Md. Akhtarul Islam

Adsorptive removal of methylene blue by tea waste.

The potentiality of tea waste for the adsorptive removal of methylene blue, a cationic dye, from aqueous solution was studied. Batch kinetics and isotherm studies were carried out under varying experimental conditions of contact time, initial methylene blue concentration, adsorbent dosage and pH. The nature of the possible adsorbent and methylene blue interactions was examined by the FTIR technique. The pH(pzc) of the adsorbent was estimated by titration method and a value of 4.3+/-0.2 was obtained. An adsorption-desorption study was carried out resulting the mechanism of adsorption was reversible and ion-exchange. Adsorption equilibrium of tea waste reached within 5h for methylene blue concentrations of 20-50mg/L. The sorption was analyzed using pseudo-first-order and pseudo-second order kinetic models and the sorption kinetics was found to follow a pseudo-second order kinetic model. The extent of the dye removal increased with increasing initial dye concentration. The equilibrium data in aqueous solutions were well represented by the Langmuir isotherm model. The adsorption capacity of methylene blue onto tea waste was found to be as high as 85.16mg/g, which is several folds higher than the adsorption capacity of a number of recently studied in the literature potential adsorbents. Tea waste appears as a very prospective adsorbent for the removal of methylene blue from aqueous solution.

Adsorption of methylene blue from aqueous solution by jackfruit (Artocarpus heteropyllus) leaf powder: a fixed-bed column study.

Continuous fixed-bed studies were undertaken to evaluate the efficiency of jackfruit leaf powder (JLP) as an adsorbent for the removal of methylene blue (MB) from aqueous solution under the effect of various process parameters like bed depth (5-10cm), flow rate (30-50mL/min) and initial MB concentrations (100-300mg/L). The pH at point of zero charge (pH(PZC)) of the adsorbent was determined by the titration method and a value of 3.9 was obtained. A FTIR of the adsorbent was done before and after the adsorption to find the potential adsorption sites for interaction with methylene blue molecules. The results showed that the total adsorbed quantities and equilibrium uptake decreased with increasing flow rate and increased with increasing initial MB concentration. The longest breakthrough time and maximum MB adsorption were obtained at pH 10. The results showed that the column performed well at low flow rate. Also, breakthrough time and exhaustion time increased with increasing bed depth. The bed-depth service time (BDST) model and the Thomas model were applied to the adsorption of MB at different bed depths, flow rates, influent concentrations and pH to predict the breakthrough curves and to determine the characteristic parameters of the column that are useful for process design. The two model predictions were in very good agreement with the experimental results at all the process parameters studied indicating that they were very suitable for JLP column design.

Optimal design of an activated sludge plant: theoretical analysis

The design procedure of an activated sludge plant consisting of an activated sludge reactor and settling tank has been theoretically analyzed assuming that (1) the Monod equation completely describes the growth kinetics of microorganisms causing the degradation of biodegradable pollutants and (2) the settling characteristics are fully described by a power law. For a given reactor height, the design parameter of the reactor (reactor volume) is reduced to the reactor area. Then the sum total area of the reactor and the settling tank is expressed as a function of activated sludge concentration X and the recycled ratio α. A procedure has been developed to calculate Xopt, for which the total required area of the plant is minimum for given microbiological system and recycled ratio. Mathematical relations have been derived to calculate the α-range in which Xopt meets the requirements of F/M ratio. Results of the analysis have been illustrated for varying X and α. Mathematical formulae have been proposed to recalculate the recycled ratio in the events, when the influent parameters differ from those assumed in the design.

Excellent durability of epoxy modified mortars in corrosive environments

Abstract The resistance of three different types of masonry mortar, namely Portland cement mortar (CM), epoxy resin-based polymer CM (PCM) and polymer mortar (PM) to corrosive aqueous media have been presented in this study. Assessment was carried out on the basis of relative loss in mass and compressive strength of the mortar specimens after immersion in different corrosive solutions such as 10 vol% sulphuric acid, 10 vol% sodium hydroxide solutions and 10 wt% brine for various periods. CM specimens were found to be vulnerable in brine, acidic and alkaline mediums, while the mortar modified with epoxy resin showed excellent resistance to the above mentioned mediums. By contrast, PM evidenced appreciable stability even after immersion for a longer period in the same environment. Experimental results suggest that the epoxy-based masonry mortars can be used as a promising external rendering material to build infrastructures.

Contribution of rice husk ash to the performance of polymer mortar and polymer concrete

Abstract This paper presents the effect of rice husk ash (RHA) as fine filler, partially replacing sand (fine aggregate) in the composition of epoxy resin based polymer mortar (PM) and polymer concrete (PC), to make them advantageous and lessen their adverse effects on the environment. Assessment was carried out on the basis of the mechanical (compressive, flexural, tensile strength), physical (water sorption, chloride ion penetration) and morphological (porosity) properties of polymer mortar and polymer concrete. The microstructure of the PM specimens (with RHA and without RHA) is examined by scanning electron microscopy (SEM). The amount of RHA in the composition of PM and PC is optimized. The experimental result shows that the optimum replacement of sand by RHA in the composition of PM and PC has a favorable influence on mechanical, physical and morphological properties of the mortar and concrete.

Thermally conductive adhesives from covalent-bonding of reduced graphene oxide to acrylic copolymer

ABSTRACT This work reports about the enhancement of the thermal conductivity of an acrylic pressure-sensitive adhesive (PSA) with the incorporation of functionalized and reduced graphene oxide (frGO) sheet in the composition. Bifunctional isocyanatoethylmetharcylate (IEMA) was intercalated (so-called ‘functionalization’) to the GO surface mainly at its –COOH sites. The remaining oxygenated groups on the GO surface were reduced by dimethyl hydrazine. The frGO was successfully incorporated into PSA matrix through in-situ polymerization of acrylic monomers and subsequently crosslinked under UV radiation. The conductivity and the peel strength of the PSA were studied as a function of filler content, filler modification (functionalization and/or reduction), UV-radiation dosage and mode of filler insertion (through in-situ polymerization or mechanical mixing). frGO/PSA showed much better properties than the PSA system with bare or IEMA-functionalized unreduced GO. In-situ polymerization was found to be more effective method for frGO insertion. Within the range of filler content (0.0–1.0) wt% and UV-radiation dosages of (400–3000) mJcm−2, the thermal conductivity and peel strength of the acrylic PSA-system under investigation varied in the range of 0.17–1.03 Wm−1K−1 and 2831–299 gf/25 mm. This is the first report on ‘reduced GO covalently bonded to polymer chain in an adhesive-composition’ providing novel idea to make PSA-system with balanced thermal conductivity and peel strength with perspective for application in miniature electronic industries.