Efficiency of Combined Processes of Coagulation and Modified Activated Bentonite with Sodium Hydroxide as a Biosorbent in the Final Treatment of Leachate: Kinetics and Thermodynamics

Introduction and Currently, leachate production and its management are major environmental problems associated with the operation of solid waste landfill. Herein, we sought to evaluate the efficiency of combined processes of coagulation and modified activated bentonite with sodium hydroxide as abiosorbent in the final treatment of leachate.
This experimental-laboratory study included chemical coagulation using polyaluminum chloride (PAC) and modified bentonite. We investigated the effect of critical operating parameters on landfill leachate treatment. These operating parameters included pH (2-10) and PAC concentration (5-25 mg/l) in chemical coagulation process, contact time (15-150 min), solution pH (2-10), bentonite concentration (0.3-1.5 g/l), and temperature (25, 35, and 45ºC) in adsorption process.
The overall efficiency rate of this process in removal of total chemical oxygen demand (COD) was 93%, with the optimum PAC concentration of 30 mg/L, pH=6 in the chemical coagulation phase, reaction time of 60 min during the adsorption process, bentonite concentration of 0.5 g/L, pH=6, and temperature of 25ºC. The kinetics of COD adsorption on modified bentonite conformed to the pseudo-second-order model.
The application of combined processes of chemical coagulation and activated bentonite is highly efficient in removing major pollutants in leachate.