Materials Science Forum Vol. 734

Abstract: The ultrasonic decolourisation of two commonly used textile dyes, Acid Red 114 (AR 114) and Reactive Blue 21 (RB 21), with different chromophoric groups, azo and phthalocyanine respectively, has been studied using TiO₂ (consisting of mixture of crystalline and amorphous phases) in the presence of rare earths ions (Pr³⁺, Ce⁴⁺). The characterisation of TiO₂ has been done through X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman spectroscopy, diffuse reflectance spectroscopy (DRS) and N₂ adsorption techniques. The decolourisation of AR 114 was faster than for RB 21 under all the experimental conditions. Almost complete decolourisation of both dyes was achieved in 5 min in the presence of US+TiO₂+Ce. Ce⁴⁺ was found to be more effective than Pr³⁺. The decolourisation reaction followed second order kinetics. The effects of initial dye concentration and amount of TiO₂ on the decolourisation of dyes have been found to be in the order; US+TiO₂+Ce > US+TiO₂+Pr > US+Ce > US+Pr > US+TiO₂ > TiO₂ >US. The decolourisation rate increased with increase in TiO₂ amount and decreased with increase in initial dye concentration.

Abstract: 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.

Abstract: Recent interest and studies in environmental photo-chemistry, in natural photosynthesis, and chemical methods for solar energy transformations has contributed greatly to our knowledge and understanding of the various phenomena related to both photo-chemistry and catalysis. As an emerging nanotechnology come together with the chemical mechanisms of photo-catalysis, the photo-catalytic nanoparticle titanium dioxide offers a new meaning of remediation and degradation on volatile organic compounds in the aqueous and airs streams. In this chapter we discuss about application of photocatalysis in environment like biological contamination, air purification, water disinfection, hazardous waste remediation, water purification, self-clean buildings, deodorizing, anti-bacterial action, anti-fogging resolving cleaning action etc.

Abstract: The aim of this work focused on the preparation of Mn²⁺ doped on TiO₂ by impregnation method for the photocatalytic degradation of Reactive Red-3 dye aqueous solution. Characterizations of the photocatalyst were carried out by using XRD, BET, SEM and UV-DRs. The extended photocatalysis were studied as functions of %wt Mn²⁺ (0%, 0.05%, 0.1%), pollutant concentration, solution pH and catalyst loading using Response Surface Method (RSM) based on Box-Behnken design. Based on results found that the anatase phase was not affected by Mn²⁺ added on the surface of TiO₂ whereas the rutile phase increased with increasing Mn²⁺ contents. The band gap energy of Mn²⁺ doped on TiO₂ did not show in red shift but it exhibited higher absorbance than neat TiO₂ in visible region. The surface area was insignificantly changed for Mn²⁺ doped on TiO₂. The degradation results were investigated that pollutant concentration, pH of solution and loading of Mn²⁺ on TiO₂ were significant parameters effecting on photocatalytic degradation of Reactive Red-3 dye. The existence of Mn²⁺ on TiO₂ decreased the activity of rectaion. The optimum condition was 0%wt of Mn²⁺, 10 ppm of Reactive Red-3, pH 4 and 4.0 g/L of catalyst loading.

Abstract: The aim of this work was focused on the photocatalytic degradation of alachlor from aqueous solution using 10%wt Fe-TiO₂, as 0.1%wt of Fe doped into TiO₂ structure, immobilized on granular activated carbon (GAC) under black light irradiation. The extended photocatalytic conditions were studied as functions of catalyst loading, number of black light, and initial pH of solution using Response Surface Method (RSM) based on Box-Behnken design (BBD). Characterizations of the photocatalyst by TGA-DTA, and XRD were investigated. Photocatalyst was calcined at 400°C under nitrogen atmosphere. As a Result of calcinations, photocatalyst consisted of only graphite crystallite while the crystallite phases of TiO₂ were not observed. The degradation results showed that the photocatalytic process gave the highest percent degradation comparing with adsorption and photolysis processes. The effects of three operating variables which are catalyst loading, number of black light, and initial pH of solution on the degradation efficiency of alachlor were examined. Photocatalyst loading was only significant parameter effecting for photocatalytic degradation of alachlor. The photocatalytic degradation slightly increased with increasing of number of black light while pH of solution did not affect photocatalytic degradation of alachlor. The photocatalytic process and adsorption process were affected from the initial alachlor concentrations as well.

Abstract: The treatment of highly colored wastewater containing hazardous industrial chemicals and dyes is one of the growing needs of the present time. To meet the motive in the present work, TiO₂ was immobilized on glass slides using heat method and acrylic binder. Heat method involves the preparation of suspension of powdered TiO₂ and then brushing the suspension on the surface of glass slides. The slides were then calcined at high temperature for attachment of TiO₂ to the glass surface. The acrylic binder method of immobilization involves preparation of acrylic emulsion and using the same to attach the TiO₂ particles to the fiber glass slides. The preared films were then characterized using XRD and SEM. The photocatalytic performance of the prepared films for degradation of Acid Red 27 dye in sunlight was evaluated and compared. The films formed with the help of heat treatment method showed better dye degradation capabilities.

Abstract: Al₂O₃-TiO₂ and ZrO₂-TiO₂ nanocomposites have been prepared by sol-gel method using polyvinylpyrrolidone-polyethylene glycol (PVP-PEG) as templating agents. While Al₂O₃ in the former is of end-centered monoclinic crystal structure ZrO₂ in the latter is a 4:1 blend of monoclinic and tetragonal phases. In both the composites TiO₂ is present as anatase. The energy dispersive X-ray spectra provide the compositions of the composites as Al:Ti::1:12 and Zr:Ti::1:1. Scanning electron micrographs display the sizes of Al₂O₃-TiO₂ and ZrO₂-TiO₂ particles as 30-77 and 38-57 nm, respectively. The diffuse reflectance spectra of both the composites show band gap excitation in the UV-A region. Both the composites display similar photoluminescence and the observed near band gap emission and deep level emission agree with those of TiO₂. The impedance spectral studies reveal that the charge-transfer resistance of ZrO₂-TiO₂ is less than that of Al₂O₃-TiO₂. Both the composites exhibit photoconductance. The photocatalytic activities of the prepared nanocomposites depend on the dye employed. While both the composites degrade methylene blue and rhodamine B effectively under UV-A light the photodegradation of methyl orange is slow. Rhodamine B degrades on both the nanocomposites under visible light also, which is through dye-sensitized photocatalytic mechanism.

Abstract: This article presents a comparative study on the synthesis and characterization of the binary and ternary ferrites for photocatalytic and photoelectrochemical applications. The importance and role of ferrite photocatalysts is discussed in context to the visible-light active photocatalyst application viz. for hydrogen production via. water-splitting. It also demonstrates that computational-exploration of any material system is key to identify, and achieve visible-light active photocatalysts.

Abstract: In the present scenario, the problem of water pollution is remarkable. The need to maintain clean water for both flora and fauna has become a major, even a critical concern. A large number of organic substances are introduced into the natural water system from various sources such as industrial effluents, agricultural runoff and chemical spills. Textiles industries specifically pollute the water sources due to the random use and discharge of various types of dyes. It may significantly affect photosynthetic activity in aquatic life and their presence in drinking water constitutes a potential human health hazard. It is therefore essential either to remove the dyes from water or to treat them in such a way so as to minimize their effects on the environment and also to decolorize the water. Various research works on different processes are reviewed and discussed in the present article. It has been observed that the advanced oxidation processes are used widely to degrade the organic compounds in water. Photocatalytic systems are effective for the degradation of many unwanted complex organic compounds through the use of efficient nanophotocatalysts activated under ultra-violet (UV) irradiation.

Abstract: Titanium dioxide (Titania; TiO₂) is one of the most widely used metal oxide semiconductor in the field of photocatalysis for removal of pollutants. It has been noted that titanium dioxide is a research friendly material as its physico-chemical and catalytic properties can be easily altered as per specific application. Since many years, researchers have tried to modify the properties of titanium dioxide by means of doping with metals and non-metals to improve its performance for photocatalytic degradation (PCD) applications. The doping of various metal ions like Ag, Ni, Co, Au, Cu, V, Ru, Fe, La, Pt, Cr, Ce, etc. in titanium dioxide have been found to be influencing the band gap, surface area, particle size, thermal property, etc. and therefore the photocatalytic activity in PCD. Moreover, photocatalytic activity of doped titanium dioxide has been observed in visible light range (i.e., at wavelength >400 nm). In this review, different synthesis route for doping of metal ions in titanium dioxide have been emphasised. The effect of metal dopant on the structural, textural and photocatalytic properties of titanium dioxide has been reviewed.