Biosorption of Congo Red from aqueous solution by crab shell residue: a comprehensive study

The abundantly available bio waste, crab shell powder was used as an adsorbent for the removal of pollutants like Congo Red. The morphological, textural and chemical characterization of the biomass was done with SEM, XRD, EDS and FT-IR studies. The nature and mechanism of the process were determined from equilibrium, kinetic and thermodynamic studies. The results exhibited that the bio waste surface is fractured, rough and porous. It is composed of various surface functional groups which attracts organic pollutants. Equilibrium studies conclude Adsorption is a favorable process and it is a monolayer covering the surface. The maximum adsorption capacity, given by non-linear Langmuir isotherm was 124.9 mg/g. In kinetic studies pseudo-second order model best described the sorption kinetics compared to other models. Thermodynamic studies conclude that the process is spontaneous, endothermic and a physical adsorption.