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The decolorization and degradation efficiency of the azo dye Reactive Black 5 (RB5) by Fenton system were investigated in this study. The operation parameters such as Fe 21 :H 2 O 2 ratio, pH value, initial concentration of RB5, reaction time, and temperature were examined. Maximum decolorization (99%) and degradation (88% COD removal) efficiencies were achieved at the Fe 21 :H 2 O 2 ratio of 0.05 and pH 3 for 15-min reaction time. The decolorization kinetic of RB5 followed pseudo-second-order reaction kinetic. The increase of temperature caused decreasing of obtained rate constants and increasing of corresponding half-lives. The article also discussed thermodynamic parameters including changes in Gibbs free energy, enthalpy, and entropy for the decolorization of RB5 by Fenton and exposed that the oxidation process was spontaneous and exothermic under natural conditions.

Removal of nickel ions from aqueous solutions containing 1-100 mg l(-1), using pine tree (Pinus nigra) materials modified with HCl, was investigated on a laboratory scale. For this purpose, two natural adsorbents such as the modified pine bark (MPB) and the modified pine cone (MPC) materials with HCl solution were studied. At first, the required concentration level of the HCl solution for the modification was observed, and then this was followed by the determinations of optimum levels of adsorbent amount, stirring rate, contact time and pH values. Various adsorption isotherms were also obtained by using different concentrations of the heavy metal cations tested in the experiment. As a result, the maximum removal efficiency levels obtained were as follows; 97% for the modified pine bark at pH 8 and 80% for the modified pine cone at pH 8.