Comparative removal of two textile dyes from aqueous solution by adsorption onto marine-source waste shell: Kinetic and isotherm studies

Scallop shell was used as a low-cost adsorbent for removal of two anionic textile dyes, Reactive Blue 19 (RB19) and Acid Cyanine 5 R (AC5R), from aqueous solutions. The adsorbent was characterized using inductively coupled plasma optical emission spectrometry (ICP-OES), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM). The dye removal efficiency of scallop shell was determined as function of contact time, solution pH, initial dye concentration and adsorbent dosage. With increasing dye concentration, the adsorption of both dyes decreased, while it increased with increasing adsorbent dosage. Optimum removal of RB19 and AC5R was achieved at pH=6. Adsorption equilibrium data were well described by the Freundlich model. The maximum dye adsorption capacity of scallop shell as estimated from the Langmuir isotherm was 12.36 and 12.47 mg/g for RB19 and AC5R, respectively. The adsorption kinetic data showed excellent correlation with the pseudosecond-order model. It was concluded that scallop shell has a remarkable potential for the sorption of RB19 and AC5R and can be used for treatment of the dye contaminated wastewater.