Béchir Hamrouni

Iron removal from brackish water by electrodialysis

The aim of this work is to study the removal of iron from brackish water using electrodialysis (ED). Experiments were carried out on synthetic brackish water solutions using a laboratory-scale ED cell. The influence of several parameters on process efficiency was studied. This efficiency is expressed by the removal rate, transport flux, current efficiency and power consumption. The applied voltage, the feed flow rate, the pH and iron initial concentration of the feed solution have a significant effect on the process efficiency and mainly on the iron transfer from dilute to concentrate compartment. Nevertheless, feed ionic strength does not have an effect on the iron removal. However, the effect is only noted on the specific power consumption.

Removal of zinc ions from synthetic and industrial Tunisian wastewater by electrocoagulation using aluminum electrodes

AbstractElectrocoagulation (EC) is an efficient technique for cleaning waste water containing heavy metals before discharge in the environment. The performance of electro coagulation for zinc ions removal using aluminum electrodes was investigated in this paper. Several electrochemical parameters such as pH, current density, electrolyte doses, energy consumption, initial concentration, EC time, the state of the aluminum plates, and heavy metal ions concentration were studied in an attempt to achieve high zinc removal efficiency. Optimum conditions for zinc removal were found at a pH value of 7, a current density of 7.35 mA cm−2, an inter-electrode potential of 5 V, a conductivity of 5.3 mS cm−1, and an EC time of 30 min. These operating conditions can simultaneously achieve a good mix, good flotation, high flocs stability, and thus efficient removal in a relatively short reaction time and low cost with a removal percentage up to 98.96. The testing of zinc removal from industrial waste water showed that th...

Influence of operating conditions on the retention of phenol in water by reverse osmosis SG membrane characterized using Speigler–Kedem model

Phenol is one of the most common organic water pollutants and strict standards were imposed for phenol content in water because of their high toxicity. Technologies using membrane processes such as reverse osmosis (RO) are increasingly employed in many industrial sectors as important alternative technologies to classical processes of separation. In this work, the removal of phenol from aqueous solutions was studied on laboratory scale by using a commercial polyamide thin film composite RO membranes spiral wound (SG 2514TF by Osmonics Company). The first objective of this work is to evaluate the characteristics of the SG membrane used in permeation experiments with aqueous solution of charged inorganic solutes. A model inspired by the phenomenological approach proposed by Speigler–Kedem was applied in order to quantify separately both parts of mass transfer occurring, the pure convection and the pure diffusion. The experimental results indicated that the retention sequence was inversely proportional to the...

Denitrification of brackish water by electrodialysis: Effect of process parameters and water characteristics

The aim of this work is to study the removal of nitrate from brackish polluted water using electrodialysis. The influence of several parameters, such as flow rates, initial feed concentration, co-existing anions and initial pH on process efficiency were studied. This efficiency is evaluated by the removal rate, demineralization rate and power consumption. The denitrification process showed to be independent of pH of feed solution. Although The flow rate as well as the initial salt concentration and also the coexisting anions on the feed solution play a significant role on the denitrification efficiency and mainly on the specific power consumption. The decrease of this parameter induces a decrease on the total energy needed to perform required operation. The denitrification of a contaminated real water sample was investigated so as to improve the efficiency of denitrification process. The nitrate concentration could be reduced from 225 to 25.5 mg L−1 (88% removal) which was lower than World Health Organization (WHO) standard (50 mg L−1). Moreover the concentrations of different species in the obtained treated water are below the amounts recommended by WHO for drinking water.

Treatment of heavy metal polluted industrial wastewater by a new water treatment process: ballasted electroflocculation

This laboratory study investigated the parameters efficiency of the new technology: ballasted electro-flocculation (BEF) using aluminum (Al) electrodes to remove cadmium and zinc from industrial mining wastewater (MWW). The principle of the BEF process is based on the use of micro-sand and polymer together to increase the weight of the flocs and the rate at which they settle is radically changing the electrocoagulation-electroflocculation settling methodology. Based on the examination of the operation parameters one by one, the best removal percentage was obtained at a current intensity of 2A, a the flow rate of 20L/h, a micro-sand dose of 6g/L, a polyéthylèneimine (PEI) polymer dose of 100mg, the contact times of 30min, a stirring speed of 50 RPM, a monopolar configuration of the electrodes, and an electrodes number of 10. The results showed that the flow rate and the current density have a preponderant effect on the variability of the quality of the settled water. In comparison, filterability was found to be more sensitive to number of electrodes, micro sand dosages and current density. It was dependent on the ratio of microsand to PEI polymer dosage, and improved when this ratio increased. Response surface methodology was applied to evaluate the main effects and interactions among stirring speed, polymer dose, current intensity, and electrodes number. The removal of Cd and Zn from industrial MWW was done for very low cost of 0.1TND/m3 equivalent to 0.04€/m3. The investigation of BEF process proposes a highly cost-effective wastewater treatment method if compared to Actiflo TM and electrocoagulation.

Optimization studies for water defluoridation by adsorption: application of a design of experiments

AbstractFluoride in groundwater is a worldwide problem. In Tunisia, it is one of the most abundant constituents occurring in groundwater, creating a major problem in safe drinking water supply. This paper aims to examine the fluoride removal from aqueous solutions by adsorption on activated alumina (AA) using a two-level full factorial design. For this sake, four operating parameters supposed to affect the removal efficiency were chosen: initial fluoride concentration, pH of the solution, adsorbent dose, and temperature. Factors that influence the fluoride removal efficiency were evaluated statistically by using factorial plots: the Pareto chart, main effect, interaction effect, normal probability plots, and the cube plot. Analysis of variance and P-value significant levels were used to check the significance of the effect on percentage removal. The statistical analysis allowed verifying that the four studied parameters have an influence on the fluoride elimination (P-values ≤0.05 and F-values >4.49). It ...

Hexavalent Chromium Removal from Model Water and Car Shock Absorber Factory Effluent by Nanofiltration and Reverse Osmosis Membrane

Nanofiltration and reverse osmosis are investigated as a possible alternative to the conventional methods of Cr(VI) removal from model water and industrial effluent. The influences of feed concentration, water recovery, pH, and the coexisting anions were studied. The results have shown that retention rates of hexavalent chromium can reach 99.7% using nanofiltration membrane (NF-HL) and vary from 85 to 99.9% using reverse osmosis membrane (RO-SG) depending upon the composition of the solution and operating conditions. This work was also extended to investigate the separation of Cr(VI) from car shock absorber factory effluent. The use of these membranes is very promising for Cr(VI) water treatment and desalting industry effluent. Spiegler-Kedem model was applied to experimental results in the aim to determine phenomenological parameters, the reflection coefficient of the membrane (σ), and the solute permeability coefficient (Ps). The convective and diffusive parts of the mass transfer were quantified with predominance of the diffusive contribution.

Competitive adsorption of fluoride and natural organic matter onto activated alumina

ABSTRACT Natural organic matter (NOM) is a major water constituent that affects the performance of water treatment processes. Several studies have shown that NOM can be adsorbed on the surface of oxides and may compete with other ions. The overall goal of this study was essentially to investigate the competitive adsorption between fluoride and NOM on activated alumina (AA). For this purpose, a humic acid (HA) was used as a model compound for NOM. The interaction of NOM with fluoride, the simultaneous competitive adsorption, and the effect of preloading AA with NOM were investigated. The specific absorbance of HA was determined at 254 nm. Size-exclusion chromatography measurements confirmed the adsorption of aromatic fractions of NOM onto AA. The presence of HA in the system inhibited fluoride sorption onto AA and the removal yield using fresh AA decreased from 70.4 % to 51.0 % in the presence of HA. The decrease was more pronounced using AA preloaded with HA, reaching 37.7 %. The interference of coexisting ions and their effect on fluoride removal capacity were evaluated, showing a severe impact of the presence of phosphate on the removal capacity unlike nitrates and sulfates, which slightly improved the fluoride sorption.

Electrodialytic Removal of Cadmium from Brackish Water: Effects of Operating Parameters

The continuous increase of environmental regulations make interesting to find effective and efficient methods for processing effluents containing metal ions. This research focuses on cadmium removal from brackish water by an electro-membrane process: The electrodialysis. Experiments were carried out on synthetic brackish water solutions and using a laboratory scale electrodialysis system. The influence of several parameters on process efficiency was investigated. The efficiency of this process was assessed by the determination of five parameters: The demineralization rate, the removal rate and the transport flux of cadmium, the current efficiency and the specific power consumption. The applied voltage, the feed flow rate, the pH and cadmium initial concentration of the feed solution have a significant effect on the process efficiency and mainly on the cadmium transfer from dilute to concentrate compartment. In contrast, feed ionic strength seems to affect only the SPC and not the R(Cd).

Intensification of light green SF yellowish (LGSFY) photodegradion in water by iodate ions: Iodine radicals implication in the degradation process and impacts of water matrix components

The results of this work showed that UV/IO3- oxidation process supplies good performance in the degradation of light green SF yellowish (LGSFY) dye in deionized water. This process generated reactive iodine radicals that make the degradation much faster than the sole UV irradiation. The assistance of UV-irradiation by 10 mM of iodate increased the LGSFY removal after 10 min from 36% to 90% for C0 = 10 mg/L and from 18% to 85% for C0 = 20 mg/L. In parallel, a 2.5 and 4.72-fold increase in the LGSFY initial degradation rate, as compared with UV alone, were recorded for, respectively, 10 and 20 mg/L of LGSFY. IO2 and IO played the most important role in the degradation of LGSFY by the UV/IO3- process. The degradation was not affected by the presence of chloride and nitrate ions even at high dosage levels (up to 0.1 M), whereas sulfate ions reduced the valuable effect of iodate to the half when they are present at 0.1 M. Correspondingly, humic acids, at usual concentrations as those measured in natural waters, did not affect significantly the LGSFY degradation upon photoactivated iodate process. These results revealed, in one part, that iodine radicals are selective oxidants and, in another part, that the process is likely to remove organic dyes from natural water which often contains mineral constitutes and humic substances.