Equilibrium and kinetics of color adsorption on agriculture by-products/wastes (sugarcane bagasse, corncob, sawdust)

In this study, sawdust, formaldehyde treated sugarcane bagasse and thermally activated corncob were used as biosorbents for the removal of reactive Congo red dye color in wastewater of an industrial unit, throwing effluent into a small stream located in the vicinity of Lahore city. The batch experiments were conducted to study the influence of pH, contact time and adsorbent dose on the removal efficiency of dye color. The equilibrium was attained after 45, 75 and 90 min for sawdust, corncob and bagasse, respectively. The adsorption efficiency was found to be in order of 78.8%, 55.1% and 45.6% for formaldehyde treated sugarcane bagasse, thermally activated corncob and sawdust, respectively. Different models were used to fit experimental data and to understand the possible sorption mechanism. The results depicted that Langmuir isotherm was more significant than Freundlich isotherm, which indicated homogenous and monolayer surface of three adsorbents. In isotherm studies, the dimensionless factor R-2 revealed that the adsorption processes more favorable for formaldehyde treated sugarcane bagasse than thermally activated corncob than sawdust. The first-order and second-order kinetic measurement were performed for dye adsorption onto three adsorbents. The q(e,exp) and the q(e,cal) values from the pseudo-second-order kinetic model were very close to each other in case of formaldehyde treated sugarcane bagasse and sawdust, while these values were in good agreement from pseudo-first-order for thermally treated corncob.