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A new adsorbent for removing copper ions from aqueous solutions has been developed and characterized. The present study deals with the sorption of Cu(II) from aqueous solution on chemically pretreated sodium carbonate-treated rice husk (SCRH). The physico-chemical characteristics of rice husks were investigated to analyze their suitability to adsorb Cu(II) ions from water and wastewater. The raw rice husk (RRH), SCRH and Cu(II) adsorbed rice husk were analyzed by SEM-EDAX analysis. FTIR spectroscopy was also applied to identify functional groups, capable of adsorbing metal ions. Batch kinetic studies were conducted for the adsorption of Cu(II) on SCRH. It has been observed that 92.9–96.0% removal of Cu(II) is achieved at 4.8 mg of Cu(II)/g of adsorbent, adsorbent dose of 10 g L–1 and initial Cu(II) concentration of 10 mg L–1 in a temperature range of 15–50 °C. It was observed that the adsorption of Cu(II) on SCRH followed pseudo second-order kinetic and time to achieve equilibrium was found to be 60 min. The maximum uptake (97%) of Cu (II) was observed at pH 6. In this paper, an attempt has also been made to develop simple and readily understandable thermodynamic parameters related to sorption process at the equilibrium for understanding the adsorption mechanism. The Gibbs free energy ΔG° values for the adsorption processes of Cu(II) at 15, 30, 40 and 50 °C were calculated as –6.16, –6.84, –8.01 and –8.53 kJ mol–1, respectively. The negative value of ΔG° indicates spontaneity of adsorption. The values of ΔH° and ΔS° for Cu(II) adsorption were calculated as 14.37 kJ mol–1 and 70.92 J K–1 mol–1, respectively. The activation energy for the adsorption of Cu(II) was found to be 9 kJ mol–1 which is a characteristic for diffusion limited processes. [ABSTRACT FROM AUTHOR]

Ruddlesden Popper (RP) oxide Sr 2 SnO 4 has been synthesized via a solid state reaction route by calcination at 1000 °C for 8 h. The Rietveld refinement of X-ray diffraction (XRD) pattern suggested tetragonal structure; I4/mmm space group and unit cell parameters a  =  b  = 4.05084(5) Å, c  = 12.59040(2) Å. Dielectric properties, electric modulus and ac conductivity have been studied as a function of both frequency (20 Hz–2 MHz) and temperature (70–600 °C) in air atmosphere. Dielectric constant and dissipation factor remains constant upto 600 °C above 1 KHz. AC conduction mechanism has been explained using Johnscher’s Power law. The value of the activation energy for conduction, E cond (obtained from DC conductivity) and dielectric relaxation, E relax (obtained from modulus) is found to be the same indicating similar mechanism for both the processes. Based on the numerical value of activation energy, the conduction and relaxation processes are attributed to transfer of electron from Sn 2+ to Sn 4+ through the thermally assisted quantum mechanical tunneling process. [ABSTRACT FROM AUTHOR]

Powder of SrCe0.98Na0.02O3 is synthesized by calcination at 1000 °C for 8 h via solid‐state ceramic route. The ceramic/pellet of this compound is obtained by sintering at 1200 °C for 12 h. X‐ray diffraction (XRD) technique is used to confirm single‐phase formation. Rietveld refinement of the XRD pattern of sintered powder has confirmed orthorhombic crystal structure and space group Pnma as reported for SrCeO3. Further, the purity of the synthesized compound is ensured using Raman and Fourier transform infrared spectroscopy analysis. Scanning electron microscopic studies have reflected dense microstructure and spherical shape grains with an average size of 1.80 µm. Complex plane impedance and spectroscopic analysis are employed to study electrical conduction and relaxation mechanisms in the temperature range 300–600 °C and frequency range 20 Hz to 2 MHz. The activation energy for DC conduction (Econ) and relaxation (Erelx) is found to be the same (0.77 eV). Based on the numerical value of activation energies, conduction and relaxation mechanisms are attributed to migration of doubly ionized oxygen vacancies (VO••). [ABSTRACT FROM AUTHOR]