27:T47b,

The removal of silver ions from aqueous solutions containing low-to-moderate levels of contamination using Turkish Beypazari low-rank coal was investigated. Carboxylic acid and phenolic hydroxyl functional groups present on the coal surface provided adsorption sites for the removal of silver ions from solution via ion exchange. The equilibrium pH of the coal/solution mixture was shown to be the principal factor controlling the extent of recovery of Ag⁺ ions from aqueous solutions. The optimum pH was measured as 4.0 and it was found that the maximum removal of silver from solution was achieved within 30 min. The maximum adsorption capacity of the Ag⁺ ions was 1.87 mg/g coal. The adsorption phenomena appeared to follow a typical Langmuir isotherm. It was observed that the use of low-rank coal was considerably more effective in the recovery Ag⁺ ions from aqueous solutions. Higher amounts of adsorbed Ag⁺ ions could be desorbed (up to 92%) using 25 mM EDTA. Low-rank Turkish coals were suitable for consecutive use for more than 10 cycles without significant loss of adsorption capacity.

28:T56b,

The technical feasibility of using Jordanian low-grade phosphate (JLGP) for the removal of lead ions from aqueous solutions was investigated in this study. To simulate real industrial wastewaters, the effects of the presence of ethylenediaminetetraacetic acid (EDTA), citric acid, tartaric acid or sodium chloride on the adsorption of lead ions on JLGP were also investigated.

The results of batch adsorption experiments demonstrated the high capability of JLGP for removing lead ions from aqueous solutions. The equilibrium data for the adsorption of lead ions onto JLGP could be fitted by the Langmuir, Freundlich, Temkin and Dubinin–Radushkevich (D–R) isotherm equations. The work presented showed that on using 1 mmol/l of an aqueous solution of any of Pb(II), Pb–NaCl, Pb–tartaric acid, Pb–EDTA or Pb–citric acid, the percentage removal of lead ions at equilibrium was in the order Pb(II) > Pb–NaCl > Pb– tartaric acid > Pb–citric acid > Pb–EDTA. Increasing the initial pH of the solution led to an enhancement in the sorption of lead ions and lead–ligand complexes onto JLGP. It was also found that increasing the concentration ratio of ligand to metal ion decreased the percentage removal of lead ions significantly. The sorption of lead ions from industrially simulated wastewater was found to follow pseudo-second-order kinetics.

29:T12e2,