Document Type : Research Paper
This study investigated the adsorption of an azo dye called Congo red from aqueous solution. The ash prepared from sunflower seed crushed, as a waste material, was used as the adsorbent. Brunauer–Emmett–Teller (BET), Scanning electron microscopy (SEM) and Fourier-Transform Infrared spectroscopy (FT-IR) analyses were performed to characterize the prepared adsorbent. Based on the results of BET, the specific active surface area was about 102 m2/g and the results of SEM indicated that the adsorbent surface had a very fine porosity that can be attributed to the presence of cellulosic materials in the adsorbent structure. In this study, the effect of the initial concentration of Congo red dye (10-50 mg/L), the concentration of adsorbent (1-5 g/L), and the processing time (10-240 min) on the rate of Congo red dye removal was investigated. The results showed that the highest percentage of dye removal i.e. 92% was achieved at a dye concentration of 50 mg/L, an adsorbent concentration of 3 g/L, and a processing time of 180 min. Under these conditions, the amount of adsorbed dye per gram of the adsorbent was 15.5 mg/g. In addition, pseudo-first order and pseudo-second order kinetic models were also used for modeling. The results of modeling indicated that pseudo-second order model had a higher level of accuracy. Finally, washing of the adsorbent by different solvents (one molar sodium hydroxide, double distilled water, and ethanol) was investigated and the results indicated that the adsorbent washed by one molar sodium hydroxide had a proper performance after five times of reuse.