The study focuses on the physicochemical regularities of the sorption of several heavy metal ions from aqueous solutions using a carbon–mineral sorbent based on rice husk. To understand and explain the sorption mechanism, the effect of pH on ion sorption was investigated. The change in sorption with successive increases in the solution-to-sorbent ratio was studied. A functional relationship α = f(V/m) was determined to predict the influence of the ratio on the extraction degree of metal ions by the obtained sorbent. Sorption isotherms were analyzed using known models (Langmuir, Freundlich, Redlich-Peterson, Dubinin-Astakhov, BET). It was found that increasing temperature decreases the sorption of these ions. Differential adsorption heats at various degrees of sorbent filling were calculated, allowing characterization of the energetic properties of its surface and the features of intermolecular interactions in surface layers. The kinetics of metal ion sorption and the time to reach sorption equilibrium were examined. Using Boyd and Morris-Webber models, the contributions of external and internal diffusion to the sorption process were analyzed. The results indicate that metal ion sorption on the obtained sorbent is a combination of physical sorption and chemical adsorption, with reversible specific interactions. It was shown that ions of this series exhibit different sorption capacities and interact differently with the sorbent surface depending on the conditions. The obtained sorbent can be effectively used for extracting trace concentrations of heavy metal ions from aqueous media.
R.N. Meretin (Wed,) studied this question.