280 ISSN 1070-4272, Russian Journal of Applied Chemistry, 2016, Vol. 89, No. 2, pp. 280−286. © Pleiades Publishing, Ltd., 2016. VARIOUS TECHNOLOGICAL PROCESSES Removal of Unsaturated Aliphatic Carboxylic Acid from Aqueous Effluent Using Quaternary Amine 1 Akanksha Swarnkar * , Amit Keshav, Pankaj Verma, and A. B. Soni Department of Chemical Engineering, National Institute of Technology, Raipur–492010, India *e-mail: akanksha.swarnkar@yahoo.com Received September 18, 2015 Abstract—Maleic acid, present in the effluent from organic intermediate producing industries, is an industrially important raw material. Its use in manufacture of alkyd and polyester resins, surface coatings, lubricant additives, plasticizers, co-polymers and agricultural chemicals, makes it necessary to explore for best possible techniques to recover it from aqueous solutions. The present work investigates the recovery of maleic acid from aqueous solution at ambient temperature. N–Methyl–n, n–dioctyloctan–1–ammonium chloride, (commercially known as Aliquat 336) is used as an extractant with three different diluents, belonging to different chemical classes: an aromatic hydrocarbon, a ketone, and an acetate. The chemical extraction results are reported in the terms of distribution coefficient, degree of extraction, and loading ratios. The results were modeled by mass action equilibria model as well as differential evolution technique. Differential evolution algorithm has been prepared. The model and experimental observations were compared and fairly good agreement was observed. DOI: 10.1134/S1070427216002018X 1 The text was submitted by the authors in English. INTRODUCTION Maleic acid (also called cis-butenedioic acid), is an unsaturated aliphatic dicarboxylic acid. It is a white crystal solid, easily soluble in water, acetone, and alcohol. It is an industrial raw material for the production of glyoxalic acid. Also, it may be used to form acid addition salts with drugs to make them more stable, such as indacaterol maleate. It also finds a significant use in the field of wastewater treatment. Commercially available polymer, copolymer of maleic acid and acrylic acid (PMA–100), can be used for the efficient removal of heavy metal ions (Cu 2+ , Zn 2+ , Ni 2+ , and Mn 2+ ) from an aqueous solution by the complexation–ultrafiltration process [1]. During the industrial production of some of organic intermediates, maleic acid is found in the process effluent (below 10 wt %), after the main product has been isolated [2]. For the sake of environmental concern, it is essential to find an efficient and low cost method to recover maleic acid from industrial wastewaters. Reactive extraction, with specified extractant giving a higher distribution coefficient, has been proposed as a promising technique for intensifying the recovery of maleic acid from aqueous phase. Reactive extraction employs an extractant and diluent for operation. The extractant used in this work, Aliquat 336 (A336), has a good extractability for carboxylic acids under both acidic and neutral pH. However, because of its high viscosity (1450 cP at 30°C) use of a suitable diluent provides easy handling. It has been found that diluents significantly influence the process of reactive extraction. Diluents which have functional groups that enable a greater solvation of the acid–amine complex include chlorinated hydrocarbon, ketone, alcohol and halogenated aromatic solvents. Other diluents which include alkanes, benzene, and alkyl- substituted aromatics provide a very low distribution of the acid in the solvent phase [3]. Zhenu et al. [4] investigated the phase equilibrium governing the reactive extraction of maleic acid from aqueous solution into solutions of TOA in the diluents chloroform, 4-methyl-2-pentanone (MIBK), n-hexane, and n-octanol and showed that amine formed 1 : 1 complexation with maleic acid. They also proposed a