M. Surianarayanan

Extraction and recovery of azo dyes into an ionic liquid

The azo dyes are commonly used in the leather and textile industries as they are quite versatile in nature. However, they are neither totally utilised during the process, nor are they recovered at the end of the process. In fact, in the leather industry, typically about 10-15% of the dye is discharged with the effluent creating both environmental and economic issues. Hence, there is a need to remove the residual dye from the large volume of aqueous effluent. In this study, for the first time, azo dyes employed in the leather industry have been successfully extracted into a neutral ionic liquid, with an extraction efficiency of 98%, potentially providing a method of minimizing pollution of waste-waters. The extraction of the dye into the ionic liquid also provides a potential analytical approach to determination of these dyes.

Multi-attribute decision making for green electrical discharge machining

This paper aims to develop a combination of Taguchi and fuzzy TOPSIS methods to solve multi-response parameter optimization problems in green manufacturing. Electrical Discharge Machining (EDM), a commonly used non-traditional manufacturing process was considered in this study. A decision making model for the selection of process parameters in order to achieve green EDM was developed. An experimental investigation was carried out based on Taguchi L9 orthogonal array to analyze the sensitivity of green manufacturing attributes to the variations in process parameters such as peak current, pulse duration, dielectric level and flushing pressure. Weighing factors for the output responses were determined using triangular fuzzy numbers and the most desirable factor level combinations were selected based on TOPSIS technique. The model developed in this study can be used as a systematic framework for parameter optimization in environmentally conscious manufacturing processes.

Choline-Based Ionic Liquids-Enhanced Biodegradation of Azo Dyes

Industrial wastewaters such as tannery and textile processing effluents are often characterized by a high content of dissolved organic dyes, resulting in large values of chemical and biological oxygen demand (COD and BOD) in the aquatic systems into which they are discharged. Such wastewater streams are of rapidly growing concern as a major environmental issue in developing countries. Hence there is a need to mitigate this challenge by effective approaches to degrade dye-contaminated wastewater. In this study, several choline-based salts originally developed for use as biocompatible hydrated ionic liquids (i.e., choline sacchrinate (CS), choline dihydrogen phosphate (CDP), choline lactate (CL), and choline tartarate (CT)) have been successfully employed as the cosubstrate with S. lentus in the biodegradation of an azo dye in aqueous solution. We also demonstrate that the azo dye has been degraded to less toxic components coupled with low biomass formation.

Spectroscopic investigations of polyacrylonitrile thermal degradation

PAN undergoes chemical decomposition in stages on thermal treatment. In the literature, several mechanisms were proposed for the degradation process. However, the decomposition pathway and the structural rearrangement of solid residue in relation to the loss of volatile products are not fully understood. The degradation process has therefore received further attention in this work by employing a combination of FT-IR, high-resolution solid-state 13C-NMR, pyrolysis GC-MS, and microelemental analysis. These investigations have established that PAN decomposes to gaseous and volatile products over a range of temperatures (150–590°C) with concurrent stabilization of the structure of residual matter occurring on a parallel course. While linear polymerization of nitrile group is the principal reaction in the decomposition process, cyclization followed by extended conjugation is the notable exothermic process. No evidence has been obtained for the formation of oxygen-containing chromophores either as intermediates or as part of the chemical structure of the residue. Temperature sensitivity of oligomer formation has been established through pyrolysis–GC-MS studies. The overall decomposition profile of PAN has thus been established.

Curcumin loaded poly(2-hydroxyethyl methacrylate) nanoparticles from gelled ionic liquid--in vitro cytotoxicity and anti-cancer activity in SKOV-3 cells.

The main focus of this study is to encapsulate hydrophobic drug curcumin in hydrophilic polymeric core such as poly(2-hydroxyethyl methacrylate) [PHEMA] nanoparticles from gelled ionic liquid (IL) to improve its efficacy. We have achieved 26.4% drug loading in a biocompatible hydrophilic polymer. Curcumin loaded PHEMA nanoparticles (C-PHEMA-NPs) were prepared by nano-precipitation method. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) analysis showed that the prepared nanoparticles were spherical in shape and free from aggregation. The size and zeta potential of prepared C-PHEMA-NPs were about 300 nm and -33.4 mV respectively. C-PHEMA-NPs were further characterized by FT-IR spectroscopy which confirmed the existence of curcumin in the nanoparticles. X-ray diffraction and differential scanning calorimetry studies revealed that curcumin present in the PHEMA nanoparticles were found to be amorphous in nature. The anticancer activity of C-PHEMA-NPs was measured in ovarian cancer cells (SKOV-3) in vitro, and the results revealed that the C-PHEMA-NPs had better tumor cells regression activity than free curcumin. Flow cytometry showed the significant reduction in G0/G1 cells after treatment with C-PHEMA-NPs and molecular level of apoptosis were also studied using western blotting. Toxicity of PHEMA nanoparticles were studied in zebrafish embryo model and results revealed the material to be highly biocompatible. The present study demonstrates the curcumin loaded PHEMA nanoparticles have potential therapeutic values in the treatment of cancer.

Exothermic and thermal runaway behaviour of some ionic liquids at elevated temperatures

The exothermic behaviour and intrinsic safety of a number of ionic liquids being considered for battery and solar cell applications have been investigated at elevated temperatures by analysing data from accelerated rate calorimetric (ARC) studies.

Thermal hazards of cracker mixture using DSC

DSC studies of cracker mixtures of different compositions of potassium nitrate, sulphur and aluminum have shown some critical characteristics either with the increase or decrease in the composition of the components. Specifically, sulphur composition below 8% showed no exothermic activity. The studies revealed that a minimum of 11% to a maximum of 17% of sulphur is required for good cracking characteristics. The kinetics of decomposition of cracker mixture is carried out employing DSC multiple heating rate kinetic method. Increase in sulphur content decrease the energy of activation facilitating easy ignition of the cracker mixtures. Arrhenius parameters for cracker mixture decomposition are reported in this paper.

Biocalorimetric and respirometric studies on biological treatment of tannery saline wastewater

This study is focused on the biodegradation of saline tannery effluent by identified halotolerant bacterial consortia in a bench-scale reaction calorimeter. A satisfactory agreement was observed between oxygen uptake rate profiles and heat flux–time curves confirming that, under strict aerobic conditions, calorimetry and respirometry provided the same information. Oxycalorific equivalent determined from our experiments was found to agree well to the theoretical value. A linear relationship was observed between chemical oxygen demand consumption and total metabolic heat production. The study confirmed that the heat release profiles could be used as an indirect parameter for online monitoring of the degradation process. The effect of salt (NaCl) inhibition on acetate and ammonia

Effect of Process Parameters on the Breathing Zone Concentration of Gaseous Hydrocarbons—A Study of an Electrical Discharge Machining Process

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