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Experimental data for the equilibrium adsorption of pentachlorophenol (PCP) onto activated carbon fibers (ACFs) in the form of felt (AC-felt) and cloth (AC-cloth) were obtained in a batch adsorber. The effect of pH on the adsorption capacity was investigated by determining the adsorption isotherm in the pH range from 6 to 12. It was found that the adsorption capacity was reduced upon increasing the pH from 6 to 12. The speciation diagram of PCP revealed that PCP was adsorbed on the ACFs as the pentachlorophenolate ion. The adsorption capacity was diminished slightly upon increasing the temperature from 15 to 35 °C. The adsorption of PCP on AC-felt was due to dispersion forces caused by π−π interactions. These interactions explained why the adsorption of PCP on the AC-felt was reversible. Also, the adsorption capacity of the AC-felt was 1.7 times higher than that of the AC-cloth because the AC-felt contained a greater concentration of basic sites that made the π−π interactions stronger. It was concluded that PCP was adsorbed considerably on the ACFs and that the adsorption capacity was highly dependent on the form and properties of the ACFs as well as the solution pH.

The ion-exchange equilibrium of Pb(II) and Cd(II) on clinoptilolite from different deposits was studied in this work. The Langmuir isotherm fitted the ion-exchange equilibrium data of both ions better than the Freundlich isotherm. The capacity of the natural zeolite to exchange Cd(II) and Pb(II) increased, augmenting the solution pH. This behaviour was attributed to the interactions between the ions in solution and the surface charge of the zeolite. Moreover, the capacity of the natural zeolite to exchange Cd(II) and Pb(II) was increased when the temperature was raised from 15 to 35• C. This tendency was explained by assuming that the ion exchange was an endothermic reaction. The selectivity of the zeolite for the metal cations decreased in the following order: Pb(II) > Cd(II). This order was not modified while reducing the solution pH, but the zeolite selectivity was increased. At pH 2 the selectivity of the zeolite for Pb(II) was nearly three times larger than at pH 4.

The potential use of spent coffee ground (SCG) for the removal of copper has been investigated as a low‐cost adsorbent for the biosorption of heavy metals. Adsorption batch experiments were conducted to determine isotherms and kinetics. The biosorption equilibrium data were found to fit well the Freundlich model and an experimental maximum biosorption capacity of copper ions 0.214 mmol/g was achieved. The biosorption kinetics of SCG was studied at different adsorbate concentrations (0.1–1.0 mM) and stirring speeds (100–400/min). The results showed an increase in the copper ion uptake with raising the initial metal concentration and the kinetic data followed the pseudo‐second order rate expression. The effect of stirring speed was a significant factor for the external mass transfer resistance at 100/min and coefficients were estimated by the Mathews and Weber model. Biosorption of copper ions onto SCG was observed to be related mainly with the release of calcium and hydrogen ions suggesting that biosorption performance by SCG can be attributed to ion‐exchange mechanism with calcium and hydrogen ions neutralizing the carboxyl and hydroxyl groups of the biomass.