Adsorption of a cationic dye by Marula (Sclerocarya birrea) fruit seed shell based biosorbent: Equilibrium and kinetic studies

Abstract

Adsorption of methylene blue from aqueous solution using a low cost Sclerocarya birrea fruit shell powder based biosorbent was investigated in a batch system. Results showed that optimum adsorption capacity was achieved at pH 8 and biosorbent dosage of 0.6 g, with a maximum adsorption capacity of 27.690 mg g-1. Equilibrium studies showed that experimental data fitted well on the Temkin isotherm (R2 = 0.9641), as well as the Langmuir isotherm (R2 = 0.9626). The adsorption process followed the pseudo-second order rate kinetics with R2 values greater than 0.999. Fourier transform infrared spectroscopy (FTIR) spectrum showed the presence of absorption bands typical of a plant based biomaterial. Given the abundant availability of the S. birrea trees in Southern Africa, the seed fruit shell can be used as a source of low cost biosorbent.   Key words: Biosorption, Langmuir, methylene blue, Sclerocarya birrea fruit, Temkin.