Department of Chemical Sciences

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    2-Aryl benzimidazoles: Synthesis, In vitro alpha-amylase inhibitory activity, and molecular docking study
    (Elsevier, 2018-03-06) Akande, Akinsola
    Despite of many diverse biological activities exhibited by benzimidazole scaffold, it is rarely explored for the -amylase inhibitory activity. For that purpose, 2-aryl benzimidazole derivatives 1-45 were synthesized and screened for in vitro -amylase inhibitory activity. Structures of all synthetic compounds were deduced by various spectroscopic techniques. All compounds revealed inhibition potential with IC50 values of 1.48 ± 0.38-2.99 ± 0.14 M, when compared to the standard acarbose (IC50 = 1.46 ± 0.26 M). Limited SAR suggested that the variation in the inhibitory activities of the compounds are the result of different substitutions on aryl ring. In order to rationalize the binding interactions of most active compounds with the active site of -amylase enzyme, in silico study was conducted.
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    a-Amylase Inhibition, Anti-glycation Property and Characterization of the Binding Interaction of Citric Acid with a-Amylase Using Multiple Spectroscopic, Kinetics and Molecular Docking Approaches
    (Elsevier, 2022-07-15) Oyetunde, Temidayo
    The quest to suppress complications associated with diabetes mellitus is ever increasing, while food additives and preservatives are currently being considered to play additional roles besides their uses in food enhancement and preservation. In the present study, the protective prowess of a common food preservative (citric acid, CA) against advanced glycation end-products (AGEs) formation and its binding interaction mechanism with a-amylase (AMY), an enzyme linked with hyperglycemia management, were examined. Enzyme inhibition kinetics, intrinsic fluorescence, synchronous and 3D fluorescence spectroscopies, ultraviolet–visible (UV–Vis) absorption spectroscopy, Fourier transform-infrared (FT-IR) spectroscopy, thermodynamics, and molecular docking analyses were employed. Results obtained showed that citric acid decreased a-amylase activity via mixed inhibition (IC50 = 5.01 ± 0.87 mM, Kic = 2.42 mM, Kiu = 160.34 mM) and suppressed AGEs formation (IC50 = 0.795 ± 0.001 mM). The intrinsic fluorescence of free a-amylase was quenched via static mechanism with high bimolecular quenching constant (Kq) and binding constant (Ka) values. Analysis of thermodynamic properties revealed that AMY-CA complex was spontaneously formed (DG < 0), entropy driven (TDS > DH), with involvement of electrostatic forces. UV–Vis, FT-IR and 3D fluorescence spectroscopies affirmed alterations in aamylase native conformation due to CA binding interaction. CA interacted with His-101, Asp-197, His- 299, and Glu-233 within AMY active site. Our findings indicated that CA could impair formation of AGEs and interact with a-amylase to slow down starch hydrolysis; vital properties in management of type 2 diabetes complications.
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    Activated Carbon from Nauclea diderrichii Agricultural Waste–a Promising Adsorbent for Ibuprofen, Methylene Blue and CO2
    (Elsevier, 2021-03-15) Omorogie, Martins
    The adsorption potential of activated carbon derived from Nauclea diderrichii biomass (NDAC) was scrupulously harnessed as a low cost and ubiquitous adsorbent for the removal of greenhouse gas (CO2), and organic pollutants such as methylene blue (MB) and ibuprofen (IB) from water. NDAC was fully characterized by scanning electron microscopy (SEM), thermo-gravimetric analysis (TGA), X-ray diffraction (XRD), universal attenuated total reflectance-infra red (UATR-IR), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), solid state nuclear magnetic resonance (NMR) and nitrogen gas adsorption–desorption by Brunauer-Emmett-Teller (BET) technique. This study showed that NDAC comprises graphitic carbons that had some surface functional groups such as C C, C O, etc, which adsorbed these environmental contaminants. The adsorption equilibrium and kinetic data that the adsorption of these environmental contaminants formed multilayers (homogeneous surfaces) with the surface of NDAC. The adsorption mechanism of CO2, MB and IB onto NDAC occurred by via electrostatic attractions and π-π conjugal interactions. The adsorption capacity of NDAC for CO2 was ca. 3.2 cm3.g−1 at 298 K. The Langmuir maximum adsorption capacity, qmax of NDAC for MB and IB was obtained as 35.09 mg.g−1 and 70.92 mg.g−1 at 328 K respectively.
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    Adicardin and Other Coumarins from Breonadia salicina (Vahl) Hepper
    (Tropical Journal of Natural Product Research, 2019) Ajibade, Sunday
    Breonadia salicina is an ethnomedicinal plant used in North Central Nigeria to treat sleeping sickness and respiratory diseases. The stem bark of the plant was extracted with methanol and the extract partitioned between dichloromethane and water. The dichloromethane soluble portion was subjected to column chromatography which resulted in the isolation of 7-(β-D apiofuranosyl (1-6)-β-D-glucopyranosyl) umbelliferone, α-amyrin, stigmasterol, 7-hydroxycoumarin and 6- hydroxy-7-methoxy coumarin. The structures of these compounds were elucidated based on NMR spectral analysis. This is the first report of these compounds from the plant.
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    Adsorption and Desorption Kinetics of Toxic Organic and Inorganic Ions using an Indigenous Biomass: Terminalia ivorensis Seed Waste
    (Springer, 2017-05-15) Omorogie, Martins
    Environmental remediation has been a strategy employed by scientists to combat water pollution problems that have led to the scarcity of potable water. Hence, in this study, Terminalia ivorensis seed waste (TISW) was explored for the removal of Congo Red, Methylene Blue, Cadmium and Lead from aqueous solutions. Some experimental variables such as pH, biosorbent dose, initial solute ion concentration, agitation time and temperature were optimised. The surface microstructures of TISW were studied using proximate analysis, bulk density, specific surface area, pH of Point of Zero Charge, Fourier Transform Infra Red Spectroscopy, Thermogravimetric/Differential Thermal Analysis, Scanning Electron Microscopy and Energy Dispersive Analysis of X-ray. The maximum Langmuir monolayer saturation adsorption capacity, qmaxL, was obtained as 175.44 mg/g for the removal of Methylene Blue by TISW. Also, the qmaxL for CR, Cd(II) ion and Pb(II) ion were 85.47, 12.58 and 52.97 mg/g, respectively. Also, the pseudo-first-order constant, k1, and pseudo-second-order rate constant, k2, are 0.008–0.026/min and 0.012–0.417 mg/g min, respectively. Hence, TISW is recommended as a good adsorbent for the removal of both toxic industrial dyes and toxic metal ions from polluted water.
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    Adsorption Efficacy of Cedrela odorata Seed Waste for Dyes: Non linear Fractal Kinetics and non linear Equilibrium Studies
    (Elsevier, 2016-08-15) Omorogie, Martins
    Alteration of the structural and functional integrity of the aquatic ecosystems due to contamination from toxic industrial dyes warrants cost effective remedial strategies. Cedrela odorata Seed Chaff (COSC) was locally sourced, indigenous and ubiquitous. In support of this proposition, the efficacy of the COSC was assessed for the adsorption of some toxic industrial dyes, namely Methylene Blue (MB), Congo Red (CR), Methyl Violet (MV) and Methyl Orange (MO) from aqueous solutions. The microstructures of Cedrela odorata Seed Chaff (COSC) were carried out using pH of Point of Zero Charge (PZC), Specific Surface Area (SSA), Bulk Density (BD), Fourier Transform Infra Red Spectroscopy (FTIR), X-Ray Diffraction (XRD), Thermogravimetric Analysis (TGA) and Scanning Electron Microscopy (SEM) which indicated that various organic moieties were present in COSC, which the toxic industrial dyes studied were adsorbed onto. Non linear equilibrium and non linear fractal models were used to fit experimental data. The experimental data best fit the Fritz-Schlunder four-parameter isotherm and the fractal-like pseudo-second order (three-parameter) kinetic equation. The Langmuir monolayer adsorption capacities, qmaxL of COSC for the uptake of MB, CR, MV and MO were 88.32–111.88 mg/g, 79.46–128.84 mg/g, 75.11–121.23 mg/g and 57.35–68.23 mg/g respectively as temperature increased from 298 to 318 K. The results support the use of Cedrela odorata Seed Chaff (COSC) as a cost effective material for removal of toxic industrial dye from an aquatic system. Large scale studies are required in the future to prove the efficacy of Cedrela odorata Seed Chaff (COSC) for toxic industrial dyes from varied environmental conditions.
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    Adsorption Kinetics of 4-Nitrophenol onto a Cellulosic Material, Mansonia Wood Sawdust and Multistage Batch Adsorption Process Optimization.
    (Elsevier, 2010-09-18) Unuabonah, Emmanuel
    The kinetics of 4-nitrophenol biosorption from aqueous solution using mansonia wood sawdust, a cellulosic material at different dose is probably a two step mechanism involving the adsorption of a hydrogen ion from solution onto the biosorbent surface followed by electrostatic attraction between the positive surface and the anionic adsorbate. The Wu’s expression for the initial biosorption showed that limitations to intraparticle diffusion were higher for higher biosorbent dose. The switch of the rate-controlling step to intraparticle diffusion was observed in the pattern of the intraparticle diffusion plots as three distinct sections. Multistage optimization studies suggested that 193.8 g of Mansonia wood sawdust, three countercurrent batch adsorption stages and 12 min 48 s are required for the removal of 99.5% of 120 mg dm−3 of 4-nitophenol from aqueous solution. The minimum contact time for removal of 4-nitrophenol in each stage is independent of the percentage removal for each stage.
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    Adsorption of Lead and Cadmium Ions from Aqueous Solutions by Tripolyphosphate-Impregnated Kaolinite Clay
    (Elsevier, 2006-06) Unuabonah, Emmanuel
    The pretreatment of Kaolinite clay with tripolyphosphate (TPP) increased the cation exchange capacity (CEC) of Kaolinite clay from 13.45 meq/100 g to 128.7 meq/100 g. The equilibrium adsorption capacity of TPP–Kaolinite clay for Pb2+ and Cd2+ was 126.58 mg/g and 113.64 mg/g, respectively. The presence of Na- and Ca-electrolytes and with increase in their concentrations reduced the selectivity of TPP–Kaolinite clay for Pb2+ than Cd2+. TPP–Kaolinite clay showed higher selectivity for Pb2+ in the presence of these electrolytes and at all concentrations of these electrolytes used for the study. Binary mixtures of Pb2+ and Cd2+ in various concentrations caused a decrease in the adsorption capacity of TPP–Kaolinite for either metal ion. However, this may have caused the adsorption of Cd2+ onto high energy sites on the surface of the TPP–Kaolinite clay. Non-linear Chi-square model analysis of adsorption data using Langmuir, Langmuir–Freudlich, Freudlich, Toth and Temkin isotherms reveals that the adsorption of Pb2+ and Cd2+ by TPP–Kaolinite clay were best described by the Toth and Freudlich isotherms, respectively. At low concentrations (≤500 mg/L) the adsorption of these metal ions showed better fits to the five models with Langmuir–Freudlich and Freudlich isotherms giving the best fits for Pb2+ and Cd2+, respectively.
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    Adsorption of Pb (II) and Cd (II) from Aqueous Solution onto Sodium Tetraborate-modified Kaolinite Clay: Equilibrium and Thermodynamic Studies
    (Elsevier, 2008) Unuabonah, Emmanuel
    Kaolinite clay sample obtained from Ubulu-Ukwu in Delta State of Nigeria was modified with sodium tetraborate to obtain NTB-modified kaolinite clay. XRD measurements of NTB-modified kaolinite adsorbent showed no observable change in the d-spacing of its crystal lattice. Also, the data of XRD confirmed that this kaolinite clay sample is a mixture of kaolinite and Illite clay minerals. The SEM of modified and unmodified samples showed irregular crystal structures. FTIR results proved the surface modification of the kaolinite at –Al–O and –Si–O centers. The NTB-modified adsorbent presented with broader peaks of inner –OH. Modification of kaolinite clay sample with sodium tetraborate decreased its PZC from pH 4.40 to 3.70 while its Specific Surface Area (SSA) was increased from 10.56 m2 g−1 to 15.84 m2 g−1 . Modification with sodium tetraborate reagent increased the adsorption capacity of kaolinite clay from 16.16 mg/g to 42.92 mg/g for Pb (II) and 10.75 mg/g to 44.05 mg/g for Cd (II) at 298 K. Increasing temperature was found to increase the adsorption of both metals onto both adsorbents suggesting an endothermic adsorption reaction. The simultaneous presence of electrolyte in aqueous solution with Pb and Cd (II) was found to decrease the adsorption capacity of NTB-modified adsorbent for Pb and Cd (II). Using the Pearson's Hard and Soft Lewis Acid and Base (HSAB) theory the higher selectivity of unmodified kaolinite clay adsorbent for Pb and NTB-modified kaolinite clay for Cd (II) was justified. The thermodynamic calculations for the modified kaolinite clay sample indicated an endothermic nature of adsorption (ΔHmean + 4.35 kJ mol−1 for Pb(II) and +3.79 kJ mol−1 for Cd (II)) and an increase in entropy as a result of adsorption of Pb (II) and Cd (II) (ΔSmean −21.73 J mol−1 K for Pb (II) and −18.30J mol−1 K for Cd (II)). The small positive values of free energy change (ΔGmean) indicated that the adsorption of Pb (II) and Cd (II) onto the modified adsorbent may require some small amount of energy to make it more feasible. Modeling equilibrium adsorption data obtained suggested that NTB-modified adsorbent sample has homogeneous adsorption sites and fit very well with Langmuir adsorption model. Regeneration studies suggest that ≈85% of the metals were desorbed from both adsorbents. On reuse of the adsorbents only ≈80% of metals were adsorbed. NTB-modified kaolinite clay sample show some very good potentials as a low-cost adsorbent for the adsorption of Pb (II) and Cd (II) from aqueous solutions
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    Adsorption of some heavy metal ions on sulfate- and phosphate-modified Kaolin
    (Elsevier, 2004) Unuabonah, Emmanuel
    Kaolin (bright white lumps) from Ubulu-Ukwu in Delta State of Nigeria was modified with 200 µg mL-1 of phosphate and sulphate anions to give phosphate- and sulfate-modified adsorbents, respectively. The adsorption of four metal ions (Pb2+, Cd2+, Zn2+, and Cu2+) was studied as a function of metal ions concentration. The metal ions showed stronger affinity for the phosphate-modified adsorbent with Pb2+, Cu2+, Zn2+, and Cd2+ giving an average of 93.28%, 80.94%, 68.99%, and 61.44% uptake capacity. The order of preference for the various adsorbents shown by the metal ions was as follows: Pb2+>Cu2+>Zn2+>Cd2+. Desorption studies showed that the phosphate-modified adsorbent had the highest affinity for the metal ions, followed by the sulfate-modified clay while the unmodified clay had the least affinity. The experimental data were fitted by both the Langmuir and Freundlich models
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    Adsorption of Zn2+ and Cu2+ onto sulphate and phosphate-modified Bentonite
    (Elsevier, 2010) Unuabonah, Emmanuel
    The modification of bentonite with sulphate and phosphate increased the cation exchange capacity (CEC) and adsorption of Cu2+ and Zn2+ but decreased the specific surface area (SSA). Phosphate modified bentonite had the highest adsorption capacity for both metal ions. The Fourier transformed infrared spectra indicated the bonding of sulphate and phosphate bentonite with sulphate and phosphate by the hypochromic and hyperchromic shifts are typical of physisorption and chemisorption mechanisms. Phosphate and sulphate were adsorbed through inner-sphere and outer-sphere complex formation. The isotherms were better fitted by the Langmuir model than the Freundlich model.
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    Adsorptive Modelling of Toxic Cations and Ionic Dyes onto Cellulosic Extract
    (Springer, 2016-12-01) Omorogie, Martins
    This work reports the abstractive potential of Parkia biglobosa seed waste (PSW) and Parkia biglobosa cellulosic extract (PBCE) for the removal of Cr(VI), Pb(II), methylene blue (MB) and congo red (CR) from aqua system. Physicochemical analyses carried out for these biomaterials were proximate analysis, Fourier transform infra red (FTIR) Spectrophotometry and scanning electron microscopy (SEM). The FTIR data showed that –O–H, –C=C–, –C=O, –C:C– and –S–H functional groups were responsible for the sequestration of Cr(VI), Pb(II), MB and CR from aqua system. The equilibrium data fitted best to Langmuir isotherm model with the highest adsorption obtained for MB, being 1498.42 mg/g at 298 K and 403.23 mg/g at 298 K for PSW and PBCE respectively. Pseudo-second order model gave the best fits for the kinetic data among two other kinetic models used. The PSW and PBCE biomaterials demonstrated good potentials for the removal of toxic Cr(VI), Pb(II), MB and CR from aqua systems.
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    Aerosol-assisted CVD of cadmium diselenoimidodiphosphinate and formation of a newiPr2N2P3 + ion supported by combined DFT and mass spectrometric studies
    (Royal Society of Chemistry (RSC), 2016-10-25) Oyetunde, Temidayo
    Aerosol-assisted chemical vapour deposition (AACVD) of Cd[(SePiPr2)2N]2 is shown to deposit cadmium selenide and/or cadmium phosphide on glass substrates, depending upon the growth conditions. The phase, structure, morphology and composition of the films were characterised by X-ray powder diffraction (XRD), scanning electron microscopy, energy dispersive X-ray analysis and X-ray photoelectron spectroscopy. The XRD indicated a hexagonal phase for cadmium selenide, whilst cadmium phosphide was monoclinic. Pyrolysis gas chromatography-mass spectrometry and density functional theory were used to deduce a breakdown mechanism for the deposition that favoured the formation of a new aromatic iPr2N2P3+ ion.
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    Agrogenic Modified Clay For The Removal Of Gram-Negative Bacteria From Water
    (run.edu.ng, 2016-08) Koko, Daniel Terlanga
    The presence of pathogens in the few available water resources which have been reported to cause diseases and subsequent deaths especially in children of ages less than five years have given rise to the development of cost-effective, environmentally friendly, efficient and convenience means of water treatment. This project reports on the preparation of Zn-modified kaolinite clay biomass Carica papaya seeds and Musa paradisiaca peels) composite adsorbents for the removal of some enteric bacteria (E. coli, S. typhi and V. cholerae ) from the water. Three composite adsorbents were prepared: Zn-modified kaolinite clay adsorbent and Carica papaya seeds (ZKPS); Zn-modified kaolinite clay and plantain peels (ZKPP) and Zn-modified kaolinite clay-papaya seeds and plantain peels (ZKPPPS). The mixtures were treated to microwave at 500 W for 10 min and washed to neutral pH. The characterization with SEM shows they are homogeneous composites, while electron mapping results showed the presence of elements obtainable from the composites. The EDX analysis confirmed the presence of the all the elements contained in the composites and their varying concentration in which Zn was observed to be highest in all the composite adsorbents. Fourier Transformed Infrared spectroscopy and X-ray Diffraction (XRD) indicates chemical functionalities involved in the interaction between Carica papaya seeds and/or plantain peels with kaolinite in the presence of an activating agent. The FTIR spectra did confirm the presence of Zn in the composite adsorbents at ca. 462 cm-1. Surface area analysis via N2 sorption shows that ZKPP composite adsorbent has the highest surface area (342 m2 /g), followed by ZKPPPS composite adsorbent with 150 m2/g while ZKPS composite adsorbent had 117 m2/g. Surface area results suggest that the particles sizes of the composite adsorbents were in the nanoscale. The pH point of zero charges (pHpzc) of the composites adsorbents were obtained to be 7.0 for ZKPP and ZKPS composites adsorbents, while that of ZKPPPS composite adsorbent was obtained to 6.47 in contrast to that of kaolinite clay obtained to 4.98. This implies that at a temperature below pHpzc the adsorption of negatively charged particles are favored. Bacterial removal activities of the three composite adsorbent showed that ZKPS composite adsorbent had better activity on S. typhi and V. cholerae because the breakthrough time was observed at 700 min (5.6 L) and 400 min (3.2 L) respectively followed by ZKPP composite adsorbent with 400 min (3.2 L) respectively for S. typhi and V. cholerae, while ZKPPPS composite adsorbent was less efficient on the two bacteria with 275 min and 200 min for S. typhi and V. cholerae respectively. The three composite adsorbents showed no good efficiency for the removal of Escherichia coli from water.
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    Biochemical Properties, In-Vitro Antimicrobial, and Free Radical Scavenging Activities of the Leaves of Annona muricate
    (Journal of Appl. Sci. Environ. Manage., 2017) Ajibade, Sunday
    Fifteen (15) male Wistar rats were completely randomized into three (3) groups. Group A was normal control, Group B received 200 mg/kg weight of ethyl acetate extract of Annona muricata leaves (AMLE) and Group C received 100 mg/kg b.weight AMLE. Single daily dose of AMLE was administered orally for twenty one (21) days after which the animals were sacrificed. The blood samples were taken for haematological and biochemical analysis. Antibacterial and antifungal activities of n-hexane, ethyl acetate and methanol extracts of Annona muricata leaves were carried out. These extracts exhibited satisfactory inhibitory activities against bacterial and fungal strains, which include; Staphylococcus aureus, Escherichia coli, Bacillus subtilis, Pseudomonas aeruginosa, Salmonella typhi, Klebsiellae pneumonae, Candida albicans, Aspergillus niger, penicillium notatum and Rhizopus stolonifer. N-hexane extract of the plant exhibited antioxidant property by scavenging DPPH radicals with IC50 of 342.44 µg/mL. GC-MS analysis of n hexane, ethyl acetate and methanol extracts of the plant principally revealed the presence of Urs-12-ene (23.15%), Squalene (48.80%) and Clionasterol (15.88%) respectively.
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    Biomass-based Hydrothermal Carbons for Catalysis and Environmental Cleanup: A Review
    (Taylor and Francis, 2022-01-21) Omorogie, Martins
    The growing demand for alternative green energy and environmental crises is a significant concern for the world population. Thus, researchers have devoted effort to finding cheap, eco-friendly, and robust functional materials. The bottleneck faced by scientists is the synthesis of a material with high surface area, highly functionalized, and cost-effective. To this end, biomass-based hydrothermal carbons are gaining increasing attention due to the presence of functional groups introduced during hydrothermal carbonization (HTC) and mild/tunable preparation conditions. This review Materials the synthesis, parameters that influence the carbonization process, and mechanisms involved during HTC. Other synthesis routes for enhancing the properties of HTC carbon materials are also discussed. The application of HTC carbon materials, including energy storage devices, catalysis, electrocatalysis, photocatalysis, and adsorption, are reported. Lastly, we present the challenges and possible strategies for improving the HTC process.
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    Biosorption of Heavy Metals from Aqueous Solutions by Parkia biglobosa Biomass: Equilibrium, Kinetics, and Thermodynamic Studies
    (John Wiley, 2015-09-25) Omorogie, Martins
    The adsorption capacities of Parkia biglobosa chaff biomass (PBC) and Parkia biglobosa pulp biomass (PBP) for Cr(III), Cd(II), Ni(II), and Pb(II) ions were studied. Experimental data suggested the highest monolayer sorption capacities of PBC and PBP, at equilibrium to be 170.07 mg/g at pH 7.0 and 324.68 mg/g at pH 6.0, for the uptake of Cr(III) ions, respectively. The minimum adsorption capacities obtained by PBC and PBP were 60.72 mg/g for Ni(II) and 16.70 mg/g for Cd(II) at pH value of 2.0, respectively. Pseudo second order kinetic model fits the all experimental data best, suggesting that the entire adsorption processes might have occurred by chemisorption mechanism. Thermodynamic data indicated that the adsorption of various metal ions by PBC and PBP was endothermic, with increase in disorderliness of the system. The Gibb’s free energy values for the uptake of Cr(III), Cd(II) and Ni(II) ions by PBC indicated the spontaneity of the processes. Moreover, the Gibb’s free energy values for the uptake of Pb(II) ion by PBC depicted the non spontaneity of the processes. Also, Gibb’s free energy values for the adsorption of various metal ions by PBP depicted the spontaneity of the processes.
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    Cadmium Sulfide and Cadmium Phosphide Thin Films from a Single Cadmium Compound
    (American Chemical Society (ACS), 2011-02-10) Oyetunde, Temidayo
    Aerosol-assisted chemical vapor deposition of Cd[(SPiPr2)2N]2 leads to the growth of cadmium sulfide and/or phosphide thin films on glass. Decomposition of the precursor has been studied by pyrolysis-gas chromatography/ mass spectrometry and modeled by density functional theory.
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    Carbon-mediated Visible-light Clay-Fe2O3–graphene Oxide Catalytic Nanocomposites for the Removal of Steroid Estrogens from Water
    (Elsevier, 2021-04-01) Omorogie, Martins
    This study reports the development of efficient photosensitive nanocomposites made from clay, Fe2O3, and graphene oxide (GO). These nanocomposites were used for the removal of steroid estrogens (E1, E2, E3 and EE2) from water under visible-light. The use of these photocatalytic nanocomposites led to oxidation of the steroid estrogens at >80 % even under simultaneous presence of all estrogens in water. Mineralization was obtained for these estrogens within the range of 58–73 %. The presence of Fe-oxide in the nanocomposites increased the photocatalytic efficiency but addition of GO further improved the photocatalytic efficiency. This improved efficiency was further doubled when the nanocomposites were prepared with a carbon source (Carica papaya seeds). The presence of carbon in the nanocomposite matrix was confirmed using X-ray photoelectron spectroscopy and Elemental analysis. The main contributors to photocatalytic efficiency of these nanocomposites are superoxide radicals (•O2-) and holes (h+). Under competitive conditions, the photocatalysts are still active although the extent of estrogen oxidation is somewhat lower. Changes in the ionic strength did not significantly influence the efficiency of the photocatalyst. This signifies that adsorption only plays a minor role in estrogen removal from water. Toxicity tests show that the treated water is safe for human consumption and the most efficient nanocomposite can be recycled three times without any significant loss of performance. Overall, the nanocomposite show high potential for the effective removal of a cocktail of estrogens in raw wastewater, tap and rain water, attaining contamination levels that are within WHO safe limits.
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    Carbon-mediated Visible-light Clay-Fe2O3–graphene Oxide Catalytic Nanocomposites for the Removal of Steroid Estrogens from Water
    (Journal of Water Process Engineering, 2020-12) Bayode, Ajibola Abiodun
    Graphene oxide (GO). These nanocomposites were used for the removal of steroid estrogens (E1, E2, E3 and EE2)from water under visible-light. The use of these photocatalytic nanocomposites lead to complete oxidation of the steroid estrogens at >80 % even under simultaneous presence of all estrogens in water. Complete mineralization was obtained for these estrogens with the range of 58–73 %. The presence of Fe-oxide in the nanocompositesincreased the photocatalytic efficiency but addition of GO further improved the photocatalytic efficiency. Thisimproved efficiency was further doubled when the nanocomposites were prepared with a carbon source (caricapapaya seeds). The presence of carbon in the nanocomposite matrix was confirmed using X-ray Photoelectron Spectroscopy and Elemental Analysis. The main contributors to photocatalytic efficiency of the nanocomposites are superoxide radicals (· ) and holes (h+). Under competitive conditions, the catalysts are still active although the extent of estrogen oxidation is somewhat lower. Changes in the ionic strength did not significantly influence the efficiency of the photocatalyst. This signifies that adsorption only plays a minor role in estrogen removal from water. Toxicity tests show that the treated water is safe for human consumption and the most efficient nanocomposite can be recycled three times without any significant loss of performance. Overall, the nanocomposite shows high potential for the effective removal of a cocktail of estrogens in raw wastewater, tap and rain water, attaining contamination levels that are within WHO safe limits