New Separation Material Obtained from Waste Rapeseed Cake for Copper(II) and Zinc(II) Removal from the Industrial Wastewater

Rapeseed cake biochar was produced by pyrolysis at 973.15 K for 2 h, in anoxic conditions. Porous structure, specific surface area and die composition of waste rapeseed cake were studied. The specific surface area of rapeseed cake biochar was 166.99 m(2)·g(−1), which exceeded most other biochars reported, which made it an attractive material during wastewater treatment. The SEM study of the material demonstrated a large number of pores formed on the cell wall, with a pore volume V(p) = 0.08 cm(3)·g(−1). The results indicate lower aromaticity and increased polarity of the tested material. The observed H/C ratio of 0.29 is similar for activated carbons. Furthermore, sorption properties of the obtained carbon material in relation to copper(II), zinc(II) and arsenic(III) ions were also studied. Moreover, the impact of parameters such as: sorption time, temperature, adsorbate concentration, sorbent mass and solution pH on the efficiency of the adsorption process of the studied cations was also examined. Sorption studies revealed that the sorbent can be successfully used for the separation of Cu(II) and Zn(II) from technological wastewaters. Rapeseed cake biochar exhibits superior Cu(II) adsorption capacity (52.2 mg·g(−1)) with a short equilibrium time (6 h). The experimental data collected show a high selectivity of the obtained carbon material relative to copper(II) and zinc(II) ions in the presence of arsenic(III) ions.