Thomas R. Gilbert

The use of silica-immobilized brown alga (Pilayella littoralis) for metal preconcentration and determination by inductively coupled plasma optical emission spectrometry

The brown alga Pilayella littoralis was used as a new biosorbent in an on-line metal preconcentration procedure in a flow-injection system. Al, Co, Cu and Fe were determined in lake water samples by inductively coupled plasma optical emission spectrometry (ICP-OES) after preconcentration in a silica-immobilized alga column. Like other algae, P. littoralis exhibited strong affinity for these metals proving to be an effective accumulation medium. Metals were bound at pH 5.5 and were displaced at pH<2 with diluted HCl. The enrichment factors for Cu(II), Fe(III), Al(III) and Co(II) were 13, 7, 16 and 11, respectively. Metal sorption efficiency ranged from 86 to 90%. The method accuracy was assessed by using drinking water certified reference material and graphite furnace atomic absorption spectrometry (GFAAS) as a comparison technique. The column procedure allowed a less time consuming, easy regeneration of the biomaterial and rigidity of the alga provided by its immobilization on silica gel.

Assessing metal sorption on the marine alga Pilayellalittoralis

Increasing interest in the development of biological materials for metal sorption led us to investigate the brown marine alga, Pilayella littoralis, as a biological sorbent. This work focuses on the harvest, preparation and evaluation of P. littoralis from Nahant beaches for use as a metal biosorbent. This biomass was used in batch tests with synthetic solutions. Its metal uptake properties, including metal binding capacity, the pH dependence of metal uptake and the kinetics of metal sorption, were investigated. Most metal sorption occurred within the first 5 min of exposure and the metals were optimally bound to the algae at pH 5.5. The algal binding capacities for Al(III), Cd(II), Co(II), Cr(VI), Cu(II), Fe(III), Ni(II) and Zn(II), were 2,000, 430, 560, 90, 850, 700, 390 and 450 micromol g(-1) of dried biomass, respectively. Metals were desorbed with 0.12 mol l(-1) HCl and determined by inductively coupled plasma atomic emission spectrometry (ICP-AES).

Isolation of humic acid from the brown algaPilayella littoralis

A standard humic acid extraction procedure has been used to isolate dark brown organic residues from samples of the macroscopic marine brown algaPilayella littoralis. The residues are insoluble in water, but soluble at high pH, and are similar in elemental composition, ash content, UV-visible, IR, PMR and X-Ray fluorescence spectra, X-Ray diffractograms and scanning electron micrographs to residues of a humic acid isolated from municipal compost. These results indicate thatPilayella produces humic acids.

Transmetalation of tetranuclear copper complexes. VIII: Transmetalation of tetranuclear copper(I) complexes with a Co(NS)3 reagent

Transmetallation des complexes (DENC) 4 Cu 4 X 4 (DENC=diethylnicotinamide), par le tris(S-methyl isopropylidenehydrazinocarbodithioate)-Co(III) dans les solvants aprotiques sous N 2

A rapid fluorescence quenching method for the determination of equilibrium parameters for copper(II) complexation by humic materials

Abstract Fluorescence quenching measurements for determining stability constants ( K ) and complexation capacities ( C L ) of copper(II) complexation by humic materials have primarily been conducted by titrating a sample with metal ion. These titrations are long and tedious, requiring many data points, pH adjustment between additions, and long equilibration times. Once collected, the data must then be manipulated using regression analyses to obtain the equilibrium parameters. This paper describes the development of a new, rapid method of determining equilibrium parameters from fluorescence quenching. The use of individual pH-buffered aliquots of sample for each point along the titration curve yields data that can be analyzed with a simplified linear data treatment to obtain values for C L and K for the sample. This rapid fluorescence quenching method was evaluated using a model ligand (salicylic acid), isolated soil and stream fulvic acids, and a natural water sample.

Determination of trace elements in non-aqueous samples by d.c. plasma emission spectrometry

Abstract Following minor modification to the sample introduction system, a d.c. plasma emission spectrometer was used to determine trace elements in five organic solvents: hexane, dichloro, trichloro and tetrachloromethane, and 4-methyl-2-pentanone. These solvents are extensively vaporized in the nebulization system, resulting in improved sample delivery to the plasma and enhanced sensitivity. The technique was used to analyse silicone fluid in the bond paper employed in photocopies and to determine trace elements in coastal seawater following solvent extraction.

Reaction bonded refractory metal carbide/carbon composites

Abstract A simple chemical process has been developed that allows the rapid conversion of carbon substrates to the refractory metal carbides (MC) of titanium, zirconium, hafnium, vanadium, niobium, tantalum and tungsten. As a demonstration of the technique, graphite rods are infiltrated with an ethanolic solution of various metal oxide-halides, and resistively fired (1350–3000°C) under an argon atmosphere. The final composite produced is found to contain a residual carbon core within a fully dense metal carbide-carbon matrix outer layer. The effects of both firing temperatures, and the number of infiltration-fire treatments, have been investigated in order to determine optimum firing conditions (i.e. maximum carbide formation) for each individual metal carbide. To demonstrate the applicability of the technique for a range of substrate materials, niobium and titanium carbides were formed on carbon fibre tows and non-porous substrates, respectively. The formation of mixed Nb-Ti carbide coatings of varying composition were investigated in order to determine the factors controlling the formation of ternary phases. The identity of the transition metal precursors and the possible pathway of their conversion to the appropriate carbide is discussed. All the composites have been characterized by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) with associated energy-dispersive X-ray (EDX) analysis, and X-ray diffraction (XRD).