Page - 84 - in Advanced Chemical Kinetics

k•OH=NORO¼ ln NORO½ �0=NORO½ �D ln 2�CP½ �0=2�CP½ �D k•OH=2�CP (16) 2-Chlorophenol (2-CP) was selected as reference compound which have recognized rate constantswith•OH,eaq �and•H(k•OH/2-CP=1.2�1010M�1 s�1,keaq–=2�CP =1.3�109M�1s�1, k•H/2-CP=1.5�109M�1 s�1) [20].Topermitonly•OHtoreactwithNORO,andscavengeeaq� and•H,O2saturatedsample (O2changeseaq �and•Htosuperoxideradicalanions,whichare less responsiveopposite to•OH)[20]wasapplied forcomputing thebimolecular rateof•OH with NORO. In the same way, the bimolecular rate constant of eaq �with NORO (keaq–/ NORO) was calculated by N2-puging the sample solution added with 0.1 M iso-propanol (iso-propanol is used to scavenges both •OH and •H) [20]. Similarly, the computation of bimolecular constant of •HwithNORO (k•H/NORO)wasmadebyN2 saturating the solution of 0.1 M tert-butanol (tert-butanol is used to scavenge •OH) [20] at pH 2.2. Low pHwas maintained togethighyieldof•Hthroughreactionof eaq �with +H[34]. A linear plotwith slope equal to k•OH/NORO/k•OH/2-CPwas observedbyplotting ln([NORO]0/ [NORO]D) vs ln ([2-CP]0/[2-CP]D) at several absorbed ionizing doses. The same calculation was implemented formeasurement of bimolecular rate constant of eaq � and •HwithNORO, respectively.Applying theobtainedslopevalues, thesecondorder rate constantsof•OH,eaq � and•HwithNOROwerecomputedtobe(8.81�0.03)�109M�1s�1, (9.54�0.16)�108M�1s�1 and(1.10�0.20)�109M�1 s�1, respectively [5],whichalso indicates thatkeaq–=NORO is lesser to k•H/NORO,or inotherwordsthereactivityofeaq � toNOROis less thanthereactivityof●Hwith NORO.Thus, in the removal ofNOROby ionizing irradiation ●His of immense importance. Thebimolecular rate constant of •OHwithNOROin the current report is analogouswith the study of Santoke et al. [35], inwhich they calculated the bimolecular rate constants of •OH with six common fluoroquinolones (orbifloxacin, flumequine, marbofloxacin, danofloxacin, enrofloxacin andmodel compound, 6-fluoro-4-oxo-1,4-dihydro-3-quinolone carboxylic acids) andwas foundtobe in therangeof6.4–9.03�109M�1 s�1. 2.3.Measurementofbimolecular rateconstantof•OHwithbezafibrate Bezafibrate (BZF) is also themost commonlydetectedpollutant amongvariouspharmaceuti- calsexcreted into thesewagesystemandiscategorizedaspersistentorganicpollutants [36]. In drinkingwater its concentrationhasbeennoticedat the levelsof27ngL�1 [37] in riversat the concentrations levelof0.1–0.15μgL�1 [37], insmallstreamsintherangeof0.5–1.9μgL�1 [37], insurfacewaters intherangeof3.1μgL�1 [38],andupto4.6μgL�1 level insewagetreatment plant effluents. Owing to its high use and persistence nature, the elimination of BZF from aqueousmediahas emergedasahot research topic. Thequalitativeandquantitativeanalysis of itsdegradationproductsbesides itsdegradationkinetics isalsoofgreatconcern.Keeping in view all these problems, the degradation of BZFwas investigated by photo catalysis using hydrothermally synthesized TiO2/Ti filmswith exposed {001} facets. Besides photo catalysis, there are othermanyadvanced treatment options for efficient removal of BZF fromaqueous media, such as nanofiltration techniques, ultraviolet (UV) radiation and advanced oxidation processes (AOPs) [39]andthesehavebeenthoroughlystudied. InAOPs(themost reliableand efficient technique), as compared to other treatment techniques the pollutant of interest is Advanced Chemical Kinetics84