Immobilization of oxime derivative on silica gel for the preparation of new adsorbent

Immobilization of unmodified aminoanthraquinone derivatives onto silica gel surface for solid-phase extraction and pre-concentration of Pb(II)

In this project, silica gel chemically bonded with derivatives of aminoanthraquinone were synthesized and characterized. Adsorbents 1,8-aminoanthraquinone-3-aminopropylsilica (SL1), 2-aminoanthraquinone-3-aminopropylsilica (SL2) and 1-aminoanthraquinone-3-aminopropylsilica (SL3) were produced and tested to adsorb heavy metal solutions including Pb(II) Cu(II) Zn(II) Cd(II) and Co(II). The concentrations of the adsorbed heavy metals solution were calculated by atomic adsorption spectrophotometry employing a batch method. The results showed that speed at 200 rpm for 30 min with pH 9 is the optimum condition for heavy metal adsorption. The result also indicated that adsorbent SL3 is the best adsorbent for Pb(II) at 82.5%, and the relative standard deviation (R.S.D.) was lower than 6%. The method detection limit was 1.1 µg L^-1 for Pb²⁺. In addition, Density Functional Theory (DFT) calculation results suggested that the adsorbent sensor formed stable complexes with Pb(II) through a large number of cation-dipole interactions. The method was also applied with satisfactory results to the pre-concentration of trace Pb(II) in environmental samples.

Organically modified silica with pyrazole-3-carbaldehyde as a new sorbent for solid-liquid extraction of heavy metals

A new chelating matrix, SiNP, has been prepared by immobilizing 1.5-dimethyl-1H-pyrazole-3-carbaldehyde on silica gel modified with 3-aminopropyl-trimethoxysilane. This new chelating material was well characterized by elemental analysis, FT-IR spectroscopy, cross polarization magic angle spinning solid state 13C-NMR, nitrogen adsorption-desorption isotherm, BET surface area, BJH pore size, and scanning electron microscopy (SEM). The new product exhibits good chemical and thermal stability as determined by thermogravimetry curves (TGA). The new prepared material was used as an adsorbent for the solid-phase extraction (SPE) of Pb(II), Cd(II), Cu(II) and Zn(II) from aqueous solutions using a batch method, prior to their determination by flame atomic adsorption spectrometry. The adsorption capacity was investigated using kinetics and pH effects. Common coexisting ions did not interfere with separation and determination.

Functionalized Silica Gel as Green Material for Metal Remediation

Advancement in industrialization and urbanization is a good indicator of the progress of humanity. However, it has an evil side as well. This advancement is identified as being responsible for deleterious effects on the health of human beings and aquatic biodiversity. Anthropogenic activities like mining and disposal of treated/untreated waste effluents containing toxic metals have resulted in severe deterioration of water quality, rendering serious environmental problems. The basic problem is that the wastewater generated through industries is not given the necessary pretreatment and is discharged directly into water resources. The metals beyond their permissible limits cause maximum negative impacts owing to their long biological half-lives and nondegradable nature. The condition is further worsening in economically deprived countries, where this metal-contaminated wastewater is directly used in various agricultural and day-to-day practices. As a solution to this, the extraction and removal of toxic metal ions from these polluted water resources at an industrial level is of paramount importance. This chapter provides the enthusiastic efforts of the scientific community to disseminate the fundamentals and practices of green analytical methods for metal removal. These methods are based on solid-phase extraction using functionalized silica gel for the separation and preconcentration of metal ions in polluted water resources. Ease of synthesis and extensive application of these organic-inorganic hybrid materials helps to fulfil the commitment of continual environmental improvement by remediating the wastewater.

Isotherms and thermodynamics for the sorption of heavy metal ions onto functionalized sporopollenin

In this study, sporopollenin of Lycopodium clavatum spores was used for the sorption experiment. Glutaraldehyde (GA) immobilized sporopollenin (Sp), is employed as a sorbent in sorption of selected heavy metal ions. The sorbent prepared by sequential treatment of sporopollenin by silanazing compound and glutaraldehyde is suggested for sorption of Cu(II), Zn(II) and Co(II) from aqueous solutions. Experimental conditions for effective sorption of heavy metal ions were optimized with respect to different experimental parameters using batch method in detail. Optimum pH range of Cu(II) has occurred at pH≥5.5 and Zn(II), Co(II) at pH≥5.0, for the batch method. All of the metal ions can be desorbed with 10 cm(3) of 0.5 mol dm(-3) of ethylenediaminetetraacetic acid (EDTA) solution. Langmuir, Freundlich and Dubinin-Radushkevich (D-R) isotherm equations were applied to the experimental data. Thermodynamic parameters such as free energy (ΔG(o)), entropy (ΔS(o)) and enthalpy (ΔH(o)) were also calculated from the sorption results used to explain the mechanism of the sorption. The results indicated that this sorbent is successfully employed in the separation of trace Cu(II), Zn(II) and Co(II) from the aqueous solutions.

Ionic liquid templated porous nano-TiO2 particles for the selective isolation of cytochrome c

Porous nano-titanium dioxide (TiO(2)) particles with anatase framework were prepared by using an effective template of hydrophobic ionic liquid, i.e., N, N-bis [2-methylbutyl] imidazolium hexafluorophosphate ([PPim][PF(6)]). The nano-TiO(2) particles were characterized with TEM and BET, resulting in the distribution of the pore diameters centering at 7.3 nm and 26.2 nm, attributed to the template effect of the ionic liquid and the aggregation of the TiO(2) particles, respectively. A much improved surface area of 68.31 m(2) g(-1) and a pore volume of 0.2814 cm(3) g(-1) were obtained with respect to 15.16 m(2) g(-1) and 0.0402 cm(3) g(-1) achieved by the non-templated nano-TiO(2) counterpart. The porous nano-TiO(2) particles were used as adsorbent for selective adsorption and isolation of cytochrome c (cyt-c) at certain conditions. An adsorption efficiency of 87% was achieved for 150 microg ml(-1) cyt-c in 1.0 ml of sample solution at pH 9.0 by using 2.0 mg of the nano-TiO(2) particles, in comparison to 30% obtained by the non-templated nano-TiO(2). In addition, an adsorption capacity of 112.6 microg mg(-1) was derived for the porous nano-TiO(2) with respect to 25.1 microg mg(-1) for the normal ones. The absorbed cyt-c could be readily recovered by stripping with a 0.1 mol l(-1) Na(3)PO(4) solution, giving rise to a recovery of ca. 90%. The porous nano-TiO(2) particles have been used for the isolation of cyt-c from human whole blood, achieving satisfactory results by assay with SDS-PAGE.