Analatycal study of intermediate products formed during the treatment of paracetamol by UV / Naclo

1 GRADUATE UNIVERSITY SCIENCE AND TECHNOLOGY QUAN CAM THUY ANALATYCAL STUDY OF INTERMEDIATE PRODUCTS FORMED DURING THE TREATMENT OF PARACETAMOL BY UV/NaClO Research field: Analatycal Chemistry Code: 62.44.01.18 SUMMARY OF DOCTORAL THESIS HA NOI - 2018 MINISTRY OF EDUCATION AND TRAINING VIETNAM ACADEMY OF SCIENCE AND TECHNOLOGY 2 This study was completed at: Vietnam Academy of Science and Technology Advisor: Assoc. prof. Le Truong Giang Reviewer 1: Reviewer 2: Reviewer 3: The thesis is presented to doctoral dissertation council, meeting at the Academy of Science and Technology - Vietnam Academy of Science and Technology and at ... hours ... day ... month ... year ... You can find the thesis at: - Library of the Academy of Science and Technology - National Library of Vietnam 3 PREFACE 1. The urgency of the thesis All activities in human life and production produce waste. Waste exists in solid, liquid and gaseous form. In addition to inorganic and organic pollutants ... there are many microorganisms in the water such as bacteria, viruses such as cholera, dysentery, typhoid, etc. Therefore, disinfection of water is an indispensable process in water treatment technology. Water disinfection is the process of eliminating potentially pathogenic microbes, which are the necessary barrier and ultimately prevent human exposure to pathogenic microbes, including viruses, bacteria, and protozoa. The basis of chemical disinfection is to use stronger oxidizers to oxidize the yeast of microbial cells and destroy them. Commonly used chemicals are: chlorine halides, bromine; chlorine dioxide; the hypoclorite and its salts; ozone, etc. Highly effective chemical disinfection methods should be used extensively with many different scales. Chlorine is a strong oxidizer, in any form, pure or compound, chlorine acts to water will generate hypochlorous acid (HOCl), a highly potent antiseptic. On the other hand, Chlorine has the advantage of being able to maintain a small concentration in water for relatively long periods of time to ensure resilience against water supply and storage. Therefore, chlorine is still used most often for disinfection. Recently, many methods of disinfection have been studied to replace chlorine, such as ozone, UV, bromine, etc. But there is no alternative to chlorine. The current trend is to combine chlorine with other methods such as UV irradiation to increase the effectiveness of disinfection and reduce the amount of chlorine needed. One of commonly used method recently is UV / HOCl / ClO-. However, the presence of chlorine in water can also lead to the formation of organic chlorine compounds, which are responsible for cancer. Natural organic substances such as humic acid, dissolved organic acids, amino acids and industrial organic pollutants are always present in natural water. These organic compounds are often complex and can react with chlorine to form hazardous compounds such as chloroform and trihalomethanes (THMs) which including trichloromethane, dibromochoromethane, bromodichloromethane, etc. These compounds Chlorophyll, especially in the human body, will cause damage to the liver and kidney and has been demonstrated to be linked to the cause of cancer. Under the influence of light, especially ultraviolet light, can lead to the dissociation of HClO and ClO- ions that form free radicals. These free radicals can oxidize organic matters and form various byproducts. The transformation of new contaminated organic compounds and their by-products into the process is a new research trend in the field of analysis in the world as well as in Vietnam. 2. Research objectives Study on the transformation and identification of Paracetamol byproducts by UV / HClO / ClO- in various environmental conditions. 3. Main research contents of the thesis - Study on the degradation of Paracetamol by UV, Chlorination and UV/HOCl/ClO - . - Study on factors affecting the degradation of Paracetamol by UV irradiation-only, UV/NaClO oxidation. - Study the optimum conditions to determine the by-products of oxidation by LC-MS/MS. 4 CHAPTER 1: OVERVIEW 1.1. Pharmaceutical pollution in water environment 1.2. Residual PRC in water environment 1.3. Advanced oxidation processes applied in water treatment 1.4. Theoretical background of photosynthesis method 1.5. Method of analyzing micropollutants in water 1.6. Situation of research in domestic and foreign CHAPTER 2: EXPERIMENTAL PROCEDURE AND METHODOLOGY 2.1. Equipments and Chemicals 2.2. Methodology 2.3. Experimental method 2.4. Experimental procedures 2.4.1. Degradation of PRC by UV, UV/NaClO, UV/H2O2 Prepare 2 liter of NaClO100μM solution (or 100mM H2O2), transfer to the reactor, stir, adjust pH = 7, add 2.0ml PRC 10μM solution, add to the reactor, then 254nm UV light for 20 minutes, the samples were taken over time starting from the UV lamp irradiance. Each time a 1.0ml sample was taken into the vial with 0.2ml Na2S2O3 2mM (ratio [NaClO]/[Na2S2O3] = 2 -3 ), UV/H2O2 system using Na2SO3 2mM with the ratio [NaClO]/[Na2SO3] = 2). PRC concentrations over time were monitored by HPLC. NaClO concentrations were determined by optical method with DPD reagent. H2O2 concentration was determined by optical method with TiCl4 reagent. 2.4.2. The experiments determine the role of free radicals Determination of • OH free radical concentration: The competitive dynamic reaction between the two compounds is PRC and NB as follows: Prepare 2 liters of NaClO100μM solution, transfer to reactor, stir, adjust pH = 7, add 2.0ml of PRC 10mM, 2.0ml of C6H5NO2 2mM solution to the reactor, UV irradiance 254nm for 30 minutes, the samples were taken over time, starting from UV irradiance. Each time a 1.0ml sample is taken into the vial with 0.2ml Na2S2O3 2mM (ratio [NaClO]/[Na2S2O3] = 2-3). The concentration of PRC, NB over time is monitored by HPLC Determination of Cl • of free radicals: The competitive dynamics between the three compounds PRC, NB and BA are as follows: Prepare 2 liters of NaClO 100 μM solution, transfer to reactor, stir, adjust pH = 7, add 2.0 ml PRC 10mM, 2.0 ml C6H5NO2 2mM solution, 2 ml C6H5COOH 2mM solution to the reactor, then UV irradiance 254nm for 30 minutes, the samples were taken over time starting from the UV irradiance. Each time a 1.0ml sample is taken into the vial with 0.2ml Na2S2O3 2mM (the ratio [NaClO]/[Na2S2O3] = 2-3). PRC, NB, BA concentrations over time were monitored by HPLC. 2.4.3. Experiment to determine the by-product of the degradation of PRC by UV, UV/NaClO Prepare 2 liters of 500 mL NaClO solution, transfer to the reactor, stir, adjust pH = 7, add 20.0 mL of PRC 10mM solution, add to the reactor, then irradiance 254nm for 20 minutes, The sample is taken over time. Each time a 0.5ml sample of the vial is available with 0.3ml Na2S2O3 2mM ([NaClO]/[Na2S2O3] = 2-3) is obtained prior to LC-MS/MS measurement. White Blank (B) is added to a separate vial of distilled water and Na2S2O3. 5 CHAPTER 3: RESULTS AND DISCUSSION 3.1. Research on the presence and distribution of pharmaceutical residues in surface water in some rivers and lakes in Hanoi 3.1.1. Quantitative pharmaceutical residue on LC-MS/MS equipment In this study we focus on the investigation of the concentration of 9 drugs, especially nonsteroidal anti-inflammatory drugs and some typical antibiotics widely used in Vietnam and in the world. 3.1.2. Residual quantities of pharmaceuticals in the rivers and lakes of Hanoi The results showed that: TMP, TC and TRA were not detected in any sample, it means that the concentration was below the detection threshold of the method. CAR, DIC are drugs with low excretion rate but the concentration is still high, especially in the sample of Lu river water corresponding to 1003ng/L and 1020ng/L. Notably, IBU and PRC were detected at high alarming levels, corresponding to a maximum concentration of 4161ng/L and 3925ng/L and were present in all samples. IBU was most commonly used in the non-steroidal anti-inflammatory drug group, 220 tonnes in France in 2006 (Haguenoer et al), and was found in four wastewater treatment plants in Spain, with a concentration of 3.73 to 603μg/L (Santos et al., 2009). For paracetamol, according to the Ministry of Health, paracetamol is the market leader in the Vietnamese pharmaceutical market with more than 2,000 registered monotherapies and other combinations. This is a popular analgesic and is offered over-the-counter. Therefore, the detection of paracetamol at high concentrations in the samples is appropriate. Large PRC concentrations are also consistent with previous releases, such as river waters in Australia, Africa and the Aire River in the UK at concentrations of 7150ng/L, 3000ng/L and 4300ng/L. 3.1.3. Changes in the content of pharmaceutical residues in the river in Hanoi Comparison of results between time intervals indicates that the content of substances may be depended on climatic and weather conditions. Research has shown that the effectiveness of the LC/MS-MS analysis method opens up new directions for analyzing a variety of sample objects, particularly water samples that are not too complex. 3.2. Influencing factors to PRC degradation by UV irradiation-only and UV/NaClO 3.2.1. Comparison of different advanced oxidation process on PRC degradation The oxidation methods used to study the degradation of PRC include: Chlorination, UV irradiation-only, UV/H2O2 and UV/NaClO. The experiments were performed with a concentration of [PRC] = 10 μM, pH = 6.5 [NaClO] = 100 μM, [H2O2] = 100 μM. Table 3.1: PRC degradation by different AOPs Experiment conditions [PRC] µM pH [H2O2] µM [NaClO] µM kobs(s -1 ) Para/UV 10 6,59 2,23 E-04 Para/UV/H2O2 10 6,65 100 3,71 E-04 Para/NaClO 10 6,38 100 5,25E-04 Para/NaClO/UV 10 6,45 100 2,36E-03 Only 10%, 20%, and 26% PRC were decomposed by direct UV photosynthesis, H2O2/UV and chlorinated with NaClO after 20 minutes of reaction, confirming that the relative PRC chemically stable for these oxidation processes. 6 3.2.2. Dynamics of degradation of PRC by UV/NaClO 3.2.2.1. Effect of UV light intensity Table 3.2: Comparison of PRC by UV irradiation-omly, NaClO and UV/NaClO CPRC=10μM, CNaClO=100μM, pH=7, temperature =25±1 o C UV light intensity I0 (10 -6 ) PRC/UV kobs(s -1 ) PRC/NaClO kobs(s -1 ) PRC/UV/NaClO ktotal(s -1 ) %UV %NaClO % Radicals 3,60E-06 1,95E-04 1,21E-04 2,01E-03 9,70 6,02 84,28 7,20E-06 3,81E-04 1,21E-04 3,36E-03 11,34 3,60 85,06 1,08E-05 5,71E-04 1,21E-04 4,81E-03 11,87 2,52 85,61 The results showed that direct photolysis and direct oxidation with NaClO contributed not much to PRC degradation. In contrast, free radicals play a major role in the degradation of PRC by UV/NaClO (degraded 85% by radical). 3.2.2.2. Effect of pH For non-UV irradiation, there are no significant differences of the rate constant at different pH values. As the pH increased from 3 to 8.4, the rate consstant increased from 1.21 × 10 -4 s -1 to 9.6 × 10 -4 s -1 . For the NaClO/UV process the results showed that PRC degraded rapidly with the rate constant increased when pH increased, specific kobs value increased from 1.82 to 10 -3 to 2.6 10 -3 s - 1 at pH 8.5. For the UV/NaClO process, the tendency of the pH to rate constant on the PRC object is very different from the situation of benzoic acid and trichloro-ethylene (Fang, Fu et al., 2014) Wang, Bolton et al. 2015) Wang, 2012: decreases as pH increases. To explain this, it is necessary to clarify the role of free chlorine radicals present in solutions such as ● Cl, ● Cl 2- , ClO ● . Specifically, determine their activity for PRC. However, it can be stated as follows: It is known that pH is the main factor affecting the degradation of HClO/ClO - in solution. HClO acids have higher quantum efficiency (free radical generation) and lower free- radical hunting ability than ClO-type. Moreover, the rate constant of the reaction between the root ● OH and OCl - are 9 × 10 9 M -1 s -1 higher than HOCl (2 × 10 9 M -1 s -1 ). Hence, the original capture reactions ● OH, ● Cl, Cl2 ● - will prevail over the case of OCl - compared to HOCl. Free radical capture reactions give rise to another free radicals, ClO ● , and this concentration increases as the pH increases. The results show that when increasing pH, the rate constant increases. This demonstrates that ClO ● radicals continue to be the decomposing agent of PRC, which contributes to this contribution to the increased PRC decay, which will offset the reduction of concentration. ● OH, ● Cl. 3.2.2.3. Effect of NaClO concentration Experiment on the effects of NaClO concentration was conducted at pH 6 - 6.5. The experiments were also carried out in the absence of UV irradiation for comparative results. Fig. 3.2.2.5 presents the PRC rate constant for the pseudo first-order rate constant and the trend for the change of the PRC over time by UV/NaClO and NaClO processes that do not show UV at neutral pH and different concentrations of NaClO (0-500 μM). The results showed that the rate of PRC degradation increased as the concentration of NaClO increased. When the concentration of NaClO increased from 10 μM to 400 μM, the apparent rate constant of the non-irradiated chlorination was almost unchanged. While the apparent speed of the NaClO/UV process is seven times higher 7 Figure 3.1. The relationship between the pseudo first-order rate constant of PRC degradation and NaClO concentration This may be explained by the free radicals scavenging capacity ( ● OH and ● Cl) of HOCl / OCl- (which exist in solution with excess residual concentrations) to form ClO ● radicals. These radicals are inactive when react with benzoic acid (<3.106 M-1s-1). In contrast to the increased linearity of the decay rate of the PRC as it increases the concentration of NaClO, it leads to the hypothesis that PRC reacts very quickly to ClO ● or Cl ● , which produces more when heated NaClO increased. 3.2.2.4. Effect of inorganic ions Study on the effect of inorganic ions on different ions: Cl - , SO4 2- , HCO3 - , NH4 + , NO3 - The results showed that the degradation rate of PRC in the presence of Cl-, SO4 2- ion decreased not much, whereas in the presence of HCO3 - , NH4 + , NO3 - ions, the reaction rate decreased significantly, especially in case of NH4 + , the NO3 - speed constant decreases nearly 10 times from 2.69 10 -3 s -1 to 2.57 10 -4 s -1 . a) The decrease of PRC concentration over time b) The pseudo first-order rate constant Figure 3.2. Effects of inorganic ions on PRC degradation by UV/NaClO process [PRC] =10 µM pH= 6.5 CPRC =10 µM pH= 6,5 CNaClO= 100 µM CH2O2 =100 µM CCl-=100 µM CSO42 - =100 µM CHCO3 - =100 µM CNH4+=100 µM CNO3 - = 100 µM 3.2.2.5. Effects of dissolved organic compounds For soluble organic compounds, this is a constant factor in surface water, sewage, even drinking water. DOM significantly impedes the efficiency of the UV/Chlorine-based pathway for the degradation of organic contaminants by the active-free radical scavenging and acts as a filter system. UV rays, UV absorbers. 0.0E+00 5.0E-03 1.0E-02 1.5E-02 2.0E-02 0 20 40 60 k o b s( s- 1 ) Tỉ lệ [PRC]o/[NaClO]o PRC/NaClO/UV PRC/NaClO 8 Figure 3.4: Effect of DOM concentration on the efficiency of PRC degradation by NaClO/UV Figure 3.2.2.9 shows that the presence of the DOM significantly decreased the apparent rate constant, the kobs decreased as the DOM concentration increased. 3.3. The role of free radicals in the degradation of paracetamol by UV/NaClO process 3.3.1. The kinetic of PRC degradation by H2O2/UV: determines the rate constant of the PRC with the ●OH radical The rate constant of the PRC with the free radical ●OH is also determined by which it is possible to evaluate the contribution of free radicals. ●OH is produced during the photosynthesis with NaClO. Table 3.4: First-order dynamics of PRC/UV and PRC/UV/H2O2 processes Experimental system [PRC,µM] [H2O2] mM pH kobs(s -1 ) PRC/UV 10 0 5.9 1.92E-04 PRC/UV/H2O2 10 100 5.8 5.24E-03 PRC/UV/H2O2 10 50 5.6 5.39E-03 The results show that the concentration of PRC decrease over time according to the first-order kinetic equation. The detailed are presented in Table 3.3.1.2. Based on the average value of kobs = 5.31x10 -3 s -1 along with the hypothesis that the original concentration ●OH generated during the reaction is constant. We can calculate the rate constant of the ●OH reaction with PRC = 4.19 (± 0.15) .109M -1 s -1 at pH 5.5-6. 3.3.2. Competitive kinetic: Determine the rate constants of ●Cl and •OCl with the UV/PRC system 3.3.2.1. Determine the rate constant of the free radicals Cl• with PRC To determine the contribution of free radicals in the system, some competitive dynamics experiments were conducted in the presence of PRC, Nitrobenzene (NB) and Benzoic Acid (BA). The decline in NB concentration over time is mainly caused by HO● active (constant rate of reaction k * HO • .NB = 3.9 109 M-1s-1). NB is inactive with free radicals such as Cl • , ClO • . In contrast, BA reacts quickly to both HO • , Cl • with large rate constants (k * HO • .BA = 5.9 109 M-1s-1; k * Cl • .BA = 1.8 1010 M-1s-1) and inactive with ClO•. 9 The experiments were carried out at pH = 5.5-6 to ensure that the concentrations of ClO● radicals are negligible in the system, so it is possible to ignore the contribution of the PRC degradation . Thus, if the assumption of the free radicals HO● and Cl • generated in the system is stable, then the concentration of HO● can be derived from the competitive dynamical experiment between the PRC and NB. ●Cl concentration through the reduction of the concentration of BA in concurrent PRC, NB and BA experiments. For the case of BA: k obs BA = k obs UV.BA + k obs NaClO.BA + k * Cl•.NB× [Cl • ]ss + k * OH.NB× [ • OH]s. After calculating the concentration of free radicals generated in the UV/NaClO system [●OH]ss = 7.28 × 10-14 and [Cl •] ss = 4.37 × 10-14 From the equation of the apparent rate constant, we can compute the second rate constant of ●Cl with PRC. kobsPRC = kobsUV.PRC + kobsNaClO.PRC + k * OH.PRC × [OH] ss + k * Cl • .PRC × [Cl •] ss kCl * .PRC = (kobsPRC - (kobsUV.PRC + kobsNaClO.PRC + k * OH.PRC × [OH] ss)) / [Cl •] ss In which: kobsUV.PRC = 2.39 10-4 (s-1) {the results of this study} kobsNaClO.PRC = 4.52 10-4 s-1 {results of this study} k * OH.PRC = 4.19 109 M-1s-1 {the results of this study} Table 3.5: Results of the apparent rate constant of reaction reagents PRC (µM) NaClO (µM) NB (µM) BA (µM) k obs PRC k obs BA k obs NB 10 100 2 2 2.23E-03 7.32E-04 4.84E-04 10 100 2 2 2.43E-03 6.97E-04 5.04E-04 10 100 2 2 2.25E-03 7.86E-04 4.97E-04 10 100 2 2 2.63E-03 8.32E-04 5.14E-04 10 100 2 2 2.32E-03 7.52E-04 5.33E-04 10 100 2 2 2.18E-03 8.64E-04 4.86E-04 From the results of the apparent rate constant obtained of PRC, NB, BA in the competitive reaction, we calcualated the rate constant of the PRC second order rate constant reaction with Cl - = 3.71 x 10 10 M -1s. 3.3.2.2. Determination the rate constant of the second order reaction rate of ClO● with PRC Dimethoxybenzene (DMOB) was used as the "probe" compound due to its reactive capacity with ClO• with a relatively large rate constant: 2.1x109 M-1s-1. To facili