Biochar efficiency in copper removal from Haplic soils

The main aim of the study was to examine the biochar efficiency in copper (Cu) ion removal from Haplic (Luvisol, Podzol) soils. In other words, the most effective biochar dose and the most favorable environment pH value were proposed. The copper removal was carried out based on the adsorption process. The results of kinetics measurements were modeled using Richie equation, whereas the adsorption isotherms using Langmuir-Freundlich and Dubinin-Radushkevich equations. The copper removal is a strongly pH-dependent process which is associated with variability of chemical Cu forms and various reactivities of organic molecules. The Cu adsorption amount was higher on silty Haplic Luvisol than on sandy Haplic Podzol mainly due to higher content of organic carbon, functional groups, clay and silt fractions as well as larger surface area. Moreover, the biochar addition increased linearly the soil surface charge and contributed to higher copper adsorption in the whole range of investigated ion concentrations. The higher the biochar dose added, the more Cu ions were adsorbed.