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Coextrusion flows of polymer solutions and melts to produce polymeric sheets are studied employing (a) the Lubrication Approximation Theory for a quick determination of interface development and pressure drops for each material; and (b) the Finite Element Method, which uses a u-v-p-T-h formulation for the velocities, pressures, temperatures, and interface location and solves in the flow domain the full conservation and constitutive equations. The determination of the interface is part of the solution process. Simulations have been carried out for several cases of two-layer coextrusion of polymer solutions (Oppanols, i.e., polyisobutylenes) and compared with experimental data available in the literature. A three-layer coextrusion case is also studied with a barrier ethylene vinyl alcohol and an adhesive layer tying a polystyrene layer, and the results are compared with experimental data. For low flow rates, the interface location agrees closely with experiments. For high flow rates, a tendency for encapsulation occurs, which cannot be captured by the present purely viscous two-dimensional simulations.

In this work, the effects of some experimental parameters (supporting electrolyte, current density, and initial pH) on the anodic dissolution of aluminum and on the electrocoagulation of tannic acid aqueous solutions as well as real industrial wastewaters containing tannic acid were investigated. Experimental results indicated that both chemical and electrochemical dissolution play an important role in the formation of hydroxo-aluminum species. The chemical dissolution of aluminum is strongly influenced by the solution pH. Corrosion studies have demonstrated that the presence of chloride ions in water accelerates dissolution of aluminum by pitting corrosion while phosphate ions inhibit the corrosion of aluminum by formation of a thick passive layer of aluminum hydroxide/phosphate on the aluminum surface. The results obtained can be used to better understand the mechanism of the electrocoagulation process due to the importance of the anode surface electrodissolution in the treatment process. Electrocoagulation using aluminum electrodes achieved high removal efficiency of chemical oxygen demand (≥80%) from aqueous solutions containing 0.51 g·L −1 tannic acid. The primary mechanism implicated in eliminating tannic acid from water by electrocoagulation using Al electrodes involves the adsorption of tannic acid molecules on the aluminum hydroxide surface. Also, results of the treatment of real wastewater obtained from the pulp and paper industry with an initial chemical oxygen demand (COD) concentration of 1450 mg·L −1 have shown that more than 60% of COD can be removed by electrocoagulation using Al electrodes under optimized experimental conditions. The specific energy required for the electrochemical process with Al electrodes was estimated to range from 1 to 2 kWh·m −3 .

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Pollutants derived from real textile wastewater present a high environmental risk. This work involves the study of the removal of chemical oxygen demand (COD), color, and turbidity from Tunisian real textile wastewater by two different water treatment technologies: chemical coagulation (CC) and electrocoagulation (EC). A comparative study between these two methods was conducted based on the separation performance and operating cost (OC). The effects of different operational parameters including electrolysis time ( t ), voltage, and pH for EC and the coagulant concentration, initial pH, and time of slow mixing ( t sm ) for CC were studied using response surface methodology. The developed quadratic models for the responses were in good agreement with the experimental data. The experiments proved the efficiency of both chemical and electrochemical techniques for the treatment of textile effluent. Indeed, by using EC, the reduction efficiencies of COD, color, and turbidity were 63.05, 99.07, and 96.31%, respectively, under optimal conditions (pH 9, t = 36.26 min, and voltage 4 V). For CC treatment, the achieved removal efficiencies of COD, color, and turbidity were 54.02, 96.21, and 93.7%, respectively, at pH 8.57, a coagulant concentration of 204.75 mg/L, and a t sm of 28.41 min as optimal operating conditions. The OC obtained for EC and CC was about 0.47 and 0.2 USD/m 3 , respectively. Even if the OC of the EC process was higher as compared to the CC process, the treated water obtained by EC meets the Tunisian Standards (NT 106.03 and NT 09-14) for textile wastewater discharge into the environment and demonstrates a high potential for its reuse in various industrial activities. EC technology can be integrated into a wastewater management system that ensures a zero liquid discharge of wastewater into the environment.