Rehabilitation of contaminated soils is a complex and time-consuming procedure. One of the most cost-effective and easy-to-use soil remediation approaches is the use of amendments that stabilize the potential toxic elements (PTE) in soil by reducing their mobility and bioavailability. The stabilization of Cu, Pb, Zn, Cd, Co, Cr, Ni in a contaminated soil using 5% and 10% amendment with thermally treated natural zeolite was investigated using a sequential extraction procedure, contamination and environmental risk factors. The results showed that after amendment, the PTE concentration decreased in the exchangeable and reducible fractions and increased in the oxidizable and residual fractions. The highest immobilization effect, consisting in the decrease of exchangeable fractions with 69% was obtained in case of 10% zeolite amendment and 90 days of equilibration time for Pb; also, more than half of the mobile fraction was immobilized in case of Zn, Cu, and Co and about one third in case of Ni, Cr, and Cd. Generally, the immobilization effect of the 5% and 10% amendment is comparable, but a higher equilibration time enhanced the immobilization effect, especially in the case of Cd, Co, Cu, Pb, and Zn.

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Gold is a highly required material for a wide range of personal and industrial applications. The high demand for gold, together with the shortage of natural resources and high pollution potential of wastes generated during mining and ore processing activities led to search for alternative sources of gold. A possible source is represented by mine wastes resulting from the processing of polymetallic or sulfidic ores. The reprocessing of wastes and old tailings with moderate to low content of gold offers not only a business opportunity, but also enhances the quality of the surrounding environment, changes the land use and offers a wide range of socio-economic benefits. Cyanidation, the most widespread Au leaching option, is progressively abandoned due to the high risk associated with its use and to the low public acceptance. Therefore, alternative methods such as thiocyanate, thiourea, thiosulphate and halide leaching gained more and more interest. This chapter presents the most important features of some Au leaching methods, emphasizing their advantages, limitations and potential applications.

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