Catalytic Ozonation Of Endosulfan In Water With Activated Carbon

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1 atalytic Ozonation Of ndosulfan In Water With Activated arbon njarlis, a,b Setijo Bismo, a Slamet, a Roekmijati W. Soemantojo a a Department of hemical ngineering, University of Indonesia, Depok6 Tel b Department of hemical ngineering, Institute Technology of Indonesia, Serpong Tangerang 5 Tel fax en_jarlis@yahoo.com Abstract The degradation of endosulfan by catalytic ozonation with activated carbon as catalyst was investigated at neutral ph and different temperatures. The aim of this work is to study the effect of the addition of activated carbon on the degradation rate of endosulfan, focusing on the rate constant (k) and the activation energy (a). ndosulfan was selected here as target organic pollutant due to its included organochlorine pesticide (OPs) may cause serious environmental concern.the presence of the activated carbon as catalyst is effect slightly in enhancing ozonation rate of endosulfanan compared to non catalytic ozonation. The rate constant (k) of endosulfan were.5 x - min - at o for catalytic ozonation, and.7 x - min - for non catalytic ozonation. The activation energy for catalytic ozonation was 6.58 kcal/mol and for non catalytic ozonation was 8,6kcal/mol. Keywords ndosulfanan, atalytic ozonation, Activated carbon. I. INTRODUTION atalytic ozonation with activated carbon as catalyst can be accelerated ozone decomposition to form OH radical, thereby increasing even further the removal efficiency of this because OH is powerfull, non-selective chemical oxidant, which acts very rapidly with most organic compounds [, ]. It has been reported that hydroxyl radicals were generated by combinations of ozone plus UV radiation, UV radiation plus H O, UV radiation plus Fenton s reagent (photo-fenton system) [] and by mixing a few milligrams of activated carbon in ozonecontaining water []. With such context, this study was investigated the degradation of endosulfan in water by catalytic ozonation at neutral ph and different temperatures, which is focused on (i) determining possible diffusion limitation (ii) determining the rate constants (k) and activation energy (a). ndosulfan was selected here as target organic pollutant due to its paradigmatic endocrine discruptors included organochlorine pesticide (OPs) may cause serious environmental concern and health problem in animals, including humans [5]. According to free radical reaction theory, OH will attack chlorinated organic compounds by hydrogen abstraction or electron transfer. Then, the organic radical will decompose further to chlorinated intermediates. These intermediates are eventually oxidized by OH to final products; organic acid and even carbon dioxide [6]. II. BASI THORY The degradation of contaminant organic in presence of activated carbon is a combination of competing homogeneous and heterogeneous reaction: direct reaction of molecular ozone, and an indirect reaction involving non selective free-radicals. Both reactions take place in the solution bulk and on activated carbon surface [7]. Therefore, the total degradation rate of contaminant organic in the presence of activated carbon can be defined as the sum of the homogeneous reaction rate, (-r ) homogen, calculated in the absence of activated carbon, and the heterogeneous reaction rate, (-r ) heterogen due to the presence of activated carbon []. The total endosulfan degradation rate can be mathematically expressed as: r = r +.. r. () As discussed earlier the activated carbon enhanced the oxidation rate of contaminant by promoting the reduction of dissolved ozone into hydroxyl radicals that cause the endosulfan degradation, the rate of equation given in Tabel. Recently, Jans and Hoigne [] pointed out that catalytic ozone decomposition can be cataloqued as another Advance Processes Oxidation (AOP) with a stoichiometric ratio (ozone decomposed/hyroxyl radical formed) equal to that of the other ozone involved in AOPs. Tabel. Rate of equation at degradation of endosulfan by ozonation in the presence activated carbon N With activated carbon o (- d /dt) hete = f (, O, OH, Ac ) With out activated carbon (- d/dt) homo = f (, O, OH ) Proceeding th Int l QIR -6 Dec 7 P-6 /5

2 (- d O /dt) hete = f (, O, OH, A ) (- d OH /dt) hete = f (, O, OH, A ) III. XPRIMNTAL RSULTS (- d O /dt) homo = f 5 (, O, OH ) (- d OH /dt) homo = f 6 (, O, OH ) ndosulfan (,,,,7,7-hexachlorobicyclo-,, heptene,-bis-hydroxy methane-5,6 sulfite) was obtained from hem. Service West hester with purity 95 %. The endosulfan solution was prepared by deionozed water obtained from Aquatron Auto Still Yamato Tipe W-8. The specific surface area of activated carbon were measured using the multipoint BT of N adsorption in a Quantachrome Autosorb -6 with surface area m /g. Ozone was produced by a RS 985 ozone generator with maximum ozone production capacity of.5 g of O /h. The experimental instrument consists of an ozone generator, a cylindrical glass column reactor with an external jacket surrounded and a water stream which was pumped from thermostatic bath to maintain the temperature at the selected value for each experiment. The dimension is of the reactor is 5 mm high with ID mm which equiped by inlet diffuser for bubbling the gas mixture, outlet gas, sampling port and magnetic stirrer. Once the experiment was started, the air-ozone mixture was fed into the flasks (KI solution) in order to determine the ozone concentration in the gas form. The reactor was filled with ml demineralized-water and the ph was adjusted to 7. The temperature was set for, 5 and o, until a predetermined of water was saturated with ozone in excess continuously by injecting ozone gas for min. The process is followed by the addition.5 g of activated carbon (for the catalytic process) and.5 x -5 mol/l endosulfan in solution. The concentration of endosulfan and ozone presence in the system was measured at,, 6,, and 5 min of treatment. The dissolved ozone concentration in aqueous solution was determined by iodometric methods, which endosulfan was analyzed by Gas hromatograph type, colum silicone ov-7 meters, D (lectron apture Detector), Shimadzu, solvent n-hexsane and mobile gas-phase N. All experiments were carried out in duplo the presence and the absence of activated carbon. The influence of variables on the degradation of endosulfan were first assessed. Non-catalytic (blank experiment) and catalytic experiments were conducted for each experimental series. Since the catalytic ozonation process involves steps of external and internal diffusion, variables studied were: activated carbon particle size and agitation speed. From experimental result agitation speed equal or higher than 75 rpm and carbon particle equal or lower. -. mm did not affect the ozonation rate. Hence, at these conditions, it can be assumed that external mass transfer rate and internal diffusion rate of ozone through pores did not control the catalyst ozone decomposition [9]. Therefore, agitation and activated carbon particle particle were kept at 75 rpm and.-. mm size. At these conditions, the kinetics should only be depended on the chemical surface ozone decomposition reaction [9]. Next, a series of experiments were then carried out at different temperatures to determining a from k. ndosulfan degradation Fig. shows the influence of the presence of activated carbon as catalyst for the degradation rate of endosulfan by catalytic and non-catalytic ozonation. From that figure, it can be seen that the degradation rate of endosulfan increased with the presence of activated carbon compared to the absence of activated carbon. This is because, the presence of activated carbon can accelerate ozone decomposition to form OH radicals which have a high reactivity to most organic micropollutants [, ] mol/l 5,,5,,5,,5,,5,,5 Fig.. ndosulfanan degradation rate by ozonation processes (x) non-catalytic (blank experiment) ( )catalytic ozonation at condition: ph 7; temperature o ; agitation speed 75 min - ;activated carbon particle.-. mm O 6.7 x - O mol/l; o 5. x - 5 mol/l Influence of temperature on the degradation of carbofuran Fig. shows the effect of temperature on degradation of endosulfan for catalytic ozonation at ph 7. From that figure, it can be stated that the higher the temperature is, the higher is the degradation rate of endosulfan. This effect is due to an increase in the rate constant of the chemical reaction. Yazgan et al [] reported that the change of temperature gave positive effect on the removal rate of the endosulfan. Although increasing Proceeding th Int l QIR -6 Dec 7 P-6 /5

3 temperature causes decreasing in dissolved ozone concentration (data are not shown), a higher oxidation rate was obtained at higher temperatures. This phenomenon can be explained by the increasing diffusion coefficient at higher temperature [].,x -5,mol/L 6 5 Fig. The effect of temperature on degradation of endosulfan by catalytic ozonation at condition: ph 7; agitation speed 75 min - ;activated carbon particle.-. mm O 6.7 x - O mol/l; o 5. x -5 mol/l; temperature o, 5 o, o Kinetics and Mechanism The observed endosulfan degradation in the presence of activated carbon results in a combination of competing homogeneous and heterogeneous reaction: direct reaction of molecular ozone, and an indirect reaction involving non selective free-radicals [7]. The degradation kinetics of endosulfan by homogeneous reaction in terms of molecular ozone and hydroxyl radical that is produced by the decomposition of ozone at neutral ph can be formulated as follows: Degradation rate of endosulfan homogeneous reaction: d. = k.. O + k.. OH dt homo () Degradation rate of endosulfan by heterogeneous reaction: d. dt () hete = k.. A + k.. O. A + k5.. Thus, since of ozone concentration in solution in excess and the constant amount of activated carbon, the amount of OH and O stayed constant during the processes (i.e., at a steady state). Therefore, q. (), () OH A and () can be rearranged to the pseudo-first-order equation in q. () as follows: = + =. d dt () r r with, k k + k. (5) ( k+ k) =. O OH and, k k + k. + k. (6) =. A O 5 OH Integrating, with initial condition = o leads to: o ln = ( k + k ) t = k (7) with, k = k + k. (8) where k total represents the apparent pseudo-first-order total rate constant for ozonation process in presence activated carbon. The degradation endosulfan by homogeneous reaction non catalytic as follows: o ln = k (9). t Figure and describe the plot of ln o / ) versus time (t) with slope as k total and k in various temperatures by catalytic and non catalytic oznation, respectively. Insert of Fig. and shows, typical Arrehnius plot for ln k against /T to endosulfan in catalytic and non catalytic ozonation processes, respectively. This linear regression indicate R =.99. From that figure, it can be stated that the higher the temperature is, the higher is the degradation rate. This effect is due to an increase in the constant rate of the chemical reaction. Similar phenomenon was reported by many researchers [, ]. The degradation of endosulfan in the presence of activated carbon slightly significantly enhancing the degradation rate of endosulfan with k total was.5 x - min - and a 6.58 kcal/mol at o compared to non-catalytic ozonation with k was.7 x - min - and a 8.6 kcal/mol. This is because of the using of activated carbon which small surface area was (6.87. m /g) compared to which was used by the other authors. They used activated carbon with surface area was larger than m /g [, ].. t Proceeding th Int l QIR -6 Dec 7 P-6 /5

4 ln ( o / ),6,,8,,6,,8, ln k to ta l, m in - /T (/.K) -,,5 -,5,,5,,5 -, -,5 -, temperatures in the range of - o by catalytic and non-catalytic ozonation ln( o/ ),5,5,5,5 ln k", (m in - ) /T (/.K) -,8,5,,5,,5 -, -,8 -, Fig onstants rate of degradation endosulfan by catalytic ozonation at condition: ph 7; agitation speed 75 min - ;activated carbon particle size.-. mm; O O mol/l; o mol/l; temperature o, 5 o, o. Insert: Arrhenius plot for degradation of carbofuran by catalytic. On other hand, compared to the degradation of carbofuran by catalytic ozonation using the same activated carbon as catalyst we obtained a slower degradation rate of endosulfan []. This is because, the reaction of endosulfan to ozone and OH is less reactive compared to the reaction of carbofuran to ozone and OH. In addition, the presence of activated carbon in ozonation processes does not really act as a catalyst, but rather as an initiator and/or a promotor for ozone transformation into OH []. Finally, from the rate constants and activation energy given in Table corresponded to the experiments completed at defferent,5 Fig. onstants rate of degradation of endosulfan by non catalytic ozonation at condition: ph 7; gas flow rate.6 L h - ; agitation speed 75 min - ; O O mol/l; o mol/l; temperature o, 5 o, o. Insert: Arrhenius plot for degradation of carbofuran by catalytic. Table. Pseudo-first order constant (k), correlation coefficient (R ), activation energy of carbofuran degradation by catalytic ozonation and non-cataytic ozonation Temperature ( o ) k. - atalytic Ozonation Non-catalytic ozonation R a (kcal/mol) R k. - (min - ) R a (kcal/mol) R (min - ).5,99.7, ,99 6,586, ,99 8.6, ,99 6.,99 Proceeding th Int l QIR -6 Dec 7 P-6 /5

5 IV. ONLUSIONS The presence of the activated carbon (catalytic ozonation) is sligtly significant in enhancing the degradation rate of endosulfan compared to noncatalytic ozonation processes. The rate constant (k) of endosulfan were.99 x - min - at o for catalytic ozonation, and.7x - min - for non catalytic ozonation. The activation energy (a) for catalytic ozonation were 8.6 kcal/mol and for non catalytic ozonation 6.586kcal/mol. RFRNS [] Jans, U., Hoigne, J. Activated carbon and carbon black catalyzed transformation of aqueous ozone into OH-radicals Ozone Sci. ng, vol, pp.67-89, 998 [] Beltran, F. J., Rivas, F. J., Fernandez L. A., Alvarez P. M., and Montero-de-spinosa, R., Kinetics of atalytic Ozonation of Oxalic Acid in Water eith Activated arbon, Ind. ng. hem. Res. vol., pp ,. [] Langlais, B., David A. R., Brink, D. R., Ozone in Water Treatment Application ngineering, ooperative Research Report. Florida. Lewis Publishing. 99. [] Jans, U., Hoigne, J. Activated carbon and carbon black catalyzed transformation of aqueous ozone into OH-radicals Ozone Sci. ng., vol, pp , 998. [5] xtoxnet,, Pesticide Information Profiles: ndosulfan, xtention Toxicology Network, Oregon State University. tm) [6] Benitez., F.J., Beltran-Heredia, J., Acero, J.L., and Rubio, F.J. Oxidation of several chlorophenolic derivatives by UV irradiation and hydroxyl radicals.j. hem. Technol. Biotechnol., vol. 76, pp. -,. [7] Valdes, H., Zaror,.A. rogeneous and homogeneous catalyti ozonation of benzothiazole promoted by activated carbon: Kinetic approach, hemosphere., vol. 65, pp. -6, 6. [8] Polo Sanchez, M., Ramos Leyva- Ramos, Rivera-Utrilla., Kinetics of,,6- naphthalenetrisulphonic acid Ozonation in presence of activated carbon.arbon vol., pp , 5. [9] Fogler Fogler, H, S. lements of hemical Reaction ngineering. rd nglewood lifft, NJ, 999 ed; Prentice-Hall: [] Yazgan, M. S., and Kinaci,., Beta- ndosulfan Removal From Water by Ozone Oxidation, Water Science & Tecnology. Vol. 8, no., pp. 5-57,. [] Benitez, F. J., Acero, J. l., and Real, F.J, Degradation of carbofuran by using ozone, UV radiation and advanced oxidation processes, Journal of Hazardous Materials vol. B89, pp. 5-65,, [] njarlis., Setijo Bismo, Slamet and Roekmijati W. Soematoyo., Kinetics degradation of carbofuran by ozonation in the presence activated carbon Proceeding th Regional symposium hemical engineering. UGM Yokyakarta. Indonesia, 7. [] Sanchez Polo, M., Gunten, U.V., Rivera-Utrilla, J. fficiency of activated carbon to transform ozone into OH radicals: Influence of operational parameters, Water Res.vol. 9, pp , 5. Proceeding th Int l QIR -6 Dec 7 P-6 5/5