Structure of Carbon Nanotube-dendrimer composite

Using all atomistic molecular dynamics (MD) simulations we report the microscopic picture of the nanotube-dendrimer complex for PAMAM dendrimer of generation 2 to 4 and carbon nanotube of chirality (6,5). We find compact wrapping conformations of dendrimer onto the nanotube surface for all the three generations of PAMAM dendrimer. The degree of wrapping is more for non-protonated dendrimer compared to the protonated dendrimer. For comparison we also study the interaction of another dendrimer, poly(propyl ether imine) (PETIM), with nanotube and show that PAMAM dendrimer interacts strongly as compared to PETIM dendrimer as is evident from the distance of closest approach as well as the number of close contacts between the nanotube and dendrimer. We also calculate the binding energy between the nanotube and the dendrimer using MM/PBSA methods and attribute the strong binding to the charge transfer between them. Dendrimer wrapping on CNT will make it soluble and can act as an efficient dispersing agent for nanotube

Base pair opening and bubble transport in a DNA double helix induced by a protein molecule in a viscous medium

We study the nonlinear dynamics of a protein-DNA molecular system by treating DNA as a set of two coupled linear chains and protein in the form of a single linear chain sliding along the DNA at the physiological temperature in a viscous medium. The nonlinear dynamics of the above molecular system in general is governed by a perturbed nonlinear Schr\"{o}dinger equation. In the non-viscous limit, the equation reduces to the completely integrable nonlinear Schr\"{o}dinger (NLS) equation which admits N-soliton solutions. The soliton excitations of the DNA bases make localized base pair opening and travel along the DNA chain in the form of a bubble. This may represent the bubble generated during the transcription process when an RNA-polymerase binds to a promoter site in the DNA double helical chain. The perturbed NLS equation is solved using a perturbation theory by treating the viscous effect due to surrounding as a weak perturbation and the results show that the viscosity of the solvent in the surrounding damps out the amplitude of the soliton.Comment: 4. Submitted to Phys. Rev.

Exploratory studies on beneficiation of low-grade Banded Iron ore Formations (BIF) of Karnataka, India

Iron ore is the basic raw material for production of metallic iron. With depletion of high-grade resources and fine dissemination of valuable minerals in the abundantly available low-grade banded iron ore formations (BIF), liberation is achieved at finer sizes. Hence, it necessitated all beneficiation techniques to be operated at this finer size. However, physical separation techniques have limitations in separation efficiency. A combination of pre-concentration technique such as magnetic separation followed by flotation of magnetic fraction proved to be promising in achieving the respectable grade. A low-grade iron ore sample (BIF) of Karnataka, India was subjected to high intensity magnetic separation followed by flotation for enhancing its grade and recovery. Laboratory scale studies on this ore assaying 39.80 Fe%, 39.62 SiO2% and 1.73 Al2O3% indicated that it could be improved to 63.78 Fe%, 3.10 SiO2% and 1.01 Al2O3% at an overall iron recovery of 24% only. However, attempts are being made to further improve the iron recovery

Flotation of low-grade graphite ore using collector derived from low density polyethylene waste

The increasing wide range of applications of graphite for electrode, lubricants, refractory applications especially the recent surging electric automobile industry, resulting in significant need of graphite in future. Graphite demand in the energy storage industry is expected to grow 15 times faster than today's demand by 2030. Due to depleting high-grade ore, utilization of low-grade ore by beneficiation becomes utmost importance for sustainable development and resource management. In this work, low-grade graphite ore from Tamil Nadu, India with 86.84% ash was beneficiated by flotation technique for recovering graphite with lower ash content. Flotation, a surface phenomena, based on the surface hydrophobicity of the mineral surface to be separated and since graphite is naturally flotation mineral, this technique is adopted for beneficiation. The mostly commonly used collector in graphite flotation is diesel. In view of continuous cost escalation of diesel, an alternate collector was developed utilizing the low-density polyethylene (LDPE) waste paving way for plastic waste utilization. The flotation efficacy of this new collector (Collector PE) derived from LDPE waste was compared with that of diesel in graphite flotation. The run-of mine graphite ore was initially size reduced for liberation of values from its associated impurities, followed by flotation. The mesh-of-grind, dosages of collector (diesel and PE) and frother (Methyl Isobutyl Carbinol, MIBC) were optimized for better process efficiency for increasing the surface hydrophobicity of graphite particles leading to better separation efficacy. The ore characterization by x-ray diffraction revealed that graphite was accompanied predominantly by quartz with minor fractions of pyrites and several other phyllosilicates such as kaolinite and muscovite. Exfoliated morphology of graphite with thick layers were observed from SEM images. Flotation reagents such as diesel, collector PE and MIBC were characterized by FTIR to analyze their functional groups that enhances the efficiency of the separation process. A graphite float (rougher concentrate) with 15.2% weight recovery and 17.7% ash content was obtained after 10 minutes of grinding (d80: 240.5µm) with 0.85kg/t of collector (diesel) and 0.07kg/t of frother (MIBC) dosages and on two-stage cleaning, a final concentrate with 12.66% weight recovery and 8.70% ash content was obtained. A graphite final concentrate with 13.04% weight recovery and 8.90 % ash was achieved with two-stage cleaning, when treated with 0.57 kg/t of collector PE and 0.07 kg/t of MIBC. These results indicate that the flotation efficiency of the collector PE derived from LDPE wastes is comparable with that of diesel and would be economical when used in large scale industrial graphite flotation

Column flotation technology for the beneficiation of coking and non-coking coal fines

The importance of coal is bound to increase for the coming years with the growth of coal consuming industries. Power sector is the most potential consumer of the non-coking coal and for coking coal iron & steel sector remains the major consumer. In future, coal gasification which is successfully adopted in China, an advanced coal-based power generation technology has the potential to provide higher generating efficiency and can be adopted to efficiently burn India’s high-ash coals. In the present study investigations are carried out on coal fines for both coking and non coking coals by conventional and column flotation techniques to suit industrial applications. Coking coal sample is taken from Jamadoba area in Jharkhand and non-coking coal is drawn from coal belt in Central Coal Fields, Jharkhand. For both the coals detailed studies are in progress for optimizing the reagent consumption and to establish the feasibility of column flotation technology for producing low ash concentrates with reasonably high recoveries

Recovery of values from tailing ponds of iron ore washing plants

Most of the Iron ore washing plants set up in India in the earlier days consist of sizing of the ore by dry / wet screening, washing and classification by screw classifiers. In this classical approach, iron values were lost in the form of fines and utrafines into the tailing ponds as they had little commercial value in those days and accumulated in huge quantities over the years. As the high grade deposits are getting exhausted and the demand for high grade finer material for pellet making is ever increasing, focus is shifting towards recovering the values from the erstwhile tailing ponds by column flotation. This is also supposed to mitigate to certain extent the environmental problems caused by the ever expanding and unmanageable tailing dams. A case study is presented wherein a composite sample is prepared from samples drawn systematically from multi - locations in a sprawling tailing dam. Laboratory scale column flotation tests on this composite tailings sample, basically originating from two operating iron ore beneficiation plants of JSW Steel Ltd., one of the leading producers of steel in India, are found to be encouraging. De-sliming followed by reverse and cationic flotation tests using flotation column resulted in the concentrate of 61.88% Fe, 4.81% SiO2, 2.52% Al2O3 and 3.30% loss on ignition (LOI) from the tailings analysing 57.86% Fe, 7.10% SiO2, 3.52% Al2O3 and 6.14% LOI with 52% weight recovery. The causes for the quality improvement could be attributed to de-sliming of unliberated ultra fines of kaoline and hydrated iron oxides and their further reduction by efficient flotation process. The process and the cationic collector developed for this purpose are adopted in the new flotation plant created to treat these tailings

STUDY ON FLOTATION OF SILLIMANITE USING PLANT-BASED COLLECTOR

The coastal lines of India are rich in placer deposits of valuable heavy minerals such as ilmenite, garnet, rutile, zircon and sillimanite. The conducting and magnetic minerals are separated first, leaving behind the non-conducting and non-magnetic sillimanite along with quartz in the processing of heavies in beach sand. Sillimanite, an important mineral for refractory application is mainly recovered by flotation technique from its associated major gangue mineral, quartz by imparting selective surface hydrophobicity on sillimanite using a suitable collector. A placer sample after the removal of heavies from eastern coast of India was studied for beneficiation using froth flotation technique. Detailed characterization studies of the feed sample and the types of collectors used for this study have been carried out using XRD and FTIR analyses. Sillimanite feed sample assaying 55.4% sillimanite along with 33.9% quartz, 1.7% magnetics, 1.4% rutile, 2.4% zircon, 5.6% kynite was subjected to beneficiation using flotation technique for enriching the sillimanite content using oleic acid and a plant-based reagent SFA as collector. The effect of variation of input parameters such as pH, depressant and collectors were evaluated and flotation process optimization was carried out. Based on the results, it was found that flotation performance of the natural source based collector has better selectivity and improved recovery as compared to that of oleic acid as collector. Weight recovery of 67.8% with 85.1% sillimanite was obtained using the plant-based collector while a weight recovery of 55.5% with 84.9% sillimanite was obtained using oleic acid. The improved sillimanite recovery by using the plant-based collector than that of the conventional oleic acid would be more economical in industrial scale sillimanite recovery in beach sand processing industries

Monitoring vegetation dynamics using multi-temporal Normalized Difference Vegetation Index (NDVI) and Enhanced Vegetation Index (EVI) images of Tamil Nadu

Vegetation indices serve as an essential tool in monitoring variations in vegetation. The vegetation indices used often, viz., normalized difference vegetation index (NDVI) and enhanced vegetation index (EVI) were computed from MODIS vegetation index products. The present study aimed to monitor vegetation's seasonal dynamics by using time series NDVI and EVI indices in Tamil Nadu from 2011 to 2021. Two products characterize the global range of vegetation states and processes more effectively. The data sources were processed and the values of NDVI and EVI were extracted using ArcGIS software. There was a significant difference in vegetation intensity and status of vegetation over time, with NDVI having a larger value than EVI, indicating that biomass intensity varies over time in Tamil Nadu. Among the land cover classes, the deciduous forest showed the highest mean values for NDVI (0.83) and EVI (0.38), followed by cropland mean values of NDVI (0.71) and EVI (0.31) and the lowest NDVI (0.68) and EVI (0.29) was recorded in the scrubland. The study demonstrated that vegetation indices extracted from MODIS offered valuable information on vegetation status and condition at a short temporal time period

Eco Friendly and Cost-Effective Reagent for Coal Flotation

Conventionally, diesel in combination with a frother is used widely in flotation of coal fines. With the continuous price escalation of petroleum products and their negative impact on environment, attempts were made to formulate an eco-friendly single reagent to replace diesel-frother system without affecting the flotation performance. Laboratory flotation tests were carried out, on a coking coal sample from eastern India, that analyzed 25.67% ash and 53.97% fixed carbon using a series of reagents developed. Among them, the performance of Sokem 590C derived from a vegetable oil was found to be encouraging. Concentrate assaying 11.77% ash and 66.40% fixed carbon was obtained with yield of 56.57%. Moreover, the reagent is biodegradable and eco friendly. Based on favorable kinetics and encouraging test results, plant trials were conducted at a coal preparation plant and the superiority of this reagent was demonstrated

Single reagent for coal flotation

Froth flotation is widely used for the beneficiation of fine coal and collectors are important for the effective separation in flotation. Conventionally, diesel in combination with a commercial frother is used in most of the coal washeries. With the escalating costs of petroleum products and their negative impact on environment, attempts were made to formulate an eco-friendly single reagent to replace diesel-frother system without hindering the flotation process performance. NML-Madras Centre in collaboration with M/s Somu Organo Chem Pvt Ltd, has been working on the formulation and evaluation of flotation reagents. Laboratory flotation tests were carried out using series of single reagents on a coking coal sample from Jharia region in the eastern part of India with an ash content of 24.9%. The best among the single reagents, Sokem 590C, yielded a float of 56.57% at 13.97% ash in the bench scale laboratory test. Based on encouraging results of flotation tests and kinetics studies, plant trials were conducted at a coal preparation plant in eastern India. The results of plant trials using this single reagent, Sokem 590C, are highly encouraging and economical as compared to diesel-frother system and this single reagent is non-petroleum based and biodegradable