P. Ilaiyaraja

Bio: P. Ilaiyaraja is an academic researcher from Indian Institute of Technology Madras. The author has contributed to research in topic(s): Nanorod & Adsorption. The author has an hindex of 15, co-authored 32 publication(s) receiving 636 citation(s). Previous affiliations of P. Ilaiyaraja include Indira Gandhi Centre for Atomic Research & VIT University.

Adsorption of uranium from aqueous solution by PAMAM dendron functionalized styrene divinylbenzene

Abstract: A new polymeric chelating resin was prepared by growing third generation poly(amido)amine (PAMAMG3) dendron on the surface of styrene divinylbenzene (SDB) and characterized by FTIR, TGA and SEM. The ideal branching of dendron in the chelating resin was determined from potentiometric titration. Adsorption of uranium (VI) from aqueous solution using PAMAMG3-SDB chelating resin was studied in a series of batch experiments. Effect of contact time, pH, ionic strength, adsorbent dose, initial U(VI) concentration, dendron generation and temperature on adsorption of U(VI) were investigated. Kinetic experiments showed that U(VI) adsorption on PAMAMG3-SDB followed pseudo-second-order kinetics model appropriately and equilibrium data agreed well with the Langmuir isotherm model. Thermodynamic parameters (ΔH°, ΔS°, ΔG°) were evaluated from temperature dependent adsorption data and the uranium adsorption on PAMAMG3-SDB was found to be endothermic and spontaneous in nature. The sticking probability value (5.303 × 10−9), kinetic and isotherm data reveal the chemisorption of uranium on PAMAMG3-SDB and adsorption capacity of the chelating resin was estimated to be 130.25 mg g−1 at 298 K. About 99% of adsorbed U(VI) can be desorbed from PAMAMG3-SDB by a simple acid treatment suggesting that the chelating resin is reusable.

Diglycolamide functionalized multi-walled carbon nanotubes for removal of uranium from aqueous solution by adsorption

Abstract: Diglycolamide functionalized multi-walled carbon nanotubes (DGA-MWCNTs) were synthesized by sequential chemical reactions for removal of uranium from aqueous solution. Characterization studies were carried out using FT-IR spectroscopy, XRD and SEM analysis. Adsorption of uranium from aqueous solution on this material was studied as a function of nitric acid concen- tration, adsorbent dose and initial uranium concentration. The uranium adsorption data on DGA-MWCNTs followed the Langmuir and Freundlich adsorption isotherms. The adsorption capacity of DGA-MWCNTs as well as adsorp- tion isotherms and the effect of temperature on uranium ion adsorption were investigated. The standard enthalpy, entropy, and free energy of adsorption of the uranium with DGA-MWCNTs were calculated to be 6.09 kJ mole -1 , 0.106 kJ mole -1 K -1 and -25.51 kJ mole -1 respectively at 298K. The results suggest that DGA-MWCNTs can be used as efficient adsorbent for uranium ion removal.

Influence of surface disorder, oxygen defects and bandgap in TiO2 nanostructures on the photovoltaic properties of dye sensitized solar cells

Abstract: We present a detailed study on the microstructural, structural and optical properties of hydrogen treated (HT) diverse TiO2 nanostructures (TNS) in comparison to the as-prepared (AP) samples. The effect of oxygen vacancies (VO), introduced in the anatase TiO2 by hydrogenation, on the photovoltaic (PV) characteristics is discussed. Raman spectroscopy shows A1g second order scattering modes due to VO-influenced surface structural changes. EELS confirm the presence of Ti4+/Ti3+ mixed states and oxygen deficiency in all TNS-HT. Bandgap (Eg) of TNS can be tuned by controlling the temperature and/or duration of annealing. The indirect bandgap is found to be larger (~3.2–3.4 eV) for TNS derived from Ti-foil, whereas TNS prepared using wet-chemical methods exhibit Eg in the range of 3.1–3.3 eV. The introduction of VO red-shifts the band-edge by ~0.25 eV. Hydrogenation decreases the PV efficiency (η) by 2–4 times compared to η=6–7% observed in DSSCs of diverse nanostructures. Despite the reduction in interfacial resistance enhancing electron generation and transport in TNS-HT samples, EIS studies indicate that the drop in η (%) is mainly due to the recapture of conduction band electrons via defect states shortening the electron lifetime.

Surface Engineering of PAMAM-SDB Chelating Resin with Diglycolamic Acid (DGA) Functional Group for Efficient Sorption of U(VI) and Th(IV) from Aqueous Medium

Abstract: A novel chelating resin obtained via growth of PAMAM dendron on surface of styrene divinyl benzene resin beads, followed by diglycolamic acid functionalization of the dendrimer terminal. Batch experiments were conducted to study the effects of pH, nitric acid concentration, amount of adsorbent, shaking time, initial metal ion concentration and temperature on U(VI) and Th(IV) adsorption efficiency. Diglycolamic acid terminated PAMAM dendrimer functionalized styrene divinylbenzene chelating resin (DGA-PAMAM-SDB) is found to be an efficient candidate for the removal of U(VI) and Th(IV) ions from aqueous (pH > 4) and nitric acid media (> 3 M). The sorption equilibrium could be reached within 60 min, and the experimental data fits with pseudo-second-order model. Langmuir sorption isotherm model correlates well with sorption equilibrium data. The maximum U(VI) and Th(IV) sorption capacity onto DGA-PAMAMG5-SDB was estimated to be about 682 and 544.2 mg g−1 respectively at 25 °C. The interaction of actinides and chelating resin is reversible and hence, the resin can be regenerated and reused. DFT calculation on the interaction of U(VI) and Th(IV) ions with chelating resin validates the experimental findings.

Adsorptive removal of thorium from aqueous solution using diglycolamide functionalized multi-walled carbon nanotubes

Abstract: Multi-walled carbon nanotubes (MWCNTs) were functionalized with diglycolamide (DGA) through chemical covalent route. The adsorption behavior of the DGA-functionalized-MWCNTs (DGA-MWCNTs) towards thorium from aqueous solution was studied under varying operating conditions of pH, concentration of thorium, DGA-MWCNTs dosages, contact time, and temperature. The effective range of pH for the removal of Th(IV) is 3.0–4.0. Kinetic data followed a pseudo-second-order model. The equilibrium data were correlated with the Langmuir, Freundlich, Dubinin-Radushkevich and Temkin models. The equilibrium data are best fitted with Langmuir model. The equilibrium Th(IV) sorption capacity was estimated to be 10.58 mg g−1 at 298 K. The standard enthalpy, entropy, and free energy of adsorption of the thorium with DGA-MWCNTs were calculated to be 8.952 kJ mol−1, 0.093 kJ mol−1 K−1 and -18.521 kJ mol−1 respectively at 298 K. The determined value of sticking probability (0.072) and observed kinetic and isotherm models reveal the chemical adsorption of thorium on DGA-MWCNTs.

Theory of the linear and nonlinear optical properties of semiconductor microcrystallites

Abstract: We analyze theoretically the optical properties of ideal semiconductor crystallites so small that they show quantum confinement in all three dimensions [quantum dots (QD's)]. In the limit of a QD much smaller than the bulk exciton size, the linear spectrum will be a series of lines, and we consider the phonon broadening of these lines. The lowest interband transition will saturate like a two-level system, without exchange and Coulomb screening. Depending on the broadening, the absorption and the changes in absorption and refractive index resulting from saturation can become very large, and the local-field effects can become so strong as to give optical bistability without external feedback. The small QD limit is more readily achieved with narrow-band-gap semiconductors.

Sustainable technologies for water purification from heavy metals: review and analysis

Abstract: Water pollution is a global problem threatening the entire biosphere and affecting the life of many millions of people around the world. Not only is water pollution one of the foremost global risk factors for illness, diseases and death, but it also contributes to the continuous reduction of the available drinkable water worldwide. Delivering valuable solutions, which are easy to implement and affordable, often remains a challenge. Here we review the current state-of-the-art of available technologies for water purification and discuss their field of application for heavy metal ion removal, as heavy metal ions are the most harmful and widespread contaminants. We consider each technology in the context of sustainability, a largely neglected key factor, which may actually play a pivotal role in the implementation of each technology in real applications, and we introduce a compact index, the Ranking Efficiency Product (REP), to evaluate the efficiency and ease of implementation of the various technologies in this broader perspective. Emerging technologies, for which a detailed quantitative analysis and assessment is not yet possible according to this methodology, either due to scarcity or inhomogeneity of data, are discussed in the final part of the manuscript.

On the Structure of "秀才秀才,错字布袋

Abstract: Sentence patterns like "秀才秀才,错字布袋"are unique in the grammatical structure, semantic structure and pragmatic function. The typical feature of this pattern is that the same word or phrase reappears continually at the very beginning. It has two parts: (1) The proceeding part("秀才秀才") includes a word and its repeated form, which is different from the reduplication in grammar and the continual repetition in rhetoric. This part can have referential functions in particular situations;and (2) The main function of the last part ("错字布袋")is to interpret the proceeding one. It is the semantic focus of the whole sentence. This sentence pattern typically shows the features of proverbs like "秀才秀才,错字布袋"in language structure,semantic meaning and pragmatic function.

Mussel-inspired fabrication of functional materials and their environmental applications: Progress and prospects

Abstract: Mussel-inspired chemistry has recently emerged as one of the most important and interest surface modification method owing to its gentle experiment conditions, high modification efficiency and universality. The mussel-inspired chemistry is mainly relied on the adhesion of dopamine toward various materials and surfaces. In recent years, great efforts have been devoted to understanding the adhesion mechanism of mussel and extending its applications in different fields. In this mini-review, we present the very recent development of mussel-inspired fabrication of functional materials for environmental applications. The surface modification strategies that based on mussel-inspired chemistry were outlined in the first part. The environmental applications (e.g. oil/water separation, environmental adsorption and catalysts) based on these functional materials are also highlighted in the following sections. Although many advances have been achieved, there still have a plenty of spaces for further development of mussel-inspired surface chemistry for functional materials and their environmental applications.

Emerging natural and tailored materials for uranium-contaminated water treatment and environmental remediation

Abstract: The rapid growth in nuclear industries such as uranium ores mining, nuclear energy generation, spent-fuel treatment and nuclear weapon manufacture has caused a legacy of uranium contamination in the aquatic environment, which poses a potential threat to the ecological environment and human health. The safe and effective disposal of uranium-contaminated water has thus been an urgent requirement. For decades, various materials have been shown to be capable for removing uranium from aqueous solution by adsorption technique, namely inorganic materials (e.g., clay minerals, metal oxides, mesoporous silica), organic polymers (e.g., resins, cellulose, chitosan), carbon family materials (e.g., mesoporous carbon, carbon nanotubes, graphene oxides), and porous framework materials (e.g., covalent organic frameworks, metal-organic frameworks). In this review, we provide a systematic and comprehensive overview of the researches conducted from 2005 to 2018 for uranium removal from aqueous solution by these emerging materials. The different approaches in the determination of the adsorption mechanisms between uranium and adsorbents are also briefly summarized, involving macroscopic experimental approaches, microscopic spectroscopic and computational approaches. Finally, we discuss the current limitations and propose future research perspectives in hopes of inspiring more dramatic advancements in the material and environment remediation fields.