0.9743 for CR, and 0.9685 for IE). Analysis of variance identified acid concentration and temperature as the dominant factors accelerating corrosion, whereas increasing DAPE concentration significantly reduced WL and CR while enhancing IE. Optimal inhibition performance was achieved at 0.80 g/L DAPE in 2 M HCl at 323 K, yielding WL = 0.027 g, CR = 0.0011 g·cm⁻²·h⁻¹ , and IE = 85.02 %. Numerical optimization predicted comparable values (WL = 0.027 g; CR = 0.0010 g·cm⁻²·h⁻¹; IE = 85.32 %), which were experimentally validated within a 95 % confidence interval. Electrochemical impedance spectroscopy and potentiodynamic polarization analyses confirmed that corrosion inhibition occurs through adsorption of DAPE phytochemicals, forming a compact, adherent, and electrically resistive interfacial film that suppresses both anodic dissolution and cathodic hydrogen evolution. The inhibitor exhibited mixed-type behavior without altering the intrinsic corrosion mechanism. Surface morphology analysis further corroborated the formation of a smooth and protective layer on the steel surface. These findings demonstrate the potential of DAPE extract as an effective, sustainable, and environmentally benign corrosion inhibitor for carbon steel in acidic media.

Balancing environmental concerns and resource recovery, this study explores an innovative approach to sewage sludge valorization in the context of a circular economy. Sewage sludge, a byproduct of wastewater treatment, presents significant disposal challenges due to its pollutant content. However, it also contains valuable nutrients and carbon that can be harnessed. In this work, we focus on fully recycling sewage sludge, ensuring that no residues or additional wastes are generated. Our primary objective is to maximize the recovery of phosphorus from sewage sludge and find practical uses for the remaining solid residue. During the pretreatment stage, we experimented with various acidic and alkaline leaching agents to determine the most efficient one for phosphorus removal. Among the agents tested (including sulfuric, nitric, hydrochloric, oxalic, and citric acids, as well as sodium and potassium hydroxides) sulfuric acid emerged as the most effective, achieving an impressive 89% phosphorus removal efficiency. Following this, the liquid fraction containing dissolved phosphorus was separated and processed, resulting in an 84% phosphorus recovery in the form of struvite. The solid residue from the separation process was then pyrolyzed to produce sludge-derived biochar, which showed potential for supercapacitor applications. This biochar exhibited a specific surface area of 208m2 g-1 and a specific capacitance of 53F g-1 in 1M H2SO4. Overall, this study demonstrates a comprehensive and sustainable method for transforming sewage sludge from a waste product into valuable resources, contributing to global efforts in waste reduction and resource recovery.

Two-step selective extraction of Ga(III) and in(III) from hydrochloric acid media using different ketones

Sustainable production of high-purity amorphous silica from rice husk: A comparative study on the impact of fresh and reused hydrochloric acid leaching

Influence of dissolved Al(III) on electrochemical iron removal from coal fly ash hydrochloric acid leachate.

Corrosion inhibition effect of coffee skin carbon dots synthesized by hydrothermal method on cold-rolled steel in hydrochloric acid medium: Experimental and theoretical calculation study

Acetoacetate-preconditioned adipose stem cells promote burn wound healing through enhanced cellular retention and paracrine signaling.

The study utilized litchi shells as precursors to synthesize N, S self-doped carbon quantum dots (LBCQDs) by a hydrothermal method for use as corrosion inhibitors. Electrochemical testing, weight loss tests, surface characterization, and density functional theory calculations were employed to investigate the corrosion inhibition performance of LBCQDs on 5052 aluminum alloy in the HCl solution. The results indicate that LBCQDs are a mixed-type corrosion inhibitor, predominantly inhibiting cathodic reactions. Their corrosion inhibition efficiency increases with concentration, reaching a maximum of 94.22% at a concentration of 300 mg·L-1. In addition, higher concentrations of LBCQDs result in a slower reduction in corrosion inhibition efficiency over a prolonged immersion time. The corrosion inhibition mechanism analysis indicates that LBCQDs can spontaneously form a protective film on the aluminum alloy surface based on the synergistic effects of physical adsorption, chemical adsorption, aggregation effect, and the chelation reaction. This increases the energy barrier of the corrosion reaction of the aluminum alloy, thereby inhibiting corrosion. This work not only provides a high-value utilization strategy for litchi shell biomass but also offers profound insights for designing eco-friendly corrosion inhibitors.

An acid-triggered cascade transformation of donor-acceptor cyclopropanes, containing a 2-indolyl fragment as a donor and an acyl group as an acceptor, into carbazole derivatives was developed. The starting cyclopropanes, which were easily synthesized via an aldol condensation/Corey-Chaykovsky reaction sequence on a gram scale, were readily converted into 4-substituted carbazoles by the action of both equimolar hydrochloric acid in methanol and catalytic HCl-dioxane in methylene chloride. The reaction mechanism involves small ring opening and common ring closure via the Friedel-Crafts reaction as key steps; however, the current results do not allow conclusions to be drawn about the order of the proceeding steps in each case.

Latilactobacillus sakei (Lb. sakei) could be isolated from various fermented foods, that could adapted under low-temperature conditions. This study investigated the potential probiotic properties of Lb. sakei J15, a strain isolated from kimchi that exhibits high β-galactosidase activity at low temperatures. The growth characteristics of Lb. sakei J15 under different temperatures, salt concentrations, and carbon sources were investigated. These results showed that Lb. sakei J15 exhibited the highest β-galactosidase activity (789.31 mU/mg) at a low temperature (15 °C), along with high survival rates under acidic (pH 3.0) and bile salt (0.3%) conditions, reaching 91.5% and 66.0%, respectively. Additionally, Lb. sakei J15 demonstrated strong tolerance in a simulated gastrointestinal digestion system, with survival rates of 63.0% after 3 h of gastric digestion and 47.0% after 8 h of intestinal digestion. The strain also exhibited notable antioxidant activity, with DPPH and ABTS radical scavenging rates of 43.0% and 71.9%, respectively, as well as a high auto-aggregation ability (96.1%). Furthermore, Lb. sakei J15 effectively utilized fructooligosaccharides (FOS) and galactooligosaccharides (GOS) as carbon sources. It also showed high lysozyme tolerance (93.7% survival rate) and displayed no hemolytic activity. In conclusion, Lb. sakei J15 showed potential as a starter culture for low-temperature dairy fermentation. Lb. sakei J15 had potential probiotc effects.

Conventional hydrochloric acid (HCl) acidizing in carbonate reservoirs is often limited by excessively rapid acid–rock reactions and preferential flow through high-permeability paths, resulting in shallow penetration and inefficient stimulation. Viscoelastic surfactant (VES)-based diverting acids have been widely applied to address these challenges; however, the intrinsic relationship between reaction retardation and diversion efficiency, particularly under varying shear conditions, remains insufficiently clarified. In this study, a VES-based diverting acid system formulated with erucamidopropyl hydroxysultaine (EH50) was systematically investigated through multiscale experiments, including rotating disk reaction kinetics, rheological characterization, porous core flooding, and fracture-scale plate flow tests. The results reveal a pronounced shear-dependent transition in the governing mechanism of the system. Under low-shear conditions, the VES system significantly reduces the apparent acid–rock reaction rate, with a maximum reduction of 77.3%, and exhibits a synergistic retardation effect in the presence of Ca2+, indicating mass transfer limitation. However, under high-shear porous media flow, the intrinsic retarding effect is substantially weakened due to partial disruption of the viscoelastic structure. Despite this attenuation of chemical retardation, effective diversion performance persists under dynamic flow conditions, manifested by pressure plateau behavior, enhanced flow redistribution, more distributed wormhole networks, and greater overall dissolution. Fracture-scale experiments further demonstrate that the diversion acid suppresses excessive inlet etching and promotes spatially distributed etching patterns favorable for fracture conductivity maintenance. These findings clarify that reaction retardation and diversion are distinct yet dynamically coupled mechanisms, whose relative dominance depends on shear intensity and ionic environment. The proposed shear-responsive mechanism framework provides new insight into the design and optimization of VES diverting acid systems for carbonate reservoir stimulation.

Colistin is a polypeptide antibiotic serving as a crucial "last-resort" agent against multidrug-resistant Gram-negative bacteria. This study aimed to develop a reliable analytical method for the determination of colistin A and B residues in food matrices using liquid chromatography-tandem mass spectrometry (LC-MS/MS). Test portions were extracted with methanol-water (1:1) under hydrochloric acid-acidified conditions, followed by a secondary extraction with 0.1 mol/L hydrochloric acid. The extracts were cleaned using a weak cation-exchange cartridge, and chromatographic separation was performed on a biphenyl column with gradient elution, followed by LC-MS/MS. The developed method produced sharp and symmetrical peaks for colistin A and B, with no significant matrix effects. Recoveries ranged from 81.0% to 105.9% across all analytes and matrices, and both repeatability and reproducibility met the target criteria specified in the Japanese guidelines for method validation. The limits of quantification were 20 ng/g in bovine and swine muscles for colistin A and 10 ng/g for others. An LC-MS/MS method was established for quantitative determination of colistin A and B residues in food matrices. The validation results met all performance criteria of the Japanese guidelines, confirming that the method provides reliable and precise measurements suitable for food residue monitoring. Reliable quantification of colistin residues was achieved using three distinct retention modes, enabling reliable monitoring of residues in foods.

ABSTRACT Sulfamethoxazole (SMA), an antibiotic, was investigated as a corrosion inhibitor for carbon steel in hydrochloric acid solutions using both chemical and electrochemical techniques. The corrosion rate decreased with increasing SMA concentration. Inhibition efficiency improved significantly, reaching up to 95.3% at a concentration of 0.005 M and a temperature of 25 °C. The inhibition mechanism is attributed to the adsorption of SMA molecules onto the surface of carbon steel. The negative values of the standard free energy of adsorption (ΔG°ads) indicate that the adsorption process is spontaneous. Depending on temperature, ΔG°ads values ranged from −38.18 to −34.34 kJ mol−¹, suggesting a mixed physisorption – chemisorption mechanism. The decrease in the adsorption equilibrium constant (K ads) with increasing temperature is attributed to desorption of SMA molecules from the steel surface into the solution. The relatively high adsorption energy confirms the effective protective performance of SMA as a good corrosion inhibitor.

ABSTRACT In clandestine laboratories, amphetamine is predominantly synthesized via the Leuckart route. In recent years, a trend is observed: Capacities of illicit production facilities for synthetic drugs in Europe increased and fewer small‐scale laboratories are encountered by police and customs authorities. One of the designer pre‐precursors currently applied is methyl α‐phenylacetoacetate (MAPA), which can be converted into the key synthesis educt benzyl methyl ketone by acidic hydrolysis. Besides replacements of former designer pre‐precursors due to scheduling (e.g., α‐phenylacetoacetonitrile [APAAN]), another trend for synthesis is observed since 2019, namely, the alkaline hydrolysis of the reaction intermediate N ‐formylamphetamine into the free amphetamine base during the second step of the Leuckart route instead of the previously predominantly applied acidic hydrolysis using concentrated hydrochloric acid. In this study, 28 samples of products and production waste seized from a dismantled large‐scale amphetamine laboratory in Germany that used MAPA as designer pre‐precursor and the modified alkaline Leuckart step two were analyzed by a nontargeted liquid chromatography—high‐resolution mass spectrometry approach for tentative identification of specific markers for the use of MAPA and the alkaline hydrolysis of N ‐formylamphetamine. After peak picking, 23 features were identified as suspects and further seven new features were tentatively identified. These seven potential marker compounds appeared to be indicative for the pre‐precursor conversion step and were found in production waste and in amphetamine base product samples. Additionally, there were hints for the formation of high molecular weight compounds during the modified Leuckart step two.

The depletion of natural resources remains an acute global problem, highlighting the importance of developing sustainable technologies that enable the simultaneous extraction of metals and recycling of waste. This paper describes a study of a technology for recycling aluminum slag from foundries to produce secondary aluminum alloy and regenerated flux. Research and processing methods include X-ray phase and spectral analysis of slag composition, multi-stage grinding in a jaw crusher and planetary mill, screening for fraction separation, and selective dissolution of the oxide–salt phase in water or hydrochloric acid followed by filtration and evaporation; obtaining regenerated flux based on phase diagrams of chloride systems; and briquetting and remelting of the extracted aluminum. The technology ensures the extraction of up to 85% of the metallic aluminum from slag and the production of regenerated flux based on the NaCl–KCl–MgCl2 system with a low melting point.

Constructing fiber-matrix interfaces that simultaneously possess thermal stability and adaptive responsiveness remains a critical challenge for high-temperature thermoplastic composites. Herein, a Tg-difference-driven dual-component colloidal suspension sizing strategy is proposed to achieve controllable interfacial evolution in carbon fiber-reinforced poly(phthalazinone ether sulfone ketone) (CF/PPESK) composites. By codepositing a rigid poly(amic acid) salt (PAAs) precursor and a flexible sulfonated poly(phthalazinone ether sulfone ketone) (SPPESK) in an aqueous medium onto the carbon fiber surface, a spontaneous phase reconstruction occurs during hot-press processing due to differences in chain mobility and Tg. The high-Tg PI segments assemble into a rigid skeleton adjacent to the fiber surface, while the low-Tg PPESK segments interdiffuse with the matrix, forming a compliant penetration layer and molecular bridging structures. Such a synergistic interfacial architecture markedly enhances interfacial wettability, chemical compatibility, and mechanical stability. The resulting composites exhibit an interlaminar shear strength (77.6 MPa) and flexural strength (1705 MPa) that are increased by 41.3% and 43%, respectively, relative to the desized fibers, while retaining over 60% of the mechanical performance at 250 °C. AFM modulus mapping reveals a smooth modulus-gradient interphase of ∼300 nm, confirming the molecular interpenetration and dynamic reconstruction mechanism at the rigid-flexible synergistic interface. This sizing strategy is also applicable to PPBESK matrices containing biphenyl units and various reinforcement forms (fabrics and short fibers), enabling universal interfacial strengthening and substantial wear-resistance improvement. The concept of Tg-difference-driven dynamic adaptive interfacial design thus provides a water based, environmentally benign, and widely applicable paradigm for high-performance thermoplastic carbon fiber composites.

This work demonstrates the successful preparation of two types of photocatalytically active nanostructured materials from an industrial waste product – Sal Ammonia Skimming – using hydrochloric acid as a leaching medium. The whole production process was developed to prepare valuable ZnO nanomaterials in both fibrous and powdered forms. This involved a sequence of hydrometallurgical processing, needle-less electrospinning, and conventional calcination of recycled environmentally polluting industrial waste. The morphologies and phase composition of the resulting ZnO powder and ZnO fibers were analyzed using SEM, EDS, and XRD analyses. The impact of the morphology of the prepared nanomaterials on the photocatalytic efficiency of the ZnO-based photocatalyst – powder versus ZnO nanofibers – was evaluated through decolorization experiments of the commonly used methylene blue dye in batch mode. Methylene blue was chosen as a model substance for toxic industrial pollutants. A 25 W UVA lamp with an emission maximum at 365 nm was used as a light source. Removal efficiencies were carefully tested and compared for different nanomaterial morphologies and preparation conditions. The most photocatalytically active ZnO-based nanomaterial was the electrospun nanofibrous one calcined at 600 °C for 1 h. This material achieved 100 % removal of a 10 −5 mol/L methylene blue dye from the solution within 700 minutes at an increased catalyst-to-dye ratio of 500 mg/50 ml. Based on the obtained results, it can be stated that the prepared materials exhibit high photocatalytic activity under UV light irradiation and have a potential for photocatalytic water remediation applications.

The development of green corrosion inhibitors from agro-waste materials presents a sustainable approach to mitigating acid-induced degradation of industrial metals. In this study, the inhibition efficiency of aqueous extract from Solanum melongena (garden egg) peel waste was systematically evaluated for carbon steel in 1.0 M hydrochloric acid using the weight loss (gravimetric) method for corrosion mitigation. Mild steel coupons were immersed in acidic solutions containing varying concentrations (100–400 ppm) of the extract for 24, 48, and 72 hours. The corrosion rate was calculated, and inhibition efficiency (%IE) determined as a function of extract concentration and exposure time. Results showed that the extract significantly reduced the corrosion rate of mild steel, with the highest inhibition efficiency of 47.89% recorded at 400 ppm after 24 hours. The inhibition efficiency increased consistently with both concentration and immersion duration, indicating a dose- and time-dependent protective effect. Adsorption studies revealed that the extract adhered strongly to the metal surface, following the Langmuir adsorption isotherm, which suggests monolayer physical adsorption of phytoconstituents such as polyphenols and flavonoids. These findings establish S. melongena peel extract as a potent, low-cost, and environmentally friendly corrosion inhibitor with promising applicability in industrial acid treatment processes.

This study investigated a feasible recycling and detoxification process for waste tire ash containing hazardous Zn and Al using acid leaching, followed by layered double hydroxide (LDH) synthesis. The novelty of this work is the direct conversion of a Zn/Al/Fe/Ca-rich real waste system into a phosphorus removal material, in which LDH-related uptake and secondary hydroxyapatite formation cooperatively immobilize phosphorus. Waste tire ash mainly consists of Zn, Al, Fe, Ca, and Si, most of which can be effectively leached with hydrochloric acid (HCl). The optimum leaching conditions for high extraction efficiency involved treatment with 10 M HCl for 10 min at 20 °C (solid–liquid ratio: 50 g/L). Under these conditions, the elution concentrations of Zn and Al from the residue decreased to 0.3 and 0.17 mg/L, respectively, meeting the Japanese leaching standards, whereas the raw ash showed significantly higher values. From the leached solution, LDH-containing products with high phosphorus removal capacity were synthesized at 40 °C for 2 h by adjusting the pH to 11.5. A phosphorus removal performance of 2.0 mmol/g was obtained owing to the formation of hydroxyapatite. The combined process of HCl leaching and LDH synthesis enables the detoxification of waste tire ash and the production of an environmental purification material.