A chemo-geotechnical approach to obtain optimal mixtures of zeolite-bentonite as heavy metal adsorbents

Abstract

The removal or reduction of heavy metal leakage from waste leachates into the soil and aquatic environment has been of interest for many years. A suitable solution is to enclose wastes in the impermeable, adsorbent, and durable layers that tolerate different ambient conditions. This indicates the need to consider geotechnical parameters along with the adsorption behavior of the adsorbents. In routine practice, a mixture of bentonite clay, zeolite, and geo-synthetics is used. This study aims to introduce suitable mixtures of zeolite and bentonite as natural adsorbents for sealing/adsorption of heavy metals in liner systems. Various mixtures of bentonite and zeolites of clinoptilolite and clinoptilolite-heulandite types were examined. Twenty-three mixed and non-mixed samples were prepared and tested. Once the soil index and soil compaction parameters were determined, an experiment program was designed to evaluate the cracking potential related to the freeze-drying process, as well as the adsorption potential of the samples at different ambient conditions (i.e., temperature and pH). It is observed that increasing the temperature up to 40 °C increases the adsorption potential. According to the results, the optimal adsorbents were found in the mixtures of zeolite/bentonite with the ratio of 4:1 in the first place and zeolite/bentonite with a ratio of 3:1 in the second, under various conditions.