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Dactyloctenium aegyptium biomass (DAB), a novel plant based material was modified with Montmorillonite (MMT) clay to form DAB-MMT nano-composite as an adsorbent for the removal of Cu(II) ions from the aqueous solution. The surface morphology of the adsorbent was characterized by using scanning electron microscopy (SEM), Energy dispersive X-ray spectroscopy (EDX) and FTIR Fourier transform-infrared spectroscopy (FT-IR) analysis. The adsorption equilibrium was reached in 60 min and the optimum pH for adsorption was found to be 6. Equilibrium isotherm data were analysed using Langmuir, Freundlich, Temkin and Dubinin–Radushkevich (D–R) isotherm models at 30, 40 and 50 °C and were best followed at 30 and 40 °C. Maximum adsorption capacity (qm) as calculated from Langmuir isotherm was found to be 18.51 mg g−1. Adsorption kinetics of Cu(II) onto DAM-MMT nano-composite was also studied using pseudo-first order, pseudo-second order and intra particle diffusion model over a wide range of concentration (10–100 mg L−1) and the adsorption of Cu(II) followed pseudo-second order kinetics showing that chemisorption process was involved. The thermodynamics parameters showed that the process was endothermic and spontaneous. The breakthrough and exhaustive capacities were found to be 10 mg g−1 and 25 mg g−1 respectively. [ABSTRACT FROM AUTHOR]

The present work explored the adsorption properties ofTerminalia arjunafruit powder for the removal of Pb(II) from aqueous solution. Effect of concentration, contact time, pH, adsorbent dose, and temperature were studied using batch process to optimize conditions for maximum adsorption of Pb(II). Kinetic data showed that the pseudo-second-order model was the best fit for the experimental data over a wide range of concentrations. Thermodynamic parameters (∆H°and ∆G°) suggested endothermic and spontaneous nature of adsorption. Mean free energies at different temperatures were in between 10.1 and 14.3 kJ mol−1indicating chemical nature of adsorption process. Equilibrium isotherm data were analyzed using Langmuir, Freundlich, Temkin and Dubinin–Radushkevich (D–R) isotherms models at 30, 40, and 50°C. The breakthrough and exhaustive capacities were found to be 5 and 15 mg g−1, respectively. Desorption studies were carried out by column method and 84% of Pb(II) ions were recovered when 0.05 N HCl was used. A single-stage batch adsorption design was proposed to predict the amount of adsorbent required for 98% removal of Pb(II) from different volumes of water. [ABSTRACT FROM PUBLISHER]

Artimisia absinthium, a medicinal plant material, showed excellent adsorption in removing mutagenic Cr(VI) from aqueous solution along with Cu(II), Ni(II), and Zn(II). Various parameters like effect of pH, contact time, temperature, and initial concentration were investigated using batch process to optimize conditions for maximum adsorption.A. absinthiumwas characterized using scanning electron microscopy (SEM). Adsorption of Cr(VI) was favorable at pH 2 as 96% of Cr(VI) could be removed from aqueous solution. However, adsorption of Cr(VI) decreased to 73% in presence of electrolyte (0.1 N KNO3) at pH 2. The point of zero charge ofA. absinthiumwas 3.9 in double distilled water. The adsorption data were analyzed using Langmuir, Freundlich, Temkin, Hasley, and Dubinin–Redushkeuich isotherm models at 30, 40, and 50°C. The maximum monolayer adsorption capacity towards Cr(VI) was found to be 46.99 mg g−1at 30°C which was relatively large compared to some other similar adsorbents reported earlier. The kinetic data showed that pseudo-second-order rate equation was better obeyed than pseudo-first-order. The intra-particle diffusion model showed that Cr(VI) adsorption involved three different stages. The breakthrough and exhaustive capacities of the adsorbent were found to be 35 and 45 mg g−1, respectively, at pH 2. Desorption study showed that 93.05% Cr(VI) could be desorbed by column operation with 0.01 N NaOH solution. [ABSTRACT FROM PUBLISHER]

Fruit peel of Litchi chinensis showed remarkable adsorption capacity towards Cr(VI) ions. The effect of temperature, pH, initial Cr(VI) concentration and time was investigated using batch process. The adsorption of Cr(VI) was maximum at pH 2. Fourier transform infrared spectroscopy (FTIR) was used to explore number and position of active functional groups available for the binding of Cr(VI) ions. Thermodynamic parameters like change in standard free energy (ΔG°), enthalpy (ΔH°) and entropy (ΔS°) indicated the spontaneous, endothermic and increased randomness nature of Cr(VI) adsorption. Equilibrium data were well fitted in Langmuir isotherm at 40°C.The value of mean free energy (E = 8.28 kJ mol-1) indicated that adsorption process was chemical in nature. The breakthrough and exhaustive capacities were found to be 30 and 50mg g-1 respectively. The results indicated that the adsorbent could be used effectively for the removal of Cr(VI) from electroplating wastewater by batch process. [ABSTRACT FROM AUTHOR]

Adsorption behaviour of Ni(II), Zn(II), Cd(II) and Cr(VI) on untreated and phosphate-treated rice husk (PRH) showed that adsorption of Ni(II) and Cd(II) was greater when PRH was used as an adsorbent. Sorption of Cd(II) was dependent on contact time, concentration, temperature, adsorbent doses and pH of the solution. The Langmuir constants and thermodynamic parameters have been calculated at different temperatures. It was found that recovery of Cd(II) from synthetic wastewater by column operation was better than a batch process.