Kinetic study of cationic dye adsorption on cellulose acetate butyrate/poly(L-lactic acid) composite beads

Cellulose acetate butyrate (CAB) and poly(L-lactic acid) (PLLA) were successfully blended through solvent blending method followed by solution dropping technique to fabricate composite CAB/PLLA beads with the variation of PLLA content (0, 10, 20, and 30 wt%) and polymer blend concentration in solution (10 wt% and 15 wt%). The obtained composite beads were applied as adsorbent for methylene blue removal from aqueous solution under the condition of various pH. Batch equilibrium adsorption was carried out to observe the effect of various PLLA content, polymer concentration, and pH on the adsorption performance (adsorption capacity and % dye removal), and to study the adsorption kinetics. The adsorption performance of the composite beads showed that the absorption capacity (Q) and dye removal percentage (%R) generally increases with the increasing of PLLA content for both polymer concentration of 10 wt% and 15 wt%. Beads fabricated from higher polymer concentration (15 wt%) possessed higher Q and %R compared to those from polymer concentration of 10 wt% under the same operation condition. Adsorption performance of beads was better in pH neutral than in acid or base condition. The highest Q and %R values were obtained by composite bead of CAB/PLLA (70/30) 15 wt%, which are 2.54 mg/g and 25.35% respectively at the adsorption condition of pH 7, temperature 30 °C, initial dye concentration of 20 mg/L, and beads dose of 2 g/L. The %R increased to 69.85% by increasing the beads dose to 20 g/L. The kinetics data obtained from the experiment fitted well with Largergren's pseudo-first-order model which is the characteristic of physically adsorption.