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 m²·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 cm³·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.

Pyrolysis is a thermochemical technology for converting biomass into energy and chemical products consisting of bio-gas, bio-oil, and biochar. Several parameters influence the process efficiency and properties of pyrolysis products. These include the type of biomass, biomass preliminary preparation, gaseous atmosphere, final temperature, heating rate, and process time. This manuscript provides a general summary of the properties of the pyrolytic products of waste rapeseed cake, with particular emphasis on the sorption properties of biochar. Biochar, produced by the pyrolysis process of biomass, is emerging as a powerful tool for carbon sequestration, reducing greenhouse gas emissions, and purifying water from contaminants such as potentially toxic elements and antibiotics. The review found that the biochar obtained as a result of pyrolysis of chemically modified waste rapeseed cake is characterised by its excellent sorption properties. The obtained sorbents are characterised by sorption capacity relative to the copper(II) ion, ranging from 40 mg·g⁻¹ to 100 mg·g⁻¹, according to the pyrolysis conditions and chemical modification method. The purified pyrolysis gas obtained in the high-temperature process can be used to generate heat and energy. Bio-oil, with its significant combustion heat of 36 MJ·kg⁻¹, can be a source of environmentally friendly green biofuel.

In the 21st century, the development of industry and population growth have significantly increased the amount of sewage sludge produced. It is a by-product of wastewater treatment, which requires appropriate management due to biological and chemical hazards, as well as several legal regulations. The pyrolysis of sewage sludge to biochar can become an effective way to neutralise and use waste. Tests were carried out to determine the effect of pyrolysis conditions, such as time and temperature, on the properties and composition of the products obtained and the sorption capacity of the generated biochar. Fourier transform infrared analysis (FTIR) showed that the main components of the produced gas phase were CO₂, CO, CH₄ and to a lesser extent volatile organic compounds. In tar, compounds of mainly anthropogenic origin were identified using gas chromatography mass spectrometry (GC-MS). The efficiency of obtaining biochars ranged from 44% to 50%. An increase in the pyrolysis temperature resulted in a decreased amount of biochar produced while improving its physicochemical properties. The biochar obtained at high temperatures showed the good adsorption capacity of Cu²⁺ (26 mg·g⁻¹) and Zn²⁺ (21 mg·g⁻¹) cations, which indicates that it can compete with similar sorbents. Adsorption of Cu²⁺ and Zn²⁺ proceeded according to the pseudo-second-order kinetic model and the Langmuir isotherm model. The biosorbent obtained from sewage sludge can be successfully used for the separation of metal cations from water and technological wastewater or be the basis for producing modified and mixed carbon sorbents.