The effects of sunflower seed shell modifying process on textile dye adsorption: kinetic, thermodynamic and equilibrium study

ABSTRACT

This study investigates the effects of natural sunflower seed shells (NSS) modifying process on the adsorption of a basic dye. For this purpose, adsorption studies were carried out with acid (H₂SO₄) treated shells and results were compared with that of NSS obtained in our previous studies. Common isotherm models were tested to evaluate the adsorption behaviours. It is concluded that Langmuir isotherm model is more suitable for modified NSS (MSS). The constants of this model were obtained as q_max = 284.45 mg/g and b = 0.017 L/mg for MSS at 30°C. The thermodynamic parameters were calculated as ΔH° = 76.24 kJ/mol, ΔS° = 336.21 J/mol and maximum ΔG° = −25.45 kJ/mol. The adsorption process was followed by the pseudo-second-order equation according to the kinetic studies. Optimum pH and adsorbent dosage were calculated as 7.4 and 10 g/L, respectively, for adsorption of astrazon red (AR) on MSS in this study. Final dye concentrations in low-cost MSS decreased at least 45% that of NSS. The dye removal efficiencies were about 99% and the best weight per volume ratio (W/V) of MSS was 4.71 g MSS/L. More suitable and improved data were observed almost in all studied parameters with the adsorbent of MSS.

Keywords:

• Modified adsorbent
• Adsorption
• Astrazon red
• Acid treatment

Acknowledgement

This research was performed in the laboratories of Ataturk University, Engineering Faculty, Environmental Engineering Department.