Nitrogen doped titanium photocatalysts with different nitrogen containing organic compounds were prepared by sol-gel method in acidic media. Among different nitrogen containing organic compounds, triethylamine doped TiO2 showed better photocatalytic activity under visible light. XRD, SEM and TEM analyses showed that the crystalline size of N-doped TiO2 was in the range of 20-24 nm. XRD and Raman spectrum showed that all peaks of N-doped TiO2 correspond to anatase crystalline structure. The formation of O-Ti-N bond in N-doped TiO2 does not lead to any new Raman band. XPS study confirmed that N replaces the O in the lattice of TiO2 and is present in the form of O-Ti-N. The photocatalytic activity of doped TiO2 was measured under UV and visible light using lindane as a target pollutant. The photocatalytic activity of anatase TiO2 and N-doped TiO2 was compared with commercially available Degussa P-25 TiO2. Intermediates formed during the degradation of lindane were monitored by GC-MS analysis. © 2010 Elsevier B.V.

Ligy Philip

Department Of Civil Engineering

Jaganathan Senthilnathan

Complexation

Crystalline materials

Cyclohexane

Insecticides

Light

nitrogen

Organic compounds

Pesticides

Photocatalysis

Photocatalysts

Sol-gel process

Sol-gels

Titanium dioxide

CRYSTALLINE SIZE

Crystalline structure

Lindane

Photo catalytic degradation

Photocatalytic activities

TARGET POLLUTANTS

Triethylamines

UV and visible light

Doping (additives)

IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

Chemical Engineering Journal

A multiple pin-plane corona discharge reactor was used to generate plasma for the degradation of 2,4 dichlorophenoxyacetic acid (2,4-D) from the aqueous solution. The 2,4-D of concentration 1 mg/L was completely removed within 6 min of plasma treatment. Almost complete mineralization was achieved after the treatment time of 14 min for a 2,4-D concentration of 10 mg/L. Effects of different water constituents such as carbonates, nitrate, sulphate, chloride ions, natural organic matter (humic acids) and pH on 2,4-D degradation was studied. A significant antagonistic effect of carbonate and humic acid was observed, whereas, the effects of other ions were insignificant. A higher first order rate constant of 1.73 min−1 was observed, which was significantly decreased in the presence of carbonate ions and humic acids. Also, a higher degradation of 2,4-D was observed in acidic pH conditions. Different 2,4-D intermediates were detected and the degradation pathway of 2,4-D in plasma treatment process was suggested. The toxicity of 10 mg/L 2,4-D was completely eradicated after 10 min of plasma treatment. © 2017 Elsevier Ltd

Chemosphere

Removal of 2,4-dichlorophenoxyacetic acid in aqueous solution by pulsed corona discharge treatment: Effect of different water constituents, degradation pathway and toxicity assay

The present paper deals with photocatalytic degradation of carbamazepine and diclofenac by using a modified catalyst with band gap excitations in visible light. The C-doped TiO2 was synthesized using a microwave digestion method from titanium oxyacetylacetate with glucose as the carbon source. The synthesized catalyst was then characterized using Scanning Electron microscopy (SEM), X-ray Diffractometry (XRD), X-ray photoelectron spectroscopy (XPS) and UV-VIS-NIR spectrophotometer. The TiO2 present was in anatase phase and showed significant absorption in visible region. The catalyst was tested for the degradation of carbamazepine and diclofenac under visible light, where complete removal was achieved and the reaction followed first order kinetics. System parameters like catalyst and pollutant concentration, light intensity and time of reaction, were optimized using response surface methodology. In optimum conditions (catalyst concentration of 244 mg/L and light intensity of 7715 lx) 99% removal was achieved. © 2017 Elsevier Ltd. All rights reserved.

Journal of Environmental Chemical Engineering

Synthesis, characterization and performance of visible light active C-TiO2 for pharmaceutical photodegradation

This work demonstrates the application of plasma generated by pulsed corona discharge for the rapid degradation of carbofuran from aqueous solution. Carbofuran with a concentration of 0.5 mg/L to 30 mg/L was effectively removed within 4 to 10 min of treatment time, at 101.5 W input power. Degradation yield (2.95 g/kWh) was much higher for 10 mg/L carbofuran concentration compared to degradation yield (0.37 g/kWh) for 0.5 mg/L carbofuran. The effect of pulsed voltage, pulsed frequency, initial pesticide concentration, pH, and effect of radical scavengers (HCO3-, CO32-, and humic acid) was also investigated in detail. Appearance of some key intermediates confirmed the possibility of formation of some demethylated products due to direct electron impaction during degradation process. Seven intermediates were identified, and possible oxidation and reduction mechanism of carbofuran degradation pathway was proposed. Microalgae ecotoxicity study confirmed the complete detoxification of carbofuran after 14 min corona discharge. © 2016 American Chemical Society.

Industrial and Engineering Chemistry Research

Rapid Removal of Carbofuran from Aqueous Solution by Pulsed Corona Discharge Treatment: Kinetic Study, Oxidative, Reductive Degradation Pathway, and Toxicity Assay

Wastewater generated from coke oven industries contains highly toxic organic and inorganic compounds. In the present study, biological reactors were integrated in sequence of anaerobic-aerobic-anoxic and tested with real coke oven wastewater obtained from a Steel Plant located in India. Among several pretreatment methods, coagulation of raw CWW was found to be effective. COD removal efficiency of 78.5% was achieved by the integrated bioreactor system after coagulation of CWW with 1000 mg/L of alum. The effluent COD, NH4-N and TCN concentration from the integrated bioreactors was 420, 152 and 20 mg/L, respectively. It was observed that 420 mg/L of COD present in the effluent after integrated bio treatment was degraded in less than 4 h to minimum COD concentration of 94 mg/L using UV-TiO2 photocatalysis. In absence of photocatalyst (TiO2), there was no COD reduction from the bio treated effluent. Similarly, there was insignificant reduction in COD from the raw CWW using photocatalysis without biological treatment. Considerable COD reduction (78.5%) was observed only in the wastewater subjected to integrated biological system. The overall COD removal efficiency of the combined treatment system was found to be 96.2%, which resulted in an effluent COD concentration less than 94 mg/L. © 2016 Elsevier B.V.

Combined biological and photocatalytic treatment of real coke oven wastewater

This paper describes an unusual chemical reaction that takes place on a graphene composite in a concerted fashion. The reaction shows the conversion of a persistent organochlorine pesticide, lindane (C<inf>6</inf>H<inf>6</inf>Cl<inf>6</inf>), present in water, to different isomers of trichlorobenzenes (TCBs, C<inf>6</inf>H<inf>3</inf>Cl<inf>3</inf>) on the surface of reduced graphene oxide-silver composites (RGO@Ag). The reaction is unique to the composite and does not occur on RGO and nanoparticles of Ag separately. The products of the reaction were isolated and extensively characterized using analytical techniques such as gas chromatography-mass spectrometry, electrospray ionization mass spectrometry, infrared and NMR, which unequivocally confirmed their identity. The as-formed TCBs were removed from the aqueous medium by adsorption on the same composite. Adsorption of lindane is physical in nature, but that of TCBs is through - interactions. The study reveals the unusual chemical reactivity of graphene-metal composites and their potential for water treatment. The uniqueness of the reaction on RGO@Ag is due to the simultaneous removal of three HCl molecules, leading to the formation of aromatic compounds and concomitant formation of silver chloride. Recycling capacity and effect of diverse species present in natural waters were tested for potential applications in sustainable water treatment. © 2015 American Chemical Society.

ACS Sustainable Chemistry and Engineering

Simultaneous dehalogenation and removal of persistent halocarbon pesticides from water using graphene nanocomposites: A case study of lindane

Lindane (1α, 2α, 3β, 4α, 5α, 6β-hexachloro cyclohexane), methyl parathion (O,O-dimethyl-O-4-nitrophenyl phosphorothioate) and dichlorvos (2,2-dichlorovinyl-O-O-dimethyl phosphate) are removed from water individually and as a mixture by photo degradation using suspended and immobilized forms of TiO2 (Degussa P-25). Studies were conducted to optimize the coating thickness of immobilized photo catalyst. The rate of degradation of pesticides was compared in both suspended and immobilized TiO2 systems. Degradation studies of mixed pesticides were carried out with low concentrations (1.0 and 2.5 mg/L) of pesticides. Only three intermediate byproducts such as methyl paraoxon, O,O,O-trimethyl phosphonic thionate and p-nitrophenol were observed during the methyl parathion degradation in suspended, immobilized TiO2 systems and mixed pesticides degradation studies. At the end of the reaction methyl parathion and its by-products were completely degraded. During lindane degradation hexachloro cyclohexane, pentachloro cyclohexane, hexachloro benzene, 1-hydroxy 2,3,4,5,6-chlorocyclohexane, 1-hydroxy 2,3,4,5,6-chlorobenzene, pentachloro cyclopentadiene, 1,2,3,4,5-hydroxy cyclopentene and 1,2,3-hydroxy cyclobutane were identified in suspended and immobilized TiO2 systems, whereas only hexachloro cyclohexane, pentachloro cyclohexane, hexachloro benzene and pentachloro cyclopentadiene were observed during mixed pesticides degradation. No intermediate by-product was observed during the photo degradation of dichlorvos. Langmuir-Hinshelwood pseudo first order kinetic equation showed that there was not much change in the rates of degradation in both suspended and immobilized TiO2 systems irrespective of the pesticide. During mixed pesticides degradation, the degradation pattern was not similar to that of single pesticide. © Taylor &amp; Francis Group, LLC.

Journal of Environmental Science and Health - Part B Pesticides, Food Contaminants, and Agricultural Wastes

Removal of mixed pesticides from drinking water system by photodegradation using suspended and immobilized TiO2

Adsorption and desorption characteristics of three insecticides on four Indian soils were studied. Insecticides used were representative of organochlorine, organophosphate, and carbomate groups. The order of adsorption of pesticides on soils was: lindane &gt; methyl parathion &gt; carbofuran. Compost soil had shown the maximum adsorption capacity. The order of adsorption capacity of various soils were: compost soil &gt; clayey soil &gt; red soil &gt; sandy soil. Adsorption isotherms were better fitted to Freundlich model and Kf values increased with increase in organic matter content of the soils. Thermodynamic parameters indicated favorable adsorption of all the three pesticides in four different soils. Adsorption was exothermic in nature. Distilled water desorbed 30-60% of adsorbed pesticides whereas; organic solvents were able to affect 50-80% of sorbed pesticides. Clay content and organic matter played a significant role in pesticide adsorption and desorption processes. Hysteresis effect was observed in red, clayey and compost soils. Hysteresis effect increased with increase in organic matter and clay content of the soils. © 2008.

Journal of Hazardous Materials

Adsorption and desorption characteristics of lindane, carbofuran and methyl parathion on various Indian soils

Nitrogen doped spherical TiO2 has been prepared by thermal decomposition of Ti-melamine complex in air atmosphere. A clear shift in the onset light absorption from UV region (&lt;400) to visible region (&gt;520 nm) has been observed for the N-doped samples. It has been deduced from the optical absorption spectra that the higher calcination temperature results in the decrease in the amount of N-doping. The XRD results revealed the phase transition of TiO2 from anatase to rutile crystalline phase, starting at calcination temperature ≥600 °C. The electron microscopic images reveal the formation of spherical and flakes of TiO2 nanocrystals (25 nm). The chemical nature of N in the N-TiO2 has been evolved through X-ray photoelectron spectroscopy. The presence of different types of N species have been observed corresponding to different oxidation states and the presence of Ti-N and O-Ti-N have been confirmed from the observed binding energy values. Photocatalytic decomposition of methylene blue has been carried out both in the visible region and UV + visible region. In the visible region, N-TiO2 showed higher activity compared to the undoped commercial TiO2 (Degussa P25). © 2007 Elsevier B.V. All rights reserved.

Applied Catalysis B: Environmental

Characterization and photocatalytic activity of N-doped TiO2 prepared by thermal decomposition of Ti-melamine complex

Journal of Solid State Chemistry

Preparation and characterization of mesoporous N-doped and sulfuric acid treated anatase TiO2 catalysts and their photocatalytic activity under UV and Vis illumination

Photo-catalytic degradation of Rhodamine B on C-, S-, N-, and Fe-doped TiO2 under visible-light irradiation

Photocatalytic degradation of lindane under UV and visible light using N-doped TiO2

Journal	Data powered by TypesetChemical Engineering Journal
Publisher	Data powered by TypesetElsevier B.V.
ISSN	13858947
Open Access	No