Degradation Of Trichlorophenol Research Articles

A facile strategy to fabricate reduced TiO2 nano-tube arrays photoelectrode and its high visible light photocatalytic performance for detoxification of trichlorophenol solution

Abstract In the research, reduced TiO2 nano-tube arrays (denoted as R-TiO2 NTAs) photoelectrode was successfully fabricated by potassium borohydride (PBH) reduction treatment. Afterwards, the as-fabricated photoelectrode was characterized by scanning electron microscope, X-ray diffraction, Raman spectra and electron spin resonance. Meanwhile, the optical and photoelectrochemical properties of R-TiO2 NTAs photoelectrode were also studied through ultraviolet-visible diffuse reflectance spectroscopy and transient photocurrent response, respectively. The photocatalytic (PC) activity of R-TiO2 NTAs photoelectrode was measured by degradation of trichlorophenol (TCP). Moreover, the change of toxic intermediates in the process of degradation TCP was further evaluated by photobacterium inhibition tests. Results suggested that an impurity level can be induced in the TiO2 NTAs band gap by solution reduction treatment due to the generation of Ti3+ and oxygen vacancies (Ov). Furthermore, R-TiO2 NTAs photoelectrode exhibited higher PC activities than that of pristine TiO2 NTAs owing to the enhancement of visible light harvesting between 450 and 800 nm and separation efficiency of photogenerated electrons-holes (e/h+) pairs. The possible pathway for TCP degradation and photocatalytic mechanism were also proposed and confirmed. Furthermore, R-TiO2 NTAs photoelectrode displayed good stability and reusability.

Synthesis, characterization and photocatalytic activity of nano sized undoped and Ga doped SrTi0.7Fe0.3O3 for 2,4,6-trichlorophenol photodegradation

Nano-sized SrTiO3 and Sr(Ti0.7Fe0.3)(1−x)GaxO3 system were prepared by the complex route precursor method (x=0, 0.01, 0.05 and 0.1). The prepared photocatalysts were characterized by XRD, TEM, XPS and UV–Vis diffuse reflectance spectroscopy. The effect of doping on the structural properties and the photocatalytic activity was studied. The average crystallite size of the prepared samples was in the range of 32–60nm. The performances of synthesized SrTiO3 and Sr(Ti0.7Fe0.3)(1−x)GaxO3 system for the efficient degradation of trichlorophenol (TCP) as a water contaminant model have been demonstrated. After 1mol% Ga doping of SrTi0.7Fe0.3O3, UV–vis absorption was appeared the red-shift at 812nm from 392nm as compared with naked SrTiO3. The photocatalytic degradation activity of 1mol% Ga doped SrTi0.7Fe0.3O3 was significantly improved to 91% degradation of TCP in 90min under visible light, which is approximately 14 times higher than that of the bare SrTiO3 and 4 times than undoped SrTi0.7Fe0.3O3.

Degradation of phenol and trichlorophenol by heterogeneous photo-Fenton process using Granular Ferric Hydroxide®: comparison with homogeneous system

The decomposition of phenol and trichlorophenol (TCP) by using granular ferric hydroxide (GFH) as a photo-Fenton catalyst was investigated and compared with homogeneous photo-Fenton process. Experiments were conducted in a batch mode, duplicate for the degradation of phenol and TCP in the presence of solar light for both the processes. The effect of operating variables for heterogeneous photo-Fenton process like pH, peroxide concentration and GFH concentration on the degradation of the model compounds was optimized by univariate approach. The optimum conditions for the degradation of phenol and TCP were pH 3.0 ± 0.2, peroxide concentration 29.4 mM for phenol and 14.7 mM for TCP at GFH concentration of 0.5 g/500 mL. At optimum conditions, the mineralization efficiency of phenol and TCP by heterogeneous process was compared with homogeneous process. The mineralization efficiency for phenol and TCP was 96 and 86 %, respectively, for heterogeneous photo-Fenton process, while almost complete mineralization (~96 %) was observed for homogeneous process. In heterogeneous photo-Fenton process, longer reaction time was witnessed for complete mineralization of the compounds studied. Low molecular weight aliphatic acids like oxalic acid, acetic acid and inorganic chloride ion (in case of TCP) were observed during both the processes. In these processes, the reaction proceeds by hydroxyl radical (·OH) abstraction of the model compound studied. The mineralization of phenol and TCP obeys pseudo-first-order kinetics irrespective of the processes studied. The results indicate that GFH can be an effective heterogeneous photo-Fenton catalyst for the degradation of phenol and TCP.

Ozone initiated dechlorination and degradation of trichlorophenol using Ce–Zr loaded metal oxides as catalysts

Oxidative dechlorination and degradation of trichlorophenol (TCP) in aqueous system initiated by ozone and catalyzed by varied loadings of cerium–zirconium oxide on metal oxides supports namely; Al2O3, SiO2 and TiO2 was investigated. Catalyst materials were synthesized and characterized by using various surface characterization techniques including XRD, BET, TPD, ICP, SEM, TEM and FT-IR. XRD showed that cerium–zirconia exists as three different phases on the surface of the catalysts. SEM and SEM–EDX indicated that cerium–zirconia oxide is well dispersed on the surface of the TiO2 with compared to Al2O3 and SiO2 supports. TEM showed that particle size of Ce–Zr is in the range of 40–80nm. Catalyst testing was done as function of reaction time and pH in a semi batch reactor. The oxidation products formed in the reaction were characterized by IR, 1H NMR and LC–MS mass spectral data. Dihydroxyfumaric acid (DHFA) and oxalic acid (OA) were the main oxidation products. The product distribution was dependent on the acidic character of the catalysts. Among the catalysts tested, 2.5% Ce–Zr/SiO2 showed good activity with 100% conversion in 4h while others needed 5h.

Phytoremediation of Trichlorophenol by Phase II Metabolism in Transgenic Arabidopsis Overexpressing a Populus Glucosyltransferase

Trichlorophenol (TCP) and its derivatives are introduced into the environment through numerous sources, including wood preservatives and biocides. Environmental contamination by TCPs is associated with human health risks, necessitating the development of cost-effective remediation techniques. Efficient phytoremediation of TCP is potentially feasible because it contains a hydroxyl group and is suitable for direct phase II metabolism. In this study, we present a system for TCP phytoremediation based on sugar conjugation by overexpressing a Populus putative UDP-glc-dependent glycosyltransferase (UGT). The enzyme PtUGT72B1 displayed the highest TCP-conjugating activity among all reported UGTs. Transgenic Arabidopsis demonstrated significantly enhanced tolerances to 2,4,5-TCP and 2,4,6-TCP. Transgenic plants also exhibited a strikingly higher capacity to remove TCP from their media. This work indicates that Populus UGT overexpression in Arabidopsis may be an efficient method for phytoremoval and degradation of TCP. Our findings have the potential to provide a suitable remediation strategy for sites contaminated by TCP.

Ultrasonic degradation of 2:4:6 trichlorophenol in presence of TiO 2 catalyst

The degradation of trichlorophenol has been studied at different intensities of irradiation using ultrasonic horn by changing the power input to the system. Effect of presence of catalyst TiO 2 and concentration of catalyst on the degradation rates has also been investigated. The rates of degradation are found to be higher at higher intensities in the absence of catalyst but reverse trend is observed in the presence of catalyst. Adsorption and desorption characteristics of trichlorophenol on TiO 2 catalyst have been examined. The catalyst enhances the rates of degradation but it also adsorbs some amount of TCP during the degradation process protecting it from ultrasonic degradation. Thus it is essential to consider the adsorption and desorption kinetics to get proper estimates of the degradation rates when the rates of degradation of TCP are calculated by analyzing the residual concentration of the compound in the liquid. The degradation of the pollutant seems to take place in the liquid only and that too only after desorption of the same from the solid particles. Solid particles seem to play a physical role in the overall degradation scheme, providing additional surface cavitation.

Fe 3+ and UV-enhanced ozonation of chlorophenolic compounds in aqueous medium

Mono-, di- and trichlorophenol including different isomers were degraded by O 3, O 3 + UV and O 3 + UV + Fe 3+. Disappearance rates are nearly identical among three ozonations. Whereas TOC elimination was not completed by ozone alone. UV illumination accelerated TOC elimination rate and the addition of Fe 3+ (O 3 + UV + Fe 3+) further accelerated it. TOC elimination rates among different chlorophenols were in the order of mono > di > tri. The effect of Fe 3+ was largest on the degradation of trichlorophenol. Hydroxylated aromatics, organic acids, formaldehyde and acetone were detected as intermediates.