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The removal of chromium (VI) from aqueous solutions by Donnan dialysis has been investigated in this paper. In this process, two anion-exchange membranes (AEMs) were used: Selemion ® AMV and Neosepta ® AFN. The amount of chromium (VI) removed was determined in terms of the following parameters: initial concentration of chromium (VI), type of anion-exchange membrane, concentration of counter-ion and magnetic stirring rate. A 24 full factorial design analysis was performed to screen the parameters affecting the Cr (VI) removal efficiency. Using the experimental results, a linear mathematical model representing the influence of the different parameters as well as their interactions was obtained. Analysis of the variance (ANOVA), the F-test and the student's test shows that the type of anion-exchange membrane is the most significant parameter affecting the chromium (VI) removal. The statistical analysis of the experimental data assumes it to be a normal distribution.

The effective removal of heavy metals from industrial wastewater is a very important issue for many countries. This paper examines the removal of cadmium ions from aqueous solutions and industrial effluents by adsorption on activated alumina. The Brunauer–Emmett–Teller (BET) specific surface area, pore diameter and pore volume of the activated alumina were 156.7 m2/g, 58.4 Å and 0.23 cm3/g, respectively. Factorial experimental design was applied to evaluate the main effects and interactions among dose of activated alumina, initial cadmium concentration, pH of the solution and temperature. Analysis of variance, the F-test and the Student's t-test shows that dose of activated alumina, initial cadmium ion concentration and temperature are the most significant parameters affecting cadmium ion removal and pH is the least significant parameter. Under optimal conditions, cadmium removal from industrial effluent samples was >98%. Furthermore, desorption and regeneration studies were carried out in order to evaluate the cost-effectiveness of activated alumina.

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Boron is widely distributed in the environment, mainly in the form of boric acid or borate salts, and its contamination of waters is a concern around the world.
This study focuses on boron removal by means of adsorption onto activated alumina. Optimum adsorption was achieved in the pH range 8.0 to 8.5. Approximately 60% (by mass) boron removal was achieved using an adsorbent dose of 5 g at an initial boron concentration of 50 mg/L. Adsorption isotherms at 10, 20, and 30°C were investigated. The results fitted with the Langmuir and Freundlich equations showed a monolayer adsorption onto a surface, with a finite number of identical sites. To study the rate‐limiting step, the adsorption kinetic data of boron were analyzed using first‐order (Lagergren) and second‐order kinetic models. The experimental results obtained showed that the adsorption process followed a second‐order kinetic model.