Phenol Degradation Process Research Articles

Assembly of MOF derived composite catalyst on the PVDF membrane matrix for high-efficient phenol removal

Integrating the heterogeneous catalysts with the membrane matrix is a promising approach for wastewater decontamination. In this study, a ZIF-67 derived cobalt‑manganese spinel catalyst MnCo2O4.5@Carbon (MCOC) was prepared using a one-pot pyrolysis process and was then blended with a polyvinylidene fluoride (PVDF) membrane through the phase inversion method. The introduction of the MCOC catalyst not only improved the permeance of the membrane but also constructed active reaction sites within the membrane matrix. As a result, the PVDF/MCOC membranes exhibited both satisfactory degradation capabilities by activating peroxymonosulfate and favorable permeation performance. Remarkably, about 99 % of phenol (20 mg/L) can be removed within 30 min, with a water flux of 649.0 L/m2∙h. Besides, the PVDF/MCOC catalytic membrane possessed favorable anti-fouling properties and stability. The flux recovery rate of the PVDF/MCOC membrane reached 85 % after three fouling/washing cycles, while the phenol removal efficiency remained consistent at 95 % after 5 consecutive cycles. Radical quenching tests and electron paramagnetic resonance analysis further indicated that sulfate radicals and singlet oxygen were the primary reactive oxygen species in the phenol degradation processes. Consequently, this work highlights an effective method to fabricate a catalytic membrane with high permeance and catalytic efficiency, potentially expanding the application of heterogeneous catalysts in wastewater decontamination.

Catalytic activation of peroxodisulfate using shape-controlled cerium-manganese composite oxide for phenol degradation: Kinetics and degradation pathway investigation

Phenol-containing wastewater is typical organic wastewater, and its treatment is arduous. An advanced method to treat this type of wastewater is persulfate activation. Environmentally friendly cerium-manganese composite oxide materials were synthesized by hydrothermal method and applied to the phenol degradation process. Various ratios of cerium and manganese, as well as the amount of sodium hydroxide, were investigated. The solid solutions of cerium and manganese were formed and confirmed by X-ray diffraction (XRD) and transmission electron microscopy (TEM). H2-temperature programmed reduction (H2-TPR) and X-ray photoelectron spectroscopy (XPS) were utilized to analyze the synergistic effect of cerium and manganese. It is found that there is a transformation between Ce4+/Ce3+ and Mn2+/Mn3+, which makes the material more trivalent manganese and thereby increases the catalytic activity. The effect of materials in catalyzing phenol degradation by peroxodisulfate (PDS) under various preparation conditions is discussed and high-efficiency removal of phenol can be achieved and the removal rate at 180 min is close to 100%. The kinetic of this process was investigated and activation energy of phenol degradation is 62.35 kJ/mol. The degradation pathway of phenol was studied and it is found that PDS can be activated by low metal ions and the ·OH and SO4·– radicals play crucial roles according to the quenching experiments.

A Z-scheme photocatalysis for phenol eradication from water using peroxymonosulfate activation Ag/AgBr/SCN nanocomposite

BackgroundThe present work was mainly focused on construction of direct Z-scheme Ag/AgBr/SCN heterostructure and their photocatalytic ability to removal of phenol using synthesized photocatalysts. Ag/AgBr/SCN photocatalyst was prepared via facile deposition-precipitation method while bare g-C3N4 (GCN) and SCN (sulphur doped g-C3N4) were prepared via simple thermal-polycondensation method. MethodsThe Ag/AgBr/SCN Z-scheme heterostructure was fabricated by integration of 2D SCN with AgBr. Doping of sulphur in GCN structure has incremented the light absorption ability of GCN via reducing the energy gap to 2.64 eV from 2.7 eV. Different spectroscopic and analytical techniques have confirmed the successful formation of photocatalysts. Significant findingsThe addition of PMS during the photocatalytic experiment has enhanced the removal efficiency of photocatalysts due to more •OH and •SO4−radicals generation. It was observed from the results that PMS assisted Ag/AgBr/SCN photocatalytic material exhibited highest removal efficiency i.e. 99% compared to other bare photocatalysts within 80 min of visible-light exposure. Proposed mechanism validated the Z-scheme charge transfer route in Ag/AgBr/SCN in accord to apt band alignment in SCN and AgBr. However, Ag metal acted as an electron mediator to just transfer the electron from CB of SCN to CB of AgBr. The transference of electron from sulphur doped g-C3N4 to AgBr through Ag improved electron transportation. This ultimately enhanced charge separation rate and reduced the charge recombination rate in Ag/AgBr/SCN nanocomposite. The proposed mechanism also presented that •OH, SO4•− and •O2− radicals were the primary reactive species during Ag/AgBr/SCN/PMS assisted photocatalytic phenol degradation process (verified through scavenging tests). Finally, the recyclability experiment confirmed the stability and reusability of the prepared photocatalyst to 5 consecutive cycles. Consequently, this work presents a new perspective to fabricate greener, cheaper and proficient visible driven photocatalytic material for wastewater detoxification and environmental remediation.

Insights into the degradation process of phenol during in-situ thermal desorption: The overlooked oxidation of hydroxyl radicals from oxygenation of reduced Fe-bearing clay minerals

In-situ thermal desorption (ISTD) has attracted increasing attention owing to the efficient removal of organic contaminants from contaminated sites. However, it is poorly understood that whether and to what extent contamination degradation occurs upon oxygenation of reduced Fe-bearing clay minerals (RFC) in the subsurface during ISTD. In this study, we evaluated the mechanism of contaminant degradation upon oxygenation of reduced clay minerals during the ISTD. Reduced nontronite (rNAu-2) and montmorillonite (rSWy-3) were selected as RFC models. Results showed that thermal treatment during ISTD could significantly enhance phenol degradation, which increased from 25.8 % at 10°C to 74.4 % at 70°C in rNAu-2 and from 17.7 % at 10°C to 49.8 % at 70°C in rSWy-3. Correspondingly, the cumulative •OH at steady-state ([•OH]ss) increased by 3.7 and 1.5 times, respectively. The acceleration of Fe(II) oxidation with increasing temperature could be mainly responsible for [•OH]ss generation, which degrades phenol. Moreover, thermal treatment improved the fast oxidation of trioctahedral entities Fe(II)Fe(II)Fe(II) (TOF) and the slow oxidation of dioctahedral entities Fe(II)Fe(II) (DTF1), AlFe(II) (DAF1), and Fe(II)Fe(III) (DTF2). Our study suggests that the overlooked degradation progress of phenol by oxygenation of RFC during ISTD, and it could be favorable for contaminant degradation during remediation.

New insight into the mechanism of ferric hydroxide-based heterogeneous Fenton-like reaction.

The heterogeneous Fenton-like reaction (HeFR) has always been a research focus for environmental applications. However, it has long been difficult to reach a consensus on the reaction mechanism because the process of metal ions dissolution and its role were not well understood. In this paper, we propose the courses of organics-mediated coordination or/and reduction dissolution of ferric hydroxide to initiate the autocatalytic kinetics of phenol degradation and illustrate it through density functional theory (DFT) and experiments. With the increase of hydrogen peroxide concentration, the degradation of phenol changes from autocatalytic kinetics to first-order kinetics. Furthermore, a novel "limit segmentation method" initiated by us indicates that homogeneous reaction plays a decisive role in the phenol degradation process. The dominant roles of the reactive organics in both iron dissolution and the iron cycle and of the homogeneous reaction in the whole degradation process in the ferric hydroxide-based HeFR system are brand-new insights that pave the pathway for future research.

Kinetic characterization of a new phenol degrading Acinetobacter towneri strain isolated from landfill leachate treating bioreactor

The objective of this study was to establish and to mathematically describe the phenol degrading properties of a new Acinetobacter towneri CFII-87 strain, isolated from a bioreactor treating landfill leachate. For this purpose, the biokinetic parameters of phenol biodegradation at various initial phenol concentrations of the A. towneri CFII-87 strain have been experimentally measured, and four different mathematical inhibition models (Haldane, Yano, Aiba and Edwards models) have been used to simulate the substrate-inhibited phenol degradation process. The results of the batch biodegradation experiments show that the new A. towneri CFII-87 strain grows on and metabolizes phenol up to 1000 mg/L concentration, manifests significant substrate inhibition and lag time only at concentrations above 800 mg/L phenol, and has a maximum growth rate at 300 mg/L initial phenol concentration. The comparison of the model predictions with the experimental phenol and biomass data revealed that the Haldane, Aiba and Edwards models can be used with success to describe the phenol biodegradation process by A. towneri CFII-87, while the Yano model, especially at higher initial phenol concentrations, fails to describe the process. The best performing inhibition model was the Edwards model, presenting correlation coefficients of R2 > 0.98 and modelling efficiency of ME > 0.94 for the prediction of biomass and phenol concentrations on the validation datasets. The calculated biokinetic model parameters place this new strain among the bacteria with the highest tolerance towards phenol. The results suggest that the A. towneri CFII-87 strain can potentially be used in the treatment of phenolic wastewaters.

Mesoporous LaVO4/MCM-48 nanocomposite with visible-light-driven photocatalytic degradation of phenol in wastewater

Dearomatization through photocatalytic oxidation is a swiftly rising phenolic compounds removal technology that works at trifling operations requirements with a special emphasis on the generation of nontoxic products. The study aims to develop a LaVO4/MCM-48 nanocomposite that was prepared via a hydrothermally approach assisting the employment of an MCM-48 matrix, which was then utilized for phenol degradation processes. Various techniques including UV–Vis DRS, FTIR, PL, Raman, TEM, and BET analyses are employed to characterize the developed photocatalyst. The developed photocatalyst presented remarkable characteristics, especially increased light photon utilization, and reduced recombination rate leading to enhanced visible-light-driven photodegradation performance owing to the improved specific surface area, specific porosities, and <2 eV narrow energy bandgap. The LaVO4/MCM-48 nanocomposite was experienced on aqueous phenol solution having 20 mg/L concentration under visible-light exposure, demonstrating exceptional performance in photodegradation up to 99.28%, comparatively higher than pure LaVO4. The conducted kinetic measurements revealed good accordance with pseudo first-order. A possible reaction mechanism for photocatalytic degradation was also predicted. The as-synthesized LaVO4/MCM-48 nanocomposite presented excellent stability and recyclability.

Modified high-efficiency carbon material for deep degradation of phenol by activating persulfate

A series of cobalt-nitrogen modified catalysts were prepared and applied to the degradation of phenol. The Mott Schottky catalyst (CoO/NGr@C) with high pyridine nitrogen content was designed to activate potassium peroxodisulfate (PDS) to generate active free radicals for phenol degradation. The structural properties of the materials are analyzed by XPS, TEM and then the charge density calculation is performed by DFT, which proves the existence of the highly active interface effect. Co–N-CMCM-41 can only degrade phenol into benzoquinone and it is difficult to achieve further degradation of benzoquinone, while the modified CoO/NGr@C can achieve deep mineralization of the intermediate benzoquinone through UV spectrum. EPR was used to prove that both hydroxyl radicals and sulfate radicals exist in the degradation process of phenol. Through the DFT simulation calculation of the material, it is proved that the existence of carbon activated by nitrogen and the electron rearrangement between cobalt and nitrogen-rich carbon lead to the catalytic activity of the material. The degradation conditions of phenol were optimized and the reaction kinetics of further phenol degradation were studied. The activation energy of phenol degradation on CoO/NGr@C is calculated to be 34.38 kJ mol−1.

Insights into the mechanism of redox pairs and oxygen vacancies of Fe2O3@CoFe2O4 hybrids for efficient refractory organic pollutants degradation

The core-shell Fe2O3@CoFe2O4 hybrids microspheres with abundant oxygen vacancies were synthesized through in-situ ion exchange-calcination method and employed to induce peroxymonosulfate (PMS) to eliminate organic pollutants. The superior catalytic activity and stability of Fe2O3@CoFe2O4 were attributed to the synergistic effects of M2+/M3+ (M denotes Co or Fe) redox cycles. SO4·-, ·OH, O2·- and 1O2 were proved to be the main reactive oxygen species (ROS) involved in the phenol degradation process through quenching experiments and EPR measurements, while the surface-bound SO4·- played a dominant role. Trace metal ions leached during the reaction enhanced the PMS activation, and the oxygen vacancies electron transfer process played a critical role in the formation of O2·-/1O2 and the cycle of M2+/M3+ redox pairs. The formation of ROS and function of 1O2 were also revealed from bulk reaction and interface reaction. This study highlighted the simultaneous evolution of PMS reduction and oxidation to generate ROS, which provided an insight into the efficient catalytic degradation of persistent organic pollutants (POPs).

Photocataytic Degradation of Phenol Using TiO2-Fe Under H2O2 Presence by Visible and Sunlight Irradiation

Phenol is one of the essential organic pollutants released into the environment because of its high stability and toxicity. It is harmful to organisms, environment, and posing a serious threat to human health at low concentration. This research investigated the photocatalytic degradation process of phenol using a TiO2-Fe catalyst under visible light irradiation and additional H2O2. The effect of various conditions process was applied, including different catalyst doses (0.2, 0.4, 0.6, and 0.8 g/L), pH (3, 6, 8, and 11), irradiation times (60, 90, 120, 150, and 210 minutes) and the presence of H2O2. The degradation process was studied at an initial concentration of phenol 5 mg/L. This study has been decreasing phenol content (90.51%) with catalyst doses 0.6 g/ L sample solution, pH solution 11, reaction time 210 minutes and H2O2 concentration 30%. This final phenol concentration after photodegradation under halogen light was 0.18 mg/L, while sunlight irradiation was 0.11 mg/L. This result is below government regulation as per Permen LH RI No. 5/2014 i.e. 0.5 mg/L. Therefore, this process possible to remove phenol in aqueous such as industrial wastewater or other resources.

Uji Kinerja Komposit TiO2-Graphene/Surfaktan dalam Mendegradasi Senyawa Fenol

Phenol is a hazardous compound that is often found in wastewater in most industries and cannot be degraded naturally. Photocatalysis is a promising method to reduce phenol waste, because it can produce more environmentally friendly compounds like CO2 and H2O. Titanium dioxide (TiO2) has been widely applied in the degradation process of waste compounds including phenol waste. To improve the performance of TiO2, graphene can be used as a dopants because it has a surface area. Modification of graphene with surfactants was carried out to increase dispersion and reduce agglomeration on TiO2 doped with graphene. The purpose of this research is to synthesize TiO2–graphene/surfactant composite which can be used to degrade phenolic compounds. Photodegradation of TiO2 composites was carried out by varying the initial concentration of phenol (10, 20, 30 ppm). Composites synthesis begins with disperse the surfactant on the surface of the graphene, then proceeds with doping graphene (surfactant) on TiO2. The resulting composites were characterized using SEM, BET, FTIR, XRD and UV-Vis spectrophotometer. The phenol degradation process was carried out using a photodegradation reactor. The highest performance TiO2–graphene/surfactant composite was obtained at an initial concentration of 10 ppm phenol is 81.02%

Effect of Adding Fe3O4 in Graphene/TiO2/Fe3O4 Composite for Phenol Photodegradation Application

In order to improve the performance of TiO2, a material that can increase the adsorption ability of TiO2 is needed, one of which is graphene. Graphene/TiO2 composites can be used to degrade phenol. The addition of a magnet material to the grapene/TiO2 composite, namely Fe3O4 is expected to facilitate the separation of the catalyst after being used in the phenol degradation process. This study aims to synthesize and characterize graphene/TiO2/Fe3O4 composites. The composite obtained was used to degrade phenol. This research begins with the modification of graphene with the surfactant cocoPAS. Synthesis of graphene/TiO2/Fe3O4 composite with various amount of Fe3O4 in composite (0.3, 0.5 and 0.7 g, respectively). Composites used for phenol degradation and separated after degradation. The composite materials were characterized by the scanning electron microscopy (SEM), X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) specific surface areas, Fourier transform infrared (FT-IR) and UV-vis absorption spectroscopy. Graphene/TiO2/Fe3O4 composite with a mass of Fe3O4 in the composite of 0.3 g indicates the highest degradation, while the catalyst separation process after phenol degradation showed the fastest time in the separation of the Fe3O4 mass in the composite, which was 0.5 g. the faster the separation time required, but the performance of the composite in degrading phenol is decreasing.

Binary TiO2/RGO photocatalyst for enhanced degradation of phenol and its application in underground coal gasification wastewater treatment

In this work, we synthesized the TiO2/reduced graphene oxide (TiO2/RGO) binary nanohybrids through the sol-anaerobic calcination method, the TiO2 nanoparticles belonging to anatase type were evenly loaded on RGO surface in the form of Ti–O–C bond. The enhanced photocatalytic performance can be ascribed to the existence of RGO that can effectively promote the transfer of photo-induced electron-hole pairs to generate more hydroxyl radicals (·OH) and superoxide anion (O2·-) degrading phenol. The TiO2/RGO nanocomposite with weight ratio of RGO to TiO2 (37.0%–55.7%) had achieved maximum degradation of phenol from aqueous solution, and about 97.87% of phenol had been removed within 180 min under UV-light illumination. Through GC-MS tracking of phenol degradation process, it can be observed that long-chain intermediates will be generated, and these intermediates will eventually be degraded, confirming that phenol can be completely removed. Additionally, around 67% TOC of simulated underground coal gasification (UCG) wastewater can be removed after 10 h degradation using TiO2/RGO binary composites as photocatalysts. All these results demonstrate that the binary nanohybrids possess great potential for the organic contaminants destruction from the actual coal chemical wastewater.

PHENOL WASTE TREATMENT USING OZONE-PLASMA HYBRID REACTOR

Phenol is one of the most dangerous ingredients in industrial wastewater, which has acute toxicity and is difficult to degrade in the environment. Therefore, Ozone-Plasma Hybrid Reactor (RHOP) is an effective phenol waste treatment used to test the performance of the treatment of synthetic phenolic compounds. Its working principle is based on the combination of ozonation reaction in the liquid plasma field of the reactor. Ozone as a reagent is produced by the ozonator, which is fed into the RHOP by mixing it with the liquid phase feed in the injector to enable the intensive the reaction of the two-phase mixture react. Furthermore, the two-phase mixture intensifies hydroxyl radicals when the liquid phase is in alkaline condition and continuously exposed in plasma. The results obtained from the performance test carried out on several wastes with high concentrations, showed that the system needed improvement. The improvements were made by changing the reactor system to Dielectric Barrier Discharge (DBD) plasma with wire cylinder configuration, to degrade synthetic waste containing phenolic compounds through active species formed in the reactor. This process has a high oxidation potential and decomposes various organic pollutants in waste. Furthermore, the ozonation technique was applied to the DBD reactor with the aim of increasing the amount of ozone and OH• radicals, therefore maximizing the phenol degradation process.

Binary TiO 2/RGO Photocatalyst for Enhanced Degradation of Phenol and its Application in Underground Coal Gasification Wastewater Treatment

In this work, we synthesize the TiO2/RGO binary nanohybrids through the sol-anaerobic calcination method, the TiO2 nanoparticles belonging to anatase type were evenly loaded on RGO surface in the form of Ti-O-C bond. The enhanced photocatalytic performance can be ascribed to the existence of RGO that can effectively promote the transfer of photo-induced electron-hole pairs to generate more hydroxyl radicals (·OH) and superoxide anion (O2·-) degrading phenol. The TiO2/RGO nanocomposite with weight ratio of RGO to TiO2 (37.0% to 55.7%) has achieved maximum degradation of phenol from aqueous solution, and about 97.87% of phenol has been removed within 180 min under UV-light illumination. Through GC-MS tracking of phenol degradation process, it can be observed that long-chain intermediates will be generated, and these intermediates will eventually be degraded, confirming that phenol can be completely removed. Additionally, around 67% TOC of simulated underground coal gasification (UCG) wastewater can be removed after 10 h degradation using TiO2/RGO binary composites as photocatalysts. All these results demonstrate that the binary nanohybrids possess great potential for the organic contaminants destruction from the actual coal chemical wastewater.

Photodegradation of Phenolic Compounds from Water in the Presence of a Pd-Containing Exhausted Adsorbent

A closed-cycle technology regarding the use of an exhausted Pd-based adsorbent as a photocatalyst in the degradation process of phenol is presented. Pd (II) represents a precious metal of great economic importance. Its obtained from natural sources become more difficult to achieve. Therefore, also considering the regulations of the “circular economy,” its recovery from secondary sources turn out to be a stringent issue in the last years. Pd(II) ions are removed from aqueous solution through adsorption onto Florisil (an inorganic solid support—magnesium silicate) impregnated with Cyphos IL 101 (trihexyl tetradecyl phosphonium chloride). It was observed that the presence of the ionic liquid (IL) in the adsorbent structure doubles the adsorption efficiency of the studied materials. The newly obtained Pd-based photocatalyst was exhaustively characterized and was used in the degradation process of phenol from aqueous solutions. The phenol degradation process was studied in terms of the nature of the photocatalyst used, time of photodegradation and solid: liquid ratio. It was observed that both the presence of IL and Pd lead to an increase in the efficiency of the phenol degradation process. The new Pd-based photocatalyst could be efficiently used in more cycles of phenol photodegradation processes. When is used as a photocatalyst the Florisil impregnated with IL and loaded with 2 mg/g of Pd, a degree of mineralization of 93.75% is obtained after 180 min of irradiation of a phenol solution having a concentration of 20 mg/L and using a solid:liquid ratio = 1:1.

Lacunary Keggin-type hetero polyoxometalate, K7PMo2W9O39, supported on nano ZnO as an efficient Photocatalyst for degradation of phenol in water solution

In the present research, Lacunary Keggin-type heteropolyoxometalate, (K7PMo2W9O39) supported on ZnO nanoparticles was prepared by the impregnation method. Nanoparticle characteristics and the remaining Keggin structure in the nanocomposites were confirmed by FTIR and XRD analyses. The photocatalytic activity of prepared K7PMo2W9O39/ZnO for degradation of phenol under UV light was investigated. H2O2 was used as oxidant in the photocatalytic degradation process of phenol. The results indicated that synthesized nanophotocatalyst could be considered an appropriate heterogonous photocatalyst in the removing of organic pollutant from aqueous solutions and heterogenization of Lacunary Keggin-type heteropolyoxometalate on ZnO nanoparticles resulted in the improved light absorption intensity and decreased band gap of nanocomposites. Degradation of phenol in the presence of the K7PMo2W9O39/ZnO could lead to the disappearance approximately 93% of phenol after 60 min. But degradation for the same experiment performed in the presence of the K7PMo2W9O39 or /ZnO was less than 60% in the same time.

The application of flow to an ultrasonic horn system: Phenol degradation and sonoluminescence

Sonochemical (SC) processes can be increased with the application of fluid flow due to changes in bubble characteristics. In this work, a novel flow through set-up was applied to an ultrasonic horn system to investigate the effects of flow on the degradation of phenol. KI dosimetry and sonochemiluminescence (SCL) were also analysed, under the same conditions, to provide comparison of degradation to other SC processes. Further, sonoluminescence (SL) in water and different concentrations of potassium iodide (KI) and phenol solutions was studied to determine the effect of flow on processes inside the bubble that result in SL. The degradation of 0.1 mM phenol solutions, KI dosimetry and SL from phenol (0.1, 20 and 60 mM) and KI (0.1, 1 and 2 M) solutions were analysed under flow rates of 0, 24, 228 and 626 mL/min. For an ultrasonic horn system, all flow rates could augment phenol degradation beyond that of the systems without flow. At the lowest applied power, the amount of degradation was significantly increased with flow, becoming greater than degradation observed at the highest power. A strong correlation between phenol degradation and SC processes indicated that degradation followed an oxidative process. SL intensity from water, KI, and phenol solutions could also be increased with flow beyond the no flow system. For water this occurred most readily at higher powers, then for the solutes there was varied behaviour dependent upon the solute concentration. It was theorised that flow may increase the transfer of radical species to solution to enhance SC processes. An increase in SL, with flow, indicates that flow is acting to change the properties of the bubbles and/or the bubble field such that the active bubbles present collapse with greater total intensity.

Synthesis and characterization of TiO2-based nanostructures via fluorine-free solvothermal method for enhancing visible light photocatalytic activity: Experimental and theoretical approach

Surface-fluorinated anatase TiO2 nanosheets have been widely prepared using hydrofluoric acid (HF) as morphology controlling agent with several titanium alkoxides. However, hazardous and other scientific problems associated with HF are major obstacles towards its global commercialization. Therefore, this study introduces a facile, green and fluorine-free solvothermal synthetic approach to prepare anatase TiO2 nanosheets (TNSs), involving commercial TiO2 nanoparticles as titanium source and N, N dimethylformamide (DMF) as morphology controlling agent under alkaline environment. A Box-Behnken-Design 3-level experimental design was applied to optimize the major key synthesis parameters for tuneable TNSs performance by manipulating the reaction temperature (120−180 °C), reaction time (3−48 hr) and dose of DMF (5−40 mL). The proposed model was verified through the analysis of variance and performing experiments at predicated optimal conditions (temperature =165.35 °C, time = 25.50 h and DMF dose =22.50 mL). The quadratic model was found to be best-fitted with the maximum correlation coefficients (R2 = 0.989 and adjusted R2 = 0.975) between predicted and actual results. The crystal growth mechanism of TNSs was also proposed. The formation of tetragonal TNSs (10 nm) containing the highest surface area with least bandgap upto 2.62 eV, confirmed through XRD, TEM, BET, DRS, FTIR and XPS measurements. The excellent photocatalytic performance was exhibited by as-developed TNSs for phenol degradation upto 95.33 % under visible-light. The photoactivity of TNSs was found to be strongly associated with synthesis parameters including hydrothermal temperature, reaction time and DMF dose. The phenol degradation data was well explained via pseudo-first-order kinetics and Langmuir isotherm models. Thermodynamic parameters were suggested the nature of phenol degradation process. This enhanced degradation activity of TNSs was attributed to the well-defined morphology, larger surface area, improved energy harvesting aptitude and abated recombination rate of photogenerated electron hole-pairs resulting an enhancement in the photogenerated charge carrier.

Photocatalytic degradation of phenol using silica SBA-16 supported TiO2

Silica SBA-16, an efficient photocatalyst support with cubic (bottle-ink) mesoporous structure, large specific surface area, large pore volume and uniform pore size and titanium oxide (TiO2), a semiconductor compound as the active site were synthesized facilely via one-pot method and photocatalysts denoted as x%TiO2/SBA-16 where x = 2, 5, 10 and 20, in order to examine their photocatalytic ability for phenol degradation in different experimental conditions such as different phenol concentration in water (ppm), various pH of the solution and amount of applied photocatalyst (g/l). In order to confirm the correct structure of the SBA-16 support and prepared photocatalysts, various types of characterization analyses such as N2 adsorption/desorption, X-ray diffraction (XRD), TEM, SEM–EDX, UV–VIS and FT-IR were applied. Based on the employed analyses, it can be claimed that the SBA-16 support and synthesized photocatalysts demonstrated mesoporous structures with cubic pores that are in agreement with reliable literature. After carrying out all of the experimental factors for the phenol degradation process, it was found that the 10%TiO2/SBA-16 photocatalyst in the specific experimental conditions including pH 7, phenol concentration of 100 ppm and 1 g/l photocatalyst dosage achieved the highest performance which was approximately 90% degradation of phenol. Hence these mentioned conditions were chosen as the optimum experimental conditions. COD and TOC tests were employed to study the final products of the process and their results showed that the 10%TiO2/SBA-16 photocatalyst was able to reduce the COD and TOC of phenol solution up to 80% and 85%, respectively, means that the major amount of phenol converted to water and CO2 that are the final products of phenol degradation process.