Open Access Original Research Article

Microwave Assisted Synthesis of Phenazines from β-Lapachones and Their Tuberculostatic Activity

Douglas Igor Santos de Oliveira, Lívia Fernandes do Amaral, Maria Cristina Silveira Lourenço, Nelilma Correia Romeiro, Vítor Won-Held Rabelo, Raphael Salles Ferreira Silva

Chemical Science International Journal, Page 1-8
DOI: 10.9734/CSJI/2017/30943

Aims: The study aimed to investigate de synthesis of phenazines by microwave assisted reactions and evaluate the tuberculostatic activity.

Study Design: The method developed in the study is an alternative for the method described in the literature employing acetic acid, an efficient solvent for the reaction, but corrosive and aggressive health. In addition tuberculostatic activities of phenazines were assessed and a brief study on molecular modeling of the phenazines was performed.

Place and Duration of Study: The experiments were performed on Instituto Federal do Rio de Janeiro (IFRJ), Fundação Oswaldo Cruz (FIOCRUZ) and Núcleo de Pesquisas em Ecologia e Desenvolvimento Social de Macaé (NUPEM) between 2012-2015.

Methodology: Quinone (1 mmol) and 5 mmols of o-phenylenediamine were dissolved in 10 ml of 1,4-dioxane in a sealed tube. Microwave reactor conditions were: temperature 150°C and 4.5 bar pressure for 15 minutes. After the reaction water was added to the reaction media and the yellow precipitate formed was filtered under vacuum and washed 3 times with water. The phenazine was purified by silica gel column chromatography using a mixture of hexane-ethyl acetate 95 : 5 as eluent, the phenazine were obtained in yields greater than 85% in all cases.

Results: Six phenazines derived from β-lapachonas were synthesized by microwave assisted reactions with good yields. The tuberculostatic activity of the five phenazines was significantly lower than phenazine from β-lapachone, a brief molecular-modeling study performed showed that the higher activity of phenazine from β-lapachone is due its polarity (µ) and Polar Surface Area (PSA).

Conclusion: The microwave irradiation was effective to synthesize phenazines from β-lapachones faster and with similar yields.

Open Access Original Research Article

Evaluation of Pozzolanic Activity of Illitic and Lateritic Raw Materials from Burkina Faso

I. Sanou, M. Seynou, L. Zerbo, Y. Millogo, R. Ouedraogo, A. Sana

Chemical Science International Journal, Page 1-13
DOI: 10.9734/CSJI/2017/30995

Aims: Evaluate the potentially use as pozzolan in cement replacement of activated Lateritic and Illitic raw materials from Burkina Faso.

Place and Duration of Study: Laboratory of Molecular and Materials Chemistry-University of Ouagadougou, National Laboratory of Building and Publics Works-Ouagadougou, Burkina Faso. Between March 2015 and June 2016. 

Methodology: The initial two raw materials were characterized to perform its chemical, mineralogical, geotechnical and microstructure properties. The two samples were activated at 680°C during 2 or 5 hours to produce amorphous reactive materials. The activated samples were characterized using infrared spectroscopy and the selective dissolution by HF acid. Pozzolanic activity was assessed using saturated lime test, Frattini test, mineralogical analysis and compressive strength test. Mineralogical analyses were carried out with X-ray diffraction and DTA/TG.

Results: The characterization of initial raw materials shown that lateritic material contain kaolinite (71%.wt) and Goethite (18%.wt) as the mains phases and the illitic material consisting by kaolinite (44%.wt) and illite (40%.wt). The activation of samples at 680°C, given amorphous phase (metakaolinite and silica) which amount around 74%.wt and 61%.wt respectively for lateric and illitic sample. The activated samples fixed at 7 days more than 80%.wt of lime. The DTA/TG test shown that at 8 days, lateric sample fixed between 33-37% and the illitic sample around 23% of portlandite produced by ement hydratation. The strength activity index, 91% and 97% respectively for lateritic and illitic samples exceeds require minimal value (75%) for pozzolan materials. Lateritic sample with finer particle and high amount of metakaolinite was presents a better pozzolan activity. However it strength is lower than those of Illitic sample. This inversion of previsible strength is due to the high contain of iron oxide in lateritic sample.

Conclusion: The two samples, after heat treatment at 680°C during 2 hours, can be used as pozzolan for cement partial replacement in the constructions.

Open Access Original Research Article

Morphological and Microstructural Characterization of Organoclays from Low Smectite Containing Clays Materials

Emeka Thompson Nwankwere, Casimir Emmanuel Gimba, George Iloegbulam Ndukwe, Adamu Kari Isuwa, Yilleng Moses Titus

Chemical Science International Journal, Page 1-17
DOI: 10.9734/CSJI/2017/29703

Two low smectite-containing clay materials were modified, using hexadecyltrimethylammonium bromide (HDTMAB) as intercalating agents, under very mild experimental conditions, to investigate their potentials as suitable organoclays for industrial and environmental applications. Changes in the general morphological and microstructural characteristics were studied by X-Ray Diffraction (XRD) analysis, Thermogravimetric Analysis (TGA), Brauner Emmet Taylor (BET) Analysis, Fourier Transform Infrared (FTIR) Spectroscopy and Scanning Electron Microscopy (SEM) before and after modification. The shift in XRD reflections after intercalation indicated that the HDTMA chains adopt monolayer and bilayer arrangements within the clay interlayers and were largely dependent on the reaction time and surfactant loading. This resulted in decreased specific surface area and increased pore sizes in the organoclay samples. The presence of typical CH stretching bands in the new materials was confirmed by FTIR analysis. Mass loss from TGA showed that the new materials were thermally stable, the amount of organic modifier in the organoclays were in good agreement with the theoretically calculated contents. The intercalated materials were hydrophobic, stable, biocompatible and were suitable materials for several industrial and environmental applications.

Open Access Original Research Article

Calorimetric Approach for the Detection of Modified Silica Efficiency as Chelating Agent for Heavy Metal Ions

Yolla Kazzi, Houssein Awada

Chemical Science International Journal, Page 1-7
DOI: 10.9734/CSJI/2017/31105

Chelating molecules with carboxyhydrazide functional group was immobilised on silica surface. The functional group was covalently bonded to the silica surface by sequential reactions of silica with dibromobutane, malonic ester and hydrazine in different media. The grafting reaction was confirmed by elemental analyses and thermal stability analysis (TGA). The flow microcalorimeter (FMC) was used as an approach to assess the performance of modified silica sorbent toward heavy metal ions. The FMC results show that this modification enhances remarkably the silica ability to retain a series of heavy metal ions on its surface. The selectivity of adsorption on modified silica was determined and the strength of the chemical bonding between metal ions and modified silica was quantified.

Open Access Original Research Article

Concentration Levels and the Associated Health Risks of Elements in Food Crops Grown in the Neighbourhood of Minjingu Phosphate Mine, Tanzania

Najat K. Mohammed, Leonid L. Nkuba

Chemical Science International Journal, Page 1-9
DOI: 10.9734/CSJI/2017/31476

The concentration levels of heavy metals in food crops (maize and mung beans) grown in the neighbourhood of Minjingu Phosphate mine were analyzed using EDXRF. The metal concentrations in both food crops followed the following pattern Fe > Zn > Cu > Cd > Cr > Pb > As. Maize accumulated higher levels of all analyzed elements than mung beans. The concentration level of metals in maize and mung beans from Minjingu were higher than those from the control site. Except for Cd in both types of samples, the concentration levels of all other metals were below the FAO/WHO recommended limits. The risk assessment showed that consumption of mug beans from Minjingu is without any safety risk while there is a risk in consumption of maize due to the concentration of Cd. However, the number of samples was not sufficient enough to make a definite conclusion; therefore, there is need for further analysis to include more data.

Open Access Review Article

Evaluation of Performance of Corrosion Inhibitors Using Adsorption Isotherm Models: An Overview

Ekemini Ituen, Onyewuchi Akaranta, Abosede James

Chemical Science International Journal, Page 1-34
DOI: 10.9734/CSJI/2017/28976

Adsorption isotherm models are an important tool for describing interaction of corrosion inhibitors with metal surfaces which they are aimed to protect. In this paper, key adsorption isotherms used in corrosion inhibition studies have been reviewed. We have examined how some deductions on the nature of metal-corrosion inhibitor interactions are obtained from certain parameters and interpreted to characterize the adsorption of the corrosion inhibitors and their mechanisms of inhibition. More attention is paid to their applications and the useful information that may be derived from them than on their background and derivation.  Efforts have also been made to identify some limitations (where applicable) and/or discrepancies in usage of some models in reporting experimental findings. Informed by some inconsistencies observed from some literature reports, critical suggestions on appropriate approaches to collection and processing of data for fitting into these isotherms have been made. This paper will be a beneficial secondary source of information to readers and invaluable reference material to experts and future researchers in the subject area.