Mining, combustion of coal and waste, and steel processing are the main industrial activities that
trigger the emission of large amounts of Zn, which reach the soil and pose a risk to its services,
functions, and groundwater quality. A frequently associated process is soil acidification, reducing
soil’s ability to retain incoming toxic metals. The soil treatments with reactive, low-cost, and locally
available materials might be a straightforward approach to decreasing the mobility of toxic metals
and alleviating the environmental risks. This study aimed to compare Zn ions sorption and retention
by several unconventional soil additives (seashell waste, bone char, and red mud) against the
performance of acidic soil. Batch experiments of Zn ions sorption were initially performed using
solutions with different Zn concentrations, followed by the determination of sorbed Zn stability in an
acidic medium. The waste materials exhibited higher pH values and superior Zn sorption capacities
with respect to the soil. The desorption experiment exposed different mechanisms of Zn ions fixation
by studied materials. While the substantial amounts of Zn sorbed by seashells, red mud, as well as
soil were released in the scope of the ion exchange and carbonate fraction, sensitive to pH decrease,
the bone char preserved Zn in more stable fractions. The investigated waste materials can potentially
prevent Zn leaching through the soil profile, with the bone char demonstrating the most significant
capability for long-term retention performance.
