Evaluation of the adsorption performance of geological materials based on limestone and green shale from the Taza Region - Morocco - Application for leachate treatment

Abstract

Leachates from landfills are a primary source of air pollution and adverse effects on health and nature. In this context, the present study focuses on the treatment of leachate landfill by a geochemical approach, by using an adsorption process on materials produced from limestone and green shale natural rocks. To this end, the rocks used for preparing materials were collected around the city of Taza -Morocco-. Then, absorbent properties of produced materials were evaluated for different types of pollutants contained in the leachate studied, through structural analyses carried out by scanning electron microscopy (SEM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) before and after the adsorption process. Moreover, the effect of temperature, contact time and leachate COD content on the abatement efficiency of COD by the two materials was evaluated, by using kinetic and isothermal models. The characterization before the adsorption process revealed that the prepared materials present a partially homogeneous surface with particles of irregular sizes and varied atomic compositions. Respective reduction rates (R%) of 39% and 43% for COD and BOD₅ were obtained after adsorption on the material prepared from limestone. The results of kinetic and isothermal models showed that the removal efficiency of DCO is significantly related to the temperature and time of contact, with reduction rates of 40% and 32% for the materials prepared from limestone and green schist respectively. Furthermore, the kinetic and isothermal models are well adjusted by the pseudo-second order and Freundlich models. Therefore, the studied materials represent an encouraging and sustainable alternative, while contributing to the enhancement of local natural resources.