Removal of COD in Leachates Through Coagulation and Adsorption Using Magnetic Iron Oxide-Activated Adsorbent

The COD concentration of leachate from Lamdeng Khunou Solid Waste Management Plant, Manipur, India, is as high as 3084 mg/L. In this study, the reduction of toxic COD was carried out through pretreatment by coagulation reducing the turbidity and COD. By using alum in the coagulation process, turbidity and COD were reduced by 70.93% and 37.7%, respectively. The study was conducted at different alum dosages and pH levels. Magnetic iron oxide-activated adsorbent (IIAC) was used in an adsorption procedure to further treat the leachate. The effects of leachate pH, adsorbent dose, and contact time were investigated to evaluate the performance of IIAC. The adsorption isotherm studies revealed that the correlation coefficient (R2) for the linearized Langmuir model was 0.9989 signifying the best fit of the adsorption isotherm data on the Langmuir model. Also, the adsorption kinetics study revealed a best fit on the pseudo second-order kinetics model yielding an R2 value of 0.9975. The observations indicate that IIAC, whose surface is primarily homogenous, adsorbed organic ions, primarily COD. Monolayer adsorption indicates that adsorption is mostly chemical because it takes place without lateral interactions between the adsorbed molecules.