Response of Artemisia herba alba to hexavalent chromium pollution under arid and semi-arid conditions.

The aim of this work is to study and evaluate in situ, the Artemisia herba alba responses to hexavalent chromium stress in the arid and semi-arid steppe Algerian soil. This metallic pollutant was selected to its high toxicity and to its great release from several industrial and agricultural activities emissions in the area of the study region. Artemisia herba alba is a medicinal plant but also a forage species widely used in pasture. It has dominated then adapted to the arid and semi-arid climate of Algerian steppe region, due principally to their morphological and physiological characteristics. To establish this work, A. herba alba species were selected in the Algerian steppe region, and their soils were treated weekly with K2CrO4 solution for about three months. Chromium concentrations were determined in the soil and in the different plants' parts to verify its absorption and translocation with and without pollution simulation. This study demonstrated that A. herba alba has a strong resistance to high concentrations of hexavalent chromium. An increase in chromium concentrations at the different parts of plant's has been noticed, without affecting its growth and vegetative development. The results of physiological and elementary analysis indicated that chromium was absorbed by A. herba alba. Cr (VI) accumulation in plant increase when they are increasing in soil. Translocation factor results indicated that Cr (VI) was mainly accumulated by A. herba alba roots. Particle size analysis showed that the soil is poor in organic substances and mostly sandy loams with 79.77% of sand and 9.76% of clay minerals.

Competitive adsorption of toxic metals on bentonite and use of chitosan as flocculent coagulant to speed up the settling of generated clay suspensions.

Evaluation of modified Algerian clay as mineral adsorbent was done for its adsorbing capacity on copper (Cu) and Zinc (Zn) cations. The results obtained show a rapid kinetic adsorption for both metals (less than 2 h) following the pseudo-second order model with high elimination rates of 67.2 and 61.8% for Cu and Zn respectively. The adsorption isotherms analyzed with Langmuir model revealed a correlation with the experimental values. While the use of obtained chitosan at room temperature, as flocculent coagulant, accelerates the decantation of the colloidal particles in suspension generated after adsorption process.

Effects of chitin and its derivatives on human cancer cells lines.

The present study is focused on the effect of chitin derivatives against human cancer cell lines RD and Hep2. As an outcome from this research, chitin was cytotoxic at IC50 = 400 µg/ml and 200 µg/ml against Hep2 cells and RD cells lines, respectively. Irradiated chitin had an IC50 value of 450 µg/ml for Hep2 and an IC50 of 200 µg/ml for RD. The lowest IC50 is attributed to chitosan, 300 µg/ml in Hep2 and 190 µg/ml in RD.

Chitosan use in chemical conditioning for dewatering municipal-activated sludge.

This work aims to evaluate the potential use of chitosan as an eco-friendly flocculant in chemical conditioning of municipal-activated sludge. Chitosan effectiveness was compared with synthetic cationic polyelectrolyte Sedipur CF802 (Sed CF802) and ferric chloride (FeCl3). In this context, raw sludge samples from Beni-Messous wastewater treatment plant (WWTP) were tested. The classic jar test method was used to condition sludge samples. Capillary suction time (CST), specific resistance to filtration (SRF), cakes dry solid content and filtrate turbidity were analyzed to determine filterability, dewatering capacity of conditioned sludge and the optimum dose of each conditioner. Data exhibit that chitosan, FeCl3and Sed CF802 improve sludge dewatering. Optimum dosages of chitosan, Sed CF802 and FeCl3allowing CST values of 6, 5 and 9 s, were found, respectively, between 2-3, 1.5-3 and 6 kg/t ds. Both polymers have shown faster water removal with more permeable sludge. SRF values were 0.634 × 10¹², 0.932 × 10¹² and 2 × 10¹² m/kg for Sed CF802, chitosan and FeCl3respectively. A reduction of 94.68 and 87.85% of the filtrate turbidity was obtained with optimal dosage of chitosan and Sed CF802, respectively. In contrast, 54.18% of turbidity abatement has been obtained using optimal dosage of FeCl3.

Anticancer activity of chemically prepared shrimp low molecular weight chitin evaluation with the human monocyte leukaemia cell line, THP-1.

In the present study, anticancer activities of chitin, chitosan and low molecular weight chitin were evaluated using a human tumour cell line, THP-1. A molecular weight-activity relationship and an electrostatic interaction-activity relationship were determined. The cytotoxic effects of chitin and derivatives were also evaluated using a normal human foetal lung fibroblastic cell line, MRC-5 and the specific cytotoxicity of chitin and derivatives to tumour cell lines was demonstrated. The high antitumour effect of low molecular weight of chitin was established.

Electrodialysis with bipolar membrane for regeneration of a spent activated carbon.

The main purpose of the present work was to develop a treatment method to regenerate granular adsorbent beds saturated with H(2)S by utilizing three electrodialysis compartments equipped with a cation or an anion exchange membrane or a bipolar membrane. Three electrodialysis compartments were utilized under various experimental parameters to determine the optimum conditions for the recovery of column particles saturated by H(2)S. The desulphurization operation is achieved with the extent of extraction close to 90% and an electric current density of about 30%. Use of the bipolar membrane makes it possible to regenerate the saturated adsorbent granules without adding chemical products. Since the only reagent was electricity, the projected economics are very attractive.

Study on the treatment of photovoltaic wastewater using electrocoagulation: fluoride removal with aluminium electrodes--characteristics of products.

In this work, treatment of synthetic fluoride-containing solutions by electrocoagulation method using aluminium electrodes has been studied. Electrocoagulation was investigated for applied potential (10-30 V), electrolysis time and supporting electrolyte (NaCl) concentration (0-100mg/L). The results showed that with increasing applied potential and electrolysis time, the Al(3+) dosage increases, and thereby favouring the fluoride ions removal. It was also observed that defluoridation is dependant on the concentration of supporting electrolyte. Finally, X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy of X-rays and Fourier transform infrared spectroscopy were used to characterize the solid products formed by aluminium electrodes during the EC process.

Application of the electrosorption technique to remove Metribuzin pesticide.

The present work deals with the removal of Metribuzin from aqueous solutions in a batch and continuous mode using electrosorption technique. This technique is based on the combination of two processes: the adsorption of Metribuzin into activated granular carbon (GAC) column and the application of the electrochemical potential. The effects of various experimental parameters (electrochemical potential, volumetric flow rate and initial Metribuzin concentration) on the removal efficiency were investigated. The pesticide sorption capacity at the breakthrough point of the GAC column reached 22 mg(pesticide)g(GAC)(-1). It was increased by more than 100% when the desired electrical potential (-50 mV/SCE) was applied in comparison with the conventional GAC column in similar experimental conditions without electrical potential. Evenmore, the electrosorption technique reduced considerably the drastic decrease encountered when passing from batch mode to continuous column mode.

Mechanism of phenol adsorption onto electro-activated carbon granules.

The main purpose of this paper is to determine the mechanisms which govern the adsorption of the phenol onto electro-activated carbon granules. This new activation technique allowed an increase of the performance of the adsorbent. Two models were utilised to understand the improvement in the performance of electroactivated carbon granules. The first, a simple external resistance model based on film resistance, gave acceptable predictions, with an error of less than 15%, between the theoretical results and experimental data independent of the activation potential and phenol initial concentration. The second linear model, based on diffusion phenomena, was more representative in describing the experiment than the first model. It was observed that the electro-activation method did not change the mechanism which governs phenol adsorption onto granular carbon. Indeed, the same mathematical model based on diffusion phenomena made it possible to predict with a very low error (less than 5%) the experimental data obtained for the favourable activation potential, without activation potential and with an unfavourable activation potential. The electro-activation technique makes it possible to increase the number of active sites that improve the performance of the electro-activated granular carbon compared with conventional granular activated carbon.

Enzymatic saccharification of solid residue of olive mill in a batch reactor.

This paper describes the enzymatic hydrolysis of solid residue of olive mill (OMRS) in a batch reactor with the Trichoderma reesei enzyme. Before enzymatic saccharification, crude lignocellulosic material is submitted to alkaline pre-treatment with NaOH. Optimum conditions of the pre-treatment (temperature of T=100 degrees C and OMRS-NaOH concentration ratio of about R=20) were determined. The optimum enzymatic conditions determined were as follows: pH of about 5, temperature of T=50 degrees C and enzyme to mass substrate mass ratio E/S=0.1g enzyme (g OMRS)(-1). The maximum saccharification yield obtained at optimum experimental conditions was about 50%. The experimental results agree with Lineweaver Burk's formula for low substrate concentrations. At substrate concentrations greater than 40gdm(-3), inhibitory effects were encountered. The kinetic constants obtained for the batch reactor were K(m)=0.1gdm(-3)min(-1) and V(m)=800gdm(-3).