nan Waheed-uz-Zaman

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 (III) by using coal as adsorbent.

The adsorption of Cr(III) by two different coal varieties from Lakhra and Thar coalfields (Pakistan) have been studied in batch mode. The effect of adsorbent dose, pH, contact time and agitation speed on the adsorption of Cr(III) by both the coals were investigated. Adsorption equilibrium was achieved in 40-50 min. The Langmuir, Freundlich and Temkin adsorption isotherms were used to elucidate the observed sorption phenomena. The maximum Cr(III) removal was 2.61 mg of Cr(III) per gram of LC (Lakhra coal) and 2.55 mg of Cr(III) per gram of TC (Thar coal) as evaluated from Langmuir isotherm. The heat of sorption was in the range 3.75-3.87 kJ/mol as evaluated from Temkin isotherm. Best results were obtained at pH>5. It is proposed that low rank coals of Pakistan can be used for removal of toxic metals like Cr(III) from industrial effluents/waste waters.

Micro-determination of arsenic in aqueous samples by image scanning and computational quantification

Arsenic is highly toxic in all of its forms found in natural groundwater. An improved method for the estimation of inorganic arsenic at low levels (μg L−1) in water has been proposed. The method involves the generation of arsine in a specially designed cell by borohydride reduction of arsenite (AsO21−). The resulting arsine is passed through a filter paper pre-dipped in mercuric bromide solution giving a yellowish brown complex. The color intensity of the spots is calculated by scanning the spotted paper and analyzing the image using specially designed software. The method was found to be effective at trace levels having a linear response at the concentration range 2–20μg L−1 (8–80ng). The detection limit of the proposed method is 1 μg L−1 (4 ng) which can be reduced further by making some modifications to the apparatus. The method was successfully applied to the analysis of synthetic samples and field samples of 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.

Computational Quantification of Spot Tests by Image Scanning-A New Analytical Technique for Micro Samples

The benefits of spectrophotometric quantitative analysis and the small sample requirements of a spot test have been merged in this new methodology for metal analysis at the sub-micro level. A 1 µL sample is transferred to a suitable medium (TLC plate) with subsequent application of reagent(s) at the same spot; the color density of the resulting spot is then measured using a flatbed color scanner connected to a PC running specially developed software. Calibration data was collected for As, Hg, and Pb in 1–5 ppb range with a correlation co-efficient better than 0.9962. The method is especially suitable for precipitation systems where absorption spectroscopy fails.

Removal of chromium from water using pea waste – a green approach

Abstract Agro-waste materials have carboxylic and phenolic groups that play the main role in metal adsorption. The advantages of these materials include easy availability, low cost, and reasonable metal removal capacity. One of the materials (usually considered as waste) is pea waste (pods). Present work comprises adsorption of chromium from aqueous solution using powder of pods of garden peas (Pisum sativum) in batch. Important parameters like adsorbent dose, pH, contact time, and agitation speed were studied. Adsorption equilibrium was explained by Langmuir, Freundlich, and Temkin isotherms. Maximum chromium uptake (q m) was 3.56 mg/g of adsorbent. Heat of adsorption, as evaluated by Temkin isotherm was 1.96 kJ/mol. It is proposed that pea pods can be an effective and environmentally benign (green) adsorbents for removal of chromium from industrial effluents and waste waters.

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.

PRODUCTION OF TEREPHTHALIC ACID FROM WASTE POLY(ETHYLENE TERPHTHALATE) MATERIALS

A comparative study of hydrolysis of PET waste has been carried out under various reaction conditions. PET was hydrolyzed with sodium hydroxide in different solvents at reflux as well as by fusion in solventless conditions at atmospheric pressure. Best results were obtained when PET chips were heated to dryness with sodium hydroxide in minimum amount of water. A 98% yield of terephthalic acid was obtained in ten minutes. Hydrolysis with aqueous ammonia was not promising. Acid hydrolysis with nitric acid also provided 97% yield of the terephthalic acid. The basic hydrolysis of the PET waste (in a minimum amount of water) is being recommended as preferred method for the formation of terephthalic acid.

Micro-determination of iron in pharmaceutical preparations by image scanning and computational quantification.

Iron has been quantified in pharmaceutical preparations by developing red spots pursuant to interaction of Fe(II) ions in the sample with 1, 10-phenanthroline on TLC plate. Soon after, TLC was scanned on a flatbed scanner and the image was transferred to the computer. Color intensity of the spot was computationally quantified with the help of native software developed for this purpose. The conditions were optimized and the results were compared with a reference method.

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.