Modeling the oxidation kinetics of Fenton's process on the degradation of humic acid

Low-pressure ultraviolet-H2O2 photolysis for restoring the anodic stripping voltammetry signal: a new strategy for the detection of heavy metal ions in complex organic matter

A new strategy based on low-pressure ultraviolet (LPUV)-H₂O₂ advanced oxidation photolysis for the quantitative determination of organic heavy metal ions (HMIs) in soil was proposed for the efficient, low-cost, accurate, and green detection of Pb(II) and Cd(II) in soil extracts by breaking the complexation of HMIs and organic matters, consequently restoring the ASV signals of target HMIs. The key parameters of the proposed LPUV-H₂O₂ photolysis system for the restoration of stripping responses were optimized; the conversion of organic matter to inorganic matter during the photolysis was investigated by total organic carbon (TOC); the degradation kinetics of humic acid sodium (HAS) was measured by UV-vis spectroscopy (UV); the pathway of HAS converted to small molecule organics during degradation was observed by fluorescence spectroscopy (FS); additionally, Fourier transform infrared spectroscopy (FTIR) was used to study the complexation between HAS and HMIs. The results showed that the stripping signals of target HMIs in the simulated soil samples can be restored to nearly 100% with a good repeatability, and the restoration ratio of the stripping signal fluctuated within 10%. And the feasibility of the proposed method for the accurate detection of HMIs in the real soil samples was verified; the results showed that 93.7% of Cd(II) and 92.5% of Pb(II) in real soil extracts were detectable.

Biodiesel production potential of microalgae, cultivated in acid mine drainage and livestock wastewater

The adaptability and biofuel production potential of two strains of microalgae isolated and cultivated in livestock wastewater effluent (LWE) with acid mine drainage (AMD) were investigated. The isolated strains of microalgae from samples obtained from LWE and AMD, two microalgal strains (Nephroselmis sp. KGE2 and Autodesmus obliquus KGE17) were selected based on their growth rate and lipid productivity. The dry cell weight of Nephroselmis sp. KGE2 and Autodesmus obliquus KGE17 after 20 days of cultivation in AMD increased from 0.05 to 0.59 g/L and from 0.05 to 0.55 g/L, respectively. These findings revealed a significant accumulation of fatty acids with increasing AMD content. Nephroselmis sp. KGE2 in LWE with 5% AMD demonstrated a higher growth rate (0.59 ± 0.03 g/L) and fatty acid production (401.5 ± 47.3 mg/L) than Autodesmus obliquus KGE17 with 5% AMD. Additionally, Nephroselmis sp. KGE2 had C16-C18 fatty acid content (92.4%) in LWE with AMD. Biodiesel produced from Nephroselmis sp. KGE2 had a higher cetane number (52.31) and iodine value (88.26 g I₂/100 g oil). Consequently, Nephroselmis sp. KGE2 can be considered a potential candidate for biodiesel production using AMD as an iron source.

Fenton pre-oxidation of natural organic matter in drinking water treatment through the application of iron nails

This study investigated for the first time the efficiency of an advanced oxidation process (AOP) zero valent iron/hydrogen peroxide (ZVI/H₂O₂) employing iron nails for the removal of Natural Organic Matter (NOM) from natural water of Regent's Park lake, London, UK. The low cost of nails and their easy separation from the water after the treatment make this AOP attractive for water utilities in low- and middle-income countries. The process was investigated as a pre-oxidation step for drinking water treatment. Results showed that UV254 removal in the natural water was lower than that of simulated water containing commercial humic acid (HA), indicating a matrix effect. Statistical analysis confirmed the maximum removal of dissolved organic carbon (DOC) in natural water depends on the initial pH (best at 4.5) and H₂O₂ dosage (best at 100% excess of stoichiometric dosage). DOC and UV254 removals under this operational condition were 51% and 89%, respectively. Molecular weight (MW) and specific UV absorbance (SUVA254) were significantly reduced to 74% and 78%, respectively. Formation of Chloroform THM in natural water sample after the ZVI/H₂O₂ process (initial pH 4.5) was below the limit for drinking water, and 48% less than the THM formation in the same water not subjected to pre-oxidation. Characterization of oxidation products on the iron-nail-ZVI surface after the ZVI/H₂O₂ treatment by SEM, XRD, and XPS identified the formation of magnetite and lepidocrocite. Results suggest that the investigated ZVI/H₂O₂ process is a promising technology for removing NOM and reducing THM formation during drinking water treatment.

Vital Role of Synthesis Temperature in Co–Cu Layered Hydroxides and Their Fenton-like Activity for RhB Degradation

Cu and Co have shown superior catalytic performance to other transitional elements, and layered double hydroxides (LDHs) have presented advantages over other heterogeneous Fenton catalysts. However, there have been few studies about Co–Cu LDHs as catalysts for organic degradation via the Fenton reaction. Here, we prepared a series of Co–Cu LDH catalysts by a co-precipitation method under different synthesis temperatures and set Rhodamine B (RhB) as the target compound. The structure-performance relationship and the influence of reaction parameters were explored. A study of the Fenton-like reaction was conducted over Co–Cu layered hydroxide catalysts, and the variation of synthesis temperature greatly influenced their Fenton-like catalytic performance. The Co–Cut=65°C catalyst with the strongest LDH structure showed the highest RhB removal efficiency (99.3% within 30 min). The change of synthesis temperature induced bulk-phase transformation, structural distortion, and metal–oxygen (M–O) modification. An appropriate temperature improved LDH formation with defect sites and lengthened M–O bonds. Co–Cu LDH catalysts with a higher concentration of defect sites promoted surface hydroxide formation for H2O2 adsorption. These oxygen vacancies (Ovs) promoted electron transfer and H2O2 dissociation. Thus, the Co–Cu LDH catalyst is an attractive alternative organic pollutants treatment.

The principle of detailed balancing, the iron-catalyzed disproportionation of hydrogen peroxide, and the Fenton reaction

The iron-catalyzed disproportionation of H₂O₂ has been investigated for over a century, as has been its ability to induce the oxidation of other species present in the system (Fenton reaction). The mechanisms of these reactions have been under consideration at least since 1932. Unfortunately, little or no attention has been paid to ensuring the conformity of the proposed mechanisms and rate constants with the constraints of the principle of detailed balancing. Here we identify more than 200 publications having mechanisms that violate the principle of detailed balancing. These violations occur through the use of incorrect values for certain rate constants, the use of incorrect forms of the rate laws for certain steps in the mechanisms, and the inclusion of illegal loops. A core mechanism for the iron-catalyzed decomposition of H₂O₂ is proposed that is consistent with the principle of detailed balancing and includes both the one-electron oxidation of H₂O₂ by Fe(III) and the Fe(II) reduction of HO₂˙.

Corrosion Inhibition and Disinfection of Heating and Cooling Water Systems Using In Situ Generated Hydrogen Peroxide

Aqueous solutions of MnCl2·4H2O and Tiron (disodium 4,5-dihydroxy-1,3-benzenedisulfonate) rapidly remove dioxygen (O2) from aqueous solution at a rate of ~20 mg∙ L -1 min-1 with turnover frequencies (TOFs) of up...

Preparation of Palm Oil Industry’s Biomass-Based Graphene Composite for the Adsorptive Removal of Methylene Blue

The ability of POME-based graphene shell composite (P-GSC), an adsorbent generated from oil palm wastes abundantly available in Malaysia such as POME and PKS, was examined in removing methylene blue (MB) dye by adsorption. Adsorption experiments, involving a batch column study and a batch equilibrium study, were conducted to investigate the efficiency of synthesized P-GSC from PKS as a base material in the removal of MB dye. The batch column study demonstrated that small-sized synthesized P-GSC from PKS as a base material could remove up to 98.5% for concentration. Therefore, the following batch equilibrium study was carried out on small-sized P-GSC only. Adsorption isotherms and kinetic isotherms were studied, from which the experimental data showed that the adsorption exhibited a good fit with the Freundlich model ( $R^2=0.8923$ ) and followed the pseudo-second order model ( $R^2>0.98$ ). FESEM, XPS, and XRD morphological and elemental analysis indicated the successful graphinization of POME on the P-GSC surface. The concept of deploying POME as the carbonaceous source to produce P-GSC, and then, deploying the resultant P-GSC as the adsorbent for MB dye removal has presented promising practical potential. Such cost-effective and environmentally friendly reuse of waste materials is envisioned to promote a ‘zero-waste industry.’

Securely anchored Prussian blue nanocrystals on the surface of porous PAAm sphere for high and selective cesium removal

Prussian blue (PB) has been well known as a pigment crystal to selectively sequestrate the radioactive cesium ion released from aqueous solutions owing to PB cage size similar to the cesium ion. Because the small size of PB is hard to deal with, the adsorbents containing PB have been prepared in the form of composites causing low sequestration efficiency of cesium. In this study, securely anchored PB nanocrystals on the surface of millimeter-sized porous polyacrylamide (PAAm) spheres (PB@PAAm) have been prepared by the crystallization of PB on the Fe³⁺ adsorbed PAAm. The securely anchored PB nanocrystals have been demonstrated to be selective and efficient adsorbents for sequestration of the radioactive cesium. The well-interconnected-spherical pores and millimeter-sized diameter of the PB@PAAm adsorbents facilitated permeation of Cs⁺ into the adsorbent and ease of handling respectively. Especially the well-interconnected-spherical pores allowed that PB@PAAm showed 90% of its maximum Cs⁺ adsorption capacity within 30 min. The PB@PAAm showed an outstanding Cs⁺ capture ability of 374 mg/g, high removal efficiency of 85% even at low concentration of Cs⁺ (10 ng/L), and superior selectivity of Cs⁺ against interference ions of Na⁺, K⁺, Mg²⁺, and Ca²⁺.

Can thermal intensification be considered a sustainable way for greening Fenton processes?

Life cycle assessment and kinetic modeling were used to elucidate the impact of thermal intensification (TI) on resource consumption and the techno-economic feasibility of a Fenton process at laboratory scale. Increasing temperature from 25 to 55 °C lowers treatment time (96.5%) and electricity use (67.8%) due to the positive impact of temperature on the reaction rate; however, beyond 50 °C no significant diminution in energy use, emissions, and operating cost was observed. The environmental footprint of the process is linked with energy use, operating pH, and the electricity share of the country; nevertheless, the impact of transport and infrastructure materials was lower. At 55 °C and pH of 2.8, emissions of precursors of freshwater and marine eutrophication, particulate matter formation, and ionizing radiation were reduced more than half; besides, in most of the midpoint categories, pondered by the ReCiPe-2016 method, emissions were lowered ca. 43.3%. The endpoint categories human health, ecosystem quality, and resource availability had a significant decline in disability-adjusted life years (46.0%), time-integrated species loss (42.0%), and surplus cost (33.1%). Harnessing the energy present in the wastewater itself decreased 41.9% global warming potential (GWP), but the use of steam for heating raised it 718.8%. In countries where electricity generation is dependent on fossil fuels, GWP could increase (2.0-20.0%) whereas GWP would decrease (8.8-9.4%) when renewable energy sources dominate. Operating at 55 °C and pH of 5.5 rose the reaction time (1835.5%), GWP (29.3%), particulate matter formation (44.3%), terrestrial acidification (21.8%), marine (48.9%), and freshwater eutrophication (66.7%). TI of Fenton processes could increase their treatment capacity with a small reduction in the quality of the effluent; furthermore, they can be made affordable for low-to-medium scale industries in emerging economies due to decreased resources consumption and emissions, leading to a lower treatment cost (US$0.49/m³).

Plutonium Redox Transformation in the Presence of Iron, Organic Matter, and Hydroxyl Radicals: Kinetics and Mechanistic Insights

Plutonium (Pu) redox and complexation processes in the presence of natural organic matter and associated iron can impact the fate and transport of Pu in the environment. We studied the fate of Pu(IV) in the presence of humic acid (HA) and Fe(II) upon reaction with H₂O₂ that may be generated by photochemical and other reactions. A portion of Pu(IV) was oxidized to Pu(V/VI), which is primarily ascribed to the generation of reactive intermediates from the oxidation of Fe(II) and Fe(II)-HA complexes by H₂O₂. The kinetics of Pu(IV) oxidation is pH-dependent and can be described by a model that incorporates Pu redox kinetics with published HA-modified Fenton reaction kinetics. At pH 3.5, the presence of HA slowed Pu(IV) oxidation, while at pH 6, HA accelerated Pu(IV) oxidation in the first several hours followed by a reverse process where the oxidized Pu(V/VI) was reduced back to Pu(IV). Analysis of Pu-associated particle size suggests that Pu oxidation state is a major driver in its complexation with HA and formation of colloids and heteroaggregates. Our results revealed the H₂O₂-driven oxidation of Pu(IV)-HA-Fe(II) colloids with implications to the transient mobilization of Pu(V/VI) in organic-rich redox transition zones.

Transformation kinetics and pathways of sulfamonomethoxine by UV/H2O2 in swine wastewater

Sulfamonomethoxine (SMM), as one of the most predominant antibiotics in animal wastewater, is pending for effective control to minimize its environmental risks. Transformation kinetics and pathways of SMM by UV/H₂O₂ in swine wastewater were systematically investigated in this study. Direct UV photolysis (as a dominant role) and ∙OH oxidation contributed to SMM degradation in UV/H₂O₂ system. The less effective reaction rate of SMM in real wastewater than synthetic wastewater (0.1-0.17 vs. ∼0.2-1.5 min^-1, despite higher H₂O₂ dosage and extended reaction time) resulted mainly from the abundant presence of conventional contaminants (indicated by COD, a notable competitor of SMM) in real wastewater. SMM degradation benefited from higher H₂O₂ dosage and neutral and weak alkaline conditions. However, the effect of initial SMM concentration on SMM degradation in synthetic and real wastewater showed opposite trends, owning to the different probability of SMM molecules to interact with UV and H₂O₂ in different matrices. Carbonate had an inhibitory effect on SMM degradation by scavenging ∙OH and pH-variation induced effect, while nitrate promoted SMM degradation by generating more ∙OH. The removal efficiency of SMM in real wastewater reached 91% under the reaction conditions of H₂O₂ of 10 mM, reaction time of 60 min, and pH 6.7-6.9. SMM degradation pathway was proposed as hydroxylation of benzene and pyrimidine rings, and secondary amine, and the subsequent cleavage of S-N bond.

Treatment of triethyl phosphate wastewater by Fenton oxidation and aerobic biodegradation

The conventional (i.e., aerobic biodegradation) and advanced (i.e., Fenton oxidation) treatment methods with implementation potentials were in parallel investigated for the treatment of industrial wastewater rich in organic phosphorus (Org.-P, dominated by triethyl phosphate (TEP)). Fenton effectively reduced Org.-P from 58 to 5 mg/L under the optimal reaction conditions of 20 mM H₂O₂, 14 mM Fe²⁺, pH 3.0, 120 mins' reaction time and the continuous dosing method (N = 4), following the first order kinetic model with a reaction rate constant of 0.07 min^-1. Nevertheless, the pretreatment prior to Fenton reaction (e.g., desalination) is recommended since high salinity significantly hindered TEP degradation, possibly due to the formation of Fe-Cl complexation and its scavenging effect to ∙OH. The Org.-P mineralization rate of ~98% was achieved by aerobic biodegradation. The excellent performance was maintained up to a salinity of 4.6% (w/w), higher than which the mineralization was seriously deteriorated. The high salinity could inhibit the microbial growth. This property might be responsible for the insufficient Org.-P removal during the on-site wastewater biological treatment. The Org.-P and COD concentrations were 6 and 405 mg/L respectively after the realistic wastewater treatment by biodegradation and coagulation, which meets with the municipal sewer discharge standard (GB/T 31962-2015).

Optimized synthesis of carbon-doped nano-MgO and its performance study in catalyzed ozonation of humic acid in aqueous solutions: Modeling based on response surface methodology

This research study focused on the optimization of the synthesis of carbon-doped nano-MgO (C-MgO) and the investigation of its catalytic capacity in a catalytic ozonation process (COP) for the removal of humic acid (HA). Characterization analyses, including SEM, EDX, XRD, BET, and photoluminescence test showed that the C-MgO was successfully synthesized. L8 orthogonal arrays according to the Taguchi methodology optimized the synthesis of the C-MgO as follows: sucrose to MgO ratio = 0.5, sonication time = 15 min, calcination temperature = 400 °C and pH = 10.5. A central composite design based on response surface methodology was employed to optimize and model the COP in the removal of HA. A quadratic polynomial model with p-value < 0.0001 and R² = 0.9988 showed a better fit to experimental responses. The optimum levels of the studied parameters in the COP based on the predictive model were obtained as follows: pH = 9.5, reaction time = 12 min, catalyst dose = 1 g/L, and HA concentration = 5 mg/L. The HA mineralization was determined to be 86.8% at the 100 min reaction time. Additionally, the COP exhibited 34% synergistic effect and the kinetic rate constant of 0.1898 min^-1 in the HA removal. The presence of tert-butanol, methanol, salicylic acid, and some anions did not significantly affect the removal of the HA in the COP. From a practical view, this report indicated that the C-MgO catalyst could be potentially applied in the COP for the treatment of the water having high concentrations of HA substances.

Feasibility analysis of homogenizer coupled solar photo Fenton process for waste activated sludge reduction

In this study, an attempt has been made to reduce the sludge using novel homogenizer coupled solar photo Fenton (HPF) process. At an optimum pH of 3 and Fe²⁺ to H₂O₂ dosage of 1:6, PF process yielded 63.7% solids reduction at a time interval of 45 min. Coupling of homogenizers with photo Fenton (PF) process effectively enhanced treatment efficiency. When homogenizer (specific energy - 1150.694 kJ/kg TS) was coupled with PF, a sharp increase in solid reduction 73.5% and decrease in reaction time (20 min) were observed. Cost benefit analysis revealed the efficiency of HPF process and achieved a net cost of 15.59 USD whereas PF achieved a negative net cost of -82.69 USD. Based on the above study it can be concluded that coupling of homogenizers with PF not only increased its efficiency but also make it field applicable.

Electrochemical treatment of humic acid using particle electrodes ensembled by ordered mesoporous carbon

In order to degrade the macromolecular pollutant of humic acid, the powder ordered mesoporous carbon (POMC, average pore diameter 4.29 nm) was first applied for preparing the granular OMC (GOMC, Φ × H = 4 × 3-6 mm) as electrodes in a continuous three-dimensional (3D) electrochemical system. The POMC was synthesized by hard-templating method and characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), particle size distribution, N₂ adsorption/desorption technology, and Fourier-transform infrared (FT-IR). The effects of electrochemical degradation parameters, such as current and hydraulic retention time (HRT), were investigated, and the degradation mechanism of HA was explored as well. The results indicated that the degradation efficiency of HA, chemical oxygen demand (COD), and total organic carbon (TOC) reached 95.3, 86.2, and 62.7%, respectively, under initial HA of 100 mg/L, current of 0.2 A, and HRT of 130 min. The detection of electron paramagnetic resonance (EPR) showed that plenty of ˙OH was generated on GOMC electrodes, which made the 3D system more effective than the conventional two-dimensional (2D) system. The cyclic voltammetry curves indicated that the reactions of HA on the OMC materials surface included both direct oxidation and direct reduction.

Fenton process on single and mixture components of phenothiazine pharmaceuticals: Assessment of intermediaries, fate, and preliminary ecotoxicity

Pharmaceuticals do not occur isolated in the environment but in multi-component mixtures and may exhibit antagonist, synergistic or additive behavior. Knowledge on this is still scarce. The situation is even more complicated if effluents or potable water is treated by oxidative processes or such transformations occur in the environment. Thus, determining the fate and effects of parent compounds, metabolites and transformation products (TPs) formed by transformation and degradation processes in the environment is needed. This study investigated the fate and preliminary ecotoxicity of the phenothiazine pharmaceuticals, Promazine (PRO), Promethazine (PRM), Chlorpromazine (CPR), and Thioridazine (THI) as single and as components of the resulting mixtures obtained from their treatment by Fenton process. The Fenton process was carried out at pH7 and by using 0.5-2mgL^-1 of [Fe²⁺]₀ and 1-12.5mgL^-1 of [H₂O₂]₀ at the fixed ratio [Fe²⁺]₀:[H₂O₂]₀ of 1:10 (w:w). No complete mineralization was achieved. Constitutional isomers and some metabolite-like TPs formed were suggested based on their UHPLC-HRMSⁿ data. A degradation pathway was proposed considering interconnected mechanisms such as sulfoxidation, hydroxylation, N-dealkylation, and dechlorination steps. Aerobic biodegradation tests (OECD 301 D and OECD 301 F) were applied to the parent compounds separately, to the mixture of parent compounds, and for the cocktail of TPs present after the treatment by Fenton process. The samples were not readily biodegradable. However, LC-MS analysis revealed that abiotic transformations, such hydrolysis, and autocatalytic transformations occurred. The initial ecotoxicity tested towards Vibrio fischeri as individual compounds featured a reduction in toxicity of PRM and CPR by the treatment process, whereas PRO showed an increase in acute luminescence inhibition and THI a stable luminescence inhibition. Concerning effects of the mixture components, reduction in toxicity by the Fenton process was predicted by concentration addition and independent action models.

Heat-activated persulfate oxidation of methyl- and ethyl-parabens: Effect, kinetics, and mechanism

We evaluated the degradation of methylparaben (MeP) and ethylparaben (EtP), two representative parabens, using the heat-activated persulfate system in a laboratory. Both sulfate and hydroxyl radicals contributed to the removal of the two parabens. The degradations of both MeP and EtP were improved by increasing the heating temperature or persulfate dose in accordance with a pseudo-first-order reaction model. The oxidation efficiency of parabens was found to be pH-dependent; decreasing in the order pH 5.0 > 7.0 > 9.0. The presence of chloride, bicarbonate, or humic acid was found to inhibit the degradation of the two parabens to some extent because of competition for the reactive radicals, with humic acid having the most serious effect. Dealkylation of the methyl unit, decarboxylation of the carboxylic group, and subsequent hydrolysis are proposed to be involved in the degradation pathway of MeP. The results suggest that the heat-activated persulfate system might be efficiently applied in the treatment of paraben-containing water samples. This was also supported by the results of applying this system to treat a real water sample containing both MeP and EtP.

Comparison of UV/hydrogen peroxide and UV/peroxydisulfate processes for the degradation of humic acid in the presence of halide ions

This study compared the behaviors of two classic advanced oxidation processes (AOPs), hydroxyl radical-based AOPs ((•)OH-based AOPs) and sulfate radical-based AOPs (SO4 (•-)-based AOPs), represented by UV/ hydrogen peroxide (H2O2) and UV/peroxydisulfate (PDS) systems, respectively, to degrade humic acid (HA) in the presence of halide ions (Cl(-) and Br(-)). The effects of different operational parameters, such as oxidant dosages, halide ions concentration, and pH on HA degradation were investigated in UV/H2O2/Cl(-), UV/PDS/Cl(-), UV/H2O2/Br(-), and UV/PDS/Br(-) processes. It was found that the oxidation capacity of H2O2 and PDS to HA degradation in the presence of halides was nearly in the same order. High dosage of peroxides would lead to an increase in HA removal while excess dosage would slightly inhibit the efficiency. Both Cl(-) and Br(-) would have depressing impact on the two AOPs, but the inhibiting effect of Br(-) was more obvious than that of Cl(-), even the concentration of Cl(-) was far above that of Br(-). The increasing pH would have an adverse effect on HA decomposition in UV/H2O2 system, whereas there was no significant impact of pH in UV/PDS process. Furthermore, infrared spectrometer was used to provide the information of degraded HA in UV/H2O2/Cl(-), UV/PDS/Cl(-), UV/H2O2/Br(-), and UV/PDS/Br(-) processes, and halogenated byproducts were identified in using GC-MS analysis in the four processes. The present research might have significant technical implications on water treatment using advanced oxidation technologies.

Degradation of phenol by a heterogeneous photo-Fenton process using Fe/Cu/Al catalysts

Cu²⁺ and Fe³⁺ can react with H₂O₂, producing Cu⁺, Fe²⁺, and ˙OH. Then ˙OH can react with phenol directly. The degradation of phenol leads to the formation of the mixed byproducts, such as catechol, benzoquinone, resorcinol and hydroquinone.

Influence of a reagents addition strategy on the Fenton oxidation of rhodamine B: control of the competitive reaction of ·OH

Microlevel competitive reactions of ·OH could be regulated by applying a macrolevel addition strategy of the Fenton reagents.

Enhancement effects of chelating agents on the degradation of tetrachloroethene in Fe(III) catalyzed percarbonate system

The performance of Fe(III)-based catalyzed sodium percarbonate (SPC) for stimulating the oxidation of tetrachloroethene (PCE) for groundwater remediation applications was investigated. The chelating agents citric acid monohydrate (CIT), oxalic acid (OA), and Glutamic acid (Glu) significantly enhanced the degradation of PCE. Conversely, ethylenediaminetetraacetic acid (EDTA) had a negative impact on PCE degradation, which may due to its strong Fe chelation and HO• scavenging abilities. However, excessive SPC or chelating agent will retard PCE degradation. In addition, investigations using free radical probe compounds and radical scavengers revealed that PCE was primarily degraded by HO• radical oxidation in both the chelated and non-chelated systems, while O2•- also participated in the non-chelated system and the OA and Glu modified systems. According to the electron paramagnetic resonance (EPR) studies, the presence of HO• in the Fe(III)/SPC system was maintained much longer than that in the Fe(II)/SPC system. The results indicated that the addition of CIT, OA or Glu indeed enhanced the generation of HO• in the first 10 min and promoted degradation efficiency by increasing the amount of Fe(III) and maintaining the concentration of HO• radicals in solution. In conclusion, chelated Fe(III)-based catalyzed SPC oxidation is a promising method for the remediation of PCE-contaminated groundwater.

Modeling the oxidation kinetics of sono-activated persulfate's process on the degradation of humic acid

Ultrasound degradation of humic acid has been investigated in the presence of persulfate anions at ultrasonic frequency of 40 kHz. The effects of persulfate anion concentration, ultrasonic power input, humic acid concentration, reaction time, solution pH and temperature on humic acid removal efficiency were studied. It is found that up to 90% humic acid removal efficiency was achieved after 2 h reaction. In this system, sulfate radicals (SO₄⁻·) were considered to be the mainly oxidant to mineralize humic acid while persulfate anion can hardly react with humic acid directly. A novel kinetic model based on sulfate radicals (SO₄⁻·) oxidation was established to describe the humic acid mineralization process mathematically and chemically in sono-activated persulfate system. According to the new model, ultrasound power, persulfate dosage, solution pH and reaction temperature have great influence on humic acid degradation. Different initial concentration of persulfate anions and humic acid, ultrasonic power, initial pH and reaction temperature have been discussed to valid the effectiveness of the model, and the simulated data showed new model had good agreement with the experiments data.

The degradation of antibiotic amoxicillin in the Fenton-activated sludge combined system

The present study investigated the removal efficiency of amoxicillin by the Fenton process, individual activated sludge process and Fenton-activated sludge combined system. For the antibiotic at 1 g L(-1), the optimal conditions of the Fenton process included: 4 mL FeSO4·7H2O solution (20.43 g  L(-1)), 6 mL H2O2 solution (3%) and 40°C. Under the optimal conditions, the removal rate of amoxicillin achieved up to 80% in 70 min. In addition, the impact of amoxicillin on microorganism limited the removal capacity of the activated sludge process. When the concentration of amoxicillin was less than 350 mg L(-1), 69.04-88.79% of the antibiotic was removed. However, the antibiotic could not be treated by the activated sludge when the concentration increased up to 650 mg L(-1). On the other hand, ifamoxicillin was pretreated partly by the Fenton process it was then degraded completely by the same activated sludge. Thus, the combined system included two steps: 80% amoxicillin was degraded in step I and was removed completely in the cheaper biological treatment (step II). Our result showed that compared with the individual activated sludge process, the Fenton process improved the removal capacity of the subsequent activated sludge process in the combined system.

A novel cell disruption technique to enhance lipid extraction from microalgae

Lipid extraction represents one of the main bottlenecks of the microalgal technology for the production of biofuels. A novel method based on the use of H2O2 with or without FeSO4, to disrupt the cell wall of Chlorella vulgaris and favor the subsequent extraction of lipids from wet biomass, is proposed. Experimental results show that, when disruption is performed under suitable operating conditions, the amount of lipids extracted is significantly increased with respect to the case where a classical approach is applied. Moreover, quality of lipids extracted after disruption seems to be improved in view of their exploitation for producing biofuels.

Fenton Oxidation Kinetics and Intermediates of Nonylphenol Ethoxylates

Removal of nonylphenol ethoxylates (NPEOs) in aqueous solution by Fenton oxidation process was studied in a laboratory-scale batch reactor. Operating parameters, including initial pH temperature, hydrogen peroxide, and ferrous ion dosage, were thoroughly investigated. Maximum NPEOs reduction of 84% was achieved within 6 min, under an initial pH of 3.0, 25°C, an H₂O₂ dosage of 9.74×10^-3 M, and a molar ratio of [H₂O₂]/[Fe²⁺] of 3. A modified pseudo-first-order kinetic model was found to well represent experimental results. Correlations of reaction rate constants and operational parameters were established based on experimental data. Results indicated that the Fenton oxidation rate and removal efficiency were more dependent on the dosage of H₂O₂ than Fe²⁺, and the apparent activation energy (ΔE) was 17.5 kJ/mol. High-performance liquid chromatography and gas chromatograph mass spectrometer analytical results indicated degradation of NPEOs obtained within the first 2 min stepwise occurred by ethoxyl (EO) unit shortening. Long-chain NPEOs mixture demonstrated a higher degradation rate than shorter-chain ones. Nonylphenol (NP), short-chain NPEOs, and NP carboxyethoxylates were identified as the primary intermediates, which were mostly further degraded.

Cosmetic wastewater treatment using the Fenton, Photo-Fenton and H2O2/UV processes

Advanced Oxidation Processes (AOPs), such as the Fenton, photo-Fenton and H2O2/UV processes, have been investigated for the treatment of cosmetic wastewaters that were previously coagulated by FeCl3. The Photo-Fenton process at pH 3.0 with 1000/100 mg L(-1) H2O2/Fe(2+) was the most effective (74.0% Chemical Oxygen Demand (COD) removal). The Fenton process with 1200/500 mg L(-1) H2O2/Fe(2+) achieved a COD removal of 72.0%, and the H2O2/UV process achieved a COD removal of 47.0%. Spreading the H2O2 doses over time to obtain optimal conditions did not improve COD removal. The kinetics of the Fenton and photo-Fenton processes may be described by the following equation: d[COD]/dt = -a[COD] t(m) (t represents time and a and m are constants). The rate of COD removal by the H2O2/UV process may be described by a second-order reaction equation. Head Space, Solid-Phase MicroExtraction, Gas Chromatography and Mass Spectrometry (HS-SPME-GC-MS) were used to identify 48 substances in precoagulated wastewater. Among these substances, 26 were fragrances. Under optimal AOP conditions, over 99% of the identified substances were removed in 120 min.

Application of circuit simulation method for differential modeling of TIM-2 iron uptake and metabolism in mouse kidney cells

Circuit simulation is a powerful methodology to generate differential mathematical models. Due to its highly accurate modeling capability, circuit simulation can be used to investigate interactions between the parts and processes of a cellular system. Circuit simulation has become a core technology for the field of electrical engineering, but its application in biology has not yet been fully realized. As a case study for evaluating the more advanced features of a circuit simulation tool called Advanced Design System (ADS), we collected and modeled laboratory data for iron metabolism in mouse kidney cells for a H ferritin (HFt) receptor, T cell immunoglobulin and mucin domain-2 (TIM-2). The internal controlling parameters of TIM-2 associated iron metabolism were extracted and the ratios of iron movement among cellular compartments were quantified by ADS. The differential model processed by circuit simulation demonstrated a capability to identify variables and predict outcomes that could not be readily measured by in vitro experiments. For example, an initial rate of uptake of iron-loaded HFt (Fe-HFt) was 2.17 pmol per million cells. TIM-2 binding probability with Fe-HFt was 16.6%. An average of 8.5 min was required for the complex of TIM-2 and Fe-HFt to form an endosome. The endosome containing HFt lasted roughly 2 h. At the end of endocytosis, about 28% HFt remained intact and the rest was degraded. Iron released from degraded HFt was in the labile iron pool (LIP) and stimulated the generation of endogenous HFt for new storage. Both experimental data and the model showed that TIM-2 was not involved in the process of iron export. The extracted internal controlling parameters successfully captured the complexity of TIM-2 pathway and the use of circuit simulation-based modeling across a wider range of cellular systems is the next step for validating the significance and utility of this method.

Global parameter of ultrasound exploitation (GPUE) in the reactors for wastewater treatment by sono-Fenton oxidation

Modeling of the sonochemical reactors presents a great challenge due to issues related to the experimental investigation and description of the primary effects of the ultrasound. The main idea proposed in this work was to establish an algorithm consisting of the viable laboratory analyses and basic elements of chemical reaction engineering. In this paper, a novel modeling approach is presented. Proposed approach is characterized by the following; ultrasound was investigated as an auxiliary source of energy and the kinetic constants determined for the basic oxidation reactions, i.e. Fenton type oxidation were treated as independent of the ultrasound. Sonochemical effectiveness factor is expressed as a global parameter of the ultrasound exploitation (GPUE) that was introduced in the kinetic model as the e(US) factor. Factor e(US) is modeled as a function of employed frequency, actual power of the transducer, portion of the cavitationally active zone, i.e. dimensionless active volume and the average temperature in the reactor. Lumped system has been assumed. In order to obtain all the necessary data, the experimental study included different sets of experiments. The kinetics of the sonochemical processes, e.g. US/Fe(2+)/H(2)O(2), US/Fe(2+)/S(2)O(8)(2-), US/Fe(2+)/HSO(5)(-) was investigated in the term of mineralization of model wastewaters containing different types of organic pollutants. The Weissler dosimetry and peroxodisulfate decomposition upon sonication, were used to facilitate the determination of e(US). They follow zero order kinetics, thus can be used as a model reaction to reflect all the primary effects of ultrasound and to establish the empirical correlation for e(US) calculation. Finally, GPUE has been introduced in the adequate kinetic models and the overall model was validated.

Effects of UV irradiation on humic acid removal by ozonation, Fenton and Fe⁰/air treatment: THMFP and biotoxicity evaluation

Effects of UV irradiation on humic acid (HA) removal by Fe(0)/air, ozonation and Fenton oxidation were investigated. The trihalomethane forming potential (THMFP) and toxicity of treated solutions were also evaluated. The experimental conditions were ozone of 21 mg min(-1), H(2)O(2) of 8 × 10(-4)M, Fe(0) of 20 g L(-1), air flow of 5 L min(-1), and UVC of 9 W. Results indicated that Fe(0)/air rapidly removed HA color (>99%) and COD (90%) within 9 min. 51-81% of color and 43-50% of COD were removed by ozonation and Fenton oxidation after 60 min. Both UV enhanced ozone and Fenton oxidation removed HA, but the Fe(0)/air process did not. Spectrum results showed all processes effectively diminished UV-vis spectra, except for ozonation. The THMFP of Fe(0)/air-treated solution (114 μg L(-1)) was much lower than those of Fenton- (226 μg L(-1)) and ozonation-treated solutions (499 μg L(-1)). Fe(0)/air with UV irradiation obviously increased the THMFP of treated solution (502 μg L(-1)). The toxicity results obtained from Vibrio fischeri light inhibition test indicated that the toxicity of Fe(0)/air-treated solution (5%) was much lower than that of ozonation- (33%) and Fenton-treated solutions (31%). Chlorination increased the solution toxicity. The correlation between biotoxicity and chloroform in the chlorinated solution was insignificant.

Humic acid coated Fe3O4 magnetic nanoparticles as highly efficient Fenton-like catalyst for complete mineralization of sulfathiazole

Humic acid coated Fe(3)O(4) magnetic nanoparticles (Fe(3)O(4)/HA) were prepared for the removal of sulfathiazole from aqueous media. Fe(3)O(4)/HA exhibited high activity to produce hydroxyl (OH) radicals through catalytic decomposition of H(2)O(2). The degradation of sulfathiazole was strongly temperature-dependent and favored in acidic solution. The catalytic rate was increased with Fe(3)O(4)/HA dosage and H(2)O(2) concentration. When 3 g L(-1) of Fe(3)O(4)/HA and 0.39 M of H(2)O(2) were introduced to the aqueous solution, most sulfathiazole was degraded within 1h, and >90% of total organic carbon (TOC) were removed in the reaction period (6h). The major final products were identified as environmentally friendly ions or inorganic molecules (SO(4)(2-), CO(2), and N(2)). The corresponding degradation rate (k) of sulfathiazole and TOC was 0.034 and 0.0048 min(-1), respectively. However, when 3 g L(-1) of bare Fe(3)O(4) were used as catalyst, only 54% of TOC was eliminated, and SO(4)(2-) was not detected within 6h. The corresponding degradation rate for sulfathiazole and TOC was 0.01 and 0.0016 min(-1), respectively. The high catalytic ability of Fe(3)O(4)/HA may be caused by the electron transfer among the complexed Fe(II)-HA or Fe(III)-HA, leading to rapid regeneration of Fe(II) species and production of OH radicals.