This paper presents results that show the effect of hydrothermal carbonization and subsequent cold plasma jet treatment with helium and argon on the structure and sorption properties of a material—spent brewery grain. Treatment of activated carbon, with a cold atmospheric plasma jet, was used comparatively. The effect of activation on the pore structure of the materials was carried out by the volumetric method at low pressure (N₂, 77 K). The specific surface area as well as the total pore volume, average pore size, and pore size distribution were determined using different theoretical models. A high improvement in the sorption capacity parameter was obtained for hydrochars after cold atmospheric plasma jet treatment with an increase of 7.5 times (using He) and 11.6 times (using Ar) compared with hydrochars before cold atmospheric plasma jet treatment. The increase in specific surface area was five-fold (He) and fifteen-fold (Ar). For activated carbon, such a large change was not obtained after plasma activation. Regardless of the gas used, the increase in structural parameter values was 1.1–1.3.

The paper presents research on the influence of grain size of selected coals and their structural parameters on the diffusion coefficient and methane sorption isotherms. Two coals from Polish hard coal mines, differing in the coal rank, were tested. Sorption isotherms for methane were determined. An unconventional sequence of pressures 0→0.1→0→0.5→0→1.5 MPa was employed to assess the speed of achieving sorption equilibrium at different pressures. The studies of CH4 accumulation kinetics were performed on various grain classes of the tested coals. Both the sorption capacity of coal and the diffusion coefficient proved to be highly sensitive to the experimental methodology. Critical measurement parameters in terms of determining the diffusion coefficient concerning the assumptions of the Crank model were indicated. The influence of the equivalent radius of coal grain on the process kinetics was demonstrated. The stepwise pressure increase factor was examined in the context of minimising the impact of sorption isotherm non-linearity on the results. The importance of the width of the grain class of coals was determined to reduce their maceral inhomogeneities. These factors are the most common reason that makes it difficult to quantitatively compare diffusion coefficient values.

The presence of various pesticides in natural streams and wastewater is a significant environmental issue due to their high toxicity, which causes harmful consequences even at low quantities. One cost-effective method to remove these pollutants from water could be through adsorption using an inexpensive, easily obtained adsorbent—biochar. The presented research demonstrates the efficacy of applying biochar obtained from wheat grains to eliminate alachlor from water. The sorption properties of the biochar and the likely removal mechanisms are defined. The study found that the biochar removed 76–94% of alachlor, depending on the initial concentration of the pesticide in water. The maximum removal of alachlor (94%) using biochar occurred at an initial pesticide content of 1 mg/L. Both the pseudo-second-order kinetic (R² = 0.999) and the Langmuir isotherm models (R² = 0.996) effectively characterized the elimination of alachlor by wheat grain biochar. The biochar’s maximum adsorption capacity for alachlor was 1.94 mg/g. The analyzed biochar, with its micropores and various surface functional groups, was able to effectively adsorb alachlor and trap it within its structure.