Ball clay was found to exhibit excellent adsorption capacity toward Cd(II) ions over a wide concentration range. The adsorption capacity was studied by heating it at different temperatures. It was found that the sample heated at 200°C showed maximum adsorption capacity toward Cd(II) ions. This research was focused on the effect of pH, time, temperature, adsorbent doses and initial Cd(II) concentration by batch experiments. The equilibrium data of Cd(II) adsorption were explained well by Langmuir and Freundlich adsorption isotherms. The kinetics data for the adsorption process obeyed pseudo-first-order and pseudo-second-order models at lower initial concentrations of Cd(II) while with the increased concentration of Cd(II) pseudo-first-order model failed. The Cd(II) desorption was performed using batch process with various desorbing solutions and 100% desorption was achieved with HCl solution

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 50 mg 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.

Seeds of bottlebrush, a novel plant material, were found to exhibit excellent adsorption capacity over a wide range of Cd(II) concentration. It was characterized by Fourier transform infrared spectroscopy and Scanning Electron Microscopy to support the adsorption of Cd(II) ions. Effect of various parameters like pH, contact time, initial concentration and different electrolytes was investigated using batch process to optimize conditions for maximum adsorption. The adsorbent data were analyzed using Langmuir, Freundlich, Temkin and Dubinin–Redushkeuich isotherm equations at 30°, 40° and 50 °C. Thermodynamic parameters such as standard enthalpy change (ΔH°), free energy change (ΔG°) and entropy change (ΔS°) were also evaluated and the results indicated that adsorption of Cd(II) are spontaneous and endothermic. Various kinetics models including the Pseudo-first-order kinetics, Pseudo-second-order kinetics and Intraparticle diffusion models have been applied to the experimental data to predict the adsorption kinetics. Kinetic study was carried out by varying initial concentration of Cd(II) at constant temperature and it was found that pseudo-second-order rate equation was better obeyed than pseudo-first-order equation supporting that chemisorption process was involved.