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Sanaei, Zahra, Ali Shamsipur, and Bahram Ramezanzadeh. Chemical Engineering Journal 451 (2023): 138872.
This work presents the first design of a novel multifunctional mesoporous nano-hybrid material with high inhibitor adsorption/targeted release capability. The method involves surface modification of reduced graphene oxide (rG) using layered Zn-Al-NO3--LDH (L), followed by in-situ growth of core-shell (CS) mesoporous ZIF-67 (Z67)/ZIF-8 (Z8) coordination polymers. The designed rGL-Z67/Z8 CS structure was loaded with trisodium phosphate (TSP) inhibitor, providing an intelligent anticorrosive epoxy system.
Loading of Inhibitor Na3PO4 into rGL-Z67 and rGL-Z67/Z8 CS Structures
Trisodium phosphate Na3PO4 (TSP) was used as the anionic inhibitor, which was incorporated into the interlayer galleries of LDH via an ion-exchange mechanism with the intercalated nitrate anions, and physically/chemically adsorbed into the MOF pores. For inhibitor loading, 0.1 g of the nano-hybrid was dispersed in 50 cc of water solution by ultrasonication. Then, a solution containing 1.5 g of TSP was added to the previous solution. The pH of the mixture was adjusted to 8 by adding a NaOH buffering solution, transferred to a vacuum conical flask, and stirred under vacuum for 1 hour. The TSP-loaded rGL-Z67 and rGL-Z67/Z8 nano-hybrids were then centrifuged, and the precipitates were washed three times with boiling deionized water. The obtained samples were denoted as rGL-Z67-TSP and rGL-Z67/Z8-TSP, respectively.
Kumar, H., Kumari, R., Yadav, A., Sharma, R., & Dhanda, T. (2020). Chemical Data Collections, 30, 100575.
The practicality of low carbon steel (MS) in manufacturing is attributed to its excellent mechanical properties and low cost. The primary issue associated with MS is its severe corrosion when used in acidic media. Compared to other alternative inhibitors, phosphates offer advantages such as low cost and non-toxicity. In this study, trisodium phosphate (TSP) is used as a corrosion inhibitor for MS in 0.1 N sulfuric acid (corrosive medium).
Inhibition Mechanism of TSP
A uniform, non-porous, and continuous TSP film was observed on the surface of MS, which prevents the corrosive sulfuric acid from contacting the MS surface. This physical adsorption is further supported by the larger Kads value (i.e., 12.47) and greater coating thickness (i.e., 245.43 μ), as observed from metallurgical research microscope techniques. The mechanism of TSP on the MS surface was understood through Langmuir adsorption isotherm studies, DFT simulation studies, impedance spectroscopy, metallurgical research microscopy, and SEM studies. Increases in capacitance loops, Warburg impedance, charge transfer resistance, coating thickness, zero-point vibrational energy, thermal internal energy, ground-state stability energy, ΔG0ads and Kads of LSI, and percent porosity, among other factors, confirmed the formation of a uniform, continuous barrier film of TSP molecules on the MS surface.
It is hypothesized that TSP molecules form stable coordinate covalent bonds between the oxygen atoms in TSP and iron atoms on the MS surface. This is an example of a donor-acceptor bond where the ligand (TSP molecule) initially donates electrons to the vacant 3d orbitals of the metal (Fe), and then the metal (Fe) reciprocally donates its electrons from the filled 3d orbitals to the vacant π* anti-bonding orbitals of the TSP molecule. The strong adsorption of TSP molecules is further supported by TSP's suitable molecular configuration, high electronegativity, global softness parameters, and high negative interaction parameter values. In summary, the adsorption mechanism of TSP as a corrosion inhibitor on MS involves physical adsorption, chemisorption, and reverse donation methods.
Okoye, P. U., A. Z. Abdullah, and B. H. Hameed. Journal of the Taiwan Institute of Chemical Engineers 68 (2016): 51-58.
Glycerol, a major byproduct of biodiesel production, can be valorized by synthesizing glycerol carbonate (GC) using anhydrous trisodium phosphate (TSP) as a reusable heterogeneous catalyst. The synthesis of GC involves the transesterification of glycerol with dimethyl carbonate (DMC) in a 250 mL three-neck round-bottom glass reactor, equipped with an automatic heater and magnetic stirrer.
Different proportions of glycerol (19.069 g)/DMC (19.5 to 97.7 g) and TSP (0.19 to 0.76 g) (equal to 1 to 4 wt% relative to the weight of glycerol) were charged into the reactor. The reaction was carried out at temperatures ranging from 50 to 80 °C for a duration of 30 to 120 minutes. Excess unreacted DMC was separated by slow evaporation under reduced pressure. The conversion and yield of glycerol and GC were quantitatively measured using gas chromatography.
