Apostichopus japonicus polysaccharide as efficient sustainable inhibitor for mild steel against hydrochloric acid corrosion

Research progress on chitosan and its derivatives in the fields of corrosion inhibition and antimicrobial activity

Chitosan stands out as the only known polysaccharide of its kind, second only to cellulose. As the second-largest biopolymer globally, chitosan and its derivatives are extensively used in diverse areas such as metal anti-corrosion prevention, food production, and medical fields. Its benefits include environmental friendliness, non-toxicity, cost-effectiveness, and biodegradability. Notably, the use of chitosan and its derivatives has gained substantial attention and has been extensively researched in the fields of metal anti-corrosion prevention and antibacterial applications. By means of chemical modification or synergistic action, the inherent limitations of chitosan can be substantially improved, thereby enhancing its biological and physicochemical properties to meet a wider range of applications and more demanding application requirements. This article offers a comprehensive review of chitosan and its modified composite materials, focusing on the enhancement of their anticorrosion and antibacterial properties, as well as the mechanisms by which they serve as anticorrosion and antibacterial agents. Additionally, it summarizes the synthesis routes of various modification methods of chitosan and their applications in different fields, aiming to contribute to the interdisciplinary development and potential applications of chitosan in various areas.

Pumpkin Leaf Extract Crop Waste as a New Degradable and Environmentally Friendly Corrosion Inhibitor

The pumpkin leaf was extracted by the decoction method, and it was used as an eco-friendly, nontoxic inhibitor of copper in 0.5 M H2SO4 corrosion media. To evaluate the composition and protective capacity of the pumpkin leaf extract, Fourier infrared spectroscopy, electrochemical testing, XPS, AFM, and SEM were employed. The results showed that the pumpkin leaf extract (PLE) is an effective cathode corrosion inhibitor, exhibiting exceptional protection for copper within a specific temperature range. The corrosion inhibition efficiency of the PLE against copper reached 89.98% when the concentration of the PLE reached 800 mg/L. Furthermore, when the temperature and soaking time increased, the corrosion protection efficiency of 800 mg/L PLE on copper consistently remained above 85%. Analysis of the morphology also indicated that the PLE possesses equally effective protection for copper at different temperatures. Furthermore, XPS analysis reveals that the PLE molecules are indeed adsorbed to form an adsorption film, which is consistent with Langmuir monolayer adsorption. Molecular dynamics simulations and quantum chemical calculations were conducted on the main components of the PLE.

Chemical substances and their activities in sea cucumber Apostichopus japonicus: A review

Apostichopus japonicus, also known as Stichopus japonicus, with medicinal and food homologous figures, is a globally recognized precious ingredient with extremely high nutritional value. There is no relevant review available through literature search, so this article selects the research articles through the keywords "sea cucumber" and "Apostichopus japonicus (Stichopus japonicus)" in six professional databases, such as Wiley, PubMed, ScienceDirect, ACS, Springer, and Web of Science, from 2000 to the present, summarizing the extraction, isolation, and purification methods for the four major categories (polysaccharides, proteins and peptides, saponins, and other components) of the A. japonicus chemical substances and 10 effective biological activities of A. japonicus. Included are anticoagulation, anticancer/antitumor activities, hematopoiesis, regulation of gut microbiota, and immune regulatory activities that correspond to traditional efficacy. Literature support is provided for the development of medicines and functional foods and related aspects that play a leading role in future directions.

Facile solvothermal synthesis of a MIL-47(V) metal-organic framework for a high-performance Epoxy/MOF coating with improved anticorrosion properties

The vanadium-based metal–organic framework MIL-47 distinguishes itself among other MOFs for its distinctive structure and unique properties (e.g., flexible structure, high thermal stability, and high surface area). The synthesis of MIL-47 has been reported from various metal precursors, including vanadium(iii) chloride (VCl₃) as a rich source of metal ions. Attempts have been made to include other starting materials, a step forward towards large-scale production. Synthesis from various solid materials is encouraged, seeking an economic and greener approach. In this study, vanadium pentoxide (V₂O₅), a readily abundant low-cost and thermodynamically stable metal source, was used to synthesize the MIL-47(V) framework via a facile solvothermal route. This precursor provides a controllable rate of metal ion production depending on the applied reaction conditions. In our method, the synthesis took place at a low temperature and reaction time (180 °C for 20 h, instead of 220 °C for 72 h), yielding MIL-47 microrods. Moreover, among its unique properties, the metal centers of MIL-47 oxidize under the influence of thermal or chemical treatments, preserving the framework structure. This unusual character is not commonly witnessed in comparable MOF structures. This property can be leveraged in anti-corrosion applications, whereby a redox reaction would sacrifice the framework components, protecting the metal in contact. However, the chemical stability of MIL-47 is doubted against a corrosive medium. Thus, an epoxy coating with 10 wt% MOF loading was incorporated in our investigation to extend the aluminum alloy (AA2024) surface protection for prolonged exposure duration. The uniformity of distribution of the prepared MOF within the epoxy matrix was confirmed using SEM/EDX. Electrochemical impedance spectroscopy (EIS) was used to evaluate the corrosion performance of the coated samples. The results showed that the inclusion of V-MOF offers extended corrosion prevention, over 60 days, for the AA2024 alloy against artificial seawater. The neat epoxy coating could not prevent the corrosion of AA2024 over two weeks of immersion, whereby pitting corrosion was clearly observed. The V-MOF could induce a series of redox reactions leading to the precipitation of vanadium on the cathodic sites of metal surfaces.

The well-known MIL-47(V) metal–organic framework was synthesized solvothermally with high quality using V₂O₅ as a precursor. Applying the MOF particles in an epoxy coating resulted in an improved anticorrosion protective barrier for the AA2024 substrate against a chloride-rich environment.