K. Seshaiah

Removal of some metal ions by activated carbon prepared from Phaseolus aureus hulls

Removal of lead [Pb(II)], zinc [Zn(II)], copper [Cu(II)], and cadmium [Cd(II)] from aqueous solutions using activated carbon prepared from Phaseolus aureus hulls (ACPAH), an agricultural waste was studied. The influence of various parameters such as effect of pH, contact time, adsorbent dose, and initial concentration of metal ions on the removal was evaluated by batch method. The removal of metal ions by ACPAH was pH dependent and the optimum pH values were 7.0, 8.0, 7.0 and 6.0 for Cu(II), Cd(II), Zn(II), and Pb(II), respectively. The sorption isotherms were studied using Langmuir, Freundlich, Dubinin-Radushkevich (D-R), and Temkin isotherm models. The maximum adsorption capacity values of ACPAH for metal ions were 21.8 mg g(-1) for Pb(II), 21.2 mg g(-1) for Zn(II), 19.5 mg g(-1) for Cu(II), and 15.7 mg g(-1) for Cd(II). The experiments demonstrated that the removal of metal ions followed the pseudo-second-order kinetic model. Desorption experiments were carried out using HCl solution with a view to regenerate the spent adsorbent and to recover the adsorbed metal ions.

Biosorption of Pb2+ from aqueous solutions by Moringa oleifera bark: Equilibrium and kinetic studies

Biosorption of Pb(2+) from aqueous solution by biomass prepared from Moringa oleifera bark (MOB), an agricultural solid waste has been studied. Parameters that influence the biosorption such as pH, biosorbent dose, contact time and concentration of metal ion were investigated. The experimental equilibrium adsorption data were tested by four widely used two-parameter equations, the Langmuir, Freundlich, Dubinin-Radushkevich (D-R) and Temkin isotherms. Results indicated that the data of Pb(2+) adsorption onto MOB were best fit by the Freundlich model. The adsorption capacity (Q(m)) calculated from the Langmuir isotherm was 34.6mgPb(2+)g(-1) at an initial pH of 5.0. Adsorption kinetics data were analyzed using the pseudo-first-, pseudo-second-order equations and intraparticle diffusion models. The results indicated that the adsorption kinetic data were best described by pseudo-second-order model. Infrared (IR) spectral analysis revealed that the lead ions were chelated to hydroxyl and/or carboxyl functional groups present on the surface of MOB. Biosorbent was effective in removing lead in the presence of common metal ions like Na(+), K(+), Ca(2+) and Mg(2+) present in water. Desorption studies were carried out with dilute hydrochloric acid for quantitative recovery of the metal ion as well as to regenerate the adsorbent. Based on the results obtained such as good uptake capacity, rapid kinetics, and its low cost, M. oleifera bark appears to be a promising biosorbent material for the removal of heavy metal ions from wastewater/effluents.

Removal of mercury from aqueous solutions using activated carbon prepared from agricultural by-product/waste.

Removal of mercury from aqueous solutions using activated carbon prepared from Ceiba pentandra hulls, Phaseolus aureus hulls and Cicer arietinum waste was investigated. The influence of various parameters such as effect of pH, contact time, initial metal ion concentration and adsorbent dose for the removal of mercury was studied using a batch process. The experiments demonstrated that the adsorption process corresponds to the pseudo-second-order-kinetic models and the equilibrium adsorption data fit the Freundlich isotherm model well. The prepared adsorbents ACCPH, ACPAH and ACCAW had removal capacities of 25.88 mg/g, 23.66 mg/g and 22.88 mg/g, respectively, at an initial Hg(II) concentration of 40 mg/L. The order of Hg(II) removal capacities of these three adsorbents was ACCPH>ACPAH>ACCAW. The adsorption behavior of the activated carbon is explained on the basis of its chemical nature. The feasibility of regeneration of spent activated carbon adsorbents for recovery of Hg(II) and reuse of the adsorbent was determined using HCl solution.

Preconcentration of trace metals on Amberlite XAD-4 resin coated with dithiocarbamates and determination by inductively coupled plasma-atomic emission spectrometry in saline matrices

Preconcentration of Cd(II), Cu(II), Mn(II), Ni(II), Pb(II) and Zn(II) in saline matrices on Amberlite XAD-4 resins coated with ammonium pyrrolidine dithiocarbamate (APDC) and piperidine dithiocarbamate (pipDTC) and subsequent determination by inductively coupled plasma atomic emission spectrometry were studied. Parameters such as effect of pH, effect of HNO(3) concentration on elution of metals from resin were studied. The results show that Amberlite XAD-4 coated with APDC was more efficient in the recovery of metal ions compared with Amberlite XAD-4 coated with pipDTC, in the concentration range of 0.1-200 mug l(-1), for 1 g of Amberlite XAD-4 coated resin. The detection limits for Cd(II), Cu(II), Mn(II), Ni(II), Pb(II), Zn(II) are 0.1, 0.4, 0.3, 0.4, 0.6, 0.5 mug l(-1), respectively, for resin coated with APDC and 0.7, 1.0, 0.8, 0.9, 1.7 and 1.2 mug l(-1) for resin coated with pipDTC. The effect of diverse ions on the determination of aforesaid metals was studied. The method was applied for the determination of trace metal ions in artificial sea water and natural water samples. The results were compared with extraction AAS method.

Synthesis, spectral characterization and antioxidant activity studies of a bidentate Schiff base, 5-methyl thiophene-2-carboxaldehyde-carbohydrazone and its Cd(II), Cu(II), Ni(II) and Zn(II) complexes.

A new Schiff base bidentate ligand (L), 5-methyl thiophene-2-carboxaldehyde-carbohydrazone and its metal (Cu(II), Cd(II), Ni(II) and Zn(II)) complexes with general stoichiometry [M(L)2X2] (where X=Cl) were synthesized. The ligand and its metal complexes were characterized by elemental analyses, IR, 1H NMR, ESR spectral analyses, and molar conductance studies. The molar conductance data revealed that all the metal chelates are non-electrolytes. IR spectra showed that ligand (L) is coordinated to the metal ions in a bidentate manner with N and O donor sites of the azomethine-N, and carbonyl-O. ESR and UV-Vis spectral data showed that the geometrical structure of the complexes are Orthorhombic. Furthermore, the antioxidant activity of the ligand and its complexes was determined by hydroxyl radical scavenging, DPPH, NO, reducing power methods in vitro. The obtained IC50 value of the DPPH activity for the copper complex (IC50=66.4 μm) was higher than other compounds. Microbial assay of the above complexes against Staphylococcus aureus, Escherichia coli, Rhizocotonia bataticola and Alternaria alternata showed that copper complex exhibited higher activity than the other complexes.

DETERMINATION OF TRACE ELEMENTS BY INDUCTIVELY COUPLED PLASMA-ATOMIC EMISSION SPECTROMETRY (ICP-AES) AFTER PRECONCENTRATION ON A SUPPORT IMPREGNATED WITH PIPERIDINE DITHIOCARBAMATE

A procedure is developed for the determination of Cd, Co, Cr, Cu, Mn, Ni, Pb, and Zn in water by inductively coupled plasma-atomic emission spectrometry (ICP-AES) after preconcentration on a piperidine dithiocarbamate supported polyurethane foam. The sorbed elements are subsequently eluted with 4 mol L−1 HNO3, and the acid eluates are analysed by ICP-AES. A 20-mL disposable syringe served as a chromatographic preconcentration column. The sorption recoveries of elements except Co and Cr were higher than 97%. The method is also applied for the analysis of natural water samples.

Separation and Preconcentration of Cd(II), Cu(II), Ni(II), and Pb(II) in Water and Food Samples Using Amberlite XAD-2 Functionalized with 3-(2-Nitrophenyl)-1H-1,2,4-triazole-5(4H)-thione and Determination by Inductively Coupled Plasma–Atomic Emission Spectrometry

A separation and preconcentration procedure was developed for the determination of trace amounts of Cd(II), Cu(II), Ni(II), and Pb(II) in water and food samples using Amberlite XAD-2 fuctionalized with a new chelating ligand, 3-(2-nitrophenyl)-1H-1,2,4-triazole-5(4H)-thione (Amberlite XAD-2-NPTT). The chelating resin was characterized by Fourier transform infrared spectroscopy (FT-IR) and used as a solid sorbent for enrichment of analytes from samples. The sorbed elements were subsequently eluted with 10 mL of 1.0 M HNO(3), and the eluates were analyzed by inductively coupled plasma-atomic emission spectrometry. The influences of the analytical parameters including pH, amount of adsorbent, eluent type and volume, flow rate of the sample solution, volume of the sample solution, and effect of matrix on the preconcentration of metal ions have been studied. The optimum pH for the sorption of four metal ions was about 6.0. The limits of detection were found to be 0.22, 0.18, 0.20, and 0.16 μg L(-1) for Cd(II), Cu(II), Ni(II), and Pb(II), respectively, with a preconcentration factor 60. The proposed method was applied successfully for the determination of metal ions in water and food samples.

Solid phase extraction of trace metals in seawater using morpholine dithiocarbamate-loaded amberlite XAD-4 and determination by ICP-AES

Abstract Application of morpholine dithiocarbamate (MDTC) coated Amberlite XAD‐4, for preconcentration of Cu(II), Cd(II), Zn(II), Pb(II), Ni(II) and Mn(II) by solid phase extraction and determination by inductively coupled plasma (ICP) atomic emission spectrometry (AES) was studied. The optimum pH values for quantitative sorption of Cu(II), Cd(II), Zn(II), Pb(II), Ni(II), and Mn(II) were 6.5–8.0, 7.0–8.5, 6.0–8.5, 6.5–8.5, 7.5–9.0, and 8.0–8.5, respectively. The metals were desorbed with 2 mol L−1. The t1/2 values for sorption of metal ions were 2.6, 2.9, 2.5, 2.6, 3.0, and 3.8 min respectively for Cu(II), Cd(II), Zn(II), Pb(II), Ni(II) and Mn(II). The effect of diverse ions on the determination of the previously named metals was studied. Simultaneous enrichment of the six metals was accomplished, and the method was applied for use in the determination of trace metal ions in seawater samples.

Determination of bismuth in natural water samples by ICP-AES after preconcentration on dithiocarbamates-coated amberlite XAD-7

A column solid-phase extraction procedure for separation and preconcentration of bismuth in natural water samples using sodium diethyldithiocarbamate (NaDTTC) or piperidene dithiocarbamate (pipDTC)-coated Amberlite XAD-7 resin prior to their determination by inductively coupled plasma atomic emission spectrometry (ICP-AES) is reported. The results showed that solution pH and flow rate would affect the sorption of bismuth. The sorbed bismuth was eluted with 4 M/L of HNO3. The extractor system has good sorption capacity values of 9.82 mg/g of Bi on NaDTTC-coated resin and 9.56 mg/g of Bi on pipDTC-coated resin. The preconcentration factor was 150 and 170 for pipDTC-coated resin and NaDTTC-coated resin, respectively. The detection limits are 0.9 and 1.2 µg/L for resin-coated with NaDTTC and pipDTC, respectively. The results showed that resin coated with NaDTTC performs slightly better in the recovery of bismuth than resin coated with pipDTC. The accuracy of the proposed method was investigated by determining the bismuth in spiked water samples. The relative standard deviations of the determination of bismuth were below 5%. The proposed procedure was applied for the determination of bismuth in natural water and seawater samples.

Removal of heavy metals from aqueous solutions using activated carbon prepared from Cicer arietinum

Removal of Cu2+, Cd2+, Pb2+, and Zn2+ from aqueous solutions by activated carbon prepared from stems and seed hulls of Cicer arietinum, an agricultural solid waste, has been studied. The influence of various parameters, such as pH, contact time, adsorbent dose, and initial concentration of metal ions on removal was evaluated. The activated carbon was characterized by FT-IR spectroscopy, X-ray diffraction, and elemental analysis. Sorption isotherms were studied using Langmuir and Freundlich isotherm models. All experimental sorption data were fitted to the sorption models using nonlinear least-squares regression. The maximum adsorption capacity values for activated carbon prepared from Cicer arietinum waste for metal ions were 18 mg g−1 (Cu2+), 18 mg g−1 (Cd2+), 20 mg g−1 (Pb2+), and 20 mg g−1 (Zn2+), respectively. The Freundlich isotherm model fit was best, followed by the pseudo-second-order kinetic model. Desorption studies were carried out with dilute hydrochloric acid for quantitative recovery of the metal ions and for regeneration of the adsorbent.