CRAB SHELL: A POTENTIAL HIGH-EFFICIENCY AND LOW-COST ADSORBENT FOR DYE WASTEWATER

Intensive shellfish production generates a large volume of shellfish wastes. In this work, the crab shell was used as a low-cost biosorbent for the removal of Congo Red (CR) from aqueous solution. The effects of various factors including contact time, CR concentration, adsorbent dose, pH value and ionic strength on CR removal were investigated. The adsorption isotherms and kinetics were analyzed as well. The CR removal increased drastically at the initial 120 min and hardly increased until achieving equilibrium at 600 min. The CR removal decreased with an increase in the initial dye concentration (50- 600 mg/L) and increased with absorbent dose (0.05- 0.5 g/mL). The acid condition and high ionic of CR solution favored the dye adsorption. The adsorption isotherms analysis indicated that the Freundlich isotherm model yielded a better fit to the experimental data as compared with Langmuir model. The adsorption kinetics analysis revealed that pseudo-secondorder model could better describe the CR adsorption on crab shell. The value of rate constant and calculated adsorption capacity were determined as 1.35×10-4 g·mg-1·min-1 and 86.21 mg/g at 293 K, respectively.