A solid phase extraction procedure was developed for preconcentration of toxic heavy metals such as cadmium, cobalt, copper, manganese, lead and zinc in sea water samples. A microcolumn packed with 6-[(4-hydroxyphenyl)diazenyl]naphthalene-2,3-diol-formaldehyde (HPDN-F) resin acts as a sorbent to retain the analyte ions by forming metal chelates. The retained trace level metal was subsequently eluted with 1 mol/L HCl and the acid eluent was analysed by Flame Atomic Absorption Spectrophotometer (FAAS). The HPDN-F chelating resin and its metal chelates were characterized by spectral and thermal analysis. The chelating property of the HPDN-F resin towards divalent metal ions was studied as a function of pH and preconcentration flow rate. The recoveries of cadmium, cobalt, copper, manganese, lead and zinc under the optimum working conditions were above 95%. The relative standard deviations were < 2%. The limits of detection were < 0.1 microg/L. The method presented was applied for the determination of cadmium, cobalt, copper, manganese, lead and zinc in sea water samples.
Preconcentration of Cu (II) from seawater using a novel phenol-formaldehyde (P-F) resin was investigated. 1,2-dihydroxybenzene-4-azo-3-hydroxybenzene-formaldehyde resin (DAHBF) was prepared by condensing 1,2-dihydroxybenzene-4-azo-3-hydroxybenzene with formaldehyde (1:2 mole ratio) in the presence of oxalic acid as catalyst. Polychelates were obtained when the DAHBF was treated with the aqueous solution of Cu (II) ions. The polymeric resin and polymer-metal complexes were characterized with thermal analysis and spectral studies. The IR spectra of polychelates suggest that the metal was coordinated through the oxygen atoms of the dihydroxybenzene moiety. The TGA data revealed the thermal stability of the resin and the polychelates. X-ray diffraction study revealed the incorporation of the metal ion significantly enhanced the degree of crystallinity. The sorption properties of the chelate forming resin towards divalent metal ion [Cu(II)] was studied as a function of pH, preconcentration time, metal concentration, amount of resin, aqueous phase volume and presence of electrolyte. This procedure was validated for recovery of copper from seawater samples. The method has adequate accuracy and it can be used for determination of copper in sea water samples.
The semiorganic nonlinear optical crystal of amino-carboxyl acid family, L-cystine hydrochloride (LCHCl) was successfully grown from its aqueous solution by the slow evaporation solution growth method. The solubility, metastable zone width and induction period were determined for the first time experimentally and there by the possibility of growing bulk crystals of LCHCl using deionized water as solvent. The induction period was recorded for the different supersaturation ratios (S = 1.2, 1.3, 1.4, and 1.5), which reveals that the induction period of LCHCl decreases with increase in supersaturation. The nucleation kinetic parameters such as critical free energy, change of volume free energy, critical radius, number of molecules in the critical nucleus and nucleation rate have been evaluated for LCHCl crystals. The interfacial energy values of LCHCl were determined for different supersaturation ratio by means of varying temperatures. The single crystal X-ray diffraction gives the lattice parameters value of the grown crystals. The second harmonic generation efficiency was confirmed by the Kurtz-Perry powder method. The laser damage threshold energy of the grown crystal indicates that grown crystal has excellent resistance to laser radiation also compared with known other nonlinear optical crystals.
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