COD reduction of waste water streams of active pharmaceutical ingredient – Atenolol manufacturing unit by advanced oxidation-Fenton process

Active pharmaceutical intermediates (API) in waste waters have adverse effects on aquatic life and environment. The API have high COD value and low BOD₃ and hence difficult to treat biologically. In this study, advanced oxidation processes (AOPs) utilizing the H₂O₂/Fe⁺², Fenton reactions were investigated in lab-scale experiments for the degradation of Atenolol containing waste water streams. The experimental results showed that the Fenton process using H₂O₂/Fe⁺² was the most effective treatment process. With Fenton processes, COD reduction of wastewater can be achieved successfully. It is suggested that Fenton processes are viable techniques for the degradation of Atenolol from the waste water stream with relatively low toxic by-products in the effluent which can be easily biodegraded in the activated sludge process. Hence, the Fenton process with H₂O₂/Fe⁺² is considered a suitable pretreatment method to degrade the active pharmaceutical molecules and to improve the biodegradability of waste water.     

Chemical Oxidative Degradation of Acridine Orange Dye in Aqueous Solution by Fenton's Reagent

Degradation of acridine orange (AO) in aqueous solution by Fenton's reagent (Fe²⁺ and H₂O₂) was investigated. The effects of different reaction parameters such as initial AO concentration, pH value of solution, ferrous concentration, hydrogen peroxide concentration, and the presence of chloride ion on the oxidative degradation of AO were investigated. Under optimum conditions, 2 mM H₂O₂, 0.4 mM Fe²⁺ and pH 3.0, the initial 0.2 mM AO solution was reduced by 95.8% within 10 min. The primary intermediates of the degradation reaction of AO were identified. The analytical results indicated that the N‐de‐methylation degradation of AO dye took place in a stepwise manner to yield mono‐, di‐, tri‐, and tetra‐N‐de‐methylated AO species generated during the Fenton process. The probable degradation pathways were proposed and discussed.     

UV light-assisted mineralisation and biodetoxification of Ponceau S with hydroxyl and sulfate radicals

The present study reports simultaneous mineralisation and biodetoxification of Ponceau S (3-hydroxy-4-(2-sulfo-4-[4-sulfophenylazo]phenylazo)-2,7-naphthalenedisulfonic acid sodium salt), an azo dye, by UV light assisted oxidation with hydroxyl and sulfate radicals. Metal ion catalysts used in the work were: Fe²⁺ and Ag⁺, and the oxidants used were: hydrogen peroxide and S₂O₈^2?. Strategies adopted to make the processes environmentally benign and economically viable by achieving maximum mineralisation in the shortest possible time are described. Mineralisation efficiency (Em) of various systems was found to follow the order: E_m(Fe²⁺/H₂O₂/UV) > E_m(Fe²⁺/S₂O₈^2?/UV) > E_m(Ag⁺/H₂O₂/UV) ≈ E_m(Ag⁺/S₂O₈^2?/UV). Thus, Fe²⁺ and HP are the most suitable metal ion catalyst and oxidant respectively, showing higher efficiency at pH 3 followed by that at pH 6.6. It is possible to enhance the Fe²⁺/H₂O₂/UV process electrical energy efficiency by maintaining the concentration of Fe at either 0.05 mM or 0.03 mM and that of the oxidant at 2.5 mM. The bioassay study revealed that the Fe²⁺/S₂O₈^2?/UV process biodetoxification efficiency is higher at pH 3 (93.7 %) followed by that at pH 6.6 (80.1 %) at the concentration of Fe ²⁺ and S₂O₈^2? of 0.03 mM and 2.5 mM, respectively. Thus, not only the concentration of Fe²⁺, but also the nature of the oxidant and pH play an important role in the biodetoxification process and S₂O₈^2? possesses higher biodetoxification efficiency than H₂O₂.     

Synergistic Anticancer Therapy by Ovalbumin Encapsulation-Enabled Tandem Reactive Oxygen Species Generation

The anticancer efficacy of photodynamic therapy (PDT) is limited due to the hypoxic features of solid tumors. We report synergistic PDT/chemotherapy with integrated tandem Fenton reactions mediated by ovalbumin encapsulation for improved in vivo anticancer therapy via an enhanced reactive oxygen species (ROS) generation mechanism. O₂^.− produced by the PDT is converted to H₂O₂ by superoxide dismutase, followed by the transformation of H₂O₂ to the highly toxic ^.OH via Fenton reactions by Fe²⁺ originating from the dissolution of co-loaded Fe₃O₄ nanoparticles. The PDT process further facilitates the endosomal/lysosomal escape of the active agents and enhances their intracellular delivery to the nucleus—even for drug-resistant cells. Cisplatin generates O₂^.− in the presence of nicotinamide adenine dinucleotide phosphate oxidase and thereby improves the treatment efficiency by serving as an additional O₂^.− source for production of ^.OH radicals. Improved anticancer efficiency is achieved under both hypoxic and normoxic conditions.     

A confined micro-reactor with a movable Fe3O4 core and a mesoporous TiO2 shell for a photocatalytic Fenton-like degradation of bisphenol A

Photocatalysis and Fenton process are two primary and promising advanced oxidation processes to degrade organic pollutants. However, the practical applications of single photocatalysis and Fenton process are still limited. Introducing one of them into another to form a combined photocatalytic Fenton-like system has shown great potential but still faces challenges in designing a well-tailored catalyst. Herein, a confined photocatalytic Fenton-like micro-reactor catalyst with a movable Fe₃O₄ core and a mesoporous TiO₂ shell has been constructed via a successive Stöber coating strategy, followed by an ultrasound assisted etching method. The resulting micro-reactor possesses well-defined yolk-shell structures with uniform mesopores (～4 nm), a large Brunauer-Emmett-Teller (BET) surface area (～166.7 m²/g), a high pore volume (～0.56 cm³/g) and a strong magnetization (～51 emu/g), as well as tunable reactor sizes (20?90 nm). When evaluated for degrading bisphenol A under solar light in the presence of peroxymonosulfate, the micro-reactor exhibits a superior catalytic degradation performance with a high magnetic separation efficiency and an excellent recycle ability. The outstanding performance can be attributed to its unique textual structure, which leads to a great synergistic effect from the photocatalytic and Fenton-like process. This study gives an important insight into the design and synthesis of an advanced micro-reactor for a combined advanced oxidation processes (AOPs).     

Fast and Long‐Lasting Iron(III) Reduction by Boron Toward Green and Accelerated Fenton Chemistry

Generation of hydroxyl radicals in the Fenton system (Fe^II/H₂O₂) is seriously limited by the sluggish kinetics of Fe^III reduction and fast Fe^III precipitation. Here, boron crystals (C‐Boron) remarkably accelerate the Fe^III/Fe^II circulation in Fenton‐like systems (C‐Boron/Fe^III/H₂O₂) to produce a myriad of hydroxyl radicals with excellent efficiencies in oxidative degradation of various pollutants. The surface B?B bonds and interfacial suboxide boron in the surface B₁₂ icosahedra are the active sites to donate electrons to promote fast Fe^III reduction to Fe^II and further enhance hydroxyl radical production via Fenton chemistry. The C‐Boron/Fe^III/H₂O₂ system outperforms the benchmark Fenton (Fe^II/H₂O₂) and Fe^III‐based sulfate radical systems. The reactivity and stability of crystalline boron is much higher than the popular molecular reducing agents, nanocarbons, and other metal/metal‐free nanomaterials.     

Fast and Long-Lasting Iron(III) Reduction by Boron Toward Green and Accelerated Fenton Chemistry

Generation of hydroxyl radicals in the Fenton system (Fe^II/H₂O₂) is seriously limited by the sluggish kinetics of Fe^III reduction and fast Fe^III precipitation. Here, boron crystals (C-Boron) remarkably accelerate the Fe^III/Fe^II circulation in Fenton-like systems (C-Boron/Fe^III/H₂O₂) to produce a myriad of hydroxyl radicals with excellent efficiencies in oxidative degradation of various pollutants. The surface B−B bonds and interfacial suboxide boron in the surface B₁₂ icosahedra are the active sites to donate electrons to promote fast Fe^III reduction to Fe^II and further enhance hydroxyl radical production via Fenton chemistry. The C-Boron/Fe^III/H₂O₂ system outperforms the benchmark Fenton (Fe^II/H₂O₂) and Fe^III-based sulfate radical systems. The reactivity and stability of crystalline boron is much higher than the popular molecular reducing agents, nanocarbons, and other metal/metal-free nanomaterials.     

Optimization and Degradation Mechanism of Photocatalytic Removal of Bisphenol A Using Zn0.9Fe0.1S Synthesized by Microwave‐assisted Method

The sulfide photocatalyst of Zn_0.9Fe_0.1S was successfully synthesized by a facile microwave‐assisted method, and Zn_0.9Fe_0.1S photocatalysts were characterized using SEM, EDX, XRD and BET. The specific surface area of synthesized Zn_0.9Fe_0.1S is 78.1 m² g^?1, and total pore volume is 0.4 cm³ g^?1. With bisphenol A (BPA) as a target pollutant, photocatalytic system of UV + Zn_0.9Fe_0.1S + H₂O₂ was set up. Some influencing parameters, including H₂O₂ dosage, initial pH value, initial concentration of BPA and Zn_0.9Fe_0.1S dosage, were investigated, and the stability of the Zn_0.9Fe_0.1S was also studied during the photocatalysis. The optimum values of operating parameters were found at an initial pH value of 5.0, a H₂O₂ dosage of 0.15 mmol L^?1 and a Zn_0.9Fe_0.1S dosage of 0.08 g when the initial concentration of BPA was 10 mg L^?1. Under the optimal conditions, the highest removal rate of BPA achieved 95%. After seven consecutive reaction cycles, the degradation efficiency of BPA could still reach 85% and there was only a little dissolution of Zn²⁺ and Fe²⁺. Compared with the traditional photo‐Fenton system, the UV + Zn_0.9Fe_0.1S + H₂O₂ system can not only improve the degradation efficiency of BPA, but also reduce the dosage of H₂O₂ and thus reduce the processing cost.     

Simple and efficient treatment of high-strength industrial waste water using commercial zero-valent iron

The zero-valent iron (ZVI)/H₂O₂ Fenton system can be considered as an effective solution for the removal of many of the organic pollutants present in the waste waters generated by the drug manufacturing industry. The hydrogen peroxide concentration and dosage rate were studied in order to improve the efficiency of the oxidant in the TOC reduction and, thereby enhance the overall catalytic performance of the ZVI/H₂O₂ Fenton system. TOC reductions of up to 80 % and BOD₅/COD ratios of up to 0.6 were achieved in the waste water as received without dilution (TOC_O approximately 5 g L^?1) using hydrogen peroxide dose-staggering. This showed that the ZVI/H₂O₂ process led not only to a decrease in TOC removal but also to an increase in the biodegradability of the by-products formed. The hydrogen peroxide was consumed more efficiently and very low concentrations of iron dissolved (7 mg L^?1) were obtained in the final effluents. The final values of COD, BOD₅, the suspended solids’ content and the conductivity of the treated waste water met the limits of the Spanish legal industrial discharge, Decree 57/2005 (Ministry of Environment, Local Government and Planning, Community of Madrid, 2005). In addition, the composite thus formed, consisting of zero-valent iron and iron oxide-oxyhydroxides, can be readily removed from the treated effluent, avoiding any post-treatment step.     

Synthesis of mesoporous functional hematite nanofibrous photoanodes by electrospinning

Iron(III) oxide (hematite, Fe₂O₃) nanofibers, as visible light‐induced photoanode for water oxidation reaction of a water splitting process, were fabricated through electrospinning method followed by calcination treatment. The prepared samples were characterized with scanning electron microscopy, and three‐electrode galvanostat/potentiostat for evaluating their photoelectrochemical (PEC) properties. The diameter of the as‐spun fibers is about 300 nm, and calcinated fibers have diameter less than 110 nm with mesoporous structure. Optimized multilayered electrospun α‐Fe₂O₃ nanostructure mats showed photocurrent density of 0.53 mA/cm² under dark and visible illumination conditions at voltage 1.23 V and constant intensity (900 mW/cm²). This photovoltaic performance of nanostructure mats makes it suitable choice for using in the PEC water splitting application as an efficient photoanode. This method, if combined with appropriate flexible conductive substrate, has the potential for producing flexible hematite solar fuel generators. Copyright © 2015 John Wiley & Sons, Ltd.     

Ferric ion-ascorbic acid complex catalyzed calcium peroxide for organic wastewater treatment: Optimized by response surface method

Hydrogen peroxide (H₂O₂) disproportionation, iron precipitation, and narrow pH range are the drawbacks of traditional Fenton process. To surmount these barriers, we proposed a ferric ion (Fe³⁺)-ascorbic acid (AA) complex catalyzed calcium peroxide (CaO₂) Fenton-like system to remove organic dyes in water. This collaborative Fe³⁺/AA/CaO₂ system presented an obvious improvement in the methyl orange (MO) decolorization, and also effectively eliminated other dyes. Response surface method was employed to optimize the running parameters for this coupling process. Under the optimized arguments (2.76 mmol/L Fe³⁺, 0.68 mmol/L AA, and 4 mmol/L CaO₂), the MO removal achieved 98.90% after 15 min at pH 6.50, which was close to the computed outcome of 99.30%. Furthermore, this Fenton-like system could perform well in a wide range of pH (3–11), and enhance the H₂O₂ decomposition and Fe ions recycle. The scavenger experiment result indicated that hydroxyl radical, superoxide anion free radical, and singlet oxygen were acted on the dye elimination. Moreover, electron spin resonance analysis corroborated that the existences of these active species in the Fe³⁺/AA/CaO₂ system. This study could advance the development of Fenton-like technique in organic effluent disposal.     

Toxicity reduction of 2-(5-nitrofuryl)acrylic acid following Fenton reaction treatment

Monitoring the enforcement of an EU-wide ban of nitrofuran antibiotics in the food production chain is a challenging task, given the nature of nitrofuran compounds. The original and modified Fenton reactions are advanced oxidation processes that can eliminate the toxicity of nitrofurans. 2-(5-Nitrofuryl)acrylic acid (I) was degraded as a model compound by the original Fenton reaction with ferrous sulphate, by Mohr’s salt at pH 3 and 7, and finally by advanced Fenton process (AFP) (Fe⁰/H₂O₂/H₂SO₄). In addition, the growth inhibition of Escherichia coli, a G⁻ bacterium, was tested both before and after AFP treatment. The results showed that a small degradation efficiency of this treatment process led to the toxicity changes and that the toxicity of I after AFP treatment process decreased. It seems that the treatment of polluted water using the Fenton reaction and its modifications would be a suitable method for degradation of nitrofuran derivatives in polluted water.     

Adsorption behavior of <Superscript>99</Superscript>Tc on Fe,Fe<Subscript>2</Subscript>O<Subscript>3</Subscript> and Fe<Subscript>2</Subscript>O<Subscript>4</Subscript>

Summary The adsorption of ⁹⁹Tc on the adsorbers Fe, Fe₂O₃ and Fe₃O₄ was studied by batch experiments under aerobic and anoxic conditions. The effects of pH and CO₃^2- concentration of the simulated ground water on the adsorption ratios were also investigated, and the valences of Tc in solution after the adsorption equilibrium were studied by solvent extraction. The adsorption isotherms of TcO₄- on the adsorbers Fe, Fe₂O₃ and Fe₃O₄ were determined. Experimental results have shown that the adsorption ratio of Tc on Fe decreases with the increase of pH in the range of 5-12 and increases with the decrease of the CO₃^2- concentration in the range of 10^-8M-10^-2M. Under aerobic conditions, the adsorption ratios of ⁹⁹Tc on Fe₂O₃ and Fe₃O₄ were not influenced by pH and CO₃^2-concentration. When Fe was used as adsorbent, Tc existed mainly in the form of Tc(IV) after equilibrium and in the form of Tc(VII) when the adsorbent was Fe₂O₃ or Fe₃O₄ under aerobic conditions. The adsorption ratios of Tc on Fe, Fe₂O₃ and Fe₃O₄ decreased with the increase of pH in the range of 5-12 and increased with the decrease of the CO₃^2- concentration in the range of 10^-8M-10^-2M under anoxic conditions. Tc existed mainly in the form of Tc(IV) after equilibrium when Fe, Fe₂O₃ and Fe₃O₄ was the adsorbent under anoxic conditions. The adsorption isotherms of TcO_4- on the adsorbers Fe, Fe₂O₃ and Fe₃O₄ are fairly in agreement with the Freundlich’s equation under both aerobic and anoxic conditions.     

On‐surface Fenton and Fenton‐like reactions appraised by paper spray ionization mass spectrometry

On‐surface degradation of sildenafil (an adequate substrate as it contains assorted functional groups in its structure) promoted by the Fenton (Fe²⁺/H₂O₂) and Fenton‐like (Mⁿ⁺/H₂O₂; Mⁿ⁺ = Fe³⁺, Co²⁺, Cu²⁺, Mn²⁺) systems was investigated by using paper spray ionization mass spectrometry (PS‐MS). The performance of each system was compared by measuring the ratio between the relative intensities of the ions of m/z 475 (protonated sildenafil) and m/z 235 (protonated lidocaine, used as a convenient internal standard and added to the paper just before the PS‐MS analyzes). The results indicated the following order in the rates of such reactions: Fe²⁺/H₂O₂ ≫ H₂O₂ ≫ Cu²⁺/H₂O₂ > Mⁿ⁺/H₂O₂ (Mⁿ⁺ = Fe³⁺, Co²⁺, Mn²⁺) ~ Mⁿ⁺ (Mⁿ⁺ = Fe²⁺, Fe³⁺, Co²⁺, Cu²⁺, Mn²). The superior capability of Fe²⁺/H₂O₂ in causing the degradation of sildenafil indicates that Fe²⁺ efficiently decomposes H₂O₂ to yield hydroxyl radicals, quite reactive species that cause the substrate oxidation. The results also indicate that H₂O₂ can spontaneously decompose likely to yield hydroxyl radicals, although in a much smaller extension than the Fenton system. This effect, however, is strongly inhibited by the presence of the other cations, ie, Fe³⁺, Co²⁺, Cu²⁺, and Mn²⁺. A unique oxidation by‐product was detected in the reaction between Fe²⁺/H₂O₂ with sildenafil, and a possible structure for it was proposed based on the MS/MS data. The on‐surface reaction of other substrates (trimethoprim and tamoxifen) with the Fenton system was also investigated. In conclusion, PS‐MS shows to be a convenient platform to promptly monitor on‐surface oxidation reactions.     

Decolorization and mineralization of yellow 5 (E102) by UV/Fe2+/H2O2 process. Optimization of the operational conditions by response surface methodology

In this study, the optimization and implementation of a homogeneous photo-Fenton process for the decolorization and mineralization of a wastewater containing highly concentrated yellow 5 (E102) dye, resulting from an industry placed in the suburbs of Medellin (Colombia), is presented. Response surface methodology was applied as a tool for the optimization of operational conditions such as initial dyestuff concentration, H₂O₂ concentration, and UV-radiation power (number of lamps). The decolorization, degradation and mineralization efficiencies were used as response variables. The following conditions were found to be optimal for decolorization and mineralization of yellow 5: UV radiation of 365 nm (4 W, one lamp), dye concentration of 200 mg/L, Fe²⁺ concentration of 1.0 mM, H₂O₂ concentration of 1.75 mL/L, treatment time of 180 min, Fe²⁺ concentration of 1 mM and pH = 3. Under these conditions (180 min), the photo-Fenton process allowed us to reach ca. 100% of color dye degradation, 99% of COD degradation, and 85% of mineralization (TOC). The scavenging effect of the Cl^– anion on the photodegradation process was also confirmed.     

Simple Chemical Route Synthesis of Fe2O3 Nanoparticles and its Application for Adsorptive Removal of Congo Red from Aqueous Media: Artificial Neural Network Modeling

Nanocrystalline Fe₂O₃ powder was synthesized by a simple chemical route involving FeCl₃ and NaOH. The Fe₂O₃ powder thus prepared was characterized using x-ray diffraction study, scanning electron microscopy, and Fourier transform infrared spectroscopy. The adsorption properties of crystalline Fe₂O₃ powder have been investigated with an aim to explore a possible low cost and efficient way to remove Congo red (CR) from waste water. Fe₂O₃ powder was found as an excellent adsorbent for CR from aqueous medium. Adsorption capacity as much as 203.66 mg g^?1 is reported at room temperature. Effect of different experimental parameters such as reaction pH, initial CR dye concentration, adsorbent dose, and reaction temperature were studied on adsorption capacity of Fe₂O₃ powder and modeled by artificial neural network (ANN). Optimal ANN structure (4–5–1) shows minimum mean squared error (MSE) of 0.00235 and determination coefficient (R²) of 0.991 with Levenberg–Marquardt algorithm. Isotherm analysis of experimental data exhibited better fit to the Langmuir isotherm. The adsorption process was found to follow second-order kinetics as depicted by the analysis of experimental results. Thermodynamic study shows that the adsorption process is endothermic, spontaneous, and thermodynamically favorable in the temperature range of 27°C to 60°C.     

Enhanced three-dimensional electrochemical process using magnetic recoverable of Fe3O4@GAC towards furfural degradation and mineralization

Furfural is as one of the major environmental pollutants in different industrial effluents such as refinery and petrochemical, paper, cardboard and oil refining. This toxic chemical is irritant and causes allergy for skin, eyes and mucous membranes. This study was developed to investigate the efficiency of a three-dimensional electrochemical process in the presence of granular activated carbon magnetized with Fe₃O₄ (Fe₃O₄@GAC) particle electrodes for removal of furfural from aqueous solution. The particle electrodes structural and morphological featured were determined via BET, VSM, XRD, FE-SEM and FTIR techniques. The experiments were performed based on central composite design (CCD) and the role of influencing factors including reaction time, pH, voltage and initial furfural concentrations at five levels were evaluated. The Quadratic model with high correlation coefficient = 0.9872 (R² and (R²_Adj = 0.9724)) was suggested for experimental data analysis. The performance of electrochemical oxidation towards furfural degradation was enhanced substantially after adding Fe₃O₄@GAC. The highest furfural removal efficiency (98.2%) was achieved under optimal conditions (furfural: 201 mg/L, electrolysis time: 69 min, voltage: 19 V, and pH: 5.0). Besides, over 78 and 74 % of COD and TOC were removed by Fe₃O₄@GAC-based three-dimensional process, respectively. Based on the COD/TOC ratio and average oxidation state (AOS) index, a significant increase was observed in the biodegradability of intermediates of furfural after treatment. Results showed that three-dimensional electrochemical process with particle electrodes is a promising technology for efficient removal of furfural, even at high concentrations. Results of Liquid chromatography–mass spectrometry (LC-MS) analysis and degradation pathway showed that furfural could be oxidized to compounds with smaller molecular masses, which eventually converted to carbon dioxide and water.     

Dual-mode Detection of Dopamine Based on Enhanced Fluorescent and Colorimetric Signals of Fe3+-H2O2-o-Phenylenediamine System

A fluorescent and colorimetric dual-mode “light-on” assay for the detection of dopamine (DA) was developed based on Fe³⁺-H₂O₂-OPD system. In general, Fe³⁺ could catalyze the H₂O₂-mediated oxidation of colorless and nonfluorescent o-phenylenediamine (OPD), and the resultant 2,3-diaminophenazine (DAP) exhibits a visible yellow color and yellow fluorescence. However, the reaction rate is extremely slow. By comparison, the introduction of DA can trigger a typical Fenton reaction that generates hydroxyl radical (?OH) continuously, thus increasing the conversion rate of OPD to DAP. Correspondingly, both color and fluorescence of the sensing system are enhanced obviously. On the basis of this fact, a sensor with dual readout for the detection of DA was established via measuring the fluorescent and colorimetric signals of the Fe³⁺-H₂O₂-OPD system. The linear ranges were 0.05–20 mM and 0.10–18 mM, and the detection limits were calculated to be 15 and 65 nM (S/N = 3) for fluorescent and colorimetric detection, respectively. The proposed dual-readout method features with simplicity, high sensitivity, visualization and good accuracy. Moreover, the method has been successfully applied to the detection of DA in human urine with satisfactory results.     

Photo fenton like process Fe3+/(NH4)2S2O8/UV for the degradation of Di azo dye congo red using low iron concentration

Degradation of Congo Red (CR) a di azo dye in aqueous solution is investigated by a Photo Fenton like process using Fe³⁺ ions as the catalyst and peroxy disulfate as the oxidant. The influence of various reaction parameters like, concentration of Fe³⁺ ions, concentration of the dye, concentration of ammonium persulfate, pH of the solution and the presence of hydroxyl radical scavenger are studied and optimal conditions are reported. The degradation rate decreased at higher dye concentration and at higher pH. The rate constant (k), catalytic efficiency (k_c) and process efficiency (Φ) are evaluated for different concentration of Fe³⁺ ions. The degradation of CR by the photo Fenton like process leads to the formation of 4-Amino, 3-azo naphthalene sulphonic acid, dihydroxy substituted naphthalene, dihydroxy substituted biphenyl, phenol, quinol etc., as intermediates, based on which probable degradation mechanism is proposed. These results show that a photo Fenton like process could be useful technology for the mineralization of di azo dyes under lower concentration of iron in acidic conditions. The present process is advantageous as it lowers the sludge production resulting from the iron comple      

Efficient separation of nitrite from aqueous solutions by grafting metalloporphyrin on Fe3O4 nanoparticles

A new sorbent comprising 3-aminopropyltriethoxy-silane-coated magnetic nanoparticles functionalized with organic moieties containing the cobalt(III) porphyrin complex Co (TCPP) [TCPP: 4,4′,4″,4″′-(21H,23H-porphine-5,10,15,20-tetrayl)tetrakis (benzoic acid)], was prepared, for nitrite removal from drinking water. Fe₃O₄ nanoparticles were synthesized by co-precipitation of Fe²⁺ and Fe³⁺, then surface of the Fe₃O₄ nanoparticles was modified with APTES and Co (TCPP). The sorbent was characterized using FTIR, TGA, XRD, SEM and TEM analysis. The batch experiments showed that the proposed sorbent can effectively be used to remove nitrite from water. Various parameters such as pH of the solution, contact time, sorbent dosage, concentration of desorbing reagent, and influence of other interfering anions have been investigated. Under optimal conditions for a nitrite concentration of 10 mg L^?1 (i.e., contact time 15 min, pH 5.5 and nanosorbents dosage 100 mg), the percentage of the extracted nitrite ions was 92.0. Nitrite sorbing material was regenerated with 10 mM NaOH up to 97.0 %. The regeneration studies also showed that nanosorbents are regenerable and can be used for a couple of times.