Abstract This study investigated metal removal efficiency of natural (N peat) and HCl treated peat (HCl peat) using batch sorption tests with real mining wastewaters. FTIR and XPS studies revealed that peat modification did not alter the structure of the sorbent. HCl peat exhihited higher maximum metal uptake capacity (22.4 mg Ni/g) than N peat (17.9 mg Ni/g). Sorbents removed arsenic most efficiently (80%, dosage 1 g/L). Optimum contact times ranged between 30–60 min. Our study revealed that although HCl peat had better settling properties, N peat displayed overall better purification performance, representing thus the most cost-effective and sustainable option.