Equilibrium and kinetics of phenol adsorption by crab shell chitosan

Abstract

Chitosan synthesized from the Pessu river crab shell was screened to coarse (CC, 600 µm), medium (MC, 300 µm) and fine (FC, 150 µm) aggregate for phenol removal. The aggregates were characterized for surface chemistry, surface morphology, thermal behavior, and surface texture. The surface chemistry showed the characteristics primary and secondary amine/amide groups of chitosan. The values of specific surface area are 191, 226, and 209 m2/g for CC, MC, and FC, respectively. The effects of initial concentration (10–300 mg/L), adsorbent dosage (0.5–2.0 g/L), contact time (0–100 min), temperature (20–70 °C) and solution pH (2.6–8.7) were evaluated in phenol removal. Coarse chitosan displayed a maximum adsorption capacity of 59.3 mg/g, in which mesopore filling and ionic interactions are the possible adsorption mechanisms. Sips isotherm model fitted well with the equilibrium data (R 2 = 0.988 and SSE = 33.74), suggesting the adsorption onto a heterogeneous surface through adsorbate-adsorbent interactions. Kinetics data are best described by the pseudo-first-order model (R 2 ≥ 0.98 and SSE ≤ 2.88), indicating that external diffusion is the significant step in phenol adsorption. Chitosan derived from crab shell is a promising adsorbent for the removal of phenol from wastewater.