Adsorption of phenol/tyrosol from aqueous solutions on macro-reticular aromatic and macro-porous polystyrene cross-linked with divinylbenzene polymeric resins

The current work aims at separating by adsorption of low-molecular-weight organic compounds in a nanofiltration concentrate of the olive mill wastewaters. The experimental investigations on adsorption of phenol/tyrosol in single and binary systems were conducted in batch mode by using the commercially available macroporous resins FPX66 and MN202. The structures of such resins were examined by FTIR before and after adsorption. The operating parameters affecting the adsorption process such as resin dosage, contact time, pH, and initial concentration of phenol/tyrosol were investigated. Fast phenol and tyrosol uptakes were observed for both resins. It can be attributed to their physical properties, for instance high specific area and microporous area. The adsorption selectivity of phenol is larger than tyrosol when using FPX66 resin, but smaller if MN202 resin is used. Acidic pH appeared to be always favourable for the adsorption. A synergetic effect between solutes was observed since adsorption of phenol and tyrosol in the binary systems was faster than the individual sorption of each solute. Five isotherms namely Langmuir, Freundlich, DubininRadushkevich, Temkin and Redlich-Peterson were selected to fit the obtained equilibrium experimental data. Finally, desorption of the examined compounds with ethanol (EtOH) allowed a maximum around 85 % of phenol, and equal to 94 % of tyrosol on FPX66 and MN202 resins

Adsorption of phenol/tyrosol from aqueous solutions on macro-reticular aromatic and macro-porous polystyrene cross-linked with divinylbenzene polymeric resins

The current work aims at separating by adsorption of low-molecular-weight organic compounds in a nanofiltration concentrate of the olive mill wastewaters. The experimental investigations on adsorption of phenol/tyrosol in single and binary systems were conducted in batch mode by using the commercially available macroporous resins FPX66 and MN202. The structures of such resins were examined by FTIR before and after adsorption. The operating parameters affecting the adsorption process such as resin dosage, contact time, pH, and initial concentration of phenol/tyrosol were investigated. Fast phenol and tyrosol uptakes were observed for both resins. It can be attributed to their physical properties, for instance high specific area and microporous area. The adsorption selectivity of phenol is larger than tyrosol when using FPX66 resin, but smaller if MN202 resin is used. Acidic pH appeared to be always favourable for the adsorption. A synergetic effect between solutes was observed since adsorption of phenol and tyrosol in the binary systems was faster than the individual sorption of each solute. Five isotherms namely Langmuir, Freundlich, DubininRadushkevich, Temkin and Redlich-Peterson were selected to fit the obtained equilibrium experimental data. Finally, desorption of the examined compounds with ethanol (EtOH) allowed a maximum around 85 % of phenol, and equal to 94 % of tyrosol on FPX66 and MN202 resins

Carcinoembryonic antigen immunosensor developed with organoclay nanogold composite film

Organoclay nanogold composite were prepared using gold nanoparticles and the natural Cameroonian clay grafted with amino organosilane. The functionnalization of clay provided abundant amino group to assemble gold nanoparticles. A label-free electrochemical immunosensor for the sensitive determination of carcinoembryonic antigen (CEA) was fabricated by immobilizing anti-CEA onto organoclay nanogold composite film modified electrode by the cross-linking method using glutaraldehyde. In addition, the preparation procedure of the immunosensor was investigated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Under optimal conditions, the resulting immunosensor displayed a high sensitivity for the detection of CEA, and responded to the CEA concentration in two ranges from 0.05 to 5.0 ng/mL (R = 0.991) and from 5.0 to 120.0 ng/mL (R = 0.998) with a detection limit of 0.01 ng/mL

Electrochemical Determination of Epinephrine in Pharmaceutical Preparation Using Laponite Clay-Modified Graphene Inkjet-Printed Electrode

Epinephrine (EP, also called adrenaline) is a compound belonging to the catecholamine neurotransmitter family. It can cause neurodegenerative diseases, such as Alzheimer’s disease, Parkinson’s disease, Huntington’s disease and amyotrophic lateral sclerosis. This work describes an amperometric sensor for the electroanalytical detection of EP by using an inkjet-printed graphene electrode (IPGE) that has been chemically modified by a thin layer of a laponite (La) clay mineral. The ion exchange properties and permeability of the chemically modified electrode (denoted La/IPGE) were evaluated using multi-sweep cyclic voltammetry, while its charge transfer resistance was determined by electrochemical impedance spectroscopy. The results showed that La/IPGE exhibited higher sensitivity to EP compared to the bare IPGE. The developed sensor was directly applied for the determination of EP in aqueous solution using differential pulse voltammetry. Under optimized conditions, a linear calibration graph was obtained in the concentration range between 0.8 μM and 10 μM. The anodic peak current of EP was directly proportional to its concentration, leading to detection limits of 0.34 μM and 0.26 μM with bare IPGE and La/IPGE, respectively. The sensor was successfully applied for the determination of EP in pharmaceutical preparations. Recovery rates and the effects of interfering species on the detection of EP were evaluated to highlight the selectivity of the elaborated sensor

Antimycobacterial, antibacterial and antifungal activities of Terminalia superba (Combretaceae)

The methanol extract from the stem bark of Terminalia superba (TSB), fractions (TSB1 - 7) and two compounds isolated following bio-assay guided fractionation namely 3,4'- di-O-methylellagic acid 3'-O-β-D-xylopyranoside (1) and 4'-O-galloy-3,3'-di-O-methylellagic acid 4-O-β-D-xylopyranoside (2) were evaluated for their antimycobacterial, antibacterial and antifungal activities. The broth microdilution, microplate Alamar Blue assay (MABA) and agar disc diffusion methods were used for the investigations. The results of the antimycobacterial assays showed that the crude extract, fraction TSB5-7 and compound 1 were able to prevent the growth of all the studied mycobacteria. The lowest minimal inhibitory concentration (MIC) value of 39.06 μg/ml for this extract was recorded on both M. smegmatis and M. tuberculosis MTCS2. The corresponding values were 19.53 μg/ml and 4.88 μg/ml for fractions and compounds respectively. The MIC determinations results on other organisms indicate values ranging from 19.53 to 78.12 μg/ml for TSB and compound 2 on 90.9% of the tested organisms, meanwhile compounds 1 as well as fractions TSB 6 and 7 exhibited detectable MIC values on all studied microorganisms. The overall results provide promising baseline information for the potential use of the crude extract from Terminalia superba, fractions 6-7 and the tested compounds in the treatment of tuberculosis, bacterial and fungal infections

Comportement electrochimique de biporphyrines adsorbees ou en solutions aqueuses acides : etude du pouvoir catalytique de la biporphyrine de cobalt, Co_2FTF4, a l'egard de la reduction de l'oxygene

SIGLECNRS T Bordereau / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

Evaluation of removal efficiency of fluoride from aqueous solution using new charcoals that contain calcium compounds.

International audienceCharcoals that contain calcium compounds have been synthesized by impregnating wood with calcium chloride followed by carbonization at 500 degrees C, 650 degrees C or 900 degrees C. The charcoals were characterized by SEM, EDAX, XRD and chemical titrations. These adsorbents were porous with the wood microstructure. XRD revealed the presence of crystallized CaCO(3) and CaO. Despite this content, all the charcoals showed acidic surface properties and pH of point of zero charge (pH(PZC)) values were around 7.4-7.7. Their performance for fluoride removal from aqueous solution was evaluated by batch experiments. Fluoride adsorption kinetic followed a pseudo-second order model. Charcoal prepared at 650 degrees C exhibited the best efficiency with a fluoride sorption capacity of 19.05 mg g(-1) calculated from the Langmuir model. A fluoride residual concentration of 0.67 mg L(-1) was achieved within 24 h from a 10 mg L(-1) solution at neutral pH. The fluoride removal was not modified by the presence of NO(3)(-), SO(4)(2-) and PO(4)(3-) in the fluoride solution, while HCO(3)(-) and Cl(-) slightly affected the defluoridation capacity. The charcoals were chemically stable in solution and the amount of dissolved Ca was found to be 3.23 mg L(-1) at neutral pH

Quaternary ammonium functionalized clay film electrodes modified with polyphenol oxidase for the sensitive detection of catechol

International audienceNaturally occurring Cameroonian smectite clay has been grafted with trimethylpropylammonium (TMPA) groups and the resulting organoclay has been deposited onto a glassy carbon electrode surface as a suitable immobilization matrix for polyphenol oxidase (PPO). High sensitivity of the electrochemical device to catechol biosensing can be achieved when the enzyme was impregnated within the organoclay film subsequent to its deposition due to favorable electrostatic interaction between PPO and the TMPA-clay layer. The bioelectrode preparation method was also compatible with the use of a mediator (i.e., ferrocene) and the best performance was obtained with a three-layer configuration made of glassy carbon coated with a first layer of ferrocene (Fc), which was then covered with the PPO-impregnated TMPA-clay layer, and finally overcoated with an enzyme-free TMPA-clay film acting as a protecting overlayer to avoid leaching of the biomolecule in solution. The electrochemical behavior of the modified film electrodes was first characterized by cyclic voltammetry and, then, they were evaluated for the amperometric biosensing of the model analyte catechol in batch conditions and in flow injection analysis. Various experimental parameters likely to influence the biosensor response have been investigated, including the electrode preparation mode (composition configuration, thickness), the usefulness of a mediator, the operating potential and pH of the medium, as well as the advantageous features of the TMPA-clay in comparison to related film electrodes based on non-functionalized clays. The organoclay was found to provide a favorable environment to enzyme activity and the multilayer configuration of the film electrode to provide a biosensor with good characteristics, such as an extended linear range for catechol detection (2 x 10(-8) to 1.2 x 10(-5)M) and a detection limit in the nanomolar range (9 x 10(-9)M)