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The ability of thermal field-flow fractionation (ThFFF) to retain and separate both submicrometer and micrometer size particles (latexes and silica) suspended in various organic carrier liquids is demonstrated. The dependence of particle retention on various factors is evaluated and discussed. These factors include solvent properties, amount of added electrolyte, particle size and composition, and cold-wall temperature. Evidence of retention perturbations due to electrostatic particle - wall interactions is provided, and the efficacy of modifying the ionic strength of the organic carriers (by adding salt) to minimize the perturbations is demonstrated. General similarities and differences in retention behavior of particles suspended in nonaqueous as opposed to aqueous carriers are determined. One notable difference is the decrease in particle retention time in nonaqueous liquids with increasing cold-wall temperature; this trend is the same as that exhibited by polymers dissolved in organic carriers but is opposite to that shown by particles suspended in an aqueous medium. Thermal diffusion coefficients of several latex/solvent combinations are obtained from the ThFFF retention data. The present studies are limited primarily to polar organic solvents, except for some measurements involving cyclohexane and aqueous carriers. The investigation of nonpolar organic suspension media was hampered by either the solubility of the latexes or immiscibility between the original suspension media of the latexes and the nonpolar organic solvents.

Heavy metals' discharge into the environment continues to pose grave concerns around the world. The efficacy of a hydrous alumino-silicate clay (AlSiM) coming obtained from some regions of Kenya to sorb heavy-metal ions from water has been evaluated in batch tests taking into account changes in adsorbent dose, pH, contact time, and temperature. Complete metal removals, from water containing up to 66 mg/L of Pb(II) was achieved using this material at pH value of 5 over a temperature range of 289-333 K. The adsorption data fitted both the Langmuir and the Dubinin-Radushkevich isotherms with R² > 0.99. The D-R adsorption energy (-11.7 kJ/mol) indicated that chemisorption was the primary reaction in the adsorption process and the derived ΔG0 value (-7.45 kJ/mol) was consistent with the spontaneity of the adsorption process. The kinetic analyses indicated a film-diffusion and surface-chemisorption controlled process. Verification of the initial results on heavy metals- containing wastewaters obtained from a tannery and a leather processing industries revealed excellent adsorption efficacies of AlSiM for Cr3+ (99-100%), Fe3+ (96-98%), Mn2+ (85-97%) and Zn2+ (78-86%). The use of AlSiM as a plausible low-cost adsorbent for heavy-metal decontamination of industrial effluents has therefore been demonstrated. [ABSTRACT FROM AUTHOR]

Reports on the ability of thermal field-flow fractionation (ThFFF) to retain and separate submicrometer and micrometer size particles suspended in various organic carrier liquids. Evaluation of the dependence of particle retention on various factors; Evidence of retention perturbations due to electrostatic particle-wall interactions.