Surfactant-modified Macadamia nutshell for enhancement of methylene blue dye adsorption from aqueous media

Abstract

This study reported the synthesis of a low-cost, and efficient adsorbent through surfactant modified macadamia nutshells (SMS) by a facile sodium dodecyl sulfonate (SDS) treatment approach. The SDS treatment resulted in increased functionalities, and ion exchangeable sites of macadamia nutshells leading to enhanced the removal of methylene blue (MB) dye from water. Factors such as pH (2-11), contact time (1-360 min), initial MB dye concentration (30-385 mg/L), and adsorbent mass (0.02 – 0.18 g/L), were tested in this study. The enhanced removal of MB removal (≥ 90%) was synergistically influenced by pH, with optimum adsorption removal around pH 7 to 11 for the SMS adsorbent. The results showed that MB removal was fast with SMS, and that the equilibrium was reached in 80 min. The batch adsorption results showed a good fit with pseudo-first-order kinetics, and the Langmuir isotherm model, in agreement with the experimental values, with a maximum adsorption capacity of 195.97 mg/g for MB. Surfactant modified macadamia nutshells (SMS) composed of surface functional groups: –OH, –C = O, -C-O, and multiple carbon-carbon bond, all contributed to synergistic mechanism interaction between the adsorbent and MB dye in this study. This study thus suggested that the SMS could be highly beneficial for eliminating anionic dye from polluted water-based solutions, thus highlighting its potential for practical usage in large pollutants removal.

Keywords

• Sodium dodecyl sulfonate
• Ion exchangeable sites
• Methylene blue adsorption
• Macadamia biomass waste
• Surfactant modification