Biosorption of cadmium(II) and lead(II) ions from aqueous solutions onto dried activated sludge

The removal of heavy-metal ions from aqueous solutions by using dried activated sludge has been investigated in batch systems. Effect of solution pH, initial metal ion concentration, and temperature were determined. The results of the kinetic studies showed that the uptake processes of the two metal ions（Cd（Ⅱ） and Pb（Ⅱ）） followed the pseudo-second-order rate expression. The equilibrium data fitted very well to both the Langmuir and Freundlich adsorption models. The FT-IR analysis showed that the main mechanism of Cd（Ⅱ） and Pb（Ⅱ） biosorption onto dried activated sludge was their binding with amide I group.

Characterization and Classification of Groundwater from Wells Using an Electronic Tongue (Kairouan, Tunisia)

A sensor array comprising 9 potentiometric chemical sensors and some pattern recognition tools for the data processing has been applied in order to characterize the groundwater in the plain of Kairouan Region (Tunisia). A total of 17 groundwater samples were collected from three different villages and analyzed for their chemical components. Nine chemical parameters were determined: Potassium, Sodium, Calcium, Ammonium, Cadmium, Chlorides, Nitrates, Fluoride and pH. Multi-sensor responses measured in each water sample were diagnosed by Principal Component Analysis (PCA) and Cluster Analysis (CA). PCA is a procedure for reducing data redundancy. CA is used to detect spatial similarity among sampling sites. This methodology is simple, rapid and the obtained results demonstrate that the electronic tongue technique based on the sensor array combined with pattern recognition method could be a useful tool for the characterization and the classification of wells water samples.

Bi-Enzymatic Conductometric Biosensor for Detection of Heavy Metal Ions and Pesticides in Water Samples Based on Enzymatic Inhibition in <i>Arthrospira platensis</i>

An original bi-enzymatic biosensor was designed by immobilizing Arthrospira platensis cells, called Spirulina, on gold interdigitated transducers. Phosphatase and esterase activities were inhibited, respectively, by heavy metals and by pesticides. Inhibition activities were observed with different mixtures of pesticides + heavy metals. The quantification limits for Cd2+ and Hg2+ are 10-20 M in mixture and in pure solution. The quantification limits of parathion-methyl, paraoxon-methyl and triazine are respectively 10-20 M, 10-18 M and 10-20 M in mixture and pure solutions. These results show that there is no synergistic effect between the two families of pollutants. Qualitative contamination of effluent samples and their purification after passing through a municipal wastewater treatment plant were observed by our bi-enzymatic biosensor and confirmed by classical analytical techniques for heavy metal ions.

An Electrochemical Nitrite Sensor Based on a Multilayer Film of Polyoxometalate

In this work, we have developed an electrochemical sensor for nitrite detection, based on a polyoxometalate (POM) namely mono-lacunary keggin anion [SiW11O39]8﹣ cited as (SiW11). Electrochemical characterization of SiW11 shows two-step reduction processes, with formal potentials of ﹣0.5 V (I) and ﹣0.68 V (II). Oppositely charged polyelectrolyte (poly (allylamine hydrochloride) (PAH)) and (SiW11) were assembled alternately to modify glassy carbon electrode. The electrochemical behavior of the modified electrode was studied in detail using cyclic voltammetry (CV). The results showed that SiW11/PAH/GC electrode present good electrocatalytic activity for the reduction of nitrite. The sensor showed a dynamic range from 100 μM to 3.6 mMof nitrite and no interference from other classical anions. Experimental factors that affect electron-transfer rate in these films, such as pH effect and layers number, were systematically analyzed.

A Simple Over-Oxidized Molecularly Imprinted Polypyrrole for the Sensitive Detection of Dopamine in Human Serum

A simple electrochemical sensor for dopamine detection, is based on molecularly imprinted and electropolymerized over-oxidized polypyrrole (OPPy). The MIP-based electrode is obtained by electrocopolymerization of pyrrole (0.1 M) in the presence of the template molecular (dopamine, DA) (10-3 M). The square wave voltammetry (SWV) is used for the detection of dopamine in buffer solution. The current peak obtained at the MIP electrode was proportional to the logarithm of the DA concentration in the range of 10-11 to 5 × 10-8 M with a detection limit of 10-11 M. The proposed sensor was used for the detection of DA in spiked blood serum, satisfactory results were obtained.

Adjunction of Avidin to a Cysteamine Self-Assembled Monolayer for Impedimetric Immunosensor

In this work an impedimetric immunosensor based on affinity immobilization method of a biotin labelled anti-human IgG antibody, used as a model system, was reported. The experimental procedure involves the growth of a self-assembled monolayer of a thiol (cysteamine) carrying terminal amine groups on gold electrodes. Glutarardehyde, a homobifunctional cross-linker, was used as a coupling reagent for the covalent linking of avidin to the amine groups of cysteamine. The attachment of the biotin labeled antibodies (anti-Human IgG) to the subsequent modified gold electrode was achieved by affinity interactions tacking advantage of the strong avidin-biotin bridge. The stepwise assembly process of the electrode was interrogated by means of cyclic voltammetry, electrochemical impedance spectroscopy and contact angle measurements. The response of the antibody modified electrode to their target antigens was investigated in the presence of BSA (bovin serum albumin) in order to alleviate non-specific adsorption problems. A proposed electrical model was used to analyse the experimental data. The resulting immunosensor has a linear dynamic range of 100 - 900 ng?ml–1 of antigen and a detection limit of 100 ng?ml–1.