Color Removal from Aqueous Solution with Pyrolysis-Treated Rice Straw

The objective of this study is to evaluate the performance of pyrolysis-treated rice straw (PPS) in the removal of methylene blue (MB) from aqueous solution. Batch studies were performed to evaluate the influences of various experimental parameters like pH (4, 5.9 (natural pH), 7, 9 and 11), initial dye concentration (5, 10, 15, and 20 mg/L), and contact time (0, 1, 5, 15, 30, 60, 90, and 120 min) at constant temperature (20 oC) and adsorbent dose (1 g/L). Also; the effect of ionic strength with the salt addition at different doses (500, 1000, 1500, 2000, and 2500 mg/L NaCl) was evaluated on the color removal efficiency from the dye solution. It was observed that the dye uptake by PPS was slightly decrease (from 8.5 mg/g to about 8.2 mg/g for qe values) when the pH of dye solution was increased from 4 to 11 and the best removal efficiency was obtained at the natural pH (5.9). Uptakes of dye were rapid and the adsorption increased with increasing contact time in all experiments. Methylene Blue removal efficiency increased slightly with increasing ionic strength. While the removal efficiency was 91 % at 2000 mg/L NaCl application, decreased to 87% at 2500 mg/L NaCl. According to the R2 values for the adsorption of MB on PPS, Langmuir model yields fit better than the Freundlich model. The maximum adsorption capacity of PPS adsorbent for MB dye was 12.5 mg/g. The kinetic experimental data fitted the pseudo-first-order model for PPS (R2=0.9952).