Pradeep Thalappil

Department Of Chemistry

Fulltext

IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

Challenges and Directions for Green Chemical Engineering—Role of Nanoscale Materials

Sustainable Nanoscale Engineering: From Materials Design to Chemical Processing

Water scarcity is one of the most alarming problems of the planet. An ambient ion based method is developed to make hydrophilic-hydrophobic patterned silver nanowires (NWs) as humidity harvesters of unprecedented efficiency. Such water harvesters are developed by two-step surface modification of the as-synthesized NWs (known from a report earlier) using electrospray. These patterned NWs of ≈20 µm length and ≈200 nm width grown over a relatively large area (2 × 2 cm2) exhibit atmospheric water capture (AWC) efficiency of 56.6 L m−2 d−1, the highest reported so far. The whole fabrication process of the surface is performed under ambient conditions with a home-built nanoelectrospray ion source, without the help of any sophisticated instrumentation. The synthesized material combines and mimics two exciting examples of AWC in nature, which are cactae and Namib Desert beetles, which utilize AWC for their living. It is believed that the combination of the special features of the above two natural species helps to achieve the highest water capture efficiency reported till date. A working prototype using this surface for AWC is also fabricated. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Advanced Materials Interfaces

Patterned Nanobrush Nature Mimics with Unprecedented Water-Harvesting Efficiency

The present study is targeted toward understanding the interaction between important and technologically relevant polymorphs of iron oxides/oxyhydroxides with arsenic species at neutral pH. The existence of various arsenic (As) species in solution was verified by Raman measurements. Their species-dependent adsorption on the affordable arsenic removal media, confined metastable 2-line ferrihydrite (CM2LF) was investigated. The results were compared with common adsorption media, hematite (α-Fe2O3) and magnetite (Fe3O4). X-ray photoelectron spectroscopy was used to investigate the changes in the core levels of Fe 2p and As 3d resulting from the uptake of arsenic species. Binding of various As species with CM2LF was confirmed by FTIR studies. Raman adsorption data were found to fit a pseudo-second-order model. Results of this study show the synthesized nanocomposite of CM2LF to be very effective for the removal of As(III) and As(V) species in comparison to various materials at neutral pH. A model for the adsorption of As(III) and As(V) species in water on a ferrihydrite particle was developed. This accounted for the large uptake capacity. Copyright © 2018 American Chemical Society.

ACS Sustainable Chemistry and Engineering

Species-Specific Uptake of Arsenic on Confined Metastable 2-Line Ferrihydrite: A Combined Raman-X-Ray Photoelectron Spectroscopy Investigation of the Adsorption Mechanism

As(III) and As(V) as well as mixed forms of the same could be effectively scavenged by a composite with fast kinetics allowing the creation of an affordable arsenic-free drinking water solution for point-of-use applications. The granular composites, composed of iron oxyhydroxide-chitosan nanostructures, were synthesized by a green synthetic route, which in general involves the hydrolysis of a metal precursor-chitosan complex using an alkaline medium followed by washing and drying at ambient conditions. Metal ion precursor used for the preparation of the composite was Fe3+. All syntheses were carried out in deionized water, while natural ground water or tap water was used for testing. An iron oxyhydroxide-chitosan nanostructure was synthesized. 25 mg of confined metastable 2-line ferrihydrite (CM2LF) was shaken with 100 mL of natural tap water. Arsenic removal efficiency of CM2LF was measured by spiking the natural tap water with As(III) and As(V) separately. Thereafter, the water was left standing for 1.5 h and subsequently the leftover arsenic concentration in treated water was analyzed using inductively coupled plasma mass spectrometry (ICP-MS) after acidification with 5% HNO3. Experiments with water filtration cartridges are described in the main Text. The unprecedented large capacity in field conditions is attributed to the inherent structure of the composite with confined metastable 2-line ferrihydrite in biopolymer cages, which allows the creation of effective adsorption sites. The arsenic adsorption capacity of the composite is 1.4 to 7.6 times better than the available compositions.

Advanced Materials

Confined Metastable 2-Line Ferrihydrite for Affordable Point-of-Use Arsenic-Free Drinking Water

We describe a simple and inexpensive cellulose-derived and layer-by-layer stacked carbon fiber network electrode for capacitive deionization (CDI) of brackish water. The microstructure and chemical composition were characterized using spectroscopic and microscopic techniques; electrochemical/electrical performance was evaluated by cyclic voltammetry and 4-probe electrical conductivity and surface area by Brunauer-Emmett-Teller analysis, respectively. The desalination performance was investigated using a laboratory batch model CDI unit, under fixed applied voltage and varying salt concentrations. Electro-adsorption of NaCl on the graphite reinforced-cellulose (GrC) electrode reached equilibrium quickly (within 90 min) and the adsorbed salts were released swiftly (in 40 min) back into the solution, during reversal of applied potential. X-ray photoelectron spectroscopic studies clearly illustrate that sodium and chloride ions were physisorbed on the negative and positive electrodes, respectively during electro-adsorption. This GrC electrode showed an electro-adsorption capacity of 13.1 mg/g of the electrode at a cell potential of 1.2 V, with excellent recyclability and complete regeneration. The electrode has a high tendency for removal of specific anions, such as fluoride, nitrate, chloride, and sulfate from water in the following order: Cl- > NO<inf>3</inf>- > F- > SO<inf>4</inf>2-. GrC electrodes also showed resistance to biofouling with negligible biofilm formation even after 5 days of incubation in Pseudomonas putida bacterial culture. Our unique cost-effective methodology of layer-by-layer stacking of carbon nanofibers and concurrent reinforcement using graphite provides uniform conductivity throughout the electrode with fast electro-adsorption, rapid desorption, and extended reuse, making the electrode affordable for capacitive desalination of brackish water. © 2015 American Chemical Society.

ACS Applied Materials and Interfaces

Cellulose derived graphenic fibers for capacitive desalination of brackish water

A new methodology has been demonstrated for ultratrace detection of Hg2+, working at the limit of a few tens of metal ions. Bright, red luminescent atomically precise gold clusters, Au@BSA (BSA, bovine serum albumin), coated on Nylon-6 nanofibers were used for these measurements. A green emitting fluorophore, FITC (fluorescein isothiocyanate), whose luminescence is insensitive to Hg2+ was precoated on the fiber. Exposure to mercury quenched the red emission completely, and the green emission of the fiber appeared which was observed under dark field fluorescence microscopy. For the sensing experiment at the limit of sensitivity, we have used individual nanofibers. Quenching due to Hg2+ ions was fast and uniform. Adaptation of such sensors to pH paper-like test-strips would make affordable water quality sensors at ultralow concentrations a reality. © 2014 American Chemical Society.

Journal	Data powered by TypesetSustainable Nanoscale Engineering: From Materials Design to Chemical Processing
Publisher	Data powered by TypesetElsevier
Open Access	No