Open Access Short Research Article

Mechanistic Investigation of Sol–Gel Reactions Using Alkoxysilane Precursor

Adam Hassan Elhaj Yousif, Mohammed Sulieman Ali Eltoum

Chemical Science International Journal, Page 25-31
DOI: 10.9734/CSJI/2020/v29i530178

The present study has been carried out to investigate the mechanisms of sol–gel reactions using TEOS as precursor in the presence of acid or base catalyst. The gels were prepared by hydrolysis of TEOS using hydrochloride acid or ammonium hydroxide catalyst. The obtained gels were also characterized by FTIR spectroscopy. The results of FTIR spectroscopy indicated the existence of silanol and siloxane bonds; due to the formation of hydrolyzed species as reactive intermediate compounds in initial stage converted by condensation reactions to gels as ultimate products. Accordingly, appropriate mechanisms have been proposed for sol – gel reaction using TEOS as precursor in the presence of acid or base catalyst. These mechanisms involve three-steps SN2 mechanisms for base catalyzed hydrolysis reaction of TEOS and SN1 mechanisms for acid catalyzed hydrolysis reaction of TEOS. Three mechanisms have been also proposed for condensation reaction as second stage in sol-gel process. These mechanisms include alcoxolation, oxolation and oltaion.

Open Access Original Research Article

Production of Biodiesel by Transesterification Reaction of Waste Cooking Oil

Donald Raoul Tchuifon Tchuifon, Serges Bruno Lemoupi Ngomade, George Nche Ndifor-Angwafor, Paul Alain Nanssou Kouteu, Tchoumboue Nsah-Ko, Richard Daris Tagaboue Nguedap, Idris-Hermann Tiotsop Kuete, Aurelien Bopda, Solomon Gabche Anagho

Chemical Science International Journal, Page 1-12
DOI: 10.9734/CSJI/2020/v29i530176

Waste cooking oils are an agro-food waste with adverse effects on the health of living organisms and the environment. The main objective of this work is to valorize waste cooking oil for the synthesis and physicochemical characterization of biodiesel. The method used is based on the transesterification reaction of the oils using methanol and a basic homogeneous catalyst. In this study we employ waste from refined palm oil used for frying doughnuts. After optimization a reaction time of 2 hours, KOH catalyst, and a molar ratio of 9:1 were selected to obtain a good quality biodiesel. Physicochemical characterization was performed on the biodiesel to obtain its density, viscosity, calorific value, acid number, saponification index and IR spectral features. The analysis shows that the biodiesel obtained after transesterification has physicochemical characteristics similar to those of diesel and is consistent with American standards.

Open Access Original Research Article

Adsorption of Copper Ions (Cu++) in Aqueous Solution Using Activated Carbon and Biosorbent from Indian Jujube (Ziziphus mauritiana) Seed Hulls

Harouna Massai, Djakba Raphael, Mouhamadou Sali

Chemical Science International Journal, Page 13-24
DOI: 10.9734/CSJI/2020/v29i530177

The present work aimed at mitigating the level of copper ions (Cu++) by adsorption in aqueous solution using activated carbon powder (AC) and biosorbent (BS) from the Indian jujube seed hulls. The AC and BS were prepared from the Indian jujube seed hulls and characterized    using standard procedures. In addition, the adsorption effects of Indian jujube seed hulls through the AC and BS were carried out using jar test experiment (batch mode) at different pH (1, 2, 3, and 4), ionic strengths (100-600 mg/L) and stirring speed (120rpm). Therefore, it was found that the adsorption time at equilibrium were 10 and 5 minutes respectively for the AC and the BS.  Furthermore, it was found that the reduction of copper ions were 99.40% and 73.08% for aqueous solutions of 100 ppm and 500 ppm respectively at the equilibrium state. It was also revealed that when the mass of the AC or the BS increases, the quantities of ions adsorbed per gram decrease. The maximum pH of adsorption for the AC was found to be pH=1, while it was found to be pH=4 for the BS. The Freundlich model indicated that the adsorption of copper ions by the Indian jujube is linear while the Temkin and Dubinin-Kagana-Radushkevich models described the adsorption as a physical reaction. It was finally observed that the adsorption of copper ions by the AC and the BS from Indian jujube seed hulls influenced by the addition of some concentration of NaCl.

Open Access Original Research Article

Biosorption of Bromophenol Blue from Aqueous Solution Using Flamboyant (Delonix regia) Pod

Ebenezer Olujimi Dada, Ilesanmi Ademola Ojo, Abass Olanrewaju Alade, Tinuade Jolaade Afolabi, Omotayo Sharafdeen Amuda, Ahmad Tariq Jameel

Chemical Science International Journal, Page 32-50
DOI: 10.9734/CSJI/2020/v29i530179

Matured flamboyant pods (FBP) activated with ZnCl2 were used for batch adsorption of Bromophenol blue (BPB) dye under the effects of concentration (10-200 ppm), contact time (20-300 min), biosorbent dosage (20-120 mg) and particle size (300-850 µm). The data obtained were fitted to Langmuir and Freundlich isotherm models as well as pseudo-first-order (PFO), pseudo-second-order (PSO) and Elovich kinetic models. The highest adsorption capacity and removal efficiency of 7.5762 mg/g and 75.76%, respectively, were obtained under the effects of initial dye concentrations. The correlation coefficient (R2) for the Langmuir and Freundlich isotherms are in the range 0.9938-0.9979 and 0.9895-0.9953, respectively, while, R2, in the ranges 0.5931-0.815, 0.9962-1.000 and 0.8046-0.8828, were obtained for the PFO, PSO, and Elovich kinetic models, respectively. The order of fit of the kinetic models is PSO > Elovich > PFO. The study suggests flamboyant pod as promising biomass for the remediation of dye-bearing industrial effluents.

Open Access Original Research Article

Comparative Theoretical Study of Stability, Lypophilicity, Dipole Moments, Acidity and Spectroscopic Properties of Non-Steroidal Anti-Inflammatory Drugs: Ibuprofen, Ketoprofen and Flurbiprofen

Assoma Amon Benjamine, Atse Adepo Jacques, Kone Soleymane, Bamba El Hadji Sawaliho

Chemical Science International Journal, Page 51-60
DOI: 10.9734/CSJI/2020/v29i530180

A comparative theoretical study of some physicochemical properties of R and S enantiomers of ibuprofen, ketoprofen and flurbiprofen is undertaken in order to understand their reactivity. To do this, DFT and TD-DFT methods at the B3LYP/6-311G(d,p) level theory are used. The partition coefficient determined is 3.72 for ibuprofen, 2.81 for ketoprofen and 4.12. for flurbiprofen. That means that these NSAIDs are characterized by a high lipophilicity. The calculated Gibbs energies show that the R enantiomer is the most stable in the case of ibuprofen and the S enantiomer in the case of ketoprofen and flurbiprofen. The study of acidity shows that S enantiomer of ibuprofen and R enantiomers of ketoprofen and flurbiprofen are the most acidic enantiomers. TD-DFT calculations show that, the absorption maxima (λmax) of ibuprofen and flurbiprofen correspond to the HOMO→LUMO transition. For ketoprofen, these are associated with the transition HOMO→LUMO+1. These results elucidate the reactivity of the investigated NSAIDs and could help to establish a classification their efficacy.