Photo-activated Periodate in Homogeneous Degradation and Mineralization of Quinoline: Optimization, Kinetic, and Energy Consumption Javad Saien, a Hooman Shafiei, a and Abbas Amisama b a Department of Applied Chemistry, Bu-Ali Sina University, Hamedan, Iran; saien@basu.ac.ir (for correspondence) b Department of Chemistry, Payame Noor University, Tehran, Iran Published online 00 Month 2017 in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/ep.12615 Aqueous solutions of quinoline (Qu) were treated with photo-activated potassium periodate (UV/KPI) process. A low consumption, cylindrical photo-reactor was employed for this purpose. Either KPI oxidant or UV irradiation alone had little effect in Qu degradation; however, the combined UV/KPI pro- cess leads to significant degradation and mineralization. Experiments were conducted based on central composite design (CCD) methodology. The established optimized condi- tions for treatment of 40 mg L 21 of the substrate were [KPI] 5 695.5 mg L 21 , pH 5 4.3 and T 5 35.6 8C. Under these conditions, 96.5% degradation and 71.5% mineralization were obtained after 70 min operations. A quadratic equation predicts the variation of degradation efficiency as a function of the influencing parameters. To investigate about the involved species, tert-butyl alcohol was used as radical scav- enger and it was found that the contribution of hydroxyl radical was about 73.1%. Kinetic study revealed that Qu degradation was a pseudo first-order reaction and the corre- sponding activation energy was determined. Meanwhile, the required irradiation energy for one order of magnitude deg- radation was estimated as 3.13 kWh m 23 . V C 2017 American Institute of Chemical Engineers Environ Prog, 00: 000–000, 2017 Keywords: quinoline, periodate, degradation, kinetics, energy consumption INTRODUCTION There are many hazardous materials in wastewaters that are difficult to remove because of their biological degrada- tion resistance. Quinoline (Qu), C 9 H 7 N, is a heterocyclic aro- matic liquid with a high water solubility (6 g L 21 at 20 8C) [1]. It has consumptions in pharmacy [2,3] and is also used as a precursor for preparation of 8-hydroxyquinoline which is a versatile chelating agent and a precursor for pesticides [4]. Oxidation of Qu affords quinolinic acid (pyridine-2,3-dicar- boxylic acid), a precursor for the herbicide, sold under the name “Assert.” Other derivatives, 2 and 4-methyl quinoline are precursors to cyanine dyes [4]. Qu is also found in proc- essing of oil shale or coal, as well as in legacy wood treat- ment sites [1]. Like other nitrogen heterocyclic compounds such as pyridine, Qu is often reported as an environmental resistive contaminant. So, it has gained high attention with respect to the high health risks [5]. Most of conventional processes in wastewater treatment have limitations due to high cost and transformation of pollu- tants into a secondary media which require further purifica- tion. Accordingly, advanced oxidation processes (AOPs) have been developed, over last decades, to oxidize organic pollu- tants via hydroxyl radical generation. One important recently developed AOP is based on homogenous treatment of pollu- tants with periodate reagents [6]. So far, there has been no leg- islated discharge requirement for iodine compounds from which I 2 and I 2 are the more toxic, but still are known of low toxicity [7]. Iodine can be recovered by ionic exchange, and periodate can be electrochemically regenerated [7,8]. The periodate ion (IO 2 4 ) has a reduction potential of 11.60 V, indicating a relatively strong oxidant and that the oxidation reactions started by this ion are known to be selec- tive [9]. However, the use of periodate ion, under UV light irradiation is known as an efficient method in non-selective degradation of organic pollutants [8]. It is since, high reactive hydroxyl radicals are produced by photo-activation of peri- odate ions [9,10]. Upon UV irradiation, periodate ion is first decomposed to IO • 3 and O •2 species by one electron transfer, and the gener- ated O •2 is then converted to hydroxyl radical, HO • , by accepting an acidic proton [9,10]. Periodate ion may also convert to H 4 IO 2 6 ion by absorbing two molecules of water and sequentially, generating hydroxyl radials under photon emission [11,12]. The mechanism reactions are presented as following: IO 2 4  ! hv IO • 3 1O •2 (1) O •2 1H 1 $ HO • (2) IO 2 4 12H 2 O ! H 4 IO 2 6 (3) H 4 IO 2 6 1H 1 ! H 5 IO 6 (4) H 4 IO 2 6  ! hv H 3 IO •2 5 1 HO • (5) H 3 IO •2 5 ! IO 2 3 1H 2 O1HO • (6) Several works have been devoted to UV/periodate applica- tions. Lee and Yoon [10], for instance, investigated the V C 2017 American Institute of Chemical Engineers Environmental Progress & Sustainable Energy (Vol.00, No.00) DOI 10.1002/ep Month 2017 1