Abstract
ABSTRACTAdsorption of methylene blue and malachite green dyes from aqueous solution by neem leaves was studied using experimental and computational chemistry approaches. The two dyes have N–H stretch, C≡C vibration vibration, C=C stretch and C–Cl stretch as common functional groups. Batch adsorption experiments were concluded by measuring absorbance (at wavelength of maximum absorption, i.e. 660 and 630 nm for methylene blue and malachite green dyes, respectively). The adsorption of the dyes on neem leaves favoured Langmuir and Temkin isotherms and was influenced by concentration, biomass dose, pH and by contact time, and favoured chemisorption mechanism. Although surface adsorption and intra particle diffusion were identified as the rate-limiting steps, a pseudo second-order kinetics was also favoured. Quantum chemical analysis supported better adsorption of methylene blue dye on neem seed surface than malachite green dye and through Fukui function analysis, the site for adsorption of the dyes was proposed.
Highlights
Dyes of various types are the essential organic compound in the textile, carpet, pulp and paper industries
Plots showing the variation of absorbance with wave length for methyl blue and malachite green dyes were used to estimate the wavelength of maximum absorption of methylene blue (MB) and MG dyes
Neem leaves is an effective adsorbent for methylene blue and malachite green dyes
Summary
Dyes of various types are the essential organic compound in the textile, carpet, pulp and paper industries. Cellulose-based wastes are good adsorbent for some dyes including methyl orange, methylene blue, rhodamine blue, Congo red, methyl violet and amido black The adsorption of these dyes was found to follow the Freundlich and Langmuir adsorption isotherms and favoured alkaline pH [1]. Iqbal and Ashiq [3] investigated the adsorption capacity of charcoal for bromophenol, alizarine red-S, methylene blue, eriochrome black-T, malachite green, phenol red and methyl violet from aqueous solution. They found that the adsorption efficiency of charcoal for these dyes depended on contact time, pH and temperature.
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