Evaluation of dyes removal by beta-cyclodextrin adsorbent

This work was aimed at evaluating the adsorptive properties of beta-cyclodextrin (β-CD) adsorbent towards methylene blue and congo red dyes removal. The adsorbent was characterized for specific surface area and surface chemistry. The results show that the surface area of β-CD adsorbent is small at 0.1 m2/g and the surface chemistry is rich in acidic oxygen groups. The dyes adsorption onto β-CD is favourable. Congo red adsorption exhibits a greater rate constant of 0.103 min−1 and a relatively shorter time to reach equilibrium at 40 min as opposed to 1500 min for methylene blue. On a molar basis, both dyes display a comparable maximum capacity of 1.80 × 10−2 mmol/g, with β-CD shows a greater affinity for congo red. The congo red adsorption is governed by hydrophobic host-guest complex interactions, while that for methylene blue is thru weak electrostatic interactions at the hydrophilic exterior of β-CD. To conclude, β-CD could be a promising adsorbent candidate for the treatment of dyes wastewater, where future works will be centred in improving the versatility and performance of the material.