Saci Nacef

Valorization of an agricultural waste, Stipa tenassicima fibers, by biosorption of an anionic azo dye, Congo red

AbstractThe removal of Congo red dye (CR) from aqueous solutions using a novel low-cost biological adsorbent, Stipa tonassicima fibers, has been investigated in this paper. Batch experiments were conducted to examine the effect of the main parameters, such as the initial CR concentration, the pH, and the temperature on the sorption of the dye. Maximum adsorption removal was observed at pH 4 and biosorption capacity of S. tenassicima was enhanced by increasing the temperature. Rate constants of pseudo-first order, pseudo-second order, and intraparticle diffusion coefficient were calculated to analyze the dynamic of the sorption process; they showed that sorption kinetics followed an intraparticle diffusion model, while the two straight lines describing experimental data indicated that intraparticle diffusion was the limiting step for biosorption. Among the tested isotherm models, the Sips isotherm was found to be the most relevant to describe CR sorption onto S. tenassicima fibers. Thermodynamic parameters...

Integration of photocatalysis and biological treatment for azo dye removal--application to AR183.

The feasibility of coupling photocatalysis with biological treatment to treat effluents containing azo dyes was examined in this work. With this aim, the degradation of Acid Red 183 was investigated. The very low biodegradability of AR183 was confirmed beforehand by measuring the biological oxygen demand (BOD5). Photocatalysis experiments were carried out in a closed‐loop step photoreactor. The reactor walls were covered by TiO2 catalyst coated on non‐woven paper, and the effluent flowed over the photocatalyst as a thin falling film. The removal of the dye was 82.7% after 4 h, and a quasi‐complete decolorization (98.5%) was obtained for 10 h of irradiation (initial concentration 100 mg L−1). The decrease in concentration followed pseudo‐first‐order kinetics, with a constant k of 0.47 h−1. Mineralization and oxidation yields were 80% and 75%, respectively, after 10 h of pretreatment. Therefore, even if target compound oxidation occurs (COD removal), indicating a modification to the chemical structure, the concomitant high mineralization was not in favour of subsequent microbial growth. The BOD5 measurement confirmed the non‐biodegradability of the irradiated solution, which remained toxic since the EC50 decreased from 35 to 3 mg L−1. The proposed integrated process appeared, therefore, to be not relevant for the treatment of AR183. However, this result should be confirmed for other azo dyes.

Separation of zinc ions from synthetically prepared brackish water using electrodialysis: effect of operating parameters

AbstractThe removal of zinc(II) at low concentrations from an aqueous saline solution was investigated using a five-compartment electrodialysis cell. In this work, the effect of key operating parameters such as initial zinc ions concentration, solution pH, applied voltage, and feed flow rate on process efficiency was studied. The separation performance was evaluated in terms of mass transfer, energy consumption, and current efficiency. The results showed that increasing the initial concentration of Zn(II) and applied voltage improves the cell performance. However, separation performance decreases with an increase in the flow rate. It was also found that specific power consumptions (SPC) are strongly dependant on ionic strength as the increase of ionic strength leads to an increase of the solution conductivity. Zinc removal rate and SPC were virtually constant and increased sharply when pH values ranged in the alkaline region.

A simple model for secondary clarifier: application to wastewater treatment plant

Abstract Wastewater treatment by low-rate activated sludge in aerobic stabilization ponds is a treatment process that has been, for most Algerian towns, the preferred tool for treating their wastewater because it has proven most reliable and easier to operate. The wastewater treatment plant of the City of Setif (Algeria) is a good example for this type of process. It has a capacity of 330,000 pop-equivalents and has been designed to accommodate 66,000 m3/d in dry weather. The work is based on the technical analysis from 2007. The mathematical model for the secondary clarifier was developed, including, propose a modified expression of the settling velocity. The treatment of the pollution parameters has been estimated. The test results have been updated, so that the results correspond to the present Algerian normalization.