Degradation Of Terephthalic Acid Research Articles

Characterization of low-pressure gaseous plasma radiation and its usage for inactivation of waterborne viruses

Water disinfection is a critical treatment step for removing harmful organisms from contaminated water sources. Vacuum ultra-violet (V-UV) radiation, generated by a low-pressure gaseous plasma discharge, consists of photons with high enough energy to break molecular bonds. In this work, we constructed and characterized a low-pressure capacitively coupled gaseous plasma and used it as a V-UV radiation source to inactivate MS2 bacteriophage, a surrogate for human enteric viruses. The treatment system allows for variation of gas composition inside the sample chamber and the modulation of V-UV radiation intensity. Both were used to separate the actual germicidal contribution of V-UV radiation from producing germicidal species by using virus inactivation to determine efficiency. OH* radical production was determined through the terephthalic acid chemical probe, which showed that when air was present in the sample chamber, it resulted in the highest OH* production and the best inactivation of MS2. Furthermore, we showcase that the OH* production rate was wavelength dependent and that ozone, generated by plasma treatment in the gas phase, leads to hydroxy terephthalic acid degradation, allowing us to determine better the actual OH* production rate with different treatment regimes. Lastly, by adding an OH* scavenger to the liquid, we were able to elucidate it as the primary inactivation agent in this setup while also providing evidence of its production in the bulk liquid by the transport and subsequent decomposition of the longer-lasting ozone molecule. This study demonstrates, for the first time, the applicability of low-pressure plasma radiation as a water treatment method.

A genetic toolbox to empower Paracoccus pantotrophus DSM 2944 as a metabolically versatile SynBio chassis

BackgroundTo contribute to the discovery of new microbial strains with metabolic and physiological robustness and develop them into successful chasses, Paracoccus pantotrophus DSM 2944, a Gram-negative bacterium from the phylum Alphaproteobacteria and the family Rhodobacteraceae, was chosen. The strain possesses an innate ability to tolerate high salt concentrations. It utilizes diverse substrates, including cheap and renewable feedstocks, such as C1 and C2 compounds. Also, it can consume short-chain alkanes, predominately found in hydrocarbon-rich environments, making it a potential bioremediation agent. The demonstrated metabolic versatility, coupled with the synthesis of the biodegradable polymer polyhydroxyalkanoate, positions this microbial strain as a noteworthy candidate for advancing the principles of a circular bioeconomy.ResultsThe study aims to follow the chassis roadmap, as depicted by Calero and Nikel, and de Lorenzo, to transform wild-type P. pantotrophus DSM 2944 into a proficient SynBio (Synthetic Biology) chassis. The initial findings highlight the antibiotic resistance profile of this prospective SynBio chassis. Subsequently, the best origin of replication (ori) was identified as RK2. In contrast, the non-replicative ori R6K was selected for the development of a suicide plasmid necessary for genome integration or gene deletion. Moreover, when assessing the most effective method for gene transfer, it was observed that conjugation had superior efficiency compared to electroporation, while transformation by heat shock was ineffective. Robust host fitness was demonstrated by stable plasmid maintenance, while standardized gene expression using an array of synthetic promoters could be shown. pEMG-based scarless gene deletion was successfully adapted, allowing gene deletion and integration. The successful integration of a gene cassette for terephthalic acid degradation is showcased. The resulting strain can grow on both monomers of polyethylene terephthalate (PET), with an increased growth rate achieved through adaptive laboratory evolution.ConclusionThe chassis roadmap for the development of P. pantotrophus DSM 2944 into a proficient SynBio chassis was implemented. The presented genetic toolkit allows genome editing and therewith the possibility to exploit Paracoccus for a myriad of applications.

Semiconductor-assisted photofermentation system for terephthalic acid degradation and methane production

The fermentation degradation approach of purified terephthalic acid wastewater remains a grand challenge, due to the low degradation efficiency of the refractory terephthalic acid (TA) compound. Here, photocatalytic semiconductors (g-C3N4 and its-derived composites) are introduced to the anaerobic reactor to construct a semiconductor-assisted photofermentation system that enables to intensify the electron transfer process, in turn enhancing the overall TA degradation performances. Specifically, the g–C3N4–added group exhibits significantly improved methane production efficiency and TA degradation rate, increasing by 67.7 % and 36.1 %, respectively. Mechanisms reveal that such enhanced TA degradation is contributed from the key direct-interspecies-electron-transfer (DIET) process (that is intensified by the produced photogenic electrons) and the photocatalytic degradation process (that is amplified by the generated photogenic holes and hydroxyl radicals capable of efficiently oxidizing TA to simple organic matters). This study underscores the importance and high-efficiency of simply constructing semiconductor-assisted photofermentation systems for TA wastewater treatments, which can be implemented to harness other types of recalcitrant compounds-contained wastewaters.

Effect of semiconductor materials on anaerobic methanogenesis of terephthalic acid: Promotion and inhibition mechanisms

AbstractThe treatment of purified terephthalic acid wastewaters via anaerobic methods poses a significant challenge due to the slow degradation rate and extended reaction time required for the most recalcitrant terephthalic acid (TA). To address this challenge, this study investigated the efficacy of various semiconductors in promoting TA degradation and determined their respective functional roles. Results showed that the addition of g‐C3N4 increased methane production by 28.38%, indicating its potential as a replacement for TiO2 in TA degradation. The improvement was attributed to the intensified direct interspecies electron transfer (DIET) process, facilitated by microorganisms that directly utilize conductive TiO2/g‐C3N4 as intermediaries to accelerate the electron transfer rate. The unfavorable methanogenesis performances of CeO2 and Fe2O3 were accredited to agglomeration phenomena and toxic effects. This study provides insights into the roles of exogenous materials in promoting or limiting the DIET process, and offers an environmentally friendly and highly‐effective strategy for treating industrial purified‐terephthalic acid wastewater.

Unexpected variations in the effects of ultrasound-assisted myofibrillar protein processing under varying viscosity conditions

The efficient synthesis of myofibrillar protein(MRN)-gallic acid (GAD) complex in ultrasound (UID)-assisted processing is a challenging problem in food manufacturing. In this investigation, the effect of viscosity characteristics on the efficiency of UID processing in MRN-based beverages was analyzed. Both viscosity and surface tension can increase sono-physico-chemical effects on the degradation of terephthalic acid and crystal violet, with surface tension having a more significant effect (negative correlation, R2 = 0.99) than viscosity (positive correlation, R2 = 0.79). The structural indicators and microstructure demonstrated that the reaggregation and refolding of the MRN structure during the modification procedure occurred with relatively small three-dimensional dimensions. Compared to the MRN/GAD4 group, the water contact angle of the MRN/GAD7 system enhanced by 129.44%, leading to greater system stability. The ABTS-scavenging capacity of the system increased by approximately 19.45% due to the increase in viscosity of these two categories.

β-Ketoadipic acid production from poly(ethylene terephthalate) waste via chemobiological upcycling.

The upcycling of poly(ethylene terephthalate) (PET) waste can simultaneously produce value-added chemicals and reduce the growing environmental impact of plastic waste. In this study, we designed a chemobiological system to convert terephthalic acid (TPA), an aromatic monomer of PET, to β-ketoadipic acid (βKA), a C6 keto-diacid that functions as a building block for nylon-6,6 analogs. Using microwave-assisted hydrolysis in a neutral aqueous system, PET was converted to TPA with Amberlyst-15, a conventional catalyst with high conversion efficiency and reusability. The bioconversion process of TPA into βKA used a recombinant Escherichia coli βKA expressing two conversion modules for TPA degradation (tphAabc and tphB) and βKA synthesis (aroY, catABC, and pcaD). To improve bioconversion, the formation of acetic acid, a deleterious factor for TPA conversion in flask cultivation, was efficiently regulated by deleting the poxB gene along with operating the bioreactor to supply oxygen. By applying two-stage fermentation consisting of the growth phase in pH 7 followed by the production phase in pH 5.5, a total of 13.61 mM βKA was successfully produced with 96% conversion efficiency. This efficient chemobiological PET upcycling system provides a promising approach for the circular economy to acquire various chemicals from PET waste.

Visible Light Driven Degradation of Terephthalic Acid: Optimization of Energy Demand by Light Modulation Techniques

Aims: The aim of this work was to investigate the impact of light modulation parameters on the degradation of terephthalic acid, an organic model pollutant, within a heterogeneous photocatalytic system under visible light. For this purpose, a fixed bed photocatalytic reactor, irradiated by white-light LEDs matrix controlled by a system for light dimming, was used. The bed consisted of a nitrogen-doped titania photocatalyst deposited on polystyrene pellets. Background: Wastewater containing TPA can be treated into conventional aerobic biological units. However, the mineralization of TPA is slow and inefficient and its presence negatively influences the biodegradation efficiency because this pollutant inhibits microbial growth. Nowadays, innovative technologies named advanced oxidation processes (AOPs), such as heterogeneous photocatalysis with UV and visible light, ozonation, and Fenton oxidation, have gained popularity for effective organic destruction of TPA from wastewater. The heterogeneous photocatalytic oxidation process of the TPA under visible light is the most advantageous process in terms of both fixed and operating costs. Objective: In this work, the successful application of light modulation techniques for degradation of TPA using a photocatalytic system with supported visible active photocatalysts (N-doped TiO2) immobilized on polystyrene pellets is reported. In particular, sinusoidal lighting has been used analyzing the influence of the period of oscillation and the amplitude of light modulation on the reaction kinetics, in such a way as to minimize the times and energy costs for the process. Methods: To evaluate the influence of light modulation on the efficiency of the TPA removal, a discontinuous system composed of a Recirculating Photocatalytic Fixed Bed Reactor (RPFBR) irradiated by a matrix of white light LEDs was used. The flat geometry of the photoreactor guarantees the efficient excitation of the photocatalyst. An amount of 250 mL of aqueous solution with the initial TPA concentration of 12.5 ppm was applied in the photocatalytic tests lasting 180 min of irradiation fixed or sinusoidal modulated. Results: The results show that the variation of the oscillation period of the sinusoidal modulation has a pertinent influence on the photodegradation of TPA and a maximum value of the apparent kinetic constant, 0.0045 min-1 is found when the period of oscillation is 0.24 s. The sinusoidal modulation with optimal amplitude occurs with current between 50-200 mA, that shows the highest value of the apparent kinetic constant equal to 0.0046 min-1. The optimal sinusoidal modulation, as a consequence is with current between 50-200 mA and period of 0.24 s. From the data collected from the tests, it is possible to evaluate the energy cost necessary to obtain the reduction of 90% of the terephthalic acid in 1 m3 of polluted water for each modulation (E E/O), and compare these values with other tests for TPA degradation reported in the literature. The internal comparison with the three systems of literature shows that the optima sinusoidal modulation of LEDs matrix permits a strong reduction in the electrical energy consumption. Conclusion: Photocatalytic tests have demonstrated the improvement of the process energy efficiency using the light modulation technique. A further confirmation of the advantage of light modulation was obtained by comparing the energy costs required for the abatement of 90% of the terephthalic acid in 1m 3 of the photocatalytic system. Finally, a mathematical model for photocatalytic degradation of terephthalic acid within the recirculating fixed bed photocatalytic reactor, irradiated by white-light LEDs was developed.

Genome analysis of the metabolically versatile Pseudomonas umsongensis GO16: the genetic basis for PET monomer upcycling into polyhydroxyalkanoates.

The throwaway culture related to the single-use materials such as polyethylene terephthalate (PET) has created a major environmental concern. Recycling of PET waste into biodegradable plastic polyhydroxyalkanoate (PHA) creates an opportunity to improve resource efficiency and contribute to a circular economy. We sequenced the genome of Pseudomonas umsongensis GO16 previously shown to convert PET-derived terephthalic acid (TA) into PHA and performed an in-depth genome analysis. GO16 can degrade a range of aromatic substrates in addition to TA, due to the presence of a catabolic plasmid pENK22. The genetic complement required for the degradation of TA via protocatechuate was identified and its functionality was confirmed by transferring the tph operon into Pseudomonas putida KT2440, which is unable to utilize TA naturally. We also identified the genes involved in ethylene glycol (EG) metabolism, the second PET monomer, and validated the capacity of GO16 to use EG as a sole source of carbon and energy. Moreover, GO16 possesses genes for the synthesis of both medium and short chain length PHA and we have demonstrated the capacity of the strain to convert mixed TA and EG into PHA. The metabolic versatility of GO16 highlights the potential of this organism for biotransformations using PET waste as a feedstock.

Accelerated Hydrolysis Method for Producing Partially Degraded Polyester Microplastic Fiber Reference Materials

Microplastic fibers (MPFs) from textiles significantly contribute to the microplastic (MP) load in many environmental matrices and have been shown to negatively impact the organisms therein. Most fate and effect studies to date rely on pristine reference MP materials that have limited relevance compared with the partially degraded MP particles and fibers typically present in the natural environment. The current study aimed to develop and validate a rapid method to generate environmentally relevant polyester (PET) MPF reference material with controllable levels of degradation. Importantly, the method produced the same degradation products (terephthalic acid (TA) and ethylene glycol (EG)) as those generated during natural UV (sunlight) exposure of PET. Alkaline hydrolysis provided linearly increasing degrees of degraded PET MPFs over just a few hours, with full decomposition into molecular fragments occurring after 3 h. The extent of physical degradation was determined by scanning electron microscopy, whereas chemical degradation was quantified by measuring the production of TA and EG degradation products. The proposed accelerated hydrolysis degradation method is relevant for producing partially degraded PET MPF reference materials for use in fate and effect studies.

Terephthalic acid decomposition by photocatalytic ozonation with VxOy/ZnO under different UV-A LEDs distributions

In this work, the degradation of terephthalic acid (TA) by vanadium oxide (VxOy) supported on zinc oxide (ZnO) was evaluated in a photocatalytic ozonation treatment based on two UV-A LEDs distributions. TEM analysis and specific surface area measurement suggest that VxOy is not supported on ZnO, while the EDXRF and XPS analysis indicated the presence of VxOy. The XPS analysis on VxOy/ZnO catalyst showed non-significant surface change between fresh and used catalyst. However, ozone decomposition showed a higher reaction rate constant for catalytic (230%) and photocatalytic ozonation (310%) in comparison with single ozone treatment. Photocatalytic ozonation with central and external irradiation arrays was evaluated in TA elimination by a kinetic study. The irradiation arrays had not statistical differences in the TA decomposition or oxalic acid formation. These results suggest that the construction of central bodies inside the reactor could be not necessary for photocatalytic processes.

A multifunctional ZnO thin film based devices for photoelectrocatalytic degradation of terephthalic acid and CO2 gas sensing applications

A hexagonal ZnO thin films have been successfully synthesized by chemical spray pyrolysis technique. Photoelectrocatalytic activity of ZnO photoelectrode is tested for photoelectrocatalytic degradation of terephthalic acid as a model organic pollutant. The degradation percentage of terephthalic acid using ZnO photoelectrode has reached up to 91% under ultraviolet illumination after 400 min. ZnO thin films are used for detecting CO2 gas and getting maximum response for operating temperature of 350 °C and response and recovery time periods are 75 and 108 s, respectively for 400 ppm CO2 gas concentration. ZnO sensor has good repeatability along with a quick response time. Thus a multifunctional ZnO thin film is the potential candidate for both for photocatalytic and CO2 gas sensing applications.

Establishment of thermophilic anaerobic terephthalic acid degradation system through one-step temperature increase startup strategy – Revealed by Illumina Miseq Sequencing

Over recent years, thermophilic digestion was constantly focused owing to its various advantage over mesophilic digestion. Notably, the startup approach of thermophilic digester needs to be seriously considered as unsuitable startup ways may result in system inefficiency. In this study, one-step temperature increase startup strategy from 37 °C to 55 °C was applied to establish a thermophilic anaerobic system treating terephthalic acid (TA) contained wastewater, meanwhile, the archaeal and bacterial community compositions at steady periods of 37 °C and 55 °C during the experimental process was also compared using Illumina Miseq Sequencing. The process operation demonstrated that the thermophilic TA degradation system was successfully established at 55 °C with over 95% COD reduction. For archaea community, the elevation of operational temperature from 37 °C to 55 °C accordingly increase the enrichment of hydrogenotrophic methanogens but decrease the abundance of the acetotrophic ones. While for bacterial community, the taxonomic analysis suggested that Syntrophorhabdus (27.40%) was the dominant genus promoting the efficient TA degradation under mesophilic condition, whereas OPB95 (24.99%) and TA06 (14.01%) related populations were largely observed and probably take some crucial role in TA degradation under thermophilic condition.

Degradation of terephthalic acid in a photocatalytic system able to work also at high pressure

Photocatalytic degradation of terephthalic acid (TPA) has been studied on commercial ZnO immobilized on polystyrene (PS) beads (mean size: 1.5×1.5×0.1cm) and located in a stainless steel flat plate reactor with an irradiation window realized in a UV transparent polymethylmethacrylate (PMMA UVT) in order to make the system able to work also at high pressure. In this way, it is possible to overcome, both the problems related to the photocatalysts separation after the wastewater treatment and those ones caused by the inlet pressure (which may be higher than atmospheric one) of incoming wastewater. The solvent casting-method used for photocatalyst preparation is able to induce the formation of ZnO particles in form of isles dispersed on PS macro surface. Moreover XRD analysis evidenced that the PS support didn’t influence the crystalline arrangement of ZnO in wurtzite phase.The structured composite photocatalyst ZnO-PS showed high ability in the degradation of TPA giving its total mineralization under UV irradiation at atmospheric pressure. Increasing the pressure, similar levels of TPA removal were observed. This finding demonstrated the possibility, for the developed photocatalytic system, to operate under moderate pressure without worsening the photocatalytic performances.

Cu and Zr surface sites in the photocatalytic activity of TiO2 nanoparticles.

The rate of methylene blue and terephthalic acid degradation assisted with double metal-modified catalyst (0.1mol% Cu and 1.0mol% Zr) was enhanced as compared with single metal-modified catalysts (0.1, 0.5mol% Cu and 1.0mol% Zr). The wet impregnation method was used for copper and zirconium modification of the surface of Aeroxide P25 TiO2 particles. Simultaneous loading of both metals on the surface of P25 leads to an increased specific surface area of the obtained material despite negative Cu influence. The tendency of stabilization and agglomerate size rising with the time for Cu and Zr-modified catalysts were traced by dynamic light scattering (DLS) measurements. The observed optical characteristics suggest that Cu compensated the broadening of band gap caused by Zr loading. Crystal structure of obtained photocatalysts was explored by XRD; morphological data and particle size were obtained by SEM. EDX was used for Zr and Cu content determination. Cu K-edge extended X-ray absorption fine structure (EXAFS) and X-ray absorption near edge structure (XANES) analytical techniques were used to investigate the local Cu neighbourhood in the samples and to identify copper coordination and valence state of copper species in the synthesized nanocomposites.

Clinoptilolite supported rutile TiO2 composites: Synthesis, characterization, and photocatalytic activity on the degradation of terephthalic acid

Abstract Clinoptilolite supported rutile TiO 2 composites were synthesized for the enhancement of its photocatalytic performance in the degradation of the aqueous terephthalic acid solution under UVC illumination by the increase in its surface area and to simplify its recovery from the treated solution after use. The XRD spectra of the composites revealed the formation of pure rutile TiO 2 on the surface of the clinoptilolite. The SEM images showed the formation of the spherical TiO 2 clusters were composed of nano fibers on the surface of the clinoptilolite. For all composites synthesized, the dispersion of the TiO 2 particles on the clinoptilolite led to a surface area larger than that of the bare TiO 2 and clinoptilolite. The materials synthesized in the present study exhibited higher catalytic activity compared with the commercial Degussa P25 and anatase. Among the catalysts synthesized the TiO 2 /clinoptilolite with a weight ratio of 0.5 was found to be the most photoactive catalyst even though it contains a lesser amount of active TiO 2 . The kinetic of the reactions for different catalyst was found to be consistent with the pseudo-first order kinetic model. The results of the Langmuir-Hinshelwood model showed the slight contribution of the adsorption on the degradation. The activity of the TiO 2 /clinoptilolite with a weight ratio of 0.5 decreased after repetitive use due to the accumulation of the TPA molecules on the surface of the catalyst.

P25 titanium dioxide coated magnetic particles: Preparation, characterization and photocatalytic activity

The photocatalytic properties of magnetic iron(II,III) oxide particles coated with different wt% of commercially available P25 TiO2 (P25) using a simple wet impregnation method were measured. The produced materials were characterized by XRD, XPS, SEM, TEM, EDX, FTIR, ICP, Magnetic Property Measurement System (MPMS) and BET (N2). After calcination at 500°C of the magnetic particles that was loaded only with P25, the P25 was strongly bound through a redox reaction with the magnetic particles. It was found that the P25 surface coverage was almost complete (>95%) at a 1:1 mass loading ratio; at higher P25 mass ratios, a thicker coating was obtained. However, the photocatalytic degradation rates of terephthalic acid (TPA) and phenol for these particles at all P25 loadings was lower than those obtained for pure P25 on a per TiO2 mass basis. Precoating the magnetic particles with a SiO2 sol-gel layer prevented the electron hole migration and oxidation of magnetite to hematite, but also led to a weakly bound P25 layer that was removed by rinsing. This was overcome by adding a second TiO2 sol-gel on top of the SiO2 coated magnetic particles coating for anchoring the P25 particles to the surface. While magnetic particles consisting of a silica undercoat followed by a TiO2 sol-gel coating as the photocatalytic layer have been reported, our approach is to use the TiO2 sol-gel coating as an adhesion layer to anchor P25 particles. The P25 adhered strongly to this underlying TiO2 sol-gel layer without significant loss of surface area. In both P25 and our produced photocatalyst, during the photocatalytic reaction P25 is in direct contact with water and the process occurs on the P25 and water interface. As a result, the photocatalytic degradation rates of TPA and phenol by the P2- coated magnetic particles were found to be equivalent to those of P25. The pseudo-first order rate constants in the P25 mass basis for photocatalytic degradation of TPA were 0.0152±0.003min−1 and 0.0144±0.007min−1 using pure P25 and SiO2 sol-gel/TiO2 sol-gel/P25 coated magnetic particles, respectively. The rate constant for phenol photocatalytic degradation was reported 0.09±0.02min−1 for pure P25 and 0.10±0.04min−1 for SiO2 sol-gel/TiO2 sol-gel/P25 coated magnetic particles. The similar specific surface area of the P25 powder and the P25 anchored to the surface in SiO2 sol-gel/TiO2 sol-gel/P25 coated magnetic particles is the reason for these similarity for rate constants.

Photocatalytic degradation of terephthalic acid on sulfated titania particles and identification of fluorescent intermediates

Terephthalic acid (TA) is toxic and known as an endocrine disruptor. In this paper, the photocatalytic degradation of TA using sulfated titanium dioxide SO42−/TiO2 photocatalysts was investigated. The photocatalysts were prepared by sol–gel method and characterized by XRD, SEM, BET, ICP/MS and spectroscopic methods. Their activities were compared with bare TiO2 and Degussa P25. The effects of catalyst sulfur content, the initial TA concentration and pre-treatment conditions (O2, N2 or non-pretreated) were studied. O2 functions were also explored. Since there had been no comprehensive study of fluorescent intermediates reported yet, we investigated the intermediates and discovered 5 new intermediates (4 fluorescent and 1 non-fluorescent) which were identified by gas chromatography–mass spectrometry (GC/MS) and fluorescence spectroscopy. These intermediates are complementary to the previously identified carboxylic acid intermediates and might provide new insights to the mechanism of photocatalytic degradation of TA. Since TA is widely used as a probing molecule for photocatalytically generated ·OH radicals, the ratios of fluorescent intermediates of TA degradation may provide new clues to the photocatalytic activity and mechanism. Based on the results obtained, the possible destruction pathway of TA is also proposed.

Electrochemical synthesis of FeS2 thin film: An effective material for peroxide sensing and terephthalic acid degradation

Electrochemically FeS2 thin films have been synthesized on ITO substrates at room temperature (25 °C). UV–Vis, X-ray diffraction (XRD) and field emission scanning electron microscope (FESEM) were used for the characterization of nanostructure FeS2 thin films. Two probe I–V measurements convey that the material is p type and a p-n junction (diode) was found to be developed between FeS2 and ITO layer. Cyclic voltametry study shows that FeS2/ITO electrode facilitates the reduction of hydrogen peroxide and exhibits excellent electro-catalytic activity towards its sensing. Photocatalytic study reveals that the synthesized thin films are also efficient to degrade terephthalic acid (TA).

Visible light photocatalytic activity of rutile TiO2 fiber clusters in the degradation of terephthalic acid

Rutile TiO2 nanoparticles, in different structural and morphological properties, were produced by the hydrolysis of titanium tetrachloride in a highly acidic reaction media at moderate temperatures without calcination. Their photocatalytic activities were investigated in the liquid-phase degradation of terephthalic acid under visible light illumination. The parameters, which are the concentration of the titanium tetrachloride solution (0.1–1 M) and reaction temperature (60–95 °C), effective on the properties of the particles, and their photocatalytic performances, were investigated. The XRD patterns indicated a pure rutile crystal structure at moderate temperatures without need of calcination. The FEGSEM images showed the formation of flower-, pinecone-, and sphere-like clusters consisting of interconnected nanofibers. The N2 adsorption–desorption isotherms pointed out the microporous structure of the clusters. Band gap energies were found to be varying between 3.02 and 3.08 eV due to the well-developed rutile crystallite structure. Systematic studies elucidated that the optimum reactant concentration and reaction temperature are 0.5 M TiCl4 and 95 °C, respectively. The rutile clusters synthesized at the optimum reaction conditions exhibited 99 % of the photocatalytic degradation of TPA under visible light illumination at shorter irradiation times compared with commercial P25 TiO2.

Effect of synthesis temperature on the structural properties and photocatalytic activity of TiO2/SiO2 composites synthesized using rice husk ash as a SiO2 source

TiO2/SiO2 composites were synthesized using titanium tetrachloride as a TiO2 precursor and rice husk ash (RHA) as the SiO2 source at low temperatures. Their photocatalytic performances were investigated in the liquid phase degradation of terephthalic acid (TPA) under UV-C illumination. The effect of synthesis temperature on the properties and photocatalytic activities of the composites were examined by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), field emission gun scanning electron microscope (SEM), thermo gravimetric analysis (TGA), N2 adsorption desorption analysis, and UV–visible diffuse reflectance spectroscopy (UV-DRS). The XRD patterns indicated the synthesis of rutile TiO2 particles due to the acidic nature of the reactant solution at low temperature without the need of calcination. The SEM images showed that the spherical and flower like agglomerates, consisting of nano fibers, are formed depending on the synthesis temperature. The TGA analysis showed no structural change or deformation in the catalysts due to heating. The N2 adsorption desorption analysis revealed a change in the pore structure of the TiO2 particles from micro- to mixed micro- and meso-porous in the TiO2/SiO2 composites with an increase in their surface areas. The differences in the structural properties of the composites varied their photocatalytic activities in the degradation reactions. The presence of SiO2 in the composites enhanced the photocatalytic activity of the TiO2 particles and simplified the recovery of the catalysts from the treated solution by increasing their rate of precipitation. The TiO2/SiO2 composites synthesized at 95°C exhibited the best photocatalytic activity confirmed by both kinetic constant and turnover frequency. All the particles and composites synthesized indicated better photocatalytic performance than that of the P25 TiO2.