Chemical Science International Journal

Organochlorine Pesticides (OCP) are organic compounds obtained by the chlorination of various unsaturated hydrocarbons. They are very toxic and therefore belong to the family of persistent organic pollutants. If formerly these pesticides were used to fight against certain vectors of diseases and thus improve the productivity of the host, today they are considered as "enemy" of the environment. To understand the origin of the toxicity of organochlorine compounds, we used 73 molecules (test set: 50 and validation: 23) containing at least one chlorine atom and for which the toxicity (LogLC₅₀) against Poecilia reticulata is known to establish QSAR models. Firstly, we used principal component analysis (PCA) to identify the best descriptors. Then, the different models were established using the method of multiple linear regression (MLR). Models established with quantum and physicochemical descriptors only showed satisfactory results. But the best model was determined with the combination of both quantum and physicochemical descriptors. The criteria of this model are as follows:

R² = 0.939 ; R²_ajusted = 0.932 ; P_{value < 0.0001; α = 0.05}

R²_{CV = 0.935 ;} R² _- R²_{CV = 0.004 ; MCE = 0.073; F = 134.701}

These criteria show that the toxicity of organochlorine compounds is well described by the combination of quantum and physicochemical descriptors namely lipophilia (LogP), polarizability (pol), entropy (S), zero-point energy (ZPE) and the number of chlorine atoms (NCl).

Aims: Preparation of the new metals-polymeric composite, Met_x-EPS (I), to be used as a green catalyst in water or in two-phase aqueous conditions.

Study Design:  Recovery and valorization of polymetallic wastes to obtain directly new catalysts using a microorganism to explore their application in removal of difficult and dangerous chemical pollutants present in aqueous environment.

Place and Duration of Study: Dipartimento di Scienze Molecolari e Nanosistemi, Università Ca’ Foscari Venezia, Venezia Mestre, Italy; University of Nova Gorica, Nova Gorica, Slovenia, Institut Jozef Stefan, Ljubljana, Slovenia and Department of Biology, Biotechnical Faculty, University of Ljubljana, Ljubljana, Slovenia, between February 2018 and January 2019.

Methodology: For the preparation of Met_x-EPS (I), the metals source was an exhausted catalytic converter that was grinded and treated with an acidic solution at 20-25°C. After filtration, the solution was concentrated, neutralized and added to a broth of Klebsiella oxytoca DSM 29614 to produce (I) where metals are embedded in a peculiar polysaccharide structure. The composite was easily recovered from the fermentation broth and purified. The process protocol was verified many times and was shown to be reproducible satisfactorily. The % recovery of metals, originally present in the converter, was good as determined by atomic absorption. The morphology and the chemical state of main metals in (I) were investigated by X-ray absorption spectroscopy methods (XANES and EXAFS).  No metallic alloy seems to be evident.

Results: As first application of (I) as catalyst, the hydrodechlorination treatment of polychlorinated biphenyls (PCBs) was studied in water/methanol.  A significant removal of higher chlorinated congeners was observed working at 1MPA of hydrogen and 60°C. This result improves significantly and surprisingly the methodology, previously studied by us using mono- or bi-metals embedded in the same polysaccharide moiety, indicating that positive synergies among the different metals were operating.

Conclusion: The preparation of this new polymetallic species embedded in a polysaccharide moiety starting from spent catalytic converters represents an alternative valorisation of metallic wastes. Moreover, a synergic effect was exerted by the different metals when the catalyst Met_x-EPS (I) was used in the hydrodechlorination treatment of polychlorinated biphenyls (PCBs) in water/methanol. Finally, a promising preliminary proof of concept for the removal of polychlorinated aromatic pollutants even in contaminated aqueous sites was carried out.

Vanillin (4-hydroxy-3-methoxybenzaldehyde) is the major flavour constituent of vanilla. It has a wide range of applications in food industry and in perfumery. Vanillin is also very useful in the synthesis of several pharmaceutical chemicals. Lignin is a phenolic polymer which is found in plant cell walls with a structure depending strongly on the source of lignin and the process condition, which should be adjusted for different samples. In this work, lignin was extracted from Kraft cooking liquor of wood ash. The amount of extracted lignin was 25.5%, based on oven dry weight of wood ash. The lignin obtained was then reacted with alkaline nitrobenzene and refluxed at 170°C for 3 hours to obtain vanillin. The FT-IR spectrum of vanillin was similar to standard. The yield obtained from oxidation with nitrobenzene was 3.9%.

The soil and edible vegetable samples were collected from Obudu Urban Area of Cross River State and were digested and analyzed for the Cd, Co, Cr, and Fe (heavy metals) concentration using Atomic Absorption Spectrometer (AAS) in the University of Calabar Laboratory. The eight vegetables considered for the study were Amaranthus spp., Corchorus olitorius, Murraya koenigii, Ocimum grattissimum, Solanum melongena, Talinum triangulare, Telferia occidentalis and Vernonia amygdalina. The results showed that the mean concentration of the metal in the soil in mgkg^-1 ranged from (0.004-0.0048) and (0.005-0.046) in rainy and dry seasons respectively for Cd, (0.004-0.025) and (0.006-0.016) in rainy and dry season respectively for Cr, and (0.112-0.173) and (0.116-0.151) in rainy and dry season respectively for Fe. The concentration of Co was not detected in the soil or vegetables. The mean concentration accumulated by the vegetables and that present in the soil was in the order: Fe> Cd> Cr> Co. These results suggest that there is no significant difference between the amount of metals in the soil or that accumulated by the vegetables in rainy and dry seasons of the year. Also the amount of metals accumulated by most of the vegetables was directly proportional to the amount present in the soil where they are planted. The bioaccumulation ratios were all less than 1. These results indicate that the concentration of Cd, Co, Cr, & Fe in the soil and vegetables were still low and within the permissible limits of WHO/FAO. Thus, the consumption of the vegetables in the area may not cause any harm for now.

This study was focused on the synthesis of cobalt nanoparticles using Mangifera indica leaf extract and the characterization of the particles via UV–Vis spectroscopy, XRD, FT-IR and SEM. The XRD results showed the formation of cobalt nanoparticles that was crystalline in nature, with an average size of 25—40 nm. The FT-IR analysis of the leaf extract reviewed some functional groups responsible for the reduction of cobalt ions to cobalt nanoparticles while the SEM indicates that the synthesised cobalt nanoparticles possess a cubic, pentagonal and irregular in shape with a smooth surface. Application of colloidal cobalt nanoparticles in detecting Mn²⁺ ions was discussed which indicated that the absorption of the Mn (II) ions decreased at increased concentration of Mn (II) ions indicating that Mn (II) ion can be detected even at a very low concentration. The minimum and maximum detection limit was found to be 5 and 25 mM of Mn (II) ions, respectively. The obtained results encourage the use of economical synthesis of cobalt nanoparticles in the development of nanosensors to detect the pollutants present in industrial effluents.