Chemical analysis of low carbon content coals and their applications as dye adsorbent.

Coal is primarily a fuel material but lately it has been utilized as an adsorbent for removing toxic metal ions. However, its usage for removing organic pollutants is not well studied. We report here a systematic study on the use of coal samples of varying carbon contents as adsorbents for removing Basic Blue 41 as a model cationic dye. The coal samples were collected from coal mines and were thoroughly characterized. The concentrations of carbon, hydrogen, oxygen, nitrogen and sulphur contents were measured by CHNS analyzer. The concentrations of aluminum, silicon, sulphur, titanium and iron were determined by EDXRF, which corresponded to silicon dioxide (quartz) and aluminium silicate (kaolinite) as the major mineral inclusions, corroborated by XRD results and micrographs showing elemental maps determined from SEM-EDAX. The coal samples with low carbon content revealed higher adsorption capacity (qe âˆ¼ 8.0-9.3 mg/g) of Basic Blue dye at optimized adsorbent dose (2 mg/mL), pH 9 and contact time (120 min). The adsorption kinetic studies satisfied pseudo second order model and the intra-particle diffusion of the dye was evident. The dye adsorption followed Langmuir adsorption isotherm, and the qmax values ranged between 17 and 30 mg/g for low carbon content coal. The FT-IR, Brunauer-Emmett-Teller (BET) surface area and zeta potential results of the coal samples could explain the adsorption phenomenon of cationic dye. The kinetic and thermodynamic studies revealed that the adsorption of Basic Blue 41 dye was based on chemisorptions mechanism.

Colorimetric method for the detection of melamine using in-situ formed silver nanoparticles via tannic acid.

Melamine toxicity has recently attracted worldwide attention as it causes renal failure and the death of humans and animals. Therefore, developing a simple, fast and sensitive method for the routine detection of melamine is the need of the hour. Herein, we have developed a selective colorimetric method for the detection of melamine in milk samples based upon in-situ formation of silver nanoparticles (AgNPs) via tannic acid. The AgNPs thus formed were characterized by UV-Visible spectrophotometer, transmission electron microscope (TEM), zetasizer and dynamic light scattering (DLS). The AgNPs were used to detect melamine under in vitro condition and in raw milk spiked with melamine. Under optimal conditions, melamine could be selectively detected in vitro within the concentration range of 0.05-1.4µM with a limit of detection (LOD) of 0.01µM, which is lower than the strictest melamine safety requirement of 1ppm. In spiked raw milk, the recovery percentage range was 99.5-106.5% for liquid milk and 98.5-105.5% for powdered milk. The present method shows extreme selectivity with no significant interference with other substances like urea, glucose, glycine, ascorbic acid etc. This assay method does not utilize organic cosolvents, enzymatic reactions, light sensitive dye molecules and sophisticated instrumentation, thereby overcoming some of the limitations of the other conventional methods.