Total Organic Carbon Conversion Research Articles

Treatment of pistachio processing industry wastewaters by supercritical water oxidation in a continuous-flow reactor

ABSTRACT The objective of the present study is the treatment of pistachio processing industry wastewaters (PPIW) using the supercritical water oxidation method. The experiments were conducted within a 400–600°C temperature range and a 30–150 s reaction time range, while maintaining a constant pressure of 25 MPa and using an O2/COD ratio of 1:1. To observe the effects of the initial PPIW and O2 concentrations on the treatment efficiency, experiments were also conducted with O2/COD ratios ranging from 0.5 to 3, while maintaining a constant reaction temperature and time of 500°C and 60 s, respectively. The influence of reaction temperature, reaction time and O2/COD ratio on the total organic carbon (TOC) and total nitrogen (TN) contents of the liquid PPIW effluents were investigated. Treatment efficiencies up to 99.75% regarding TOC conversion and 78.72% regarding TN conversion were obtained in very short reaction times. Additionally, the kinetics of oxidation of PPIW was studied, and reaction rate expressions based on TOC and TN were proposed.

Kinetics study of total organic carbon destruction during supercritical water gasification of glucose

AbstractThe kinetics of total organic carbon (TOC) destruction during supercritical water gasification (SCWG) of glucose were studied at 400–500°C and 25 MPa in a 600 mL batch reactor. Both TOC and water concentrations are critical for the conversion of TOC in supercritical water, especially at longer residence times. Initially, it was assumed that the TOC destruction reaction followed first‐order kinetics ignoring the water concentration. However, experimental results showed that the feed‐to‐water ratio had a significant effect on TOC decomposition. Considering the water concentration in the reaction, the reaction orders of TOC (2.35) and water (1.45) were calculated using nonlinear regression analysis (the Runge‐Kutta method). The estimated pre‐exponential factor (k’) and activation energy (E) were calculated to be 8.1 ± 2/min and 90.37 ± 9.38 kJ/mol respectively.

Preparation of a new B-CNTs/PSSF composite catalyst for catalytic wet peroxide oxidation of phenol in structured fixed bed

A new structured catalyst consisting of boron-doped carbon nanotubes growing directly on paper-like stainless steel fibers support (B-CNTs/PSSF) was developed for continuous catalytic wet peroxide oxidation (CWPO) of phenol in a structured fixed bed. Firstly, B-CNTs/PSSF was synthesized by chemical vapor deposition (CVD) with phenyboronic acid as a single precursor and CNTs/PSSF was prepared with camphor for comparison. Secondly, the effects of different deposition temperatures, deposition times, and phenylboronic acid dosages on the morphology and properties of B-CNTs were investigated, respectively. The results verified that under the conditions of deposition temperature of 750 °C, deposition time of 20 min, and phenylboronic acid dosage of 2 g, the B-CNTs/PSSF composite catalyst with uniform growth density, wavy and kinked morphology, abundant oxygen-containing functional groups and defect sites, and boron-doped content of 2.96% was successfully prepared. Then, the performance of B-CNTs/PSSF for continuous CWPO of phenol was evaluated. Catalytic results revealed that the B-CNTs/PSSF showed excellent catalytic activity in phenol degradation within 7 h (phenol conversion reached about 100% and total organic carbon (TOC) conversion was up to 68%). In contrast, the average phenol and TOC conversion of CNTs/PSSF were about 75% and 35%, respectively. It indicated that boron doping endowed CNTs with higher catalytic activity.

Enhanced mineralization of bisphenol A by electric arc furnace slag: Catalytic ozonation

The catalytic ozonation of bisphenol A (BPA) was performed using an industrial solid waste as catalyst: electric arc furnace slag (EAFS). The characterization of the catalyst (SEM/EDS, XRD, surface area, pHPZC and Mössbauer spectroscopy) showed low surface area, alkaline nature and a composition rich in Fe, Ca, Si, C oxides, with minor content of Mg, Mn and Al. Ozonation experiments were carried out in a semi-batch reactor at room temperature at different initial pH conditions: from alkaline (natural pH 10.5) to acidic (controlled pH 3) aqueous media. Catalytic ozonation experiments showed complete BPA removal and remarkable total organic carbon conversions (62–80 %) over the broad pH range explored. The highest mineralization levels were obtained under basic pH, which was attributed to the generation of hydroxyl radical given by the presence of OH− and precipitation reactions of intermediates promoted by Ca oxides. Under acidic conditions the presence of EAFS notoriously enhanced BPA mineralization compared to single ozonation, due to the activity of leached species. The stability of the material was tested in 4 ozonation cycles. EAFS activity was mostly sustained under acidic conditions while a reduction was observed under uncontrolled pH condition, which was associated with a marked pH decrease. However, the residual activity still allowed complete BPA degradation and high mineralization levels (> 50 %). EAFS is a low-cost material that exhibits high activity and reasonable stability in catalytic ozonation of BPA. The valorization of this waste constitutes a technological alternative that could benefit both metallurgical and water treatment plants.

Treatment of Effluent Containing p-Cresol through an Advanced Oxidation Process in a Batch Reactor: Kinetic Optimization

The present research is related to the study of p-cresol oxidation reaction in aqueous phase. Firstly, the conventional advanced oxidation process (AOP) in a lab-scale batch reactor was used, seeking to identify the most impacting process variables and then to propose an optimization approach for ensuring the complete p-cresol degradation and the highest total organic carbon (TOC) conversion. In the AOP with the use of hydrogen peroxide as the oxidizing agent, the oxidation reaction was optimized with the aid of a factorial design, and a maximum TOC conversion of 63% was obtained. The Lumped Kinetic Model (LKM) was used to describe the profile of residual TOC concentration due to chemical species, which were categorized into two groups (refractory and non-refractory compounds). The model was able to satisfactorily describe the profile of the residual fractions of these two classes of organic compounds and allowed estimating the related kinetic constants (k) at two different temperatures, namely (a) 3.19 × 10−1 and 2.82 × 10−3 min−1 for non-refractory and refractory compounds at 80 °C and (b) 4.73 × 10−1 and 5.09 × 10−3 min−1 for the same compound classes at 90 °C, while the activation energy (Ea) of the process was 42.02 and 62.09 kJ mol−1, respectively. The kinetic modeling of organic pollutants oxidation in liquid effluents would allow to perform in situ seawater treatment on vertical reactors installed in offshore platforms and to properly release treated water into the oceans. In this way, ocean contamination caused by the exploration on offshore platforms of oil and natural gas, the main energy sources and vectors in the current world, may be remarkably reduced, thus favoring a more eco-friendly energy production.

Vertical distribution of Fe, P and correlation with organic carbon in coastal sediments of Yellow Sea, Eastern China

The coastal zone is considered as a major carbon pool. Iron minerals and phosphates are vital factors affecting the amounts and occurrence of total organic carbon (TOC) in sediments. However, coupling mechanisms of iron (Fe) and phosphorous (P) in the source-sink transition of TOC in coastal sediments is poorly understood. This study characterized the distribution of Fe, P and TOC contents of three independent 170 cm sediment cores sampled from a coastal aquaculture area in the eastern Jiangsu Province, and quantified the correlations among Fe, P, median grain diameter (Dx(50)), and TOC. The results showed total phosphorus (TP) content ranges in a scope of 337.4-578.0 mg/kg, and many depths recorded moderate P eutrophication. Inorganic phosphorus (DA + IP) and biogenic apatite were the primary components of TP, accounting for 25.19–55.00 and 26.71–49.62%, respectively. The Fe contents varied from 987.9 mg/kg to 2900.7 mg/kg, in which oxidized iron (Fe ox ) accounted for about 62.2–79.4%. In the vertical profile, the TOC was positively correlated with the contents of low-crystallinity Fe-bearing carbonates (Fe carb ), high crystallinity pyrite (Fe Py ), iron-bound phosphorus (P CDB ), manganeses (Mn), and nitrogen (N), while it was negatively correlated with DA + IP, organic phosphorus (OP), and Dx(50). Based on the the partial least squares (PLS) model, we proposed that the higher Fe Py , Mn, magnetite (Fe Mag ), Fe carb , P CDB , amorphous exchangeable Fe (Ex-Fe), and authigenic apatite phosphorus (Bio-P) in sediments represent the high capacity for TOC sink, whereas, higher DA + IP, and OP indicate a TOC conversion to the source. The non-siginificat indication of Fe ox on TOC source-sink is due to its surplus and strong reactivity relative to TOC content. These revealed correlations provide a theoretical reference for understanding and regulating the burial rate and storage of TOC by changing the input of Fe minerals and P components into coastal sediments.

A new catalyst CHCP-Fe2O3 for enhanced removal of tetracycline through the Fenton-like process: Economical synthesis, catalytic performance, and practicability

Oxidation by the Fenton-like (Fe3+/H2O2) process is considered an economically feasible technology for wastewater degradation, which relies heavily on the reactivity of the Fe2O3 catalyst. In this study, a new catalyst CHCP-Fe2O3 was fabricated by calcining an Fe-containing hyper-crosslinked polymer (HCP). The catalyst displayed outstanding catalytic performance (98.56 % removal rate and 57.96 % total organic carbon conversion efficiency) in the activation of H2O2 for tetracycline degradation. By in situ impregnation, the Fe2O3 in the catalyst can bond better with the carbon carrier, and the CHCP-Fe2O3-2 catalyst results in more structural defects and richer pores, which could supply more exposed reaction active sites and accelerate mass and electron transfer. This study demonstrates that the CHCP-Fe2O3/H2O2 system exhibits excellent practical application potential because of its excellent recyclability and wide pH range (pH = 3–10) for the abatement of hazardous organic pollutants, which provides a facile and promising design of Fenton-like catalysts for wastewater treatment.

Catalytic wet peroxide oxidation of phenol through mesoporous silica-pillared clays supported iron and/or titanium incorporated catalysts

Catalytic performances of Silica Pillared Clay (SPC) supports synthesized in different silica amounts both from standard SWy-2 clay mineral and Hançılı region bentonite rock (HWB), and iron (Fe) and/or titanium (Ti) incorporated SPCs in different combinations were evaluated in various advanced Catalytic Wet Peroxide Oxidation (CWPO) of phenol. Host clay mineral type led to different oxidation performances and metal loading created significant increases in the catalytic performance. CWPO performance of Fe-loaded SPCs was better than Ti-loaded ones, so oxidation parameters for Fe–SPCs were studied in detail. Catalyst amount and rise in temperature increased phenol conversion values significantly, and catalysts were more effective in lower pH reaction medium. Aromatic intermediates such as catechol, hydroquinone and benzoquinone formed at the beginning of oxidation were oxidized to carboxylic acids with an advancing oxidation time. The presence of carboxylic acids such as oxalic and formic acid resulted in relatively low total organic carbon (TOC) conversion values. The highest catalytic activity was obtained with high silica content Fe–SPCs synthesized with both host clays. Complete conversion was nearly achieved within 60 min with an experimental condition of T = 30 °C, pH = 3.7 and catalyst/solution ratio = 2 g/L for SWy-2 based catalyst by applying either CWPO or PCWPO (Photo Catalytic Wet Peroxide Oxidation) techniques. SCWPO (Sono Catalytic Wet Peroxide Oxidation) technique also yielded this value at the same oxidation conditions for HWB based catalyst. TOC conversion values at 240 min oxidation time were determined as 33% and 48% for SWy-2 based catalyst with CWPO and PCWPO techniques, respectively, and 37% for HWB based catalyst with SCWPO technique. SWy-2 based catalyst still retained its performance after 3 cycles.

Kinetic modelling of total organic carbon degradation in dairy wastewater

ABSTRACT Several treatment strategies have been proposed to minimize the environmental impact of dairy wastewaters. However, their complex and variable composition makes it difficult to predict the degradation kinetics of organic compounds. In this study, we used a mathematical approach to describe the kinetics of total organic carbon degradation in real dairy wastewater by photo-Fenton oxidation. The reactions were conducted under different ultraviolet light intensities, pH, temperature and Fenton reagent concentrations, obtaining a maximum TOC removal of 90.84%. The kinetic model was developed based on well-established photo-Fenton reactions. The present approach considers that account that small and large molecules of unknown contaminants are present in the effluent, and the smaller molecules are consumed first. The specific degradation rate (kd ) was considered as an exponential function of total organic carbon conversion, comprising this effect of molecular size distribution on the treatment process. Fitting of experimental data to model predictions provided mean R 2 values of 0.843–0.953.

Aqueous-phase reforming of water-soluble compounds from pyrolysis bio-oils

Aqueous-phase reforming (APR) of model compounds of bio-oil aqueous fraction (AFB) was studied at different operating conditions. Substrate conversion, carbon-to-gas yield (CCgas) and hydrogen and alkanes production were evaluated. Levoglucosan, hydroxyacetone, furfural and acetic acid were selected as representative of AFB and tested in batch APR at different concentrations (1–5 %wt.), temperatures (175–220 °C) and reaction times (0.5–4 h), using 3% (wt.) Pt/CB catalysts. Best results were obtained at 220 °C and 1%, with 70–90% substrate conversions, 45–70% CC gas and hydrogen production up to 50 mmol per gram of total organic carbon (TOC). Catalyst stability was checked in APR of levoglucosan during five successive 4 h reaction cycles. The catalyst exhibited high stability, CCgas remained constant and hydrogen production increased and became stable after first reaction cycle with only a slight decrease of TOC conversion. The catalyst with well dispersed metal phase and high contribution of nanoparticles smaller than 2 nm showed a higher production of hydrogen. APR was proved to be a feasible option for the valorisation of AFB.

High-Ionic-Strength Wastewater Treatment via Catalytic Wet Oxidation over a MnCeO x Catalyst.

Catalytic wastewater treatment has rarely been applied to treat high-ionic-strength wastewater (HISWW) as it contains large amounts of catalyst poisons (e.g., Cl–). This work investigates the catalytic wet oxidation (CWO) of phenol over a MnCeOx catalyst in the presence of high NaCl concentrations where the combination of MnCeOx and NaCl promoted the CWO of phenol. Specifically, in the presence of NaCl at a concentration of 200 g L–1 and MnCeOx at a concentration of 1.0 g L–1, phenol (initially 1.0 g L–1) and total organic carbon (TOC) conversions were ∼98 and 85%, respectively, after a 24 h reaction. Conversely, under the same reaction conditions without NaCl, the catalytic system only achieved phenol and TOC conversions of ∼41 and 27%, respectively. In situ Attenuated Total Reflection infrared spectroscopy identified the nature of the strongly adsorbed carbon deposits with quinone/acid species found on Ce sites and phenolate species on Mn sites in the single oxides and on MnCeOx. The presence of high concentrations of NaCl reduced the carbon deposition over the catalyst, promoting surface oxidation of the hydrocarbon and reoxidation of the catalyst, resulting in enhanced mineralization. Moreover, the used MnCeOx catalyst in the salt water system was efficiently regenerated via a salt water wash under the reaction conditions, showing the great potential of MnCeOx in practical HISWW treatment.

Cu- and Fe-substituted ZSM-5 zeolite as an effective catalyst for wet peroxide oxidation of Rhodamine 6 G dye

Several Cu-exchanged and Fe-exchanged ZSM-5 catalysts were prepared and studied for the decoloration, degradation and mineralization of Rhodamine 6 G in catalytic wet peroxide oxidation (CWPO). The Cu-ZSM-5 catalysts were shown to be more effective than the parent H-ZSM-5 zeolites (containing Fe-ions as impurity) and Fe-exchanged ZSM-5 to Rhodamine 6 G oxidation by hydrogen peroxide. Effects of copper loadings, Si/Al ratio, structure of copper species, and initial pH were ascertained on catalytic behavior of Cu-ZSM-5 and copper leaching under CWPO conditions. At acid pH, the highest decoloration of Rhodamine 6 G was typical of Cu-ZSM-5 with Si/Al equal to 30 and Cu content of ca. 0.5 – 0.65 wt% having isolated Cu2+ ions, whereas the maximal conversions of total organic carbon (TOC) were exhibited by catalysts with 1.5 – 2.8 wt% Cu and CuO-like clusters on the external zeolite surface. At alkali pH, the over-exchanged 2.8% Cu-ZSM-5 with CuO-like clusters was more active than under-exchanged 0.5% Cu-ZSM-5 to decoloration of Rhodimine 6 G, while both catalysts provided identical TOC conversions. Catalyst with 0.5 wt% copper loading showed reproducible activity up to 7th cycle. According to UV-Vis DR and EPR studies, the high efficiency of Cu-ZSM-5 to Rhodamine 6 G oxidation in acid solution is provided by the isolated Cu2+ ions, while the nanostructured square-planar CuO-like clusters (on the zeolite surface) ensure activity at alkali pH. Two mechanisms of organic substrate oxidation, i.e. radical (Fenton-like) mechanism activated by isolated Cu2+ ions and nucleophilic substitution via copper-hydroperoxide complex generation, were discussed.

Adsorption and Fenton-like Degradation of Ciprofloxacin Using Corncob Biochar-Based Magnetic Iron-Copper Bimetallic Nanomaterial in Aqueous Solutions.

An economical corncob biochar-based magnetic iron–copper bimetallic nanomaterial (marked as MBC) was successfully synthesized and optimized through a co-precipitation and pyrolysis method. It was successfully used to activate H2O2 to remove ciprofloxacin (CIP) from aqueous solutions. This material had high catalytic activity and structural stability. Additionally, it had good magnetic properties, which can be easily separated from solutions. In MBC/H2O2, the removal efficiency of CIP was 93.6% within 360 min at optimal reaction conditions. The conversion of total organic carbon (TOC) reached 51.0% under the same situation. The desorption experiments concluded that adsorption and catalytic oxidation accounted for 34% and 66% on the removal efficiency of CIP, respectively. The influences of several reaction parameters were systematically evaluated on the catalytic activity of MBC. OH was proved to play a significant role in the removal of CIP through electron paramagnetic resonance (EPR) analysis and a free radical quenching experiment. Additionally, such outstanding removal efficiency can be attributed to the excellent electronic conductivity of MBC, as well as the redox cycle reaction between iron and copper ions, which achieved the continuous generation of hydroxyl radicals. Integrating HPLC-MS, ion chromatography and density functional theory (DFT) calculation results, and possible degradation of the pathways of the removal of CIP were also thoroughly discussed. These results provided a theoretical basis and technical support for the removal of CIP in water.

Use of Ni-containing catalysts for synthetic olive mill wastewater steam reforming

The olive oil mill wastewater (OMW) is a by-product (with a high organic load) derived from the production of the olive oil. The OMW steam reforming (OMWSR) process was studied herein, aiming to decrease the environmental damage of such effluents; simultaneously, the waste is economically and energetically valorized with the H2 production. Several Ni-containing catalysts were prepared and tested to compare their performances for the OMWSR using a synthetic OMW effluent; still, stability tests were also carried out. The materials were extensively characterized: thermogravimetric analysis, temperature-programmed oxidation/reduction, temperature-programmed desorption of CO2/NH3, chemisorption of H2, inductively coupled plasma optical emission spectrometry and physical adsorption-desorption of N2 at −196 °C. Amongst the materials tested, the Ni–Ru/SiO2 sample stood out, exhibiting high catalytic performance: at 400 °C, the H2 yield (>8 molH2·molOMW-1) and conversion of total organic carbon (≈75%) were high during all the 24 h of the long-term test, with only a small deactivation being noticed.

Enhancing electronic metal support interaction (EMSI) over Pt/TiO2 for efficient catalytic wet air oxidation of phenol in wastewater

Phenol is one of the major hazardous organic compounds in industrial wastewater. In this work, a highly active Pt/TiO2 catalyst for catalytic wet air oxidation (CWAO) of phenol was obtained by supporting pre-synthesized Pt on TiO2. During the followed hydrogen reduction, strong hydrogen spillover occurred without the migration of TiO2 onto Pt. The reduced support then enhanced the electron transfer from TiO2 to Pt, increasing the percentage of partially negative Pt (Ptδ-), which has been confirmed by XPS. The strong EMSI made the obtained catalyst far more active than Pt/TiO2 prepared by impregnation method. The electron-enriched Pt/TiO2 achieved total organic carbon (TOC) conversion of 88.8% and TOF 149 h−1 at 100 °C and 2 MPa O2, while conventional Pt/TiO2 gave TOC conversion of 39.5% and TOF 41 h−1 for CWAO of phenol. Our work indicates that the enhancement of EMSI between metal and support can be an effective approach to develop highly active catalysts for phenol treatment.

Treatment of real industrial pharmaceutical wastewater using wet peroxide oxidation

AbstractThe presence of recalcitrant organic molecules with high amounts of chemical oxygen demand, low biodegradability, and lack of effective treatment for pharmaceutical wastewater result in environmental pollution. Batch wet peroxide oxidation (WPO) experiments have been performed to study the effect of temperature (150°C‐250°C), oxidant coefficient (OC 0‐3), and reaction time (20 minutes‐60 minutes) on degradation efficiency of industrial pharmaceutical wastewater. Box‐Behnken design (BBD) with response surface methodology was used to study the effect of independent parameters on total organic carbon (TOC) removal response. The optimum temperature, oxidant coefficient, and reaction time of the process were found to be 250°C, OC 3, and 60 minutes, which resulted in TOC conversion of 57.96%. The obtained quadratic model has been able to predict the response with minimum deviation. The experimental modelling results conveyed that influence of process parameters followed the order: temperature > time > oxidant coefficient. To improve the mineralization efficiency, process parameters were changed to attain the near complete conversion (~99%) of the pharmaceutical wastewater. The qualitative analysis also showed that only a few components of pharmaceuticals were present in the treated effluent.

Degradation of m-cresol over iron loaded carbon nanotube microfibrous composite: Kinetic optimization and deactivation study

Degradation of organic pollutant through catalytic wet peroxide oxidation (CWPO) is becoming more and more important in modern industry. As a commonly used organic synthetic material, excessive discharge of m-cresol may lead to severe damage of the environment and become a potential threat to human health. In this study, m-cresol was degraded over novel iron loaded carbon nanotube microfibrous composite (Fe-CNT-MF) catalyst packed fixed bed reactor. The kinetic parameters were first optimized, and then the deactivation mechanism of catalyst was also studied. The optimization model showed that total organic carbon (TOC) conversion of m-cresol degradation can reach about 70% under optimum conditions. Then the catalyst deactivation test was conducted with four consecutive runs (32 h in total). Fe-CNT-MF performed high m-cresol and TOC conversions (99% and 40%, respectively) as well as high H2O2 decomposition efficiency (100%) with no iron leaching. Besides, the effect of co-existing organic pollutants on m-cresol degradation was investigated with presence of 4-Ethylphenol and 2,5-dimethylphenol. Fe-CNT-MF exhibited good catalytic activity in multi-pollutant wastewater with 99% conversion for all pollutants. Finally, deactivation analysis results showed that the deactivation mechanism of Fe-CNT-MF included carbon deposition, surface property change and additional oxygen functionalities. A regeneration study was proceeded to further confirm the suggested mechanism, indicating that Fe-CNT-MF has a good regenerability.

Use of Ni-Containing Catalysts for the Olive Mill Wastewater Steam Reforming

The olive oil mill wastewater (OMW) is a by-product (with a high organic load) derived from the production of the olive oil. The OMW steam reforming (OMWSR) process was studied herein, aiming to decrease the environmental damage of such effluents; simultaneously, the waste is economically and energetically valorized with the H2 production. Several Ni-containing catalysts were prepared and tested to compare their performances for the OMWSR using a synthetic OMW effluent; still, stability tests were also carried out. The materials were extensively characterized: thermogravimetric analysis, temperature-programmed oxidation/reduction, temperature-programmed desorption of CO2 /NH3, chemisorption of H2, inductively coupled plasma optical emission spectrometry and physical adsorption-desorption of N2 at -196 oC. Amongst the materials tested, the Ni-Ru/SiO2 sample stood out, exhibiting high catalytic performance: at 400 oC, the H2 yield (> 8 molH2·molOMW) and conversion of total organic carbon (≈ 75 %) were high during all the 24 h of the long-term test, with only a small deactivation being noticed.

Stability and deactivation of graphene catalyst for phenol degradation in a fixed-bed reactor

Stability and deactivation of paper-like sintered stainless steel fibers-graphene (PSSF-Gr) catalyst for catalytic wet peroxide oxidation (CWPO) of phenol are investigated in a fixed-bed reactor. First, the PSSF-Gr catalyst with three-dimensional structure is synthesized by a chemical vapor deposition (CVD) technique. Then, the effect of residence time on the stability of the PSSF-Gr catalyst is explored by different catalyst bed height. Finally, the deactivation mechanisms of the PSSF-Gr are investigated by SEM, EDS, XRD, Raman spectroscopy, AAS, FTIR, TG, NH3-TPD, CO2-TPD, GC and XPS, respectively. The PSSF-Gr with residence time of 1.46 min exhibits a high phenol conversion (above 90%) after continuously operation for 72 h, but the total organic carbon (TOC) conversion experiences a downward 38 h later. However, when the residence time is increase to 5.84 min, the PSSF-Gr always achieves complete phenol conversion after continuously treatment for 96 h, and the TOC conversion always remains more than 81% within 72 h, but the TOC removal starts to decline 72 h later. After analyzing fresh and these two used PSSF-Gr catalysts, it can be summarized that the deactivation of PSSF-Gr is ascribed to the collapse of PSSF support structure, the change of graphene intrinsic properties, and the deposition of carbonaceous compounds.

Photocatalytic Oxidation of Methyl Tert-Butyl Ether in Presence of Various Phase Compositions of TiO2

MTBE (methyl tert-butyl ether) represents a rising threat to the environment, especially drinking water, and its effective removal (with all by-products) is necessary. Even a very low concentration of MTBE makes the water undrinkable; therefore, an effective treatment has to be developed. This work is focused on MTBE photocatalytic oxidation in presence of various TiO2 photocatalysts with different phase composition prepared by different methods. It was confirmed the phase composition of TiO2 had the most significant influence on the photocatalytic degradation of MTBE. The rutile phase more easily reduces adsorbed oxygen by photogenerated electrons to superoxide radical, supporting separation of charge carriers. The presence and concentrations of by-products have to be taken into account as well. The conversion of total organic carbon (TOC) was used for the comparison, 40% of TOC was removed after 1 h of irradiation in presence of TiO2–ISOP–C/800 photocatalyst composed of anatase and rutile phase.