Final TOC Research Articles

Recycling Fe and improving organic pollutant removal via in situ forming magnetic core-shell Fe3O4@CaFe-LDH in Fe(II)-catalyzed oxidative wastewater treatment

Due to its high efficiency, Fe(II)-based catalytic oxidation has been one of the most popular types of technology for treating growing organic pollutants. A lot of chemical Fe sludge along with various refractory pollutants was concomitantly produced, which may cause secondary environmental problems without proper disposal. We here innovatively proposed an effective method of achieving zero Fe sludge, reusing Fe resources (Fe recovery = 100%) and advancing organics removal (final TOC removal > 70%) simultaneously, based on the in situ formation of magnetic Ca-Fe layered double hydroxide (Fe3O4@CaFe-LDH) nano-material. Cations (Ca2+ and Fe3+) concentration (≥ 30 mmol/L) and their molar ratio (Ca:Fe ≥ 1.75) were crucial to the success of the method. Extrinsic nano Fe3O4 was designed to be involved in the Fe(II)-catalytic wastewater treatment process, and was modified by oxidation intermediates/products (especially those with COO− structure), which promoted the co-precipitation of Ca2+ (originated from Ca(OH)2 added after oxidation process) and by-produced Fe3+ cations on its surface to in situ generate core-shell Fe3O4@CaFe-LDH. The oxidation products were further removed during Fe3O4@CaFe-LDH material formation via intercalation and adsorption. This method was applicable to many kinds of organic wastewater, such as bisphenol A, methyl orange, humics, and biogas slurry. The prepared magnetic and hierarchical CaFe-LDH nanocomposite material showed comparable application performance to the recently reported CaFe-LDHs. This work provides a new strategy for efficiently enhancing the efficiency and economy of Fe(II)-catalyzed oxidative wastewater treatment by producing high value-added LDHs materials.

Application of Photo-Fenton, Electro-Fenton, and Photo-Electro-Fenton processes for the treatment of DMSO and DMAC wastewaters

Biological treatment, due to the formation of hazardous chemicals to remove organic compounds such as dimethyl sulfoxide (DMSO) and N, N-dimethylacetamide (DMAC), has limited potential. Advanced oxidation processes (AOPs) are regarded as a viable alternative for treating molecules containing carbon-hydrogen bonds that cannot be broken down by traditional physico-chemical methods. In this investigation, various AOPs such as Photo-Fenton, Electro-Fenton, and Photo-Electro-Fenton processes were studied to treat wastewaters containing DMSO and DMAC. The effects of the operating parameters, including various initial concentrations of DMSO and DMAC, initial pH, reaction time, different concentrations of Fenton’s reagent, power of UV lamp, different concentrations of electrolytes, the distance between electrodes and current intensity, were investigated. The findings of the experiments revealed that a pH of 3 and a reaction time of 120 min were optimal. At 2000 mg L−1 of DMSO, maximum degradation and the final concentration of TOC were 98.64 % and 256.8 mg L−1, respectively, by the Electro-Fenton process under the optimal conditions. The Electro-Fenton process was successful in determining the maximum degradation of DMAC (96.31 %) and the final TOC concentration (10.03 mg L−1) at 250 mg L−1 of DMAC under optimal conditions. Finally, it can be concluded that the Electro-Fenton process was the best process for the efficient removal of DMSO and DMAC. The second step of the kinetic model follows a pseudo-first-order reaction for 250 and 500 mg L−1 of pollutants and obeyed a pseudo-second-order kinetic model for concentrations of 1000, 2000 mg L−1.

Gentle one-step co-precipitation to synthesize bimetallic CoCu-MOF immobilized laccase for boosting enzyme stability and Congo red removal

Laccase has received extensive attention in pollutant degradation due to its high efficiency and environmental friendliness, but free laccase has poor stability, easy inactivation, and difficulty in recycling, which limited its application. It was a smart strategy to construct a synergistic system for the efficient adsorption and degradation of pollutants by enzyme immobilization to improve the stability and recyclability of the enzyme. In this study, the materials were synthesized by a one-step co-precipitation method. With Cu-MOF as the main body, Co2+ was introduced to construct bimetallic CoCu-MOF as the protective carrier of the enzyme. The enzyme-carrying capacity and enzyme activity of Lac@CoCu-MOF were 2-fold and 3.5-fold higher than those of Lac@Cu-MOF, respectively. Lac@MOF composites had a good protective effect on enzyme in various interfering environments. At pH = 7, free laccase was completely inactivated and Lac@CoCu-MOF maintained 51.76% enzyme activity. In addition, the removal rate of Congo red by Lac@CoCu-MOF reached 90 % in 1 h at pH = 4 % and 95 % in 5 h at pH = 7, and the final TOC mineralization rate reached 86.05 %. After six cycles, the degradation rate of Lac@CoCu-MOF remained above 75 %. Therefore, Lac@CoCu-MOF was constructed with the advantages of enzyme immobilization (enhanced stability and easy operation), material adsorption, and biocatalysis (fast diffusion and high activity), which has great guiding significance for the industrial application of enzyme.

Pyridine degradation characteristics of a newly isolated bacterial strain and its application with a novel reactor for the further treatment in pyridine wastewater

A pyridine-degrading strain Gemmobacter sp. ZP-12, isolated from an activated sludge, was able to use pyridine as the sole carbon and nitrogen source for the growth. The strain could effectively degrade pyridine and remove TOC over a wide range of initial pyridine concentrations. The pyridine degradation rate for 100, 500, 1000, 1500 and 2000 mg/L was 2.90 ± 0.17; 13.72 ± 0.21, 20.40 ± 0.24, 31.09 ± 0.26, 27.63 ± 0.17 mg/L/h, respectively. During the pyridine degraded, a large amount of NH4+-N was released and accumulated. The accumulation of NH4+-N increased with the increase of pyridine concentration. For further removing the NH4+-N producing in pyridine degradation, an aerobic-moving bed biofilm reactor coupled with intermittent-aeration membrane biological reactor (a-MBBR-IMBR) was constructed, in which the strain and the aerobic / anoxic mixed sludge combined to remove the pollutants in the wastewater containing 500 mg/L pyridine. After 96 h of operation, the final TOC removal efficiency was 96.5 ± 1.05 %. The average residual concentration of NO3−-N and NH4+-N was respectively 9.09 ± 4.13 mg/L and 7.85 ± 3.88 mg/L. The study provides a viable option for treating pyridine wastewater.

Ni-Fe layered double hydroxides catalized ozonation of synthetic wastewater containing Bisphenol A and municipal secondary effluent

Ni-Fe Layered Double Hydroxides (Ni-Fe LDHs) was prepared, characterized and used as catalyst in heterogeneous catalytic ozonation of Bisphenol A (BPA) and other organic compounds in secondary effluent. The characterization and ozonation results revealed that the Ni-Fe LDHs possessing a Ni: Fe ratio of 3:1 had the best crystalline and the highest affinity for ozone. Under the optimized conditions, the final TOC and COD removal achieved was 56% and 68%, respectively. BPA in the secondary effluent could be removed completely by Ni3-Fe LDH catalyzed ozonation. The organic compounds removal was mainly attributed to the oxidation by free active radicals such as hydroxyl radicals (OH). In this research the accumulative ·OH in the reaction system was determined to be 28.2 μmol at the reaction time of 60 min. The free active radicals were mostly generated through the electron transfer among different valences of metals on Ni-Fe LDHs surface, and subsequently diffused into bulk solution to oxidize the target organic compounds there.

Physico-chemical and biological aspects of a serially connected lab-scale constructed wetland-stabilization tank-GAC slow sand filtration system during removal of selected PPCPs

A serially connected lab-scale Greater duckweed constructed wetland (CW)-stabilization tank (ST)-GAC sandwich slow sand filtration system was tested to remove four widely detected pharmaceuticals and personal care products (PPCPs) from natural water with a spiked concentration of 25 μg/L. High removals were achieved rapidly (93.5–100%), being on average 95.9%, 99.1%, 98.1% and 97.4% for DEET, paracetamol, caffeine and triclosan (n = 3), respectively. Except for DEET, no significant difference was observed between overall removals with and without artificial aeration in CW tank (p > 0.05), showing good stability of the system. COD was considerably removed under aeration and final TOC removal was 64.7%. Nitrite, nitrate, ammonia and phosphate were not detected at the end of the test (day 26). The microbial community structure in three connected units of the tested system showed differences and good stability after the aerators were removed. Proteobacteria was the most dominant phylum among the 47 phyla found. Microbes attaching to the Greater duckweed contributed more to the microbial community structure in CW and ST tanks than original natural water. However, at the end of the run, the structural differences among three units decreased. After aeration stopped, phylum composition became more stable in ST tank while CW tank showed small structural variation throughout the test. Various correlations were found between detected phyla, among which Proteobacteria and Bacteroidetes showed a significant negative correlation (R = −0.73, p < 0.001, FDR corrected). Good removal of target PPCPs and stability of the system show the potential application of this combined treatment process.

Approaching zero discharge concept in refineries by solar–assisted photo-Fenton and photo-catalysis processes

To undertake a better water management in Oil&Gas sector, it is essential to decrease the wastewater generation by increasing the current reused water rates. Focused on this motivation, this study presents the performances of solar-assisted photo-Fenton and heterogeneous photo-catalysis on refinery wastewater treatment for reuse purposes with the aim of zero discharge. While initial tests were made on synthetic refinery wastewater, real case studies were performed with two types of refinery effluent in order to test the feasibility of using AOPs either as a secondary or tertiary treatment. Even though heterogeneous photo-catalysis and a combined process showed promising results for the treatment of the refinery effluents, photo-Fenton treatment revealed a superior effectiveness for application in both secondary and tertiary treatment, considering the improvements on TOC removal, toxicity and biodegradability. Photo-Fenton as secondary treatment resulted as efficient as the biological treatment, reaching final TOC values ca. 20 mg/L and 88% of COD removal presenting values lower than those achieved after the biological treatment. Moreover, a marked increase in the BOD5/COD ratio from 0.38 to 0.83 was obtained. Furthermore, as a tertiary treatment, photo-Fenton process either with H2O2/COD = 10 and H2O2/Fe2+ = 50 or H2O2/COD = 4 and H2O2/Fe2+ = 10 provided a final TOC value <4 mg/L. This result reveals the possibility to reuse the effluent in the refinery plant, thus increasing the sustainability.

Paracetamol mineralization by Photo Fenton process catalyzed by a Cu/Fe-PILC under circumneutral pH conditions

This study presents an iron-pillared clay (Fe-PILC) ion-exchanged with copper (Cu/Fe-PILC), as an efficient catalyst to conduct the mineralization of paracetamol through photo-Fenton process at near to neutral pH without precipitation of Fe complexes and without adding any chemicals to modify the initial pH. The specific surface area of the catalyst was of 110 m2 g−1 and with the following phases FeO, Fe3O4, Cu2O, CuO determined by XPS analyses. Around 80% of mineralization was reached either by conducting the process at acidic and circumneutral pH conditions, and the efficiency was not significantly higher at pH = 2.7. The intermediate reaction products generated at both pH conditions essayed and detected by LC–MS were hydroquinone, acetamide and oxamic acid. Catalyst Cu/Fe-PILC showed an iron leaching of about 3% after reaction while the reusability of the catalyst involved a decrease in mineralization of only 3% under circumneutral conditions. The final TOC of about 20% can be ascribed to the presence of acetamide that was found to be the most reluctant towards oxidation.

Removal of imidazolium- and pyridinium-based ionic liquids by Fenton oxidation.

The oxidation of imidazolium (1-hexyl-3-methylimidazolium chloride, HmimCl) and pyridinium (1-butyl-4-methylpyridinium chloride, BmpyrCl) ionic liquids (ILs) by Fenton's reagent has been studied. Complete conversion was achieved for both ILs using the stoichiometric H2O2 dose at 70°C, reaching final TOC conversion values around 45 and 55% for HmimCl and BmpyrCl, respectively. The decrease in hydrogen peroxide dose to substoichiometric concentrations (20-80% stoichiometric dose) caused a decrease in TOC conversion and COD removal and the appearance of hydroxylated oxidation by-products. Working at these substoichiometric H2O2 doses allowed the depiction of a possible degradation pathway for the oxidation of both imidazolium and pyridinium ILs. The first step of the oxidation process consisted in the hydroxylation of the ionic liquid by the attack of the ·OH radicals, followed by the ring-opening and the formation of short-chain organic acids, which could be partially oxidized up to CO2 and H2O. At H2O2 doses near stoichiometric values (80%), the resulting effluents showed non-ecotoxic behaviour and more biodegradable character (BOD5/COD ratio around 0.38 and 0.58 for HmimCl and BmpyrCl, respectively) due to the formation of short-chain organic acids. Graphical abstract ᅟ.

Electrocatalytic phenol degradation by a novel nanostructured carbon fiber brush cathode coated with graphene ink

A new promising electrochemically-exfoliated graphene-based cathode for the electrocatalytic Fenton process was elaborated by an ink-coating technique. For this purpose, a method to coat graphene ink over a carbon-fiber brush substrate (referred to as Gr-Brush) was optimized and a 1:3 (w/w) Nafion®:graphene ratio increased the H2O2 accumulation yield by 40% (4.23 mg-H2O2 L−1 cm−2), as compared to an uncoated brush. Such improvement was attributed to the higher electroactive surface area and conductivity of Gr-Brush, a fact confirmed by cyclic voltammetry and impedance measurements. Due to a remarkable raise of OH production during the electro-Fenton (EF) process, the phenol degradation rate more than doubled and the mineralization yield increased from 78% (final total organic carbon, TOC, concentration of 5.28 mg-C L−1) with an uncoated brush to 98.5% (final TOC concentration of 0.34 mg-C L−1) with Gr-Brush, following 6 h of EF treatment. Furthermore, the energy required to achieve 40% of phenol mineralization with Gr-Brush was as low as 0.10 kWh g-1 TOC, which outcompeted any other existing graphene-based carbon cathode material coated with either electrochemically-exfoliated graphene (e.g., 0.20 kWh g-1 TOC with carbon cloth) or reduced graphene oxide (rGO) (e.g., 0.53 kWh g-1 TOC with carbon felt), a crucial feature for prospective applications of the novel electrode.

Electrochemical Treatment of 4-Hydroxyphenylacetic Acid in Olive Oil Mill Wastewater

INTRODUCTION The decontamination of olive oil mill wastewater (OMWW) is of great interest in Mediterranean countries as the main producers of olive oil worldwide. The large variety of recalcitrant substances contained in OMWW and the difficulty to remove them or recycle the large volumes of wastewater encourage the development of new technologies for decontamination, like electrochemical advanced oxidation processes (EAOPs) that present high performance for recalcitrant compounds [1,2]. 4-Hydroxyphenylacetic acid (4-HPA) is a main component of this kind of wastewater [3]. This communication presents the effective removal of 4-HPA from an OMWW matrix by EAOPs including anodic oxidation with electrogenerated H2O2 (AO-H2O2), electro-Fenton (EF) and UVA photoelectro-Fenton (PEF). EXPERIMENTAL Analytical grade 4-HPA was purchased from Sigma. The OMWW was provided by a local company of olive oil extraction, which was characterized by analyzing its metal content, BOD, COD, TOC, conductance, TS, TDS and organic components before use. As a first step, the OMWW was filtered with a 45 µm cloth. As a second step, several mixtures with 100 mg L-1 TOC of 4-HPA in OMWW were prepared. The OMWW/water ratio was varied from 20/80 to 100/0 v/v. Experiments were also carried out using 100 mg L-1 TOC of 4-HPA in 50 mM of Na2SO4 to clarify the matrix effect. AO-H2O2, EF and PEF experiments were performed with 100 mL of each solution at pH 3.0 and 25 ºC using a stirred tank reactor with a 3 cm2 boron-doped diamond (BDD) anode and a 3 cm2 carbon-polytetrafluoroethylene air-diffusion cathode by applying 16.7 mA cm-2 for 540 min. In the two latter methods, 0.50 mM Fe2+ was added as catalyst for Fenton’s reaction. PEF trials were run with a 6W UVA light. RESULTS The characteristics of the real OMWW were: 505.35 mg L-1 of TOC, 1.51 mS of conductance, 1600 mg L-1 of BOD, 5536 mg L-1 of TS and 82 mgL-1 of TDS. For each method, a gradual decay in TOC was found as the OMWW ratio in the sample increased. For example, a final TOC removal of 89% was achieved by AO-H2O2 in 50 mM Na2SO4, whereas it was reduced by 75% in a 60/40 OMWW/water mixture and 60% in pure OMWW. The best results were obtained by PEF, with final TOC decays of 98%, 88% and 87% in a the above media due to the combined action of ●OH produced at the BDD surface from water oxidation, the ●OH formed during Fenton’s reaction and the extra decomposition of Fe(III)-carboxylate complexes by UVA light. The kinetic assays also showed a drop in 4-HPA decay with raising OMWW content. Thus, total disappearance of the substrate was attained in 360 min by AO-H2O2 in 50 mM Na2SO4 and in 500 min for the other solutions. For the best process (i.e., PEF), these times diminished to 60 and 80 min, respectively. CONCLUSIONS 4-HPA can be effectively degraded in an OMWW matrix using the EAOPs studied, especially PEF. This process was the most efficient one, reaching an almost total mineralization, to a larger extent in pure Na2SO4. The decay and mineralization of 4-HPA rose in the order AO-H2O2 < EF < PEF, regardless of the matrix used. The oxidation power of ●OH formed from water oxidation at the BDD surface in AO-H2O2 was strongly enhanced by the additional ●OH in the bulk from Fenton’s reaction, being the degradation improved under the potent action of UVA irradiation in PEF. For all the EAOPs studied, the presence of OMWW decelerated TOC removal and 4-HPA decay. This can be related to the parallel reactions of ●OH with the organic components present in OMWW that act as oxidant scavengers. ACKNOWLEDGEMENTS We are grateful for economical support from project CTQ2016-78616-R (MINECO, FEDER, EU) and for the scholarship given to N.E Flores from SENESCYT (Ecuador). BIBLIOGRAPHY [1] A. Thiam, E. Brillas, F. Centellas, P.L. Cabot, I. Sirés, Electrochemical reactivity of Ponceau 4R (food additive E124) in different electrolytes and batch cells, Electrochim. Acta 173 (2015) 523. [2] A. Thiam, E. Brillas, J.A. Garrido, R.M. Rodríguez, I. Sirés, Routes for the electrochemical degradation of the artificial food azo-colour Ponceau 4R by advanced oxidation processes, Appl. Catal. B: Environ. 180 (2016) 227. [3] C. Belaid, M. Khadraoui, S. Mseddi, M. Kallel, B. Elleuch, J.F. Fauvarque, Electrochemical treatment of olive mill wastewater: Treatment extent and effluent phenolic compounds monitoring using some uncommon analytical tools, J. Environ. Sci. 25 (2013) 220.

Synergetic effect of gliding arc discharge treatment and biosorption for removal of nitrophene and glycine from aqueous solution

The degradation of simulate house effluent containing Nitrophene and Glycine was carried out using gliding arc plasma reactor, one of the upcoming advance oxidation techniques. Aiming to reduce energy cost of treatment, the effect of various parameters such as treatment time, post-discharge phenomenon and addition of Jatropha natural biomass have been discussed. The experiments were conducted at a gas flow rate of 800L/h. The degradation rate depends on the flow of highly oxidizing species formed in the plasma arc and on the sorbent/liquid contact surface time. Furthermore, the kinetic process of the in-situ treatment follows the pseudo-first order model while the post-discharge phenomenon is governed by the general order kinetic model. The initial high polluted solution with 950mg/L TOC is degraded to 658mg/L as final TOC after 1h of in-situ treatment and to 460mg/L TOC after 6h in post-discharges. The use of Jatropha shell as biosorbent in addition of the plasma treatment reduces the TOC from 950 to 530mg/L for in-situ treatment and, to 280mg/L after 6h in post-discharge. These results have showed that it is possible to significantly improve the efficiency of plasma treatment by incorporating modified agricultural residues. The occurrence of CO2 is detected during the plasma treatment by Dräger tube analyser, while NO2− and NO3− are also identified by colorimetric tests.

Electrochemical treatment of artificial humidity condensate by large-scale boron doped diamond electrode

Electrochemical treatment of artificial humidity condensate (AHC) in confined space has been conducted. Large-scale boron-doped diamond (BDD) film was deposited on Ta substrate by hot filament chemical vapor deposition, and its uniformity was evaluated by the Raman shift intensities on the basis of statistical analysis. BDD electrode was used as anode for the oxidation of organic compounds, and almost 98% final TOC removal efficiency of AHC was achieved. Higher oxidation rate constant, higher initial instantaneous current efficiency and lower specific energy consumption were obtained for the larger surface area electrode. Based on the detection of intermediates by HPLC and IC, a possible degradation pathway of AHC was also proposed. In addition, the potential utilization of H2 generated on cathode for fuel cell was discussed. It is estimated that about 5% electric energy can be offset the electrochemical treatment cell by using the integrated operation.

Hydrogen production using Pt-loaded TiO2 photocatalysts

A series of synthesised TiO2-based and commercial photocatalysts were modified by Pt photodeposition and a study made of their photocatalytic activity in hydrogen production. The modified commercial photocatalysts were Evonik P25, Kronos vlp7000 and Hombikat UV-100, and the other modified photocatalysts were synthesised by our group using sol–gel and sol–gel hydrothermal processes (SG400, SG750 and HT). Pt weight percentages used in the study were 0.5, 1.0 and 2.1 wt.% (Pt/TiO2). The photocatalysts were extensively characterised by X-ray diffraction (XRD), UV–vis diffuse reflectance, Brunauer–Emmett–Teller (BET) surface area measurement, transmission electron microscopy (TEM), scanning electron microscopy (SEM–EDX), Fourier transform infrared spectroscopy (FTIR) and laser light dispersion. Methanol (25% vol.) was used as sacrificial agent over the 8 h of the hydrogen production tests and measurements were taken of the final concentrations of formaldehyde and formic acid as well as initial and final TOC. Photoactivity of all photocatalysts increased in the presence of Pt. The most efficient of the synthesised photocatalysts was SG750 and of the commercial photocatalysts P25. Maximum production of SG750 was 1846 μmol h−1 at 1.0 wt.% Pt and its production per surface unit was notably higher than that of P25.

Aerobic degradation of phenolics and aromatic hydrocarbons in presence of cyanide

Present study focused on the degradation of a mixture of phenol, cresol, xylenol, quinoline, and indole along with cyanide, commonly found in coke oven wastewater, using aerobic mixed culture. It was found that xylenol and indole were difficult to degrade, when the concentrations were above 250mg/L. It was observed that free cyanide (2.5mg/L and above) has the potency to holdup the oxidation of organics (250mg/L) until the cyanide concentration drops to a minimum level. Final TOC in the mixed pollutant system was less than 4mg/L, indicating the absence of other organic byproducts. Experimental results highlight effect of free cyanide on removal of organics and the combined toxic influence of cyanide and organics on the microbes treating coking wastewater. The proposed mathematical model was able to predict the biodegradation of mixed pollutant system satisfactorily.

Strategies for enhanced CWPO of phenol solutions

The performance of a commercial CuO/alumina catalyst used in the catalytic wet peroxide oxidation (CWPO) of 1g/l phenol solutions is investigated in a batch reactor. The effect of temperature, catalyst load, hydrogen peroxide concentration and dosage strategies on phenol mineralization, hydrogen peroxide consumption efficiencies and catalyst stability was studied. Experiments were performed at 298, 323 and 343K, using catalyst loads of 1g/l or 25g/l and concentrations of hydrogen peroxide 1.3, 2.6 and 3.9 times the stoichiometric requirement added at once or in distributed doses. The critical goal of the CWPO in terms of Process Intensification is to achieve total phenol mineralization working at optimal hydrogen peroxide consumption efficiencies while retaining catalyst stability. The present work highlights the complexity of this objective and shows viable working alternatives.Results indicate that high temperatures and concentrations of catalyst and hydrogen peroxide (added at once) can be employed when fast mineralization and high pH values are required in order to prevent catalyst leaching, although oxidant consumption efficiencies are then low. However, simultaneous high mineralization and hydrogen peroxide consumption efficiencies are obtained with a proper oxidant dosage strategy at high temperature, using high catalyst load. Then, hydrogen peroxide degradation into non-oxidising (parasitic) species is minimized with final TOC conversions close to 90%. The drawback of this strategy is that the rate of reaction is lower because of the limited amount of oxidant available.

Photo Fenton degradation of high concentration Orange II (2 mM) using catalysts containing Fe: A comparative study

Photo Fenton discoloration and mineralization of high concentration Orange II (2 mM) was conducted by using three catalysts containing Fe in the presence of 2 × 8 W UVC light (254 nm) and 100 mM H 2O 2 at an initial solution pH of 3.0. The three catalysts are laponite clay based Fe nanocomposite (Fe-Lap-RD), betonite clay based Fe nanocomposite (Fe-B), and iron oxide hydrated (FeOOH). All of them showed a good photo catalytic activity in the discoloration of 2 mM Orange II. 100% discoloration was achieved within 120 min in the presence of 1.0 g Fe-Lap-RD/L while 100% discoloration needs 180 min reaction in the presence of 1.0 g Fe-B or FeOOH. In terms of discoloration, the efficiency of the catalysts follows the order: Fe-Lap-RD > Fe-B ≈ FeOOH. However, in the mineralization of 2 mM Orange II, only Fe-Lap-RD and Fe-B showed good photo catalytic activity while FeOOH showed poor photo catalytic activity after 300 min reaction. In the cases of 1.0 g Fe-Lap-RD/L and Fe-B, more than 95–98% TOC removal of 2 mM Orange II can be achieved while only 82% TOC removal was obtained in the presence of 1.0 g FeOOH/L. In terms of the final TOC removal, the efficiency of the three catalysts follows the order: Fe-Lap-RD > Fe-B > FeOOH. The efficiency of 1.0 g Fe-Lap-RD/L is similar to that of 10 mg Fe 3+/L. The results revealed that using Fe-Lap-RD as a heterogeneous catalyst for the degradation of high concentration Orange II is successful. Furthermore, our results also illustrate that both homogeneous and heterogeneous photo Fenton reactions are responsible for the complete discoloration and mineralization of high concentration Orange II.

Kinetics of 2,6-dimethylaniline degradation by electro-Fenton process

A new approach for promoting ferric reduction efficiency using a different electrochemical cell and the photoelectro-Fenton process has been developed to degrade organic toxic contaminants. The use of UVA light and electric current as electron donors can efficiently initiate the Fenton reaction. 2,6-Dimethylaniline (2,6-DMA) was the target compound in this study. Effects of initial pH (pH i), Fe 2+ loading, H 2O 2 concentration and current density were determined to test and to validate a kinetic model for the oxidation of organic compound by the electro-Fenton process. Kinetic results show evidence of pseudo-first-order degradation. When reaction pH was higher than 2, amorphous Fe(OH) 3(s) was generated. Increasing ferrous ion concentration from 1.0 to 1.5 mM increased the hydroxyl radicals and then promote the degradation efficiency of 2,6-DMA. The optimal H 2O 2 concentration for 2,6-DMA degradation in this study was 25 mM. The degradation of 2,6-DMA was increased with the increase of current density from 3.5 to 10.6 A/m 2. Oxalic acid was the major detected intermediate of 2,6-DMA degradation. The final TOC removal efficiencies were 10%, 15%, 60% and 84% using the electrolysis, Fenton, electro-Fenton and photoelectro-Fenton processes, respectively.

The reactor design and comparison of Fenton, electro-Fenton and photoelectro-Fenton processes for mineralization of benzene sulfonic acid (BSA)

A new approach for promoting ferric reduction efficiency using a different electrochemical cell and the photoelectro-Fenton process has been developed. The use of UVA light and electric current as electron donors can efficiently initiate the Fenton reaction. Benzene sulfonic acid (BSA) was the target compound in this study. The parameters investigated to evaluate the reactor design include the electrode working area, electrode distance, energy consumption. Furthermore, the study also contains the intermediates and the mineralization efficiency of electrolysis, Fenton, electro-Fenton and photoelectro-Fenton process. Oxalic acid, the major intermediate of aromatic compound degradation, can complex with ferric ions. Meanwhile, a double cathode reactor could increase the current efficiency by 7%, which would translate to greater ferrous production and a higher degradation rate. Although the current efficiency of an electrode distance 5.5 cm device is 19% higher than 3.0 cm, results show that after 2 h of electrolysis the electronic expense using an electrode gap of 5.5 cm is much higher than 3.0 cm. The final TOC removal efficiency was 46, 64 and 72% using the Fenton, electro-Fenton and photoelectron-Fenton processes, respectively.

Factors influencing inactivation of Klebsiella pneumoniae by chlorine and chloramine

Inactivation of Klebsiella pneumoniae cultures by chlorine and chloramine was evaluated under different growth conditions by varying nutrient media dilution, concentrations of essential inorganic nutrients (FeCl 3, MgSO 4, phosphate, and ammonium salts), and temperature. All inactivation assays were performed at room temperature (22–23°C) and near neutral pH (7.2–7.5). C * T 99.9 values for chlorine increased >20-fold and for chloramine increased 2.6-fold when cells were grown in 100-fold diluted nutrient broth (2NB) solutions (final TOC of 35–40 mg/L). Background levels of Mg: 6.75×10 −2 mM and Fe: 3.58×10 −5 mM or high levels of FeCl 3 (0.01 mM) and MgSO 4 (1 mM) during growth resulted in the highest resistances to chlorine with C * T 99.9 values of 13.06 (±0.91) and 13.78 (±1.97) mg-min/L, respectively. Addition of low levels of FeCl 3 (0.001 mM) and MgSO 4 (0.1 mM) to K. pneumoniae cultures during growth resulted in the lowest bacterial resistances to inactivation; C * T 99.9 values ranged from 0.28 (±0.06) to 1.88 (±0.53) mg-min/L in these cultures. Increase in growth temperature from 22.5°C to 35°C for unamended 2NB cultures resulted in a 42-fold decrease in C * T 99.9 values for chlorine. A similar change in temperature resulted in no significant change in C * T 99.9 values for chloramine. These results indicate that inactivation of K. pneumoniae cultures by chlorine was highly sensitive to changes in growth conditions unlike inactivation by chloramine.