Volume 96, Issue 6 - Special Issue: African Early Career Chemists Workshop; 8th ACS Nigerian Chapter Symposium

This preface introduces the proceedings of the African Early Career Chemists Workshop & 8th Annual Symposium of the American Chemical Society (ACS), Nigeria International Chapter, which was held both virtually and onsite from June 4th to 8th, 2023. This special issue of Pure and Applied Chemistry (PAC) journal includes 8 manuscripts covering a range of topics from pure to applied chemistry.

The research considers the design and simulation of 30 000 tons per year of cumene plant using Aspen HYSYS as the simulation tool. The feed (material content) used is the characterized natural gas from Utorogu Gas Field with composition of 0.9019 methane, 0.0694 ethane, 0.0209 propane, 0.00361 n-butane, 0.00414 i-butane, 0.00005 n-pentane and 0.00007 i-pentane. The cumene plant consist of the cryogenic distillation column, de-hydrogenator (Continuous Stirred Tank Reactor), Alkylator (Plug Flow Reactor), storage tanks, separators, pumps, heat exchanger and mixers. The size/design models of basic plant units such as de-hydrogenator, alkylator, separators, storage tanks and distillation column were developed using the principles of mass and energy balance. The result of design or size specifications in terms of equipment diameter of basic plant units obtained from HYSYS simulation are 0.8 m and 0.319 m for the cryogenic and cumene columns; 1.931 m, 2.244 m and 1.366 m for the propane, propene and cumene storage tanks; 1.868 m and 2.076 m for the de-hydrogenator and alkylator; 1.931 m and 2.146 m for propene and cumene separators respectively. The power or capacity of propane and propene pumps configured in the plant are 0.02 kW and 0.005 kW respectively. The result of the reactor and distillation column thickness specification to withstand corrosion, pressure or stress during plant operation in terms of cylindrical shell and ellipsoidal doomed head are 17.36 mm and 4.31 mm respectively. The economic evaluation (overall cost) including the cost of utilities, catalyst, operating, and maintenance for entire plant is $ 3.004 M.

COVID-19, the global pandemic caused by SARS-Corona virus 2 (SARS-CoV-2), recently ravaged the World with various efforts charged towards finding therapeutic drug targets for this novel virus. The identification of COVID-19 main protease (Mpro) opened the possibility of testing new families of inhibitors as potential anti-coronaviral drugs. Protein-drug interaction is of pivotal importance to understanding the structural features essential for any ligand affinity. This study evaluated the efficacy of an isolated bioactive plant compound and synthetic tetraazamacrocycles against COVID-19 Mpro by molecular docking. Molecular docking investigations were performed using PyRx, Auto Dock vina and Discovery Studio (DS) to analyze the inhibition probability of these compounds against COVID-19. COVID-19 Mpro (PDB ID: 6LU7: Resolution 2.16 Å) was docked with 1 flavonoid and 3 tetraaza-macrocyclic compounds comparatively with known anti-viral drugs (Remdesivir (REMD) and Nelfinavir (NELF)) and hydroxychloroquine (HCQ). Docking studies showed H-TEAD, 5 interacting with 5 residues having the highest binding affinity of −9.4 kcal/mol, followed by TEAD with 5 residue interactions and a binding affinity value of −9.4 kcal/mol, HA-TEAD, 7 has 5 interactions with a binding affinity of −9.3 kcal/mol, and Siam1 has 6 interactions with a binding energy of −7.8 kcal/mol. All the docked potential drugs have binding energies higher than the reference drugs HCQ, 1 and REMD, 2 connoting greater activity except NELF, 3 whose value is only lower than the 3 macrocycles (HA-TEAD, 7 and H-TEAD, 5 and TEA1, 6 ). They are bound through hydrogen bonds, arene-anion and arene-cation interactions. The trend of binding affinity show H-TEAD (−9.4 kcal/mol) = TEAD1 (−9.4 kcal/mol) > HA-TEAD (−9.3 kcal/mol) > NELF (−8.7 kcal/mol) > Siamone (−8.8 kcal/mol) > HCQ (−7.2 kcal/mol) > REMD (−6.2 kcal/mol) while the number of interactions shows REMD > HA-TEAD = HCQ > Siamone > NELF > H-TEAD > TEAD1. This study, hence, validates the activity of HCQ against COVID-19 and provides a foundation for advanced experimental research, to evaluate the real pharmaceutical potentials of these compounds, towards finding a cure for COVID-19 and other related diseases.

Among the many drawbacks of the current wastewater treatment systems are their high energy consumption and creation of harmful sludge. Carbon nanotubes (CNTs) are advantageous for the treatment of water due to their strong adsorption capacity and selectivity towards various pollutants. Thus, creating methods for treating water by producing CNTs from Moringa oleifera leaf extract can greatly help with the clean water problem. The synthesised material’s Ultra Visible (260–385 nm), FTIR (764–3295 cm −1 ) and Scanning Electron Microscope (SEM) characterizations have demonstrated their CNTs characteristics. The repeatability testing yielded the %RSD values for Ca = 0.4, Cu = 0.24, Mg = 0.9, Pb = 1.06 and Zn = 0.36 which suggest that the AES approach demonstrated a high degree of precision. The findings show that the quantity of recovered metals increases with retention period. Mg > Cu > Zn > Ca > Pb was the order of the metal adsorption capacity throughout retention durations of 3, 6, 24, and 48 h. As the initial concentrations of the components under research were doubled and tripled, so were the removal capacities of CNTs increased which may be as a result of an increase in metal ions in the solution. The outcomes show how well the synthetic CNTs can remove heavy metals from wastewater.

Zeolite Y is the active phase of the modern fluid catalytic cracking (FCC) catalyst. However, a functional and active FCC catalyst comprises, in addition to zeolite Y, matrices and a binder that introduce some levels of synergistic interaction between the catalyst components, impacting its activity. This study investigates the interactive properties of a zeolite-matrix-binder composite on a typical FCC catalyst using various characterization techniques. Characterization of synthesized FCC catalyst samples reveals changes in the structural composition of zeolite Y dependent upon the type and ratio of binder materials. The binder is important in the crystallization of the final composite. Acidic binder induces dealumination of zeolite, leading to amorphization, loss of Brønsted acid sites, framework structure impairment, and the formation of defective sites. TEM indicates the formation of zeolite-matrix interfaces upon binding of zeolite by the matrix. Depending on the extent and severity of thermal processing, the clay–alumina–silica binder undergoes dehydroxylation to varying degrees by cross-linking of terminal hydroxyl groups between neighboring binder particles, which contributes to the increased thermal and mechanical stability of the bound catalysts.

The global economy has led to an increase in oil transportation and exploitation, posing a threat to aquatic and terrestrial ecosystems. Crude oil spilled water purification is a major challenge worldwide. Researchers are focusing on finding adsorbents that improve oil adsorption capability. In the present study the adsorption of crude oil using synthesized carbon nanotubes (CNTs) prepared from coconut shell was investigated by batch adsorption experiments under varying parameters (adsorbent dosage and contact time) after analytical techniques (UV–vis, FTIR and SEM) confirmed the formation of the CNTs. The morphological modification significantly increased the hydrophobicity of the adsorbent, thus creating a synthesized CNTs with a much better adsorption capacity for crude oil removal having a maximum adsorption capacity of 4855.8 mg/g. The experimental results showed that the percentage of crude oil removal increased with an increase in adsorbent dosage and the contact time respectively. According to the correlation coefficient ( R 2  = 0.9801) value obtained from the adsorption isotherm investigations, the isotherms were found to fit the Freundlich isotherm somewhat better than the Langmuir isotherm model, which is consistent with the findings reported in the literature. These findings have made the synthesised CNTs an attractive, useful, and environmentally friendly adsorbent for controlling crude oil spill.

The present study investigates the electrochemistry spectroscopy of Sm(III), and electrodeposition of samarium metal in neutral ligand-based ionic liquid (solvate ionic liquid). Mixture consisted of a samarium precursor (either samarium triflate or samarium nitrate hexahydrate) in the solvate ionic liquid, 1.3-dimethyl-2-imidazolidone (DMI). FT-IR analysis of Sm(III)-DMI electrolytes indicates that Sm 3+ ion coordinates with DMI through carbonyl group (C=O); the band splits into two with emergence of new peak at 1630 cm −1 and 1649 cm −1 for the triflate and nitrate solutions, respectively. Raman spectroscopy also confirms the solvation of Sm(III) with DMI through oxygen atom of the carbonyl group. Voltametric behaviour of Sm(III) ion indicates two-step reduction mechanism via Sm(III)/Sm(II) at ca.  −2.0 V and Sm(II)/Sm(0) at ca.  −3.0 V vs. Ag/Ag + for both samarium(III)-containing electrolytes. Diffusion coefficient value of Sm(III) was determined to be 2.185 × 10 −6  cm 2 /s and 2.418 × 10 −8  cm 2 /s for triflate and nitrate electrolytes, respectively. Electrodeposition of samarium was achieved through constant potential electrolysis using copper substrate as the working electrode which yielded compact deposits from triflate-DMI and non-uniform granular deposit from nitrate-DMI electrolyte. Ex situ X-ray photoelectron spectroscopy analysis of the as-deposited samples revealed the presence of metallic Sm (1081 eV) co-existing with its oxide form (1083 eV).

All current theories concerning the conductivity of polyelectrolytes ignore the dielectric friction effect undergone by the polyion chains according to their conformation. Indeed, Manning’s theory is limited to the case of stretched chains and only takes into account hydrodynamic, electrophoretic and ionic frictions; while scaling approach theories take into account the formation of different types of blobs within the chain but are restricted to hydrodynamic and electrophoretic frictions. In this work, we present a different approach that explains the variation of the equivalent conductivity of polyions having coiled or almost or completely stretched conformations and that takes into account the four frictions. In addition, the introduction of the dielectric friction effect allowed us to interpret the dependency of the equivalent conductivity of a polyion λ P,X on the nature of its counterions X. A likely correlation between this effect and Hofmeister’s is discussed.