N. Drouiche

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.

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.

The Influence of Parameters Affecting Boron Removal by Electrocoagulation Process

Boron removal in seawater desalination presents a particular challenge. In seawater reverse osmosis (SWRO) systems boron removal at low concentration (<0.5 mg/L) is usually achieved by a second pass using brackish water RO membranes. However, this process requires chemical addition and important additional investment, operation and maintenance, and energy costs. Electrocoagulation (EC) process can be used to achieve such low boron concentration. In this work, the removal of boron from aqueous solution was carried out by EC process using aluminum and iron electrodes. Several operating parameters on the removal efficiency such as initial pH, current density, initial boron ion concentration, feed concentration, gap between electrodes, and electrode material, were investigated. In the case of bipolar electrocoagulation (BEC), an optimum removal efficiency of 96% corresponding to a final boron concentration of 0.4 mg/L was achieved at a current density of 6 mA/cm² and pH = 8 using aluminum electrodes. The concentration of NaCl was 2,500 mg/L and the gap between the electrodes of 0.5 cm. Furthermore, a comparison between monopolar electrocoagulation (MEC) and BEC using both aluminum and iron electrodes was carried out. Results showed that the BEC process has reduced the current density applied to obtain high level of boron removal in a short reaction time compared to MEC process. The high performance of the EC showed that the process could be used to reduce boron concentration to acceptable levels at low-cost and more environmentally friendly.

HF wastewater remediation by electrocoagulation process

ABSTRACT Wastewater from surface treatment of silicon wafers is rich in fluoride ions. This is attributed to the use of hydrofluoric acid in huge quantities during stripping operation. Lime precipitation is insufficient to comply with environmental standards. In this work, the electrocoagulation (EC) was used for polishing treatment after neutralizing step. Synthetic solutions were used for the investigation into main operational factors affecting fluoride removal performance such as electrode material, initial pH, current density, salt nature, etc. The experimental results showed that EC is efficient for the removal of fluoride ions. This performance is ascribed to the effect of anodically generated coagulants. A removal efficiency of more than 99% of fluoride may be obtained. The quality of the effluent water met the specifications for the national discharge standard.

Degradation of Disperse Red 167 Azo Dye by Bipolar Electrocoagulation

This study investigates the influence of variables on the removal efficiency of solution containing azo dye Disperse Red 167 by bipolar electrocoagulation (BEC). Current density, time of electrolysis, interelectrode distance, supporting electrolyte concentration, and total surface area were the variables that mostly influenced the azo dye removal. The efficiency of different electrode materials (Fe, Al) for azo dye removal is compared. The obtained results showed the effectiveness of the aluminum and iron electrodes for azo dye removal. The present study allows achieving a high level of decolorization (100%) with a short reaction time for both electrodes. The method was found to be highly efficient and relatively fast compared to conventional existing techniques.

Purification, characterization, and molecular cloning of an extracellular chitinase from Bacillus licheniformis stain LHH100 isolated from wastewater samples in Algeria.

An extracellular chitinase (ChiA-65) was produced and purified from a newly isolated Bacillus licheniformis LHH100. Pure protein was obtained after heat treatment and ammonium sulphate precipitation followed by Sephacryl S-200 chromatography. Based on matrix assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF/MS) analysis, the purified enzyme is a monomer with a molecular mass of 65,195.13 Da. The sequence of the 27 N-terminal residues of the mature ChiA-65 showed high homology with family-18 chitinases. Optimal activity was achieved at pH 4 and 75 °C. Among the inhibitors and metals tested, p-chloromercuribenzoic acid, N-ethylmaleimide, Hg(2+), and Hg(+) completely inhibited enzyme activity. Chitinase activity was high on colloidal chitin, glycol chitin, glycol chitosane, chitotriose, and chitooligosaccharide. Chitinase activity towards synthetic substrates in the order of p-NP-(GlcNAc)n (n = 2-4) was p-NP-(GlcNAc)2 > p-NP-(GlcNAc)4 > p-NP-(GlcNAc)3. Our results suggest that ChiA-65 preferentially hydrolyzed the second glycosidic link from the non-reducing end of (GlcNAc)n. ChiA-65 obeyed Michaelis-Menten kinetics, the Km and kcat values being 0.385 mg, colloidal chitin/ml and 5000 s(-1), respectively. The chiA-65 gene encoding ChiA-65 was cloned in Escherichia coli and its sequence was determined. Above all, ChiA-65 exhibited remarkable biochemical properties suggesting that this enzyme is suitable for bioconversion of chitin waste.

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.

Assessment of the recovery of photovoltaic cells cutting fluid by chemical pretreatment and ultrafiltration

abstract The main objective of the work was to regenerate a cutting fluid HS20 used in the manufacturing of silicon wafers. Centrifugation at ambient temperature is initially considered for the treatment of the cutting fluid HS20. However, the slurry being heavily loaded with mineral colloids, tests conducted following the use of this process, have proved its efficiency to be low. Indeed, the best results for colloidal matter abatement have never exceeded 30%. By contrast, an ultrafiltration through a polyethersulfone membrane with a cutoff of 1 kDa shows excellent efficiency and affinity towards the fluid (HS20) to be considered, allowing its full recovery by maintaining its original cutting fluid characteristics. However, this process does present some drawbacks. A strong resistance to flow across the membrane of up to 60% of the total resistance is observed and a drop in permeation flux of about 90% are observed. Given these results, reinforcement of ultrafiltration, under the same operating conditions...

Modeling of the adsorption of metribuzin pesticide onto electro-activated granular carbon

AbstractThe main purpose of the present study is to investigate the mechanism which governs the adsorption of the pesticide onto electro-granular activated carbon (GAC). The operating conditions assessed are: electrical potential, electro-activation time, the initial metribuzin—electro-activated GAC concentration ratio (R = Cp/CGAC). In the first step, it has been confirmed using an experimental design that the C/C0 ratio is much more affected by the electrochemical potential application than by R ratio. The mathematical model indicates that the electrochemical potential has a significant effect during the metribuzin adsorption during the first half an hour on GAC and thereby demonstrates the electroactivation beneficial effect. In the second step, a mass transfer model has been applied in order to evaluate the effect of the electro-activation of GAC on the kinetic constant. Indeed, the results showed that the electro-activation accelerates the process with kinetic constants 2–3 times higher than those ob...

Development of an integrated electro-coagulation–flotation for semiconductor wastewater treatment

AbstractIn this study, an electro-coagulation–flotation process was used as a polishing treatment of semiconductor wastewater after precipitation. Batch mode experiments were undertaken using aluminium sheets as anode and stainless steel as cathode. Experiments on a synthetic solution showed that coupling electro-coagulation with electro-flotation in the same cell is efficient for simultaneous defluoridation and clarification. This combination was carried out by proper electrode arrangement and material choice. The performance is ascribed to the combined effect of anodically created coagulants and hydrogen micro-bubbles evolving on the cathode. The effects of the main parameters: electrode nature and arrangement, treatment time, current intensity, initial pH, initial concentration, type and concentration of supporting electrolytes were studied. Defluoridation efficiency may reach 90% corresponding to residual fluoride of 4.61 mg/L, while, turbidity removal efficiency may reach about 85% which corresponds ...