Suresh C. Ameta

Photocatalytic Degradation of Organic Pollutants: A Review

Water pollution is increasing at an ever increasing pace and the whole world is in the cancerous grip of this pollution. Various industries are discharging their untreated effluents into the nearby water resources; thus, adding to the existing water pollution to a great extent. Hence, there is a pressing demand to develop an alternate technology for wastewater treatment and in this context; photocatalysis has emerged as an Advanced Oxidation Process with green chemical approach for such a treatment. This chapter deals with photocatalytic degradation of different kinds of organic pollutants; mainly surfactants, pesticides, dyes, phenols, chloro compounds, nitrogen containing compounds etc. Mechanisms of their degradation have also been discussed with hydroxyl and allied radicals as the main active oxidizing species.

Synthesis, Characterization and Thermal Degradation of Substituted Acetophenone Based Terpolymers Having Biological Activities

The terpolymer resins have been synthesized by the condensation of p- hydroxyacetophenone and p-chloroacetophenone with formaldehyde/furfuraldehyde in the presence of catalyst in 1:1:5 molar proportions of reactants. The molecular structures were confirmed by FT-IR and Pyrolysis GC-MS. The number average molecular weights of these resins were determined by conductometric titration in non-aqueous medium. Viscometric measurements in tetrahydrofuran (THF) have been carried out with a view to ascertaining the characterstic functions and constant. Detailed thermal degradation studies of the terpolymer have been carried out to ascertain its thermal stability. A multiple linear regression (MLR) method has been used to calculate activation energies and frequency factor. Formaldehyde based terpolymer (E a= 22.3 KJ/mol, Z = 0.77) has a greater activation energy and frequency factor as compared to furfuraldehyde based terpolymer (E a=18.8 KJ/mol, Z = 0.25). Thermodynamic parameters such as free energy (ΔG), entropy change (ΔS*) and rate constant (k r) have also been evaluated on the basis of data of the Ozawa, Flynn and Wall method. All the synthesized polymers have shown excellent antimicrobial activities as compared to the standard Ciprofloxacin and Amphotericin-B drugs.

Photocatalytic Reduction of Carbon Dioxide

World is facing problems of global warming as well as energy crisis. Both these problems can be solved to a reasonable extent by photoreduction of carbon dioxide. Here, photocatalysis enters the scene. Photocatalytic reduction to synthetic organic fuels like formaldehyde, methanol, formic acid, acetic acid, methane, etc. will provide a solution to the problem of energy crisis as it will give us alternate fuels, which can be burnt into fuel cells to generate electricity. Once we get electricity at the cost of carbon dioxide, one can convert this form of energy to any other form of energy. Secondly, it will give a solution to put a check on the increasing amount of carbon dioxide, which is the main culprit of global warming. Any conventional fuel on burring will add some molecules of carbon dioxide in the atmosphere, but synthetic fuels derived by photocatalytic reduction of carbon dioxide will not add even a single molecule of carbon dioxide in the environment. It can be considered as a short term loan of carbon dioxide from the atmosphere as the carbon dioxide molecules utilized in the synthesis of alternate fuels are generated back on burning it in fuel cell.

Synthesis, Characterization, and Antimicrobial Properties of p-Chloroacetophenone Oxime-Based Furan Resins

A copolymer resin, p-chloroacetophenone oxime-furfuraldehyde (CAOFU), and a terpolymer resin, p-chloroacetophenone oxime-formaldehyde-benzoic acid (CAOFUBA), were synthesized in the presence of hydrochloric acid as catalyst. The structures of copolymer and terpolymer were established by FT-IR and 1H NMR techniques. Molecular weight and polydispersity index were determined by gel permeation chromatography. The thermal stability was evaluated by thermogravimetric analyses (TGA). Softening temperatures (Ts) of these polymers were obtained from differential scanning calorimetry (DSC). All the synthesized polymers have shown reasonably good antimicrobial activities.

Effect of transition metal ions on photocatalytic activity of ZnO in bleaching of some dyes

The photocatalytic bleaching of some dyes (erythrosin-B, fast green FCF and eosin Y) was carried in the presence of semiconducting zinc oxide and was observed spectrophotometrically. The effects of various operating variables like pH, concentration of dyes, amount of semiconductor and light intensity on the efficiency of the reaction were also observed. Attempts have been made to study the effect of the addition of other metal ions (Fe2+, Ni2+, Ag+, Cu2+, Co2+, V2+ and Mn2+). All the added metal ions increase the reaction rate to some extent. It was also observed that Fe2+ is most effective in photobleaching of erythrosin-B, whereas V2+ is more effective in the cases of fast green FCF and eosin Y. A tentative mechanism has been proposed.

Synthesis, Characterization, and Thermal Studies of Terpolymers Derived from Vanillin, Furfural, and Halo-Substituted Acetophenones

The terpolymer resins have been prepared by polycondensation of vanillin (V) and chloro/bromo-substituted acetophenone (CA/BA) with furfural (FU) in the presence of 1 M HCl in 1:1:2 molar proportions. The characterization and structural elucidation of terpolymers were confirmed by FT-IR, pyrolysis GC-MS, and non-aqueous conductometric titration. Activation energy during curing process was determined by the Kissinger method, whereas thermal decomposition was determined by the Ozawa-Flynn-Wall method. Both terpolymer resins have shown excellent antimicrobial activity as compared to the standard ciprofloxacin and amphotericin-B drugs.

Spectral and thermal characterization of halogen-bonded novel crystalline oligo(p-bromoacetophenone formaldehyde).

A novel oligomer p-bromoacetophenone-formaldehyde (OPBAF) was prepared by condensation polymerization in the presence of an acid as catalyst. It was characterized by FT-IR, NMR, pyrolysis GC/MS, XRD, GPC, and TG-DTG. The crystallographic parameters and space group for hexagonal OPBAF were a = b = 2.0810 Å and c = 9.2340 Å and P3̅m1, respectively. The degradation activation energy of the oligomer was studied by the Kissinger method. The kinetic parameters were also obtained. Halogen bonding interactions in the crystalline oligomers are identified between halogen···carbonyl and halogen···halogen. Little correlation was found in the halogen bonding motifs exhibited as a function of bromine present in this oligomer, and a unique bifurcated Br···Br/Br···O═C halogen bonding synthon was identified. This newly developed oligomer may be used as an interesting material for the development of 3D-designed structural products.

Microwave Assisted Synthesis of Some Pyridine Derivatives Containing Mercaptotriazole and Thiazolidinone as a New Class of Antimicrobial Agents

A fast and facile procedure for the synthesis of pyridomercaptotriazole 4a–e and pyridothiazolidinone 5a–e is being reported starting from dihydropyridine 1a–e . Subsequent oxidation with nitrating mixture (HNO 3 /H 2 SO 4 ) produced the anticipated 2,6-dimethylpyridine derivatives 2a–e , which were subsequently condensed with thiosemicarbazide in ethanol to produce the key intermediate 2,2′-[4-(4-substituted phenyl)- 2,6-dimethylpyridine-3,5-diyl]dicarbonyldihydrazine carbothioamides 3a–e . In the final step pyridomercaptotriazole derivatives 4a–e were synthesized by treating 3a–e in alkaline media. In parallel pyridothiazolidinone derivatives 5a–e were obtained by the reaction of 3a–e with ClCH 2 COOH/CH 3 COONa. All the reactions were carried out on microwave irradiation in good yield with short time. The structures of all the compounds have been confirmed on the basis of their analytical, IR, 1 H NMR, and Mass spectral data (Table I and Table II). The potent antimicrobial effects of the synthesized compounds were also investigated.

Use of Strontium Chromate as Photocatalyst for Degradation of Azure-A

The photocatalytic activity of strontium chromate (SrCrO4) is for the photodegradation of azure-A dye. The progress of photodegradation reaction was monitored by measuring the absorbance of the reaction mixture at definite time intervals. The effect of various parameters such as pH, the concentration of dye, amount of semiconductor and light intensity were varied to achieve the optimum rate of photodegradation. It was observed that strontium chromate has the highest catalytic activity in basic medium. A tentative mechanism for the reaction has been proposed.

PHOTOCATALYTIC ACTIVITY OF CdS - ZnS COMPOSITE AND THEIR COMPONENTS

A composite of CdS and ZnS was prepared by simple solid state mechanochemical method and it was used for photocatalytic degradation of Evan’s blue. The photocatalytic efficiency of CdS-ZnS composite was compared with pure CdS and ZnS. The effect of various parameters such as pH, concentration of dye, amount of semiconductor and light intensity was observed. The optimum conditions obtained for this degradation were: Evan’s blue = 1.3 × 10‾ 5 M, pH = 5.5, amount of composite = 0.12 g and light intensity = 50.0 mWcm‾ 2 . It was found that coupled chalcogenide CdS - ZnS shows better photocatalytic activity as compared with pure CdS and ZnS for the degradation of Evan’s blue in the presence of visible light