Photochemically enhanced degradation of phenol using heterogeneous Fenton-type catalysts

The degradation of phenol was carried out using heterogeneous Fenton-type catalysts in the presence of H_2O_2 and UV. Catalysts were prepared by exchanging and immobilizing Fe 2+ in zeolite 13X, silica gel or Al_2O_3. The concentration of phenol solution was 100 mg/L. The amount of H_2O_2 added was the stoichiometric amount of H_2O_2 required for the total oxidation of phenol. Under the irradiation of medium pressure light (300 W) phenol was mineralized within 1 h in the presence of Fe 2+/zeolite 13X. The COD removal rate was enhanced in the presence of Fe 2+/zeolite 13X compared to that of Fe 2+/silica gel or Fe 2+/Al_2O_3. Analogous homogenous photo-Fenton reaction with equivalent Fe 2+ was also carried out to evaluate the catalysis efficiency of Fe 2+/zeolite 13X. Results showed that the COD removal rate was near to that of homogeneous Fenton, while heterogeneous Fe 2+/zeolite 13X catalyst could be recycled.

Membrane enhanced COD degradation of pulp wastewater using Cu_2O/H_2O_2 heterogeneous Fenton process

Both activity and stability of the catalyst can be improved in heterogeneous Fenton reaction,in particular,with no limitation for the working p H and no production of the sludge.In this work,a combination of catalyst Cu_2O and pore-channel-dispersed H_2O_2is proposed to treat the pulp wastewater.Degradation degree of CODs in the wastewater was up to 77%in the ceramic membrane reactor using Cu_2O powder(2.0 g·L^(-1))and membranefeeding H_2O_2(0.8 ml·L^(-1))within 60 min.Evolution of·OH radical formation in the advanced oxidation process was analyzed with a fluorescent method.Utilization efficiency of H_2O_2was successfully enhanced by 10%with the membrane distributor.Further on,the catalyst recyclability was evaluated in a five-cycle test.The concentration of copper ions being dissolved in the treated water was monitored with ICP.After Cu_2O/H_2O_2(membrane)treatment the effluent is qualified to discharge with COD concentration lower than 15 mg·L^(-1)with regard to the national standard GB25467-2010.

Precursor-driven structural tailoring of iron oxychloride for enhanced heterogeneous Fenton activity

Iron oxychloride(FeOCl)is a unique layered material with tunable electronic properties.The conventional synthetic route of chemical vapor transition involves a thermodynamics-driven gas-solid interfacial reaction which often generates macroscopic crystals with stable facets.In this study,through analyzing the effects of the synthetic parameters on the FeOCl synthesis,we discovered the dominant contribution of theα-Fe_(2)O_(3)precursors on the chemical property of the FeOCl product,and subsequently developed a highly-controllable synthetic route of tailoring the FeOCl structures into small sizes and exposed high-energy facets via a facile and scalable mechanical-chemical approach.The synthesized products could be systematically tuned by the ball-milling conditions of theα-Fe_(2)O_(3)precursors.With increased milling time,the FeOCl crystallites demonstrated reduced sizes and more exposed(110)facets.Intriguingly,these smallsized FeOCl catalysts exhibited much faster Fenton-like kinetics than the pristine macroscopic FeOCl materials.Specifically,FeOCl catalysts with a 12-hour milling time showed nearly 39 times higher efficiency toward phenol degradation than the pristine FeOCl.The structure-reactivity relationship was further elucidated using the combinatory analysis via density functional theory calculation,electron paramagnetic resonance and radical quenching probe experiments.This work provides a rationale for tailoring the surface structures of FeOCl crystallites for potential applications in environmental catalysis.

Advanced treatment of biologically pretreated coal gasification wastewater by a novel heterogeneous Fenton oxidation process

Sewage sludge from a biological wastewater treatment plant was converted into sewage sludge based activated carbon（SBAC） with Zn Cl2 as activation agent, which was used as a support for ferric oxides to form a catalyst（Fe Ox/SBAC） by a simple impregnation method.The new material was then used to improve the performance of Fenton oxidation of real biologically pretreated coal gasification wastewater（CGW）. The results indicated that the prepared Fe Ox/SBAC significantly enhanced the pollutant removal performance in the Fenton process, so that the treated wastewater was more biodegradable and less toxic. The best performance was obtained over a wide p H range from 2 to 7, temperature 30°C, 15 mg/L of H2O2 and 1 g/L of catalyst, and the treated effluent concentrations of COD, total phenols,BOD5 and TOC all met the discharge limits in China. Meanwhile, on the basis of significant inhibition by a radical scavenger in the heterogeneous Fenton process as well as the evolution of FT-IR spectra of pollutant-saturated Fe Ox/BAC with and without H2O2, it was deduced that the catalytic activity was responsible for generating hydroxyl radicals, and a possible reaction pathway and interface mechanism were proposed. Moreover, Fe Ox/SBAC showed superior stability over five successive oxidation runs. Thus, heterogeneous Fenton oxidation of biologically pretreated CGW by Fe Ox/SBAC, with the advantages of being economical, efficient and sustainable, holds promise for engineering application.

Heterogeneous Fenton-like degradation of 4-chlorophenol using iron/ordered mesoporous carbon catalyst

Ordered mesoporous carbon supported iron catalysts （Fe/OMC） were prepared by the incipient wetness impregnation method and investigated in Fenton-like degradation of 4-chlorophenol （4CP） in this work. XRD and TEM characterization showed that the iron oxides were well dispersed on the OMC support and grew bigger with the increasing calcination temperature. The catalyst prepared with a lower calcination temperature showed higher decomposition efficiency towards 4CP and H202, but more metals were leached. The effect of different operational parameters such as initial pH, H202 dosage, and reaction temperature on the catalytic activity was evaluated. The results showed that 96.1% of 4CP and 47.4% of TOC was removed after 270 min at 30℃, initial pH of 3 and 6.6 mmol/L H202.88% of 4CP removal efficiency was retained after three successive runs, indicating Fe/OMC a stable catalyst for Fenton reaction. 4CP was degraded predominately by the attack of hydroxyl radical formed on the catalyst surface and in the bulk solution due to iron leaching. Based on the degradation intermediates detected by high performance liquid chromatography, possible oxidation pathways were proposed during the 4CP degradation.

Interfacial mechanisms of heterogeneous Fenton reactions catalyzed by iron-based materials： A review

The heterogeneous Fenton reaction can generate highly reactive hydroxyl radicals（·OH）from reactions between recyclable solid catalysts and H2O2 at acidic or even circumneutral pH.Hence,it can effectively oxidize refractory organics in water or soils and has become a promising environmentally friendly treatment technology.Due to the complex reaction system,the mechanism behind heterogeneous Fenton reactions remains unresolved but fascinating,and is crucial for understanding Fenton chemistry and the development and application of efficient heterogeneous Fenton technologies.Iron-based materials usually possess high catalytic activity,low cost,negligible toxicity and easy recovery,and are a superior type of heterogeneous Fenton catalysts.Therefore,this article reviews the fundamental but important interfacial mechanisms of heterogeneous Fenton reactions catalyzed by iron-based materials..OH,hydroperoxyl radicals/superoxide anions（HO2./O2^-.）and high-valent iron are the three main types of reactive oxygen species（ROS）,with different oxidation reactivity and selectivity.Based on the mechanisms of ROS generation,the interfacial mechanisms of heterogeneous Fenton systems can be classified as the homogeneous Fenton mechanism induced by surface-leached iron,the heterogeneous catalysis mechanism,and the heterogeneous reaction-induced homogeneous mechanism.Different heterogeneous Fenton systems catalyzed by characteristic iron-based materials are comprehensively reviewed.Finally,related future research directions are also suggested.

Effect of phosphate on heterogeneous Fenton oxidation of catechol by nano-Fe_(3)O_(4):Inhibitor or stabilizer?

The effect of phosphate on adsorption and oxidation of catechol, 1,2-dihydroxybenzene,in a heterogeneous Fenton system was investigated. In situ attenuated total reflectance infrared spectroscopy（ATR-FTIR） was used to monitor the surface speciation at the nano-Fe_3O_4 catalyst surface. The presence of phosphate decreased the removal rate of catechol and the abatement of dissolved organic compounds, as well as the decomposition of H2O2. This effect of phosphate was mainly due to its strong reaction with surface sites on the iron oxide catalyst. At neutral and acid pH, phosphate could displace the adsorbed catechol from the surface of catalyst and also could compete for surface sites with H2O2. In situ IR spectra indicated the formation of iron phosphate precipitation at the catalyst surface. The iron phosphate surface species may affect the amount of iron atoms taking part in the catalytic decomposition of H2O2 and formation of hydroxyl radicals,and inhibit the catalytic ability of Fe3O4 catalyst. Therefore, phosphate ions worked as stabilizer and inhibitor in a heterogeneous Fenton reaction at the same time, in effect leading to an increase in oxidation efficiency in this study. However, before use of phosphate as pH buffer or H2O2 stabilizer in a heterogeneous Fenton system, the possible inhibitory effect of phosphate on the actual removal of organic pollutants should be fully considered.

Mechanochemically sulfured FeS1.92 as stable and efficient heterogeneous Fenton catalyst

Fenton reaction is one of most promising approaches for efficient removal of various robust organic pollutants in wastewater,however it faces several intrinsic challenges such as acidic condition,sludge waste and sensitive to sulfide-containing compound.Here we reported a novel FeS1.92 as an efficient and sulfide resistant heterogeneous Fenton catalyst under mild condition.This novel FeS1.92 was facilely prepared through a mechanochemical synthesis of mackinawite(FeS) with sulfur powder(S) by ball milling.The sulfured mackinawite(FeS1.92) exhibits high performance in activating H2 O2 to generate hydroxyle radicals for organic waste remediation.Furthermore,this FeS1.92 based heterogeneous Fenton catalyst is highly sulfide resistant and shows improved performance for degrading sulfide-containing organic pollutants.This study provides an effective mechanochemical approach to fabricate heterogeneous Fenton catalysts for sulfide-containing wastewater treatment.

Heterogeneous fenton oxidation of methylene blue with Fe-impregnated biochar catalyst

Fe-impregnated biochar(Fe-BC)as high-efficiency heterogeneous Fenton catalyst was synthesized and evaluated in detail for its catalytic activity,stability and reusability under various conditions.The optimal conditions for the Fenton oxidation of methylene blue(MB)as model dye were determined as 0.075 g/L H_(2)O_(2),0.5 g/L Fe-BC for 0.1 g/L MB,which resulted in optimum Dye:Fe_(cat):H_(2)O_(2) ratio of 1:5:0.75(on g/L basis)or[Dye]:[Fe_(total)]:[H_(2)O_(2)]molar ratio of 1:6.2:7.0 respectively.The effective degradation of MB was identified over a wider pH range,and even after four consecutive runs Fe-BC maintained above 95%MB removal rate within 3 min of treatment with low Fe release,indicating strong stability and reusability.Under the optimum Dye:Fe_(cat):H_(2)O_(2)(g/L)condition at initial pH 4,the Fe-BC achieved 99.9%removal efficiency of MB within 3 min in heterogeneous Fenton reaction(HEFR)with much less H_(2)O_(2) concentration and low catalyst dosage,demonstrat-ing its efficiency and cost-effectiveness compared to other Fenton reaction catalysts.The removal velocity of MB showed two rate steps:a fast first stage followed by a slow stage with the rate in the order of H_(2)O_(2)/Fe-BC⋙H_(2)O_(2)/biochar>biochar>H_(2)O_(2).Overall,the developed Fe-BC is more economical with strong stability and recyclability for use in HEFR for treating recalcitrant pollutants.

Removal of ofloxacin antibiotic using heterogeneous Fenton process over modified alginate beads

The aim of this work is to study the heterogeneous oxidative degradation of ofloxacin antibiotic using a composite material prepared from sodium alginate and cyclohexane dinitrilo tetraacetic acid（CDTA）. The characterization tests indicated the successful incorporation of metal chelator and iron. It was also demonstrated that the synthesized beads are mesoporous. The influence of several experimental parameters（i.e.： H2O2 dose,working temperature, beads loading and initial drug concentration） on the process performances was evaluated. The reaction temperature significantly affects the drug conversion efficiency. It was also observed that the synthesized material was efficient toward the target antibiotic degradation in the presence of small quantities of hydrogen peroxide. Under optimum conditions（0.05 g of granules, initial drug concentration = 10 mg/L,25 μL of 10 mmol/L H2O2）, conducted in a batch reaction, 94% degradation of ofloxacin was reached. The results also indicate that the composite material showed a reasonable stability;a relatively low decrease of activity after four successive runs（only 9%） and a negligible iron leaching（0.8%） have been observed. The synthesized composite material offered interesting advantages in terms of simplicity, good stability, ease of recovery from the liquid medium after use and its efficiency in the presence of low quantities of oxidant. It constitutes a good candidate in the water treatment area.

Preparation and Characterization of Magnetic Banana Peels Biochar for Fenton Degradation of Methylene Blue

Co-precipitation method was used for the synthesis of biochar/Fe3O4 to heterogeneously degrade methylene blue (MB) in an aqueous medium. This catalyst was characterized by different techniques such as Fourier Transform Infrared (FTIR) Spectroscopy, X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDX) and Raman Microscopy. The analysis highlighted the presence of iron oxides on the surface of the biochar in the form of magnetite (Fe3O4). Catalytic tests performed on this composite showed significant degradation and simple magnetic separation in the solution for reuse. Maximum degradation was carried out after stirring it for 90 minutes in an MB aqueous solution at different concentrations. The percentages of degradation were 99% and 98.6% 93.3% and 91% for concentrations of MB 40 mg/L and 60 mg/L, 80 mg/L and 120 mg/L respectively. The reactions followed a second-order kinetics with correlation coefficients r2 = 0.9598, 0.9247, 0.9548 and 0.9614 for the same concentrations of MB at pH = 2, 0.2 mL/L H2O2 and 15 mg of biochar/Fe3O4. This work provides a simple and an effective method for the preparation of biochar/Fe3O4 and its use for the oxidation of MB by means of heterogeneous Fenton.

Fenton-Like Oxidation of Acid Yellow 23 in the Presence of Iron Rich Soil

Treatment of yellow dye 23 by heterogeneous Fenton-like process was studied using iron rich soil as an iron source. The iron rich soil sample was characterized by XRD, SEM and BET analysis. XRD pattern indicates that the iron rich soil is made of goethite and hematite. The reaction was systematically investigated under various experimental conditions such as pH, iron rich soil dosage, oxidant and dye concentrations. The result revealed that using iron rich soil as catalyst led to high discoloration efficiency (97.71% for 140 min of treatment) at pH = 2.5, 2 g/L iron rich soil and 16 m·mol/L H2O2. The degradation kinetics of acid yellow 23 can be described by a pseudo-first-order reaction following the Langmuir-Hinshelwood mechanism. The main roles of hydroxyl radicals in degradation process were investigated by adding of various radical scavengers.