Dipak V. Pinjari

A critical review on textile wastewater treatments: Possible approaches.

Waste water is a major environmental impediment for the growth of the textile industry besides the other minor issues like solid waste and resource waste management. Textile industry uses many kinds of synthetic dyes and discharge large amounts of highly colored wastewater as the uptake of these dyes by fabrics is very poor. This highly colored textile wastewater severely affects photosynthetic function in plant. It also has an impact on aquatic life due to low light penetration and oxygen consumption. It may also be lethal to certain forms of marine life due to the occurrence of component metals and chlorine present in the synthetic dyes. So, this textile wastewater must be treated before their discharge. In this article, different treatment methods to treat the textile wastewater have been presented along with cost per unit volume of treated water. Treatment methods discussed in this paper involve oxidation methods (cavitation, photocatalytic oxidation, ozone, H2O2, fentons process), physical methods (adsorption and filtration), biological methods (fungi, algae, bacteria, microbial fuel cell). This review article will also recommend the possible remedial measures to treat different types of effluent generated from each textile operation.

Phase transformation of nanostructured titanium dioxide from anatase-to-rutile via combined ultrasound assisted sol-gel technique

An effort was made to synthesize nanostructured TiO(2) via sol-gel technique to obtain a 100% rutile polymorph of nanostructured TiO(2). The sol-gel synthesis technique was suitably modified by incorporating ultrasound to study the effect of cavitation on the phase transformation, crystallite size, crystallinity and morphological (scanning electron microscopy) properties of the obtained nano-TiO(2). It was observed that using ultrasound, yield of the nano-TiO(2) was improved from 86.35% to 95.078%. The phase transformation of anatase-to-rutile of TiO(2) was studied for both (ultrasound assisted and conventional) the processes. Complete phase transformation of the TiO(2) was observed as expected with and without the use of ultrasound but the marked reduction in the required calcination temperature for obtaining 100% phase transformation with ultrasound was the major achievement in the present study, leading to 70% energy savings during calcination.

Ultrasound assisted synthesis of doped TiO2 nano-particles: characterization and comparison of effectiveness for photocatalytic oxidation of dyestuff effluent.

The present work deals with the synthesis of titanium dioxide nanoparticles doped with Fe and Ce using sonochemical approach and its comparison with the conventional doping method. The prepared samples have been characterized using X-ray diffraction (XRD), FTIR, transmission electron microscopy (TEM) and UV-visible spectra (UV-vis). The effectiveness of the synthesized catalyst for the photocatalytic degradation of crystal violet dye has also been investigated considering crystal violet degradation as the model reaction. It has been observed that the catalysts prepared by sonochemical method exhibit higher photocatalytic activity as compared to the catalysts prepared by the conventional methods. Also the Ce-doped TiO(2) exhibits maximum photocatalytic activity followed by Fe-doped TiO(2) and the least activity was observed for only TiO(2). The presence of Fe and Ce in the TiO(2) structure results in a significant absorption shift towards the visible region. Detailed investigations on the degradation indicated that an optimal dosage with 0.8 mol% doping of Ce and 1.2 mol% doping of Fe in TiO(2) results in higher extents of degradation. Kinetic studies also established that the photocatalytic degradation followed the pseudo first-order reaction kinetics. Overall it has been established that ultrasound assisted synthesis of doped photocatalyst significantly enhances the photocatalytic activity.

Room temperature synthesis of crystalline CeO2 nanopowder: advantage of sonochemical method over conventional method.

In the present study, nano-sized ceria (CeO(2)) powders were prepared using conventional and sonochemically assisted precipitation method, without any stabilizers, using cerium nitrate as a starting material and sodium hydroxide as a precipitating agent. The synthesized ceria powders were characterized by XRD, TGA and SEM to determine crystallite size, % crystallinity, thermal weight loss and shape respectively. It was found that the crystallite size obtained in both the synthesis methods were below 30 nm. It was also found that sonochemical synthesis method is energy efficient method saving more than 92% of energy as compared to that utilized by the conventional synthesis method. There was also a significant reduction in the reaction duration.

Ultrasound and deep eutectic solvent (DES): A novel blend of techniques for rapid and energy efficient synthesis of oxazoles

The present work deals with the synthesis of novel oxazole compounds by using effective combination of ultrasound (US) and deep eutectic solvent (DES). The reaction was also conducted by thermal method (NUS) and the comparative studies are provided. It was observed that applying ultrasound not only improved yields and reduced reaction times but also saved more than 85% energy as shown by energy consumption calculations. The advantages of using DES as reaction medium is highlighted from the fact that it is bio-degradable, non-toxic, recyclable and could be easily prepared using inexpensive raw materials. The recyclability for DES was studied wherein it was found that ultrasound has no negative effects on DES even up to four runs. In addition, the present work is the first report on the combinative use of DES and US in organic synthesis.

Cavitation milling of natural cellulose to nanofibrils.

Cavitation holds the promise of a new and exciting approach to fabricate both top down and bottom up nanostructures. Cavitation bubbles are created when a liquid boils under less than atmospheric pressure. The collapse process occurs supersonically and generates a host of physical and chemical effects. We have made an attempt to fabricate natural cellulose material using hydrodynamic as well as acoustic cavitation. The cellulose material having initial size of 63 micron was used for the experiments. 1% (w/v) slurry of cellulose sample was circulated through the hydrodynamic cavitation device or devices (orifice) for 6h. The average velocity of the fluid through the device was 10.81m/s while average pressure applied was 7.8 kg/cm(2). Cavitation number was found to be 2.61. The average particle size obtained after treatment was 1.36 micron. This hydrodynamically processed sample was sonicated for 1h 50 min. The average size of ultrasonically processed particles was found to be 301 nm. Further, the cellulose particles were characterized with X-ray diffraction (XRD) and differential scanning calorimetry (DSC) to see the effect of cavitation on crystallinity (X(c)) as well as on melting temperature (T(m)). Cellulose structures consist of amorphous as well as crystalline regions. The initial raw sample was 86.56% crystalline but due to the effect of cavitation, the crystallinity reduced to 37.76%. Also the melting temperature (T(m)) was found to be reduced from 101.78 degrees C of the original to 60.13 degrees C of the processed sample. SEM images for the cellulose (processed and unprocessed) shows the status and fiber-fiber alignment and its orientation with each other. Finally cavitation has proved to be very efficient tool for reduction in size from millimeter to nano scale for highly crystalline materials.

Synthesis of titanium dioxide by ultrasound assisted sol–gel technique: Effect of amplitude (power density) variation

Titanium dioxide was successfully synthesized by utilizing sol-gel technique modified by incorporation of ultrasound as a reaction aid. The effect of amplitude of irradiation (power input varied from 19.9 to 80.8 W) on % Rutile, % yield, % crystallinity, crystallite size and morphological (scanning electron microscopy) properties of the obtained nano-TiO(2) was studied. Calcination temperatures of all the samples were kept constant at 750 degrees C. With increasing ultrasonic irradiation amplitude it is observed that the values of % Rutile (after calcination) increased and reached a peak value after which further increase in amplitude resulted in a decrease in the % Rutile. A similar trend was observed in the case of % crystallinity and % yield of the reaction. On the basis of these results an optimum operating ultrasonic irradiation amplitude for the reaction has been suitably established.

Analysis of semibatch emulsion polymerization: role of ultrasound and initiator.

In this work semibatch miniemulsion was carried out wherein the effect of free radicals produced by ultrasound and an external addition of initiator was examined. Influence of different variables on polymerization rate and polymer particle size has also been investigated. Over a range of 0-4% (by wt) initiator, the polymerization rate was found to increase over a range of 0.56-1.33 g L(-1) min(-1). Similarly monomer concentration range (7.2-15 wt.%) changed the polymerization rate from 1.33 to 2.61 g L(-1) min(-1). Under optimum parametric conditions polymer particle size 50 nm were obtained with a narrow size distribution. Syndiotactic phase of PMMA was observed by controlling the formulation recipe. Although, number of reports could be found in the literature [9,13,17,18,20,22] related to batch emulsion polymerization, this experimental data could be useful for the production of large scale monodispersed PMMA latex as all of the scale-up and design parameters have been qualitatively addressed.

Synthesis of zirconium dioxide by ultrasound assisted precipitation: Effect of calcination temperature

Nanostructured zirconium dioxide was synthesized from zirconyl nitrate using both conventional and ultrasound assisted precipitation in alkaline medium. The synthesized samples were calcinated at temperatures ranging from 400°C to 900°C in steps of 100°C. The ZrO(2) specimens were characterized using X-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). The thermal characteristics of the samples were studied via Differential Scanning Calorimetry-Thermo-Gravimetry Analysis (DSC-TGA). The influence of the calcination temperature on the phase transformation process from monoclinic to tetragonal to cubic zirconia and its consequent effect on the crystallite size and % crystallinity of the synthesized ZrO(2) was studied and interpreted. It was observed that the ultrasound assisted technique helped to hasten to the phase transformation and also at some point resulted in phase stabilization of the synthesized zirconia.

Degradation of reactive orange 4 dye using hydrodynamic cavitation based hybrid techniques.

In the present work, degradation of reactive orange 4 dye (RO4) has been investigated using hydrodynamic cavitation (HC) and in combination with other AOPs. In the hybrid techniques, combination of hydrodynamic cavitation and other oxidizing agents such as H2O2 and ozone have been used to get the enhanced degradation efficiency through HC device. The hydrodynamic cavitation was first optimized in terms of different operating parameters such as operating inlet pressure, cavitation number and pH of the operating medium to get the maximum degradation of RO4. Following the optimization of HC parameters, the degradation of RO4 was carried out using the combination of HC with H2O2 and ozone. It has been found that the efficiency of the HC can be improved significantly by combining it with H2O2 and ozone. The mineralization rate of RO4 increases considerably with 14.67% mineralization taking place using HC alone increases to 31.90% by combining it with H2O2 and further increases to 76.25% through the combination of HC and ozone. The synergetic coefficient of greater than one for the hybrid processes of HC+H2O2 and HC+Ozone has suggested that the combination of HC with other oxidizing agents is better than the individual processes for the degradation of dye effluent containing RO4. The combination of HC with ozone proves to be the most energy efficient method for the degradation of RO4 as compared to HC alone and the hybrid process of HC and H2O2.