Biosorption Kinetic Models on the Removal of Congo Red Onto Unripe Calamansi (Citrus Microcarpa) Peels
Total Page：16
File Type：pdf, Size：1020Kb
ORIENTAL JOURNAL OF CHEMISTRY ISSN: 0970-020 X CODEN: OJCHEG An International Open Free Access, Peer Reviewed Research Journal 2016, Vol. 32, No. (6): Pg. 2889-2900 www.orientjchem.org Biosorption Kinetic Models on the Removal of Congo red onto Unripe Calamansi (Citrus microcarpa) peels DERICK ERL P. SUMALAPAO1, 2,*, JERIC R. DISTOR3, IRIS D. DITAN3, NINA THERESE S. DOMINGO3, LOUIE F. DY3 and NELSON R. VILLARANTE4 1Biology Department, College of Science, De La Salle University, 2401 Taft Avenue, Manila, Philippines. 2Mathematics Area, School of Multidisciplinary Studies, De La Salle-College of Saint Benilde, 2544 Taft Avenue, Manila, Philippines. 3College of Medicine, University of the Philippines Manila, 547 Pedro Gil Street, Manila, Philippines. 4Department of Physical Sciences and Mathematics, College of Arts and Sciences, University of the Philippines Manila, Padre Faura Street, Manila, Philippines. *Corresponding author E-mail: [email protected] http://dx.doi.org/10.13005/ojc/320607 (Received: May 24, 2016; Accepted: October 03, 2016) ABSTRACT Unripe calamansi peels were prepared and used as a bioadsorbent in the removal of congo red from an aqueous solution using batch adsorption studies. The efficiency of adsorption was evaluated by varying adsorbent dose and contact time. The removal of congo red increased at higher adsorbent dose and longer contact time. The overall rate of adsorption processes appeared to be in accordance with the pseudo-second order reaction mechanism. Higher initial adsorption rate, extent of surface coverage, and activation energy were favored at a lower adsorbent dose, while the intraparticle diffusion was relatively faster at a higher adsorbent dose. The intraparticle diffusion, Elovich, and MacArthur-Wilson models were adequate in describing the chaotic behavior of the kinetic processes involved in the removal of congo red dye onto unripe calamansi peels. Keywords: Biosorption kinetics, Pseudo-second order, Elovich, MacArthur-Wilson, Intraparticle diffusion, Citrus microcarpa. INTRODUCTION water1. Due to their high water solubility and ability to color vividly at low concentrations, dyes easily Dyes are colored organic compounds which contaminate the wastewater produced by industries2. are used in industries that produce textiles, paper, This affects gas solubility and transparency of and distilleries. As a result of incomplete binding with bodies of water, which have a detrimental effect on fibers during the dyeing process, dyes are found in aquatic life1. One of these dyes is congo red which highly colored wastewaters which pollute bodies of is a common, toxic, and carcinogenic dye used 2890 SUMALAPAO et al., Orient. J. Chem., Vol. 32(6), 2889-2900 (2016) for coloration of paper products. Paper industries adsorption and potential limiting steps will be dispose of congo red in large amounts and are described using several equations, namely the usually found in sediments in polluted canals3. When pseudo-first order, pseudo-second order, Elovich, dyes such as congo red enter the water systems, they MacArthur-Wilson, and intraparticle diffusion can cause pollution, consequently harming humans nonlinear kinetic models. and aquatic organisms4. Nonlinear models, in general, are more As such, one way to address this problem difficult to specify, identify, and estimate than linear is through biosorption. It is a physico-chemical models, and it involves nonlinear iterative processes process which makes use of biological materials in determining the solution. Gauss-Newton, as one of to adsorb pollutants from aqueous solutions5. the iterative methods employed in classic nonlinear Currently, activated carbon is one effective yet regression analysis, was considered in estimating expensive biosorbent used in treating groundwater the parameters of nonlinear models in this study. and industrial wastes6. Agricultural wastes are being The adequacy and sufficiency of the various models considered as an alternative adsorbent compared were individually assessed. It is important to be to other materials due to its availability in large able to predict the rate at which hazardous wastes quantities, renewability, and inexpensiveness7. are removed from an aqueous solution in order to Compared to conventional physical and chemical design appropriate adsorption treatment systems. methods, biosorption studies are looking for easier Moreover, exhaustive exploration on the adsorption and less costly treatment, often making use of these kinetics involving wastewater treatment is important agricultural wastes as bioadsorbents6. in providing better understanding of the reaction pathways and possible mechanisms involved. Currently, no biosorption studies have been conducted for calamansi (Citrus microcarpa) peels, The use of commercial water treatment although there have been for orange peels8, which processes such as activated carbon is limited in the belong to the same family. Finding potential uses textile industry due to the high cost of production and for these discarded peelings may reduce waste and problems with regeneration6. Hence, this necessitates pollution. Hence, this study explores on the removal a need for cheaper and more efficient alternative of congo red from an aqueous solution by unripe methods, and one of these is biosorption. One reason calamansi peels in a single component adsorption that makes biosorption a potential alternative to the system at varying adsorbent doses and contact times current commercial methods is the abundance of using spectrophotometry. biomass9. Utility of calamansi peels as bioadsorbent would help in the reduction of agricultural waste and In addition, this study attempts to elucidate pollution. In a system design perspective, aggregate the mechanisms governing the removal of congo analysis of varying adsorption rates is a prerequisite red, and to find a suitable mathematical model for practical application and this requires examination for the kinetics of the removal involving adsorbent of the controlling mechanism of the adsorption dose and contact time. In particular, comparison process which includes the mass transfer, chemical on the removal of congo red from an aqueous reaction, and diffusion control. As such, several solution using calamansi peels under constant pH, adsorption kinetic models were tested using the dye concentration, and temperature will be made. obtained experimental data. Therefore, the study Only unripe calamansi peels as adsorbent with could provide potential alternatives to other dye- congo red as the adsorbate were used in this study. removal methods like membrane filtration, reverse Furthermore, factors such as the dye concentration, osmosis, coagulation or flocculation, and fenton pH, and temperature were kept constant at 0.1 g/L, reagents which are not economically feasible6. 4.00, and room temperature (27oC), respectively. The Considering the lack of studies exploring calamansi bioadsorptive properties of calamansi peels were peels as bioadsorbent, the study will provide baseline measured across different contact times, namely information on the adsorptive properties of calamansi 10, 20, 30, 40, 50, and 60 min under 0.25 g and peels. 0.50 g adsorbent doses. The mechanisms of SUMALAPAO et al., Orient. J. Chem., Vol. 32(6), 2889-2900 (2016) 2891 MATERIALS AND METHODS of zero, and the surface of an adsorbent will be positive and will attract anions if the pH is lower than Preparation of Adsorbents and Adsorbate pHpzc, while a negatively charged surface will favor Calamansi Peels the adsorption of cationic substances if the pH is 9 Citrus microcarpa is a fruit available in above the pHpzc . At pH below the isoelectric point, a the Philippines year-round, but is most abundant dye exists predominantly in its molecular form, while from August to October10. Due to its varied uses, above the isoelectric point, it exists with a higher the plant is cultivated both on a large and small proportion in its dissociated form. The isoelectric scale throughout the country. Unlike oranges, which point of congo red is 3, thus it would be negatively are also part of the Rutaceae family, calamansi charged at pH range of 5.0-10.018,19. Considering the fruit peelings have not been tested for adsorptive anionic nature of congo red, it can be said that setting properties. the stock solution to an acidic pH will theoretically allow better adsorption. Rice husk ash was observed Five kilograms of unripe calamansi was to exhibit a high adsorption capacity on congo red procured from Villa Colongan, Barangay Colongan, at pH 4.020. Ibaan, Batangas, Philippines and subsequently peeled after two days. The peels were washed Congo red solution with a concentration with distilled water to remove impurities and other of 0.1 g/L was prepared by dissolving 0.1 g congo particles, cut into small pieces, and dried in an oven red in 1 L acetate buffer with a pH of 4.00. A buffer at 100°C for 90 min8. The dried peels were then solution with a pH of 4.00 was prepared using 0.1 M crushed using a mortar and pestle, then grounded NaOH and 1 M acetic acid12. The flask was wrapped into granules and sifted through a 1.00 mm mesh in aluminum foil and stored inside an icebox until it in order to control particle size. Degraded cells offer was needed. a larger available surface area and intracellular component resulting to increase in the availability of Establishment of Calibration Curve more surface binding sites and modifies the functional A calibration standard for the congo groups