Degradation of EDTA in H2O2 -containing wastewater by photo-electrochemical peroxidation.

Semiconductor wastewater currently contains H2O2 which is an important reagent in wafers cleaning. Recalcitrant organic pollutant such as EDTA are always present in this type of wastewater and may represent a threat for the environment. In this work, a new photoelectrochemical reactor is proposed to remove EDTA from H2O2 contaning wastewater. First, photolysis, electrochemical peroxidation and photo-electrochemical peroxidation were compared. The results showed that the removal efficiency decreases in the sequence: UV/H2O2 «EC/H2O2

Removal of fluoride, SDS, ammonia and turbidity from semiconductor wastewater by combined electrocoagulation-electroflotation.

Semiconductor industry effluents contain organic and inorganic pollutants, such as sodium dodecyl sulfate (SDS), fluoride and ammonia, at high levels which consists a major environmental issue. A combined EC-EF process is proposed as a post-treatment after precipitation for simultaneous clarification and removal of pollutants. In EC step, a hybrid Fe-Al was used as the soluble anode in order to avoid supplementary EC step. EC-Fe is more suitable for SDS removal; EC-Al is more suitable for fluoride removal, while EC with hybrid Al-Fe makes a good compromise. Clarification and ammonia oxidation were achieved in the EF step. Effects of anodic material, initial pH, current, anion nature, chloride concentration and initial pollutant concentration were studied. The final concentrations may reach 0.27, 6.23 and 0.22 mg L-1 for SDS, fluoride and ammonia respectively. These concentrations are far lower than the correspondent discharge limits. Similarly, the final turbidity was found 4.35 NTU which is lower than 5NTU and the treated water does not need further filtration before discharge. Furthermore, the EC-EF process proves to be sufficiently energy-efficient with less soluble electrode consumption.

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.

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.