Combination of electrocoagulation and adsorption processes to remove methyl orange from aqueous solution

Abstract

The purpose of this study was to investigate the performance of an integrated EC–adsorption system to remove methyl orange from aqueous solution. In this study, the integrated EC–adsorption system consisted of two electrodes, which were kept at 2 cm, and an iron electrode used as the cathode and stainless steel sieve box as the anode which filled by modified pumice as an adsorbent whereas the effective surface of electrodes was 3 × 10 cm. To improve the performance of the anode, pumice was used as an adsorbent due to its characteristics such as low specific gravity, porous and light structure, impermeability to sound and heat, and high abrasive power. The surface of pumice was also modified with Cetyltrimethylammonium bromide (CTAB) surfactant to improve the anode performance. The main process variables including initial concentration 50–150 mg/L, pH (3–11), adsorbent dosage (0.5–1.5 g) and voltage (30–50 V) were examined to find an optimum condition. Each run took 1 h, and the volume of the system was 1.5 L also during the experiment an aquarium pump for aeration and mixing was applied. The experimental design was conducted by Design-Expert software, and the Box–Behnken method was used to examine the four variables at three levels. The 3-D diagrams were analyzed for interaction between parameters so, the best optimal conditions for the removal of methyl orange was obtained at C i = 50 mg/L, pH = 7, adsorbent dosage = 1 g, V = 40 V, which result of removal yield was 93.1 %. According to ANOVA result’s, initial concentration and interaction between initial concentration and pH have the most impacts on the methyl orange removal among other factors which the coefficients are 9.16 and 7.10, respectively. • A novel combined electrocoagulation–adsorption system is prepared to remove methyl orange. • Adsorbent modified by CTAB to increase the adsorbent capacity, and SEM tests are taken before and after the modification. • The ranking of the importance of the parameters was determined. • The maximum methyl orange removal efficiency is obtained at neutral pH and accurate adsorbent dosage.