Multicomponent Adsorption and Desorption of BTX Compounds Using Coconut Shell Activated Carbon: Experiments, Mathematical Modeling, and Numerical Simulation Adriana Dervanoski Luz,* Selene Maria de Arruda Guelli Ulson de Souza, Cleuzir da Luz, Ricardo Vicente de Paula Rezende, and Antônio Augusto Ulson de Souza Chemical Engineering Department, Federal University of Santa Catarina, Laboratory of Numerical Simulation of Chemical Systems, Campus Universita ́ rio, 88040-900 Florianó polis, Santa Catarina, Brazil ABSTRACT: A numerical and experimental study of the monocomponent and multicomponent adsorption and desorption of BTX compounds (benzene, toluene, and o-xylene) in a batch reactor and fixed-bed column was carried out in aqueous solution at 23 °C, using coconut shell activated carbon as the adsorbent. The monocomponent Langmuir isotherm model best represented the experimental results (average R 2 = 0.9952) and the multicomponent Langmuir model, using the multicomponent parameters, represented the multicomponent data obtained in a fixed-bed column better than the monocomponent model. The equations which describe the phenomenology were discretized using the Finite Volumes Method with the WUDS and CDS formulations. The results for the monocomponent breakthrough curves obtained through simulation showed good agreement when compared with the experimental data (maximum error of 11.52%). For the monocomponent breakthrough curves the greatest deviation was observed for the compound which had the least affinity for the solid phase (benzene). The best results for the desorption of the BTX compounds from the adsorbent were obtained using ethanol as the desorbent solvent, and the average removal percentages in three cycles of regeneration in the column were 90% for benzene, 82% for toluene, and 78% for o-xylene. 1. INTRODUCTION The contamination of natural resources, mainly water resources, has increased the general public’s awareness of the need for environmental preservation. Environmental legislation, monitoring tools, and economic implications have been fundamental instruments of environmental policy with regard to the discharge of effluents. Thus, studies are being directed toward the treatment of contaminated streams at the source (integrated approach) and the treatment of final effluents (end- of-pipe approach). 1-4 In industry, the search for new technologies is focused on the need for more efficient processes for the removal of contaminants, seeking less demanding processes with low installation and operation costs, and more compact units which operate with greater flexibility and with good performance in the removal of toxic compounds. 5 The BTX compounds, benzene, toluene, and xylenes, present in petroleum industry effluents, are hydrocarbons which have a high contamination potential. 6-9 The United States Environ- mental Protection Agency (USEPA) has classified these compounds as priority chemical contaminants. 10,11 They are powerful depressors of the central nervous system and have chronic toxicity and potential mutagenicity, even in low concentrations. Benzene is the most toxic of the BTX compounds, due to its confirmed carcinogenic action, and it can cause leukemia and tumors in multiple organs. Acute exposure by inhalation or ingestion can even lead to death. 1,10,11 According to Lin and Huang, 12 there are several treatment technologies available for the removal of these organic compounds from aqueous effluents, such as biological processes, incineration, oxidation, and adsorption. Each of these processes has its advantages and disadvantages; however, adsorption is the most effective method for effluent treatment. Also, the other processes are generally more expensive and are not able to reach the concentration limits established for effluents discharged to water bodies. A commonly used and low-cost adsorbent which has a great affinity for organic compounds is granulated activated carbon. This is recommended as an adsorbent for the elimination of volatile organic compounds. According to Leitã o and Rodrigues, 13 Chatzopoulos et al., 14 and Wibowo et al., 15 adsorption with activated carbon is a proven and reliable technology for the industrial removal of small quantities of organic compounds which are soluble in water and industrial effluents. According to Wibowo et al., 15 activated carbon is one of the most important microporous adsorbents from the industrial point of view, and it can be regenerated and reused for several adsorption cycles. However, the regeneration of adsorbents saturated with organic compounds, particularly in aqueous solutions, has received relatively little attention. 14 Most studies available in the literature have centered on the efficiency of the adsorbate extraction using organic solvents 16 or supercritical CO 2 . 17 In this context, the aim of this study was to investigate the monocomponent and multicomponent adsorption and desorp- tion of BTX compounds under different operational conditions using thermally activated vegetal carbon (coconut shell). The Received: October 18, 2012 Revised: May 15, 2013 Accepted: May 24, 2013 Published: May 24, 2013 Article pubs.acs.org/IECR © 2013 American Chemical Society 7896 dx.doi.org/10.1021/ie302849j | Ind. Eng. Chem. Res. 2013, 52, 7896-7911