Duduku Krishnaiah

Preparation of titanium dioxide photocatalyst loaded onto activated carbon support using chemical vapor deposition: A review paper

Various methods to prepare and characterize TiO(2) photocatalyst loaded onto activated carbon (AC) support have been developed over the last decade. This photocatalyst has been used in a variety of investigations, i.e. from water decontamination to direct pollutant degradation in aqueous and gas phase systems using UV irradiation and lately with the assistance of ultrasonic sound waves. Chemical vapor deposition (CVD) method is one of the most promising and well-researched methods for deposition of catalysts onto supports. Given its advantage, from an engineering and fundamental aspect, CVD method also has commercial applications. A detailed search of published reports of these investigations was carried out and analyzed in this paper with focus on CVD techniques, activated carbon support and sonication.

Sonophotocatalysis in advanced oxidation process: A short review

Sonophotocatalysis involves the use of a combination of ultrasonic sound waves, ultraviolet radiation and a semiconductor photocatalyst to enhance a chemical reaction by the formation of free radicals in aqueous systems. Researchers have used sonophotocatalysis in a variety of investigations i.e. from water decontamination to direct pollutant degradation. This degradation process provides an excellent opportunity to reduce reaction time and the amount of reagents used without the need for extreme physical conditions. Given its advantages, the sonophotocatalysis process has a futuristic application from an engineering and fundamental aspect in commercial applications. A detailed search of published reports was done and analyzed in this paper with respect to sonication, photocatalysis and advanced oxidation processes.

A review of polymer nanofibres by electrospinning and their application in oil-water separation for cleaning up marine oil spills.

The growths of oil and gas exploration and production activities have increased environmental problems, such as oil spillage and the resulting pollution. The study of the methods for cleaning up oil spills is a critical issue to protect the environment. Various techniques are available to contain oil spills, but they are typically time consuming, energy inefficient and create secondary pollution. The use of a sorbent, such as a nanofibre sorbent, is a technique for controlling oil spills because of its good physical and oil sorption properties. This review discusses about the application of nanofibre sorbent for oil removal from water and its current developments. With their unique physical and mechanical properties coupled with their very high surface area and small pore sizes, nanofibre sorbents are alternative materials for cleaning up oil spills.

Parametric and adsorption kinetic studies of methylene blue removal from simulated textile water using durian (Durio zibethinus murray) skin

In this study, durian (Durio zibethinus Murray) skin was examined for its ability to remove methylene blue (MB) dye from simulated textile wastewater. Adsorption equilibrium and kinetics of MB removal from aqueous solutions at different parametric conditions such as different initial concentrations (2-10 mg/L), biosorbent dosages (0.3-0.7 g) and pH solution (4-9) onto durian skin were studied using batch adsorption. The amount of MB adsorbed increased from 3.45 to 17.31 mg/g with the increase in initial concentration of MB dye; whereas biosorbent dosage increased from 1.08 to 2.47 mg/g. Maximum dye adsorption capacity of the durian skin was found to increase from 3.78 to 6.40 mg/g, with increasing solution pH. Equilibrium isotherm data were analyzed according to Langmuir and Freundlich isotherm models. The sorption equilibrium was best described by the Freundlich isotherm model with maximum adsorption capacity of 7.23 mg/g and this was due to the heterogeneous nature of the durian skin surface. Kinetic studies indicated that the sorption of MB dye tended to follow the pseudo second-order kinetic model with promising correlation of 0.9836 < R(2) < 0.9918.

Kinetic and thermodynamic characteristics of seaweed dried in the convective air drier.

This study reveals the drying kinetics, specific heat and enthalpy of seaweed dried in the convective air drier. Comparison between convective hot air and sun drying process was also studied. At 50°C air temperature with 23.45 percent relative humidity and 1.55 ms-1air flow rate, it has been found that the moisture removal required 4 hours to reach moisture content of 19.66 percent wet basis with its drying rate at 0.28 x 10-3 kg water h-1. The data of drying rate showed that the drying process took place in the falling rate period. The specific heat and initial enthalpy were found to be 1.3842 kJkg-1°C-1 and 1672.69 kJkg-1, respectively. It was observed that the drying kinetics, specific heat, and enthalpy values vary significantly as functions of air temperature which seem to have more effect when compared to air flow rate and seaweed loading. Hence, the best method for seaweed drying was to use convective air system rather than sun drying because it required less drying time and has better drying efficiency.

Variation of reaction stages and mole composition effect on melamine-urea-formaldehyde (MUF) resin properties

MUF resin is widely used as an adhesive in wood industries, coating technology, paper industries and a main material in kitchenware production. In various applications, different resin properties are needed to suit its application. Important resin properties are for example higher resin solubility, low curing period with lower temperature and catalyst amount, good stability for longer shelf life, and lower free )brmaldehyde emission, as formaldehyde is very toxic, and can cause cancer. One of the factors that affecting the MUF resin properties is the mole composition. The mole composition is a ratio of/brmaldehyde to amino compound i.e. melamine or urea, in each reaction stages. Besides that addition of other chemical such as sorbitol, may be added to enhance the resin properties. In Turin (1998)and Gapud et al. (1999) researches, addition of sorbitol has improve the resin stability and solubility in water and also cured resin flexibility. Using experimental design such as Surface Response Method optimises the product formulation. This method is more satisfactory and effective than other methods such as classical one-at-a-time or mathematical methods because it can study many variables simultaneously with a low number of observations, saving time and costs. Hence in this research, statistical experimental design or mixture design is used in this work in order to optimise the MUF resin formulation.

Removal of chlorinated phenol from aqueous solution utilizing activated carbon derived from papaya (carica papaya) seeds

Activated carbons (ACs) were prepared from papaya seeds with different dry weight impregnation ratios of zinc chloride (ZnCl2) to papaya seeds by using a two-stage self-generated atmosphere method. The papaya seeds were first semi-carbonized in a muffle furnace at 300 °C for 1 h and then impregnated with ZnCl2 before activation at 500 °C for 2 h. Several physical and chemical characteristics such as moisture, ash, pH, functional groups, morphological structure and porosity of prepared ACs were studied and presented here. AC2, with the impregnation ration of 1: 2 (papaya seeds: ZnCl2), yielded a product that had the highest adsorption capacity, 91.75%, achieved after 180min contact time. The maximum Brunauer, Emmett and Teller (BET) surface area of AC2 was 546m2/g. Adsorption studies indicated that AC2 complied well with the Langmuir isotherm (qm=39.683mg g−1) and the pseudo-second-order (qe=29.36mg g−1). This indicated that chemisorption was the primary adsorption method for AC2. The intraparticle diffusion model proved that the mechanism of adsorption was separated into two stages: the instantaneous stage and the gradual adsorption stage. Overall, this work demonstrated the suitability of using papaya seeds as a precursor to manufacture activated carbon.

Sonolysis, Photolysis, and Sequential Sonophotolysis for the Degradation of 2,4,6-Trichlorophenol: The Effect of Solution Concentration

Ultrasonic sound waves, ultraviolet-A irradiation, and a combination of these two techniques were applied to a non-catalytic aqueous system containing 2,4,6-trichlorophenol (TCP) to study the effectiveness of sonolytic, photolytic, and sonophotolytic oxidation processes for the degradation of TCP. The operating parameters for the horn-type sonicator and the UV-A lamp were kept constant along with the solution temperature, but the TCP concentration was varied from 30 to 90 ppm. A first-order kinetic rate model was used to study the synergistic effect of the sonophotodegradation process. It was found that at a lower TCP concentration of 30 ppm, sonophotodegradation exhibited a synergistic effect, but at a TCP concentration of 70 ppm and higher, sonophotodegradation resulted in an antagonistic effect. The synergistic effect was explained in terms of an increase in the •OH radical formation by the combined process complemented by the photolysis of H2O2 formed by sonolysis. In contrast, the antagonistic effect was explained in terms of the combined effect of viscosity increase resulting in the reduction of the cavitation efficiency and degradation rate, and by considering the dynamics of bubble growth and implosion.

Decolorization of Low Molecular Compounds of Seaweed by Using Activated Carbon

Commercially available carrageenan powder which is extracted from seaweed possesses yellowish color and off-odor that deter their usage in human food, pharmaceutical and cosmetic industries. The objective of this study was to investigate of decolorization of low molecular compounds of seaweed using activated carbon (AC). The effects of changes on AC dosage, temperature and contact time were investigated. The effect of color concentration was analysed using Hunter Laboratories ColorFlex® Colorimeter. Colors were measured in reflectance mode using the Hunter L a b system, with D65 as the illuminant and a 10 o standard observer angle. It was observed that an increase in activated carbon dosage decreases color. UV VIS Spectrophotometer was used to investigate whether adsorbed sample gives an effect to the molecular compounds before and after AC addition. In conclusion, the treatment using AC gives complete decolorization of carrageenan solution. This study also confirms contact time not really affected on bleaching process.

Spray Drying of Morinda Citrifolia L. and Beta Vulgaris L. Fruit Extract and Its Synergistic Effect

 Abstract—This study was to examine the antioxidant potential of Morindacitrifolia L. and Beta vulgaris L. fruits and its synergistic effect. The bioactive components of these fruits were extracted and then microencapsulated by spray drying technique. The antioxidant activities of these fruits were analyzed, before and after the spray drying process through DPPH radical scavenging activity, total phenolic content and total flavonoid content. The encapsulation yield of the spray drying process was also quantified. Among the spray drying samples encapsulation yield was found maximum 8 % for the mixed fruit extract. Similarly, synergistic effect between the two fruits showed the highest antioxidant activity of 30% and the individual fruit extract also exhibited significant antioxidant activity.