Post treatment of sanitary landfill leachate by adsorption on zeolite
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Date
2025-10-14
Authors
Μάμαλης, Ελευθέριος
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Abstract
Leachates from waste management, such as landfills, is a particularly hazardous liquid due to the high concentration of toxic substances, metal ions and especially ammonia (NH₃/NH₄⁺). Even after primary treatment, such as reverse osmosis, the concentration of ammonia ions often remains at levels that exceed the limits set by environmental legislation, endangering aquatic ecosystems and human health due to eutrophication and possible chemical migration. The need for effective secondary treatment makes it imperative to seek alternative methods. Among these, adsorption on natural or synthetic carrier materials, such as zeolite, stands out for its ability to selectively bind ammonia through ion exchange, offering economic viability, minimal side effects and high efficiency even at low pollutant concentrations. These characteristics make it a privileged solution for sustainable leachate management.
The present work aims to investigate the efficiency of ammonium ion (NH₄⁺) adsorption on natural zeolite through experimental studies on standard solutions and real landfill leachate, and to collect and analyze data to develop tools to predict the behavior of the system under fixed-bed column conditions. Particular emphasis is placed on understanding the parameters that influence the process, and on the potential to exploit the findings for larger scale applications. At the same time, the reuse of saturated zeolite as a soil amendment material is proposed, based on previous literature evidence, contributing to the circular economy and the integrated management of byproducts.
Before applying the experiments to real leachate, a preliminary study was carried out through intermittent adsorption experiments in standard NH₄⁺ solutions to investigate the effect of different initial concentrations and amounts of zeolite. This study provided valuable information on the process dynamics and contributed to the design of the main experimental phase.
This was followed by intermittent sorption experiments with real landfill leachate, in which the influence of individual parameters on the NH₄⁺ ion removal process was studied. The adsorption mechanism was analyzed through isothermal models (Langmuir, Freundlich) and kinetic models (pseudo-first-order and pseudo-second-order), with the results showing that the Freundlich isothermal model and the pseudo-second-order kinetic model provided the best fit to the experimental data, indicating multilayer adsorption and chemosorption mechanism, respectively.
In the next stage, experiments were carried out in fixed-bed columns under continuous flow, with variations in initial concentrations, flow rate and zeolite mass. The resulting breakthrough curves allowed the correlation of the operational parameters with the process performance and formed the basis for the development of a mathematical prediction model.
Based on the results of the column experiments, an algorithm was developed in the MATLAB environment to systematically analyze the experimental data, perform fitting procedures, and ultimately identify and apply the most appropriate model for describing the observed adsorption behavior. Through statistical processing of the results, prediction equations were fitted expressing the model constants as functions of the initial conditions. This tool allows the calculation of the concentration at the column outlet under new operating conditions and was evaluated for its accuracy and predictive ability. From now on, it will be referred to in this paper as LEAF (Leachate Environmental Analysis & Forecasting).
Overall, the work provides a comprehensive and practically applicable framework for the effi-cient post-treatment of landfill leachate using natural zeolite. Through a combination of experimental documentation and computer simulation, the understanding of the adsorption process is enhanced and a prediction tool is provided that can be used in the design and optimization of real treatment plants.
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Keywords
Adsorption, Zeolite, Batch experiments, Column experiments, Process modeling