Shogo Taniguchi

Degradation of common pharmaceuticals and personal care products in mixed solutions by advanced oxidation techniques

Widespread detection of pharmaceutical compounds in water environment has been a serious concern recently, while conventional sewage treatments are ineffective for their elimination. But, advanced oxidation techniques are very promising to remove varieties of organic contaminants in water. This research aims to elucidate oxidation potentials of sixteen commonly used pharmaceutical compounds in mixed solutions by seven advanced oxidation techniques in laboratory batch experiments. The removal profiles exhibited four distinct patterns: a) easily degradable by all seven techniques, b) not easily degradable by all seven techniques, c) easily degradable by ozone-based techniques, but not by ultraviolet radiation-based techniques and d) easily degradable by ultraviolet radiation-based techniques, but not by ozone-based techniques. Ozone-based techniques rather than ultraviolet radiation-based techniques were very powerful for simultaneous removal of the compounds efficiently. Moreover, ozonation combined with ultraviolet radiation was the most appropriate technique for simultaneous removal of the tested compounds efficiently. Increased ozone dissolution and decomposition with ozone-based techniques did not always enhance the compounds’ removal. Physicochemical properties of the compounds and solution pH also presumably played an important role on the removal which merits further attention.

PHOTOCATALYTIC OZONATION OF 2, 4-DICHLOROPHENOXYACETIC ACID IN WATER WITH A NEW TIO2 FIBER

More effective techniques are required to mineralize the increasing number of recalcitrant organic contaminants at low concentrations in the water environment using advanced oxidation process. Though relatively new, photocatalytic ozonation (O3/UV/TiO2) is considered superior to ozonation (O3) and photocatalysis (UV/TiO2), due to synergistic effects and use of immobilized TiO2 photocatalysts is a milestone in advance oxidation process. This article aimed to elucidate 2, 4-dichlorophenoxyacetic acid (2, 4-D) mineralization characteristics in low aqueous solutions by O3/UV/TiO2 using the world’s first high-strength TiO2 fiber catalyst in laboratory experiments. 2, 4-D degradation and TOC removal in O3, UV/TiO2 and O3/UV/TiO2 followed pseudo-first order reaction kinetic. The removal rates for 2, 4-D and TOC in O3/UV/TiO2 were respectively about 1.5 and 2.4-fold larger than the summation of the corresponding values in O3 and UV/TiO2. The O3/UV/TiO2 process was characterized by short-lived few aromatic intermediates, faster degradations of aliphatic intermediates and dechlorination as a major step in 2, 4-D mineralization. The significantly enhanced 2, 4-D mineralization in the process was attributed to increased ozone decomposition and reduced electron-hole recombination on TiO2 surface resulting to a large number of OH generation. The O3/UV/TiO2 process with the TiO2 fiber catalyst was very promising with respect to the major challenges being faced in AOP involving TiO2, namely separation of powder catalyst in suspension and reduced efficiency of immobilized catalysts (e.g. TiO2 film/fiber).

A novel use of TiO2 fiber for photocatalytic ozonation of 2,4-dichlorophenoxyacetic acid in aqueous solution.

More efficient oxidation methods are needed to degrade especially newly emerging recalcitrant organic contaminants at low concentrations in the water environment. Reduced photonic efficiency of immobilized TiO2 is a major challenge in TiO2-assisted advanced oxidation processes (AOP). Mineralization of 2,4-dichllorophenoxyacetic acid (2,4-D) in low aqueous solution by O3/UV/TiO2 using the worlds first high-strength TiO2 fiber was investigated and compared with O3, UV/TiO2, and O3/TiO2 in laboratory batch experiments. The 2,4-D degradation and total organic carbon (TOC) removal followed pseudo first-order reaction kinetic, while their rates in O3/UV/TiO2 were respectively about 1.5 and 2.4 times larger than the summation of the values in 03 and UV/TiO2. The O3/UV/TiO2 was characterized by few aromatics with very low abundance, fast disappearance of aliphatics and more than 95% dechlorination. The discrepancies in organic carbon mass balance among the intermediates and 2,4-D were attributed mainly to few apparently major unidentified intermediates. The significantly enhanced 2,4-D mineralization in O3/UV/TiO2 was attributed to increased ozone dissolution followed by its decomposition, and reduced electron-hole recombination in presence of dissolved ozone resulting in a large number of hydroxyl radical (*OH) generation from more than one parallel path. The removal efficiencies of the systems can further be enhanced by optimizing design parameters, and O3/UV/TiO2 with the TiO2 fiber is promising to mineralize recalcitrant organic contaminants in water at low concentrations.

UV photolysis of perfluorooctanoic acid (PFOA) in dilute aqueous solution

Perfluorooctanoic acid (PFOA) is very persistent in the environment and widely detected in the water environment. Only some advanced methods with extreme reaction conditions are shown to be capable of degrading the compound efficiently, and almost all the earlier investigations used very high PFOA concentrations. The compound is detected normally at very low concentrations in the water environment, while mild reaction conditions for its degradation are preferable. This article aimed to elucidate photodegradation of PFOA in dilute aqueous solutions by combined UV wavelengths (185 nm+254 nm) and 254 nm using a newly designed UV jacket. PFOA degradation was greatly enhanced with the combined wavelengths with almost one hundred percent PFOA removals in four-hour reaction. The removals were well described by the first-order reaction kinetic. The removal efficiencies and rate values significantly decreased with smaller initial PFOA concentrations. But defluorination was greatly enhanced with smaller PFOA concentrations possibly due to accelerated decomposition of fluorinated intermediates of PFOA. Formic acid and acetic acid were two tentatively identified intermediates of PFOA photolysis while the former was a major intermediate predominantly controlling solution pH during the oxidation. The results demonstrated that PFOA photolysis by the combined wavelengths with mild reaction conditions can be greatly enhanced by proper design of UV jacket and reactor system.

Efficacy of ultraviolet radiation and hydrogen peroxide oxidation to eliminate large number of pharmaceutical compounds in mixed solution

Ultraviolet photolysis and ultraviolet and hydrogen peroxide oxidation of fourteen commonly used pharmaceutical compounds and two personal care products in mixed solution using low pressure ultraviolet lamp was investigated in laboratory batch experiments. Removal of the compounds followed the first-order reaction kinetic. Three distinct impacts of hydrogen peroxide on ultraviolet and hydrogen peroxide oxidation of the compounds (positive, negative and no significant effect) were observed. Removal behavior of the several tested compounds in mixed solution varied significantly than their respective behavior in absence of coexisting compounds. Clofibric acid, diclofenac, fenoprofen, isopropylantipyrine, ketoprofen, phenytoin and triclosan were removed very efficiently (> 96 %) by ultraviolet photolysis alone. Residual hydrogen peroxide during ultraviolet and hydrogen peroxide oxidation was quantitated for the first time. Hydrogen peroxide addition to ultraviolet photolysis was not worthy for majority of the tested compounds as their removal did not increase significantly and very big fractions (> 85 %) of the added hydrogen peroxide (0.29 ∼ 1.47 mM) remained unused presumably due to small fluence of the lamp, very small molar absorption for hydrogen peroxide at 254 nm (27.06 /M.cm) and acidic pH of reaction solution (< 5.7). Further exploration on ultraviolet and hydrogen peroxide oxidation with higher fluence lamp and alkaline solution pH will clarify usefulness of the method to treat pharmaceutical contaminated waters.

Rejection of pharmaceuticals and personal care products (PPCPs) and endocrine disrupting chemicals (EDCs) by low pressure reverse osmosis membranes

This paper aims to elucidate retention characteristics of some pharmaceuticals and personal care products (PPCPs), and endocrine disrupting chemicals (EDCs), by two polyamide low pressure reverse osmosis (LPRO) membranes. Feed solution pH did not have an influence on rejections of undissociated solutes, which was most likely governed by adsorption, size exclusion and diffusion simultaneously. Size exclusion was presumably dominant, especially with tight membranes (UTC-70U). Rejections of the solutes with low dipole moment (<1.0 debye) decreased with increasing octanol-water partition coefficient (K(ow)). The solutes with large K(ow) values were most likely adsorbed on membrane and subsequently passed through it resulting in larger diffusion coefficient (D(p)). The rejections decreased with increasing D(p) values irrespective of their dipole moments. Rejections of solutes with comparatively larger dipole moments might be dominated by diffusion and/or convection rather than their hydrophobicity. However, rejections of solutes with hydroxyl and carboxyl functional groups by UTC-60 increased with solution pH. More than 80% rejections were obtained for degree of dissociation (alpha)>0.5. Electrostatic repulsion played a key role for rejection of dissociated solutes, especially by loose LPRO membranes. Therefore, assessing the dissociation degree at desired pH values can be a key step to obtain an insight of rejection mechanisms by polyamide membranes.

Heterogeneous photocatalytic ozonation of 2,4-D in dilute aqueous solution with TiO2 fiber

Photocatalytic ozonation (O(3)/UV/TiO2) is an emerging oxidation method for recalcitrant organic contaminants in water. However, immobilised TiO2 catalysts suffer from reduced photonic efficiency. Therefore, TiO2 catalysts with excellent mechanical and thermal properties and enhanced photonic efficiencies are sought. This paper aimed to elucidate the mineralisation of low concentration 2,4-D (45.0 microM) by O(3)/UV/TiO2 using the worlds first high-strength TiO2 fibre in laboratory batch experiments. 2,4-D degradation and TOC removal followed pseudo first-order reaction kinetic. The removal rates for 2,4-D and TOC in O(3)/UV/TiO2 were 1.5 and 2.4-fold larger than the summation of the values for ozonation (O3)) and photocatalysis (UV/TiO2), respectively. O(3)/UV/TiO2 was characterised by few aromatic intermediates with low abundance, fast degradations of aliphatic intermediates and dechlorination as a major step. The significantly enhanced 2,4-D mineralisation in O(3)/UV/TiO2 was attributed to increased ozone dissolution and decomposition, and reduced electron-hole recombination resulting in large number of hydroxyl radical (*OH) formation from more than one parallel path. The discrepancies in the organic carbon mass budget were attributed to few apparently major unidentified intermediates, while chlorine mass balance was reasonably acceptable. The mineralisation efficiency of O(3)/UV/TiO2 with the TiO2 fibre can further be enhanced by optimisation of experimental design parameters. The new TiO2 fibre is very promising to overcome the problem of reduced efficiency of TiO2 catalyst in an immobilised state.

Water matrix effect on UV photodegradation of perfluorooctanoic acid

The widespread detection of perfluorinated compounds (PFCs) in the water environment has been a concern for the last several years, while effluents from wastewater treatment facilities are the major sources of these compounds. Even advanced oxidation technologies (AOTs) are not useful for mineralization of the compounds due to their very high stability. Photochemical techniques using particularly vacuum UV (VUV) have been found to be very promising in this regard. But the use of VUV in UV-based AOTs has still not progressed much. Moreover, the impact of water quality on PFCs photomineralization is unknown. This investigation aimed to assess photomineralization potentials of perfluorooctanoic acid (PFOA) in ultrapure water (UPW), tap water (TW), surface water and treated wastewater effluent using a reactor setup enabling maximum utilization of VUV emission of low pressure lamp in laboratory batch experiments. Neya River water (NRW) and the Nakahama Wastewater Treatment Plant Effluent (NWWTPE) represented surface water and treated wastewater effluent respectively. Also, tests were carried out in 50% diluted NRW and NWWTPE. PFOA photomineralization in terms of PFOA removal, defluorination and total organic carbon (TOC) removal are discussed. The usefulness of the method for PFOA mineralization in organic-rich wastewaters, and further research needs are also highlighted.

Significance of water quality and radiation wavelength for UV photolysis of PhCs in simulated mixed solutions

Ultraviolet (UV) photolysis of sixteen pharmaceutical compounds (PhCs) in mixed solutions with four types of water and two sets of UV radiation was investigated. UVC (254 nm) photolysis was ineffective at eliminating a large number of PhCs while a big number of them were refractory. However, vacuum UV (VUV: 185 nm + 254 nm) photolysis in the same experimental conditions eliminated the PhCs almost completely. The eliminations in ultrapure water (UPW), tap water (TW) and Neya River water (NRW) and their organic/inorganic contents were inversely correlated, which was more evident in VUV photolysis. Natural organic matter (NOM) in NRW did not have an impact in indirect photolysis, but effluent organic matter (EfOM) in secondary-treated effluent (NWTPE) enhanced indirect photolysis, which was more evident in VUV photolysis underlining the point that radiation wavelength/intensity can be a limiting factor in organic-rich waters. Moreover, VUV photolysis was far superior (90% mineralization) to UVC photolysis (10% mineralization) for PhCs mineralization. The greatly enhanced elimination and mineralization efficiencies observed for VUV photolysis were attributed to accelerated direct photolysis with 185 nm wavelength and indirect photolysis involving ·OH. The results demonstrated efficacy of VUV photolysis in wastewater treatment and its potential use as a tertiary treatment.

Efficacies of UVC and VUV photolysis for mineralization of pharmaceutical compounds in mixed aqueous solution

AbstractThe usefulness of ultraviolet-C (UVC: 254 nm) and vacuum UV (VUV: 185 +  254 nm) photolysis for elimination and mineralization of four selected pharmaceutical compounds (PhCs) in mixed aqueous solution were tested in laboratory batch experiments. UVC photolysis was unable to eliminate moderate and refractory PhCs. Moreover, it was not at all useful for mineralization of the PhCs (<10% TOC removal, 30 min reaction) and longer reaction period (i.e. 60 min) had no significant positive impact on the mineralization efficiency. On the other hand, VUV photolysis eliminated the PhCs almost completely in a short reaction period irrespective of their nature, and 90% mineralization was achieved in an hour. The greatly enhanced elimination and mineralization efficiencies for VUV photolysis were attributed to accelerated direct and indirect photolysis reactions. Based on the results, it was concluded that VUV photolysis was very promising over UVC photolysis for mineralization of PhCs in mixed aqueous solution...