Özet:

In this study; the adsorption of crystal violet (CV) dyestuff in cationic form on waste green tea leaves was investigated and the effects of adsorbent particle size, initial dyestuff concentration, stirring speed, initial pH, temperature and adsorbent amount on adsorption capacity and dye removal efficiency were optimized. To determine the characterization of waste green tea leaves, pHpzc analysis was performed and pHpzc of waste green tea leaves was determined as 5.511. In adsorption of CV dye on waste green tea leaves, the highest dye removal efficiency was obtained at the natural pH (5.58) of the solution. As the initial dye concentration increased, the amount of dye adsorbed per unit adsorbent increased, while the dye removal efficiency decreased. It has been observed that increasing temperature decreases the adsorption capacity. While CV adsorption capacity of waste green tea leaves was 227.049 mg g-1 at 0.1 g L-1 adsorbent dosage, CV adsorption capacity decreased to 8.788 mg g-1 at 5 g L-1 adsorbent dosage. Freundlich, Langmuir, Halsey and DubininRadushkevich models were used for mathematical modeling of adsorption equilibrium on CV adsorption. The degree of suitability of isotherms for adsorption of CV dye is Freundlich=Halsey>Langmuir>Dubinin-Radushkevich, respectively. Two different kinetic models (pseudo-first-order and pseudo-second-order) were used for the kinetic data, and the calculated kinetic parameter constants showed that the adsorptions fit the pseudo-second-order kinetic model. In addition, thermodynamic parameters of CV adsorption showed that the adsorption process occurs spontaneously (∆Go<0) and is exothermic (∆Ho˃0).

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