Seshaiah Kalluru

The mesoporous silica (SBA-15) was successfully functionalised with 2,2ʹ- dipyridyl ketone by post grafting method. The mesoporous structure and functionalization with organic moiety were examined using different physicochemical techniques such as Low angle X-ray diffraction (XRD), Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), ¹³C NMR Spectroscopy, ²⁹Si NMR Spectroscopy, N₂ adsorption/desorption studies and TGA studies. The application of the hybrid material as sorbent in solid-phase extraction of Pb(II) and Cd(II) from environmental samples prior to determination by Flame Atomic Absorption Spectroscopy was studied. The analytical parameters such as pH, eluent type and its volume, sorbent dosage, flow rates, sample volume and effect of co-existing ions were studied and optimised. The prepared sorbent showed the preconcentration factor of 160 for both the metal ions with Limits of Detection of 0.20 µgL⁻¹ and 0.27 µg L⁻¹ and Limits of Quantification of 0.67 µg L⁻¹ and 0.90 µg L⁻¹ for Pb(II) and Cd(II) respectively. The adsorption capacity of the prepared sorbent found as 185.49 mg g⁻¹ and 103.41 mg g⁻¹ for Pb(II) and Cd(II), respectively. The proposed method was validated using a certified reference material NIST SRM-1640a with good agreement values. The proposed solid-phase extraction method was successfully applied to environmental water samples.

Biosorption of Pb(II) and Ni(II) ions onto the Eclipta alba stem powder (EAS) was investigated in a batch system. The biosorbent was characterized by fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), X-ray diffraction analysis (XRD), transmission electron microscopy (TEM) and elemental analysis. Adsorption influencing factors like pH, adsorbent dose, initial metal ion concentration and contact time were investigated. The adsorption mechanism of Pb(II) and Ni(II) followed the pseudo-second-order kinetic model (R² > 0.998). The Langmuir isotherm model fitted well and the maximum monolayer adsorption capacity of the sorbent for Pb(II) and Ni(II) was found to be 66.2 ± 1.9 mg g⁻¹and 62.5 ± 1.8 mg g^−1, respectively. Desorption and recovery were carried out using dilute HCl solution.

Sapindus saponaria bark powder (SSBP), an agro-waste material was investigated as a biosorbent for the removal and recovery of Cu(II) from aqueous solution. This biosorbent was characterized by infrared spectroscopy, X-ray diffraction, scanning electron microscopy and elemental analysis. The influence of various parameters such as effect of initial pH, contact time, metal ion concentration and sorbent dose on the removal of Cu(II) was investigated using batch process. Langmuir, Freundlich and Dubinin–Radushkevich isotherm models were applied to describe the adsorption isotherms. The Langmuir model fitted the equilibrium data better than the other isotherm models. The maximum adsorption capacity of Cu(II) was calculated from the Langmuir isotherm and found to be 37.09 mg g⁻¹ at pH 5.0. The kinetic studies revealed that the biosorption of Cu(II) onto SSBP followed the pseudo-second-order rate model. Evaluated thermodynamic parameters, ∆G°, ∆H° and ∆S°, showed that the biosorption of Cu(II) onto SSBP was an endothermic process. Desorption studies were carried out with dilute hydrochloric acid for quantitative recovery of the metal ions as well as to regenerate the adsorbent.

In this paper, a new mesoporous hybrid material was fabricated by anchoring 2-mercaptobenzaldehyde (2MB) onto the surface of SBA-15. The adsorbent (2MB-SBA-15) was characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), nitrogen adsorption–desorption isotherm measurements and thermogravimetric analysis (TGA) and applied as a sorbent in the preconcentration of Cd(II) in water samples and food samples. The effect of various analytical parameters such as pH, dose of sorbent, amount of eluent, sample flow rate and interfering ions was investigated. The preconcentration capacity of the prepared material under optimized conditions for Cd(II) was 0.94 ± 0.01 mmol g⁻¹. The Cd collected onto the sorbent was eluted out with 10 mL of 1 M HNO₃ and determined by AAS. The LOD, LOQ and preconcentration factor of the present method were found to be 6.93 × 10⁻⁶, 1.21 × 10⁻⁵ mM and 100, respectively. The relative standard deviation for four preconcentration experiments was found to be ≤5%.

Equilibrium, thermodynamic, and kinetic studies on the biosorption of Cu(II) using biomass, Trichoderma viride were carried out. The biosorbent was characterized by Fourier transform infrared spectroscopy and Scanning Electron Microscopy. The Langmuir and Freundlich isotherm models were applied to describe the biosorption process. The influence of pH, the biomass dosage, the contact time, the initial metal ion concentration, and the temperature of the solution on the biosorption was studied. The maximum Cu(II) biosorption was attained at pH 5. The equilibrium data were better fit by the Langmuir isotherm model than by the Freundlich isotherm. The maximum biosorption capacity of T. viride biomass was found to be 19.6 mg/g for Cu(II). The kinetic studies indicated that the biosorption of Cu(II) followed the pseudo-second-order model. The calculated thermodynamic parameters, Gibbs-free energy (ΔG^o), enthalpy (ΔH^o), and entropy (ΔS^o) showed that the biosorption of Cu(II) onto T. viride biomass was spontaneous and endothermic. It can be concluded that the T. viride biomass has the potential as an effective and low-cost biosorbent for Cu(II) removal from aqueous solutions.