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Morigaon, India

Sarma A.,Morigaon College | G. Bhattacharyya K.,Gauhati University
Desalination and Water Treatment | Year: 2015

Mature leaves of the neem tree (Azadirachta indica) were converted into fine powder, the neem leaf powder (NLP), which was used for adsorption of fluoride from water. Adsorption was 82.6% at pH 2.1, 97.5% at pH 7.0 and 99.4% at pH 10.0 at a fluoride concentration of 15 mg/L. Adsorption kinetics conformed to pseudo-second-order model with a rate coefficient of 2.04 × 10−2–11.83 × 10−2 min/mg/g for a NLP amount of 1.0–6.0 g/L. The adsorption enthalpy, ∆H, decreased slightly from 26.06 to 24.85 kJ/mol as the fluoride concentration increased (2.50–20 mg/L). In the same concentration range, the adsorption entropy, ∆S, varied from −66.92 to 86.47 J/mol/K. Spontaneity was ensured by Gibbs energy decrease from −5.75 to −0.99 kJ/mol (fluoride 15.0 mg/L) and from −1.79 to −2.65 kJ/mol (fluoride 20.0 mg/L) in the temperature range of 308–318 K. However, at lower concentrations of fluoride, ∆G had values >0 which still decreased with increasing temperature. The influence of competing ions on fluoride adsorption by NLP showed a significant influence of Cl−, (Formula presented.), (Formula presented.), (Formula presented.) and (Formula presented.) ions. Dynamic study on a NLP column showed a breakthrough volume of 2,800 mL for a fluoride loading of 20 mg/L, a flow rate of 0.4 mL/min and a column bed depth of 1.5 cm. © 2015 Balaban Desalination Publications. All rights reserved. Source

Bhattacharyya K.G.,Gauhati University | Sarma A.,Morigaon College
World Environmental and Water Resources Congress 2011: Bearing Knowledge for Sustainability - Proceedings of the 2011 World Environmental and Water Resources Congress | Year: 2011

A biosorbent developed from waste leaves of Mango trees (magnifera indica) has been used for the removal of Cu(II) from aqueous solution. The use of the biosorbent, Mango lea powder (MLP) was evaluated with respect to the effects of pH, Cu(II) concentration, contact time, and biosorbent loading. The sorption dynamics were including kinetics and isotherm fitting, and mechanistic considerations of the processes were discussed in combination with the thermodynamic parameters. Column operations were carried to simulate industrial conditions and parameters like breakthrough volumes were found applying standard procedures. The bed-depth-service-time (BDST) model was applied successfully to the sorptive removal of Cu(II). The biosorptive capacity for Cu(II) at 90 breakthrough on MLP column decreased from a maximum value of 100 mg g-1 for feed flow rate of 2.0 mL min-1 to 45.00 mg g-1 for 11.2 mL min-1. Reduction in the residence time of the solute at a higher flow rate is likely to create a non-equilibrium situation with Cu(II) ions not having enough time to interact with the biosorbent in the column and thus, resulting in a decrease of the amount biosorbed. A slower flow rate also increases biosorption when intra-particle mass transfer controls the sorption process. A lower flow rate or longer contact time is required for effective biosorption of Cu(II) ions and an optimal flow rate of 2.0 mL/min could be selected for column design. © 2011 ASCE. Source

Bhattacharyya K.G.,Gauhati University | Sarma A.,Morigaon College | Sarma J.,Gauhati University
Adsorption Science and Technology | Year: 2010

In the present work, Azadirachta indica (neem) leaves were converted to a powder for use in the separation of Cu(II) ions from water. The powdered biomass was investigated as a sorbent for Cu(II) ions employing pH, time, initial Cu(II) ion concentration and the amount of sorbent as the experimental variables. At very low pH, Cu(II) ions were incapable of competing effectively with H+ ions for the sorption sites, but at the natural pH (5.6) of the aqueous Cu(II) ion solution up to 90% of the Cu(II) ions could be separated by sorption onto 4 g of Azadirachta indica leaf powder (AILP) from an aqueous solution of 50 mg/l concentration. The experimental data were well fitted by the Langmuir and Freundlich isotherm equations and followed pseudo-second-order kinetics. The Langmuir monolayer capacity of AILP for Cu(II) ions was 6.7-33.3 mg/g, which could be considered as reasonable. Azadirachta indica leaf powder could be a very effective sorbent for Cu(II) ions from an aqueous medium. The cellulosic units present in AILP provide a matrix of OH-, COO -, CN- and other anions that bind Cu(II) ions to the surface. The process was exothermic with ΔH0 values of -96.1 kJ/mol to -105.4 kJ/mol, reflecting the strong Cu(II)-AILP linkages formed. This was supported by an appropriate increase in the standard entropy change and a decrease in the Gibbs' free energy. Source

Sarma J.,Gauhati University | Sarma A.,Morigaon College | Bhattacharyya K.G.,Gauhati University
World Environmental and Water Resources Congress 2011: Bearing Knowledge for Sustainability - Proceedings of the 2011 World Environmental and Water Resources Congress | Year: 2011

A biosorbent was made from mature, dried Azadirachta indica (Neem) leaves, which was used for removal of Acid Blue 25 from aqueous solutions using the batch adsorption process. Effects of solution pH, temperature, agitation time, dye concentration and adsorbent amount on the adsorption process have been investigated. The biosorbent was effective at the natural pH of the dye solution and both Langmuir and Freundlich isotherms agreed with the adsorption results. The kinetics of the process followed pseudo second order mechanism with a rate coefficient of 5.87 × 10-3 to 32.46 × 10-3 g mg-1 min-1. The results indicate that Azadirachta indica leaf powder is an effective adsorbent for the dye in aqueous solution. © 2011 ASCE. Source

Bhattacharyya K.G.,Gauhati University | Barua P.,Gauhati University | Sarma A.,Morigaon College
World Environmental and Water Resources Congress 2011: Bearing Knowledge for Sustainability - Proceedings of the 2011 World Environmental and Water Resources Congress | Year: 2011

Mango (Magniferra Indica) Leaf Powder (MLP) was prepared as a biosorbent from the mature leaves of mango trees by thoroughly washing them with water, drying in an air oven at 373-383 K for 3-4 hours and grinding into a powder. The biosorbent, MLP, was obtained by separating the 50-100 mesh fractions, washing the same repeatedly with water to remove soluble materials, dyes and pigments, and finally drying at 373-83 K for 4 h in an air oven. MLP was characterized with measurements of surface area and topography, cation exchange capacity, XRD and FTIR. Batch adsorption studies with MLP were carried out with three toxic heavy metals, Cd(II), Ni(II), Pb(II), in solution with respect to effects of pH, amount of biosorbent, concentration of the metal ions, adsorption time and temperature. The kinetics and the isotherm relations for the equilibrium processes were worked out to establish the optimum conditions for metal ion uptake by trying several available mathematical models. The second order kinetic model was found to be the most suitable to describe the interactions of the metal ions with the biosorbent. Langmuir monolayer capacity of 16 - 46 mg/g for Cd(II), 11 - 32 mg/g for Ni(II), and 37 - 45 mg/g for Pb(II) could be considered as sufficient for indicating good potential of MLP as a biosorbent. It was found that Ni(II) biosorption was exothermic while that of Cd(II) and Pb(II) was endothermic, but the overall thermodynamic parameters support the practical application of MLP as a biosorbent. © 2011 ASCE. Source

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