Amara Dar

Removal of Pb(II) and Cd(II) from water by adsorption on peels of banana.

The adsorption of lead(II) and cadmium(II) on peels of banana has been studied in batch mode using flame atomic absorption spectroscopy for metal estimation. Concerned parameters like adsorbent dose, pH, contact time and agitation speed were investigated. Langmuir, Freundlich and Temkin isotherms were employed to describe adsorption equilibrium. The maximum amounts of cadmium(II) and lead(II) adsorbed (qm), as evaluated by Langmuir isotherm, were 5.71 mg and 2.18 mg per gram of powder of banana peels, respectively. Study concluded that banana peels, a waste material, have good potential as an adsorbent to remove toxic metals like lead and cadmium from water.

Removal of Chromium on Polyalthia longifolia Leaves Biomass

Adsorption is an environmental friendly process for removal and/or recovery of heavy metals from wastewater. In recent years, it has been substantiated as a popular technique to treat industrial waste effluents, with significant advantages. In this work, batchwise removal of chromium (III) ions from water by Polyalthia longifolia leaves was studied as a function of adsorbent dose, pH, contact time, and agitation speed. Surface characteristics of the leaves were evaluated by recording IR spectra. The Langmuir, Freundlich, and Temkin adsorption isotherms were employed to explain the sorption process. It was found that one gram of leaves can remove 1.87 mg of trivalent chromium when working at pH 3.0. It has been concluded that Polyalthia longifolia leaves can be used as cost-effective and benign adsorbents for removal of Cr(III) ions from wastewater.

A Rapid, Economical, and Eco-Friendly Method to Recycle Terephthalic Acid from Waste Poly (Ethylene Terphthalate) Bottles

A method has been proposed to rapidly degrade waste PET (polyethylene terphthalate) bottles and recover terephthalic acid (TPA) in good yield. The method involves fusion of PET bottle chips with caustic soda in a china-clay crucible placed on the silicon carbide (SiC) slab by exposure to microwaves in a domestic oven. The PET waste was converted to water-soluble sodium salt of TPA in just 4 minutes. Afterwards, the solution was acidified with HCl to recover TPA in high yield. The method can be used to design environmentally benign and fast industrial prototypes to recycle terephthalic acid from waste PET bottles.

Novel methods to determine sulfide in aqueous samples by quantification of lead sulfide spots

Two new, simple, accurate, and economical methods to find out sulfide (S2−) at low levels (10−9 g) in aqueous samples have been proposed. The first method involved the generation of hydrogen sulfide (H2S) in a specially designed small cell by interacting sulfide solution with hydrochloric acid. The resulting H2S is passed through a filter paper pre-dipped in lead acetate solution that made dark brown lead sulfide spots on the paper. In the second method, micro-liter drops of sulfide solution are applied on silica gel TLC pre-moistened with the lead acetate solution that developed lead sulfide spots. The color densities of the spots were calculated by scanning the spotted paper and TLC and analyzing the image using a specially developed software. The TLC method was more effective at trace levels having a linear response in the range 5–100 ng in comparison to 100–900 ng of the H2S method. Statistical examination of the calibration line validated the pertinence of these methods for the analysis of reduced form of sulfur in aqueous samples, particularly when dealing with small sample volumes.

Removal of sulfide ions from water using rice husk

Sulfide is an unwanted anion present in tannery effluents. In this study, a raw material namely rice husk has been used to check its performance to remove sulfide ions from water in batch adsorption experiments. The effects of various physical parameters such as contact time, pH, shaking speed and temperature have been investigated to optimize the conditions for maximum adsorption efficiency. Rice husk was further pretreated with calcium chloride, zinc chloride and organic solvents to check any change in uptake capacity of the adsorbent. Langmuir, Freundlich and Temkin isotherms were used to explain the nature and mechanism of adsorption. The results argue that rice husk could be a useful material to treat sulfide-containing wastewaters. GRAPHICAL ABSTRACT

Estimation of sulfur by gas-phase molecular absorption spectroscopy (GPMAS) and use in pharmaceutical analysis

In the present study, gas-phase molecular absorption spectroscopy (GPMAS) is used to estimate sulfur in organic compounds and drugs. Organosulfur compounds or drugs were fused with sodium (metal) to convert available sulfur to sodium sulfide, followed by dissolution in water. Afterwards, the filtered solution was treated with sulfuric acid (concentrated) to release H2S. Hydrogen sulfide swept with nitrogen into a long absorption cell through which light of wavelength 198 nm produced by suitable lamp passed to record absorbance. The proposed method was also used to find out the effect of concentration and time on the stability of sulfide solutions. The method has low standard deviation and can produce accurate results down to 2 μg/mL−1 sulfide concentration.

Catalytic Depolymerisation of Polystyrene

Polystyrene waste was depolymerised by using various acidic and basic catalysts. Among the metal oxides, calcium oxide was found to be the cheapest and most effective catalyst for the depolymerization of waste polystyrene into styrene. Metal carbonates provided pure styrene, but in low yields. Acids were found to be poor catalysts for depolymerisation, since they led to further reactions leading to side products.