3-1 Research Flowchart
Figure 3-1 Research flowchart Relevant literature review
Diclofenac analytical techniques
Evaluation of ozonation treatment
Ozonation by-products formation
Kinetic model and pathway
Experimental design
Semi-batch reactor
Initial target compound C0 = 10 mg/L
Three levels of ozone dose
Analytical method development
Diclofenac
TOC, ammonia, chloride, aldehydes
Ozonation intermediates
Variable pH value (Sec. 4-1)
Without buffer
Monitoring pH on line
Fixed pH value (Sec. 4-2)
With phosphate buffer
pH = 5, 7, and 9
Engineering evaluation (Sec. 4-3)
Health risk
Optimization Kinetic study (Sec. 4-4, 4-5)
Mass balance
Proposition of pathway
Expected results
To evaluate intermediates formation of dicofenac
To establish degradation reaction kinetic model.
To assess the effects of operation conditions on diclofenac removal
To
To
3- 2
3-2 Synthetic Water Preparation
The synthetic water of diclofenac salt was prepared in 10 mg/L, phosphate buffer, including monosodium and disodium phosphate, were added to adjust pH values ,to 5.1, 7.4, and 8.9, and ionic strength was controlled at 50 mM.
3-3 Methods
3-3-1 Experimental Design
The experiment could be divided into two stages. The detailed experiment design is shown in Figure 3-2. In stage 1, a quantitative method for the extraction and determination of diclofenac in synthetic water was developed and this method was applied to the analysis of diclofenac concentration in the ozonation.
The purpose of stage 2 was to evaluate the diclofenac decay and ozonation intermediates and by-products formation in ozonation and O3/UV process. In stage 2, in order to predict diclofenac decay and by-products formation in the ozonation, experiments conducted a period of 60 min. Sampling time was 0, 1, 3, 5, 10, 20, 40, and 60 min or 0, 1, 2, 4, 6, 8, 10,15, 20,25, 30, 40, 50, and 60 min.
3- 3
(1)
(2)
(5) Hood
(4)
Hood
Hood (3)
(4)
(6)
(7)
Figure 3-2 The experiment apparatus of ozone semi-batch reactor: (1) Oxygen cylinder, (2) ozone generator, (3) Ozone reactor, (4) KI traps, (5) thermostat, (6) flow meter
3- 4
Preparation of synthetic water
· Consentration of diclofenac : 10 mg/L
Diclofenac analytical method development
Substtrate addition
· Phosphate buffer (50 mM) Blank sample
Ozonation/AOP processes
· Ozone dosage : 20, 60, 110 mg/L
· pH:5.5,7.4,8.9
Analysis of experimental data
Concentration
· Ozonation by-poducts
· Diclofenac
· Ozone dose Background water quality
· TOC
· Ammonia
· Chloride
Analysis of diclofenac degradation and ozonatin by-products formation mechanism
Development of diclofenac degradation kinetic model
Semi-batch reactor
· Gas phase and liquid phase ozone dose
Figure 3-3 Flowchart of experiments
3- 5
3-3-2 Establish Intermediates Analytical Method
Preparation of synthetic water
· Consentration of diclofenac : 70 mg/L
· Phosphate buffer
· In the presence and absence of OH radical scavenger
· Ozone dose =60 ppm
SPE
· Sample volume = 50 ml
· Column: Commercial Oasis™ HLB(divinylbenzene/N-vinylpyrrolidone copolymer) cartridges (60 mg, 3 mL) from Waters (Mildford, MA, USA).
· Condition: Column was conditioned with 2 mL of methanol, 2 mlof DI water, 2 ml HCl(0.1N), and 2 mL of water HPLC-grade water.
· Elution: Elution was performed with 2×2 mL of methanol at a flow rate of 1mL/min.
·
GC/MS analysis of diclofenac
· Column:
· Temperature program used : 105 ℃ for 1 min, 25 ℃/min to 180℃, 5℃/min to 230 ℃, the GC–MS interface and the ion-trap temperature were set at 300 ℃ for 20 mins.
Figure 3-4 Flowchart of experiments to analyze intermediates of diclofenac.
3- 6
1. Method
According to Pérez-Estrada et al, 2005 2. Apparatus
a. GC (HP 7890) b. EI-MASS (HP 5973) 3. Reagents
a. Organic free water for rinse and sample dilution
b. Methanol (LC/MS grade, purity 100%, made by J.T. Baker) c. Hydrochloric acid (made by Merck)
d. Standards: 2,6-dicloroaniline (Sigma-Aldrich);
5-hydroxyldiclofenac (Sigma-Aldrich) 4. Procedure of pretreatment
a. The cartridges made by Oasis HLB were conditioned with 2 mL of methanol, deionized water, 0.1 N of HCl, and water.
b. Loaded 50-mL water samples and eluted with 2 mL of methanol.
c. The eluates were evaporated by nitrogen stream and recomposed to a final volume of 0.1mL.
d. Analyze by GC-MS.
5. Condition of GC-MS: Separation in GC-MS was carried out after 10 µL of the samples were injected into the capillary column (30 m × 0.25 mm × 0.25 µm VF-5ms, Agilent, USA). The temperature program was: initial 105 oC for 1 min, then rising to 180 oC at 25 Co/min, and finally rising to 250 oC at 5 Co/min standing for 1 min. The spilt-splitless injector was operated at initial pressure of 30 psi standing for 1.5 min and the spilt flow was 50 mL/min.
3- 7
3-3-3 Analytical Methods
3-3-3-1 General Analytical Methods
The detailed analytical methods for traditional methods are shown as the following;
or in the Appendixes.
Chloride: The concentration of chloride was determined by ion chromatography (Metrohm 790 personal IC; Metrosep A Supp 4-250 column; 1.8 mM Na2CO3/1.7 mM NaHCO3 eluent; 1 mL/min eluent flow rate).
Ammonia: The concentration of ammonia was determined by flow injection analysis (FIA), using Berthelot reaction to produce a high absorbable dark blue color. By measuring the absorbance at wavelength 630 nm, one can calculate then know the concentration of ammonia.
TOC : Total organic carbon (TOC) was determined by a total organic carbon analyzer (O.I. Corporation, Model 700).
Residual ozone: Orbisohere Model 3600
Ozone dose : Ozone in the in-gas and off-gas were monitored continuously by means of UV-mini 1240 UV-Vis spectrophotometer at 258 nm quipped with a quartz cell.
pH value: Metrohm 780 pH meter
3-3-3-2 Analytical Methods for diclofenac
The concentration of diclofenac was measured by HPLC with UV detector. For the analysis of diclofenac, a C-18 column (Varian, 250x4.6mm) was equipped and the detection wavelength was set at 280 nm. The flow rate was 1.25 mL/min, and the mobile phase was consisted of 50% of ammonium formate (10 mM) and 50% of acetonitrile. (Coelho et al., 2009)
3- 8
3-3-3-3 Analytical Methods for Ozonation By-Products 1. Method
According to Standard method 6252 (APHA, 2005) 2. Apparatus
a. GC (HP 7890) b. EI-MASS (HP 5973) 3. Reagents
a. Organic free water for rinse and sample dilution
b. Methanol (LC/MS grade, purity 100%, made by J.T. Baker) c. Anhydrous potassium biphthalate, KHP (made by Merck)
d. O-(2,3,4,5,6-pentafluorobenzyl)hydroxylamine‧HCl, PFBHA (made by Aldrich)
e. Sulfuric acid (made by Merck)
f. n-Hexane (ACS grade, purity > 99.0%, made by Merck) g. Standards:
Compound Origin Purity (%) Density
Formaldehyde Merck 37.0 1.083
Acetaldehyde R.D.H. 99.5 0.78
Glyoxal Sigma 40 1.265
Methyl glyoxal Sigma 40 1.178
Acetone J.T. Baker 98
1,2-dibromopropane (internal standard) Acros 97 1.937
4. Procedure of pretreatment
a. Remove samples and standard solution from storage and equalize them at room temperature (about 10 min).
3- 9
b. Take 20- mL samples from the original sample vials and place in another vial.
c. Add 200 mg of potassium hydrogen phthalate (KHP) to each sample.
d. Add 1 mL of 15 g L-1 of PFBHA solution to each sample vial, and swirl gently.
e. Place all samples in a constant-temperature water bath with temperature which was controlled at 35 ± 0.5 ℃ for 2 h.
f. Remove samples from water bath and cool to the room temperature.
g. Add 0.05 mL of concentrated H2SO4 to each sample as to quench the derivatization reaction.
h. Add 4 mL of Hexane working solvent containing the internal standard and then shake the mixture manually for about 3 min.
i. Stand by approximately for 5 min until the samples are delaminated.
j. Draw off top hexane layer into a 7- mL vial containing 3 mL of 0.2 N H2SO4. k. Shake for 30 sec and let it stand for approximately 5 min until the samples are
delaminated.
l. Draw off top hexane layer and place the sample into a 1.8- mL vial.
m. The proposed scheme of PFBHA derivatization is shown below:
n. GC/MS separation and quantification
3- 10
3-3-4 Risk Assessment
Both the carcinogenic risk of aldehyde in the water distribution systems of the advanced and the conventional water treatment plants were assessed. Equations 3-3-1 and 3-3-2 show the human exposure concentration through ingestion and dermal
where CW is the concentration of the chemical in question in the water (mg/L), IR is the ingestion rate (L/d), EF is the exposure frequency (d/y), ED is the exposure duration (y), BW is the body weight (kg), AT is average time (d), SA is the surface area of skin (cm2), PC is the permeability contact (cm/h), ET is the exposure time (h/d), CF is the conversion factor (L/cm3), and k is the permeability coefficient. The following parameters were selected: IR = 2 L/d, EF = 365 d/y, ED = 70 years, BW = 70 kg, AT = 70 y × 365 d/y, SA = 18000 cm2, PC = 1.9 × 10-3, ET = 0.29 h/d, and CF = 10-3 L/cm3 (Chinery et al., 1993, US EPA).
The carcinogenic risk (Equation 3-3-3) was calculated based on a carcinogenic risk of 10-6 as the maximum acceptable value.
factor various exposure pathways were adapted from the Office of Environmental Health Hazard Assessment of US OEHHA. The SF of formaldehyde for ingestion exposure route is 2.1 × 10-2 (mg/day/kg)-1. The exposure concentration needs to be modified to the risk level of 10-6.