Montmorillonite/Poly(Pyrrole) for Low-Cost Supercapacitor Electrode Hybrid Materials.

Conductive polymers such as polypyrrole have been widely used as pseudo-capacitive electrodes for supercapacitors. This work demonstrates a simple method to improve the performance of conductive polymer electrodes by adding montmorillonite in order to perform capacitive behavior. Conductive composite polymers (CCPs) based on montmorillonite/polypyrrole (MMT/PPy(Cl)) have been synthesized by polymerization using FeCl3 as an oxidizing agent. During the preparation of CCP, the effect of MMT/pyrrole mass ratio and the influence of the amount of added H+ and temperature of the synthesis medium on the electrochemical performance of the composite have been investigated. The investigation associated with conductivity measurement allowed us to determine the best conditions to reach a high specific capacitance of 465 F gr-1 measured by cyclic voltammetry with respect to the CCP synthesized at ambient temperature (220 F gr-1) and a 35% increase in capacity compared to its homologue synthesized in neutral conditions at a low temperature. These performances have been advantageously correlated both to the edge acidity of the host material and to the evolution of its conductivity according to the preparation conditions. The galvanostatic charge/discharge tests also confirm the stability of the obtained composite, and a capacitance of 325 F g-1 for the best CCP is recorded with a regime of 1 A g-1. In addition, the durability of the device shows that the proposed material has a relatively good stability during cycling.

Investigation of ammonium adsorption on Algerian natural bentonite.

Adsorption of several chemical contaminants onto clay minerals is the most recommended technique applied in the wastewater treatment field, owing to its low economic cost, efficiency, and low power consumption. In this context, natural bentonite particles with 80-µm diameter were investigated for the ammonium adsorption in aqueous solution using an incubator that kept the constant temperature and stirring speed at 200 RPM. The study of different experimental parameters effect on the adsorption process revealed that the raw bentonite have adsorbed approximately 53.36 % of the initial ammonium concentration at pH 7 and temperature of 30 °C. This percentage has been improved by increasing the adsorbent dosage in solution, which could reach up to 81.2 % at 40 g/L of bentonite with an initial ammonium concentration of 10 mg-NH4+/L. Moreover, experimental data modeling allowed us to conclude that the adsorption isotherm obeys to both models of Langmuir and Freundlich.

Novel approach for the ammonium removal by simultaneous heterotrophic nitrification and denitrification using a novel bacterial species co-culture.

Agricultural activities lead excessive emission of ammonia nitrogen in the environment and can profoundly interfere the equilibrium of the natural ecosystems leading to their contamination. Actually, the biological purification of wastewaters is the most adopted technique thanks to its several advantages such as high performance and low energy consumption. For this reason, two novel strains of Alcaligenes sp. S84S3 and Proteus sp. S19 genus were isolated from an activated sludge and applied in the treatment of ammonium and nitrite in aqueous solution. Under the optimum operating conditions of temperature (30 °C), pH (7), carbon substrate (2 g/L of glucose) and duration of incubation time (69 h), the strain Alcaligenes sp. S84S3 could oxidize 65% of the ammonium as high as 272.72 mg-NH4(+)/L. Moreover, during 48 h, the nitrate reduction rate performed by the strain Proteus S19 was about 99 % without production of nitrite intermediate (negligible concentration). Moreover, the coculture of the strains Alcaligenes sp. S84S3 and Proteus sp. S19 could eliminate 65.83% of the ammonium ions without production of toxic forms of nitrogen oxides during a short time of incubation (118 h) at the same operational conditions with providing the aeration in the first treatment phase. The coculture of our isolated strains is assumed to have a good potential for nitrification and denitrification reactions applied in the treatment of wastewater containing ammonium, nitrite and nitrate. As a result, we can consider that the mixed culture is a practical method in the treatment of high-strength ammonium wastewater with reducing of sludge production.

Production of biosurfactant on crude date syrup under saline conditions by entrapped cells of Natrialba sp. strain E21, an extremely halophilic bacterium isolated from a solar saltern (Ain Salah, Algeria).

A bacterial strain E21 was isolated from a sample of water collected in the salt lake located close to Ain Salah, Algeria. The analysis of 16S rRNA gene sequence had indicated that the strain had 93 % sequence similarity with the genus Natrialba sp. strain E21 (GenBank, FR750525.1) and was considered extremely halophilic. Production of biosurfactant by the strain E21 with free and entrapped cells was investigated using soluble starch in the saline conditions. Biosurfactant synthesis was followed by measuring the surface tension and emulsifying index 9 days under optimal conditions (40 °C, pH 7). Some diffusional limitations in alginate and agar beads affected the kinetics of biosurfactant production when compared to that obtained with free cells culture. The minimum values of surface tension were 27 and 30 mN m(-1) achieved after 9 days with free and immobilized cells, respectively, while the corresponding maximum E24 values were 65.3 and 62.3 %, respectively. The re-use of bacterial cells along with the limited cell losses provided by the immobilized system might lead to significant reduction of the biosurfactant production cost.