Abstract

Many of the dyes are carcinogenic in nature and their existence in the aquatic system prevents normal biochemical reactions
occurring in living systems creating a major problem for the environment. Dyes impart color, which is esthetically unacceptable,
and reduces sunlight penetration into natural water. Among the techniques for the removal of dyes from water, adsorption on
a suitable adsorbent is a low cost and environment friendly process. In the present study, water spiked with the common dye,
methylene blue, has been interacted with Saraca asoca leaf powder (SALP), a low cost, locally available biomaterial as an
adsorbent. The batch adsorption process was carried out with pH, initial concentration of dye, adsorbent loading, and temperature
as the variables. The adsorbent material was characterized with scanning electron microscopy, energy dispersive X-ray, Fourier-
transform infrared, CHNS, zeta potential, thermogravimetric analyzer, atomic absorption spectrophotometer measurements and
a number of physical parameters such as bulk density, and moisture content were also determined. Adsorption kinetics was
tested with Lagergren pseudo-first order, Ho’s pseudo-second order, and intra-particle diffusion models. Validity of Langmuir,
Freundlich, and Temkin isotherm models were tested with the adsorption equilibrium data to work out the adsorption capacities.
The batch adsorption under appropriate conditions can remove the dye from water from 82 to 96%. Langmuir adsorption
capacity had the values of 30–125 mg g−1. These results along with the thermodynamic measurements indicated SALP to be a
promising adsorption for removal of the dye, methylene blue from water.