# Characteristics of Removal of Lead, Cadmium and Chromium from Soil Using Biosorbent and Biochar
## 1 Introduction
Wood sawdust, generated on a large scale as industrial waste during cutting, sawing, or milling of wood, requires careful disposal due to potential environmental problems. Improper burning or open disposal of sawdust can lead to serious health problems and environmental pollution [15]. In developing countries, these problems can be particularly acute, leading to additional environmental challenges. Therefore, the appropriate use of sawdust, such as its use in environmental remediation or biofuel production, is not only beneficial due to its low price, but also due to the diverse properties that can be used in various technological processes [16]. There are several studies available on the use of sawdust as a biosorbent of heavy metal ions and organic dyes [17]. [PERSON] et al. proposed the chemical modification of sawdust of Ayous wood with APTES. Preliminary experiments showed that AW@APTES-0.5 is the best adsorbent for the removal of RB-4 dye from aqueous effluents [18]. Studies have been conducted on the use of wood sawdust as a raw material for the production of activated carbons. The results have shown that activated carbons obtained from wood biomass have promising properties, such as appropriate surface area, pore size, and volume, the presence of functional groups on the surface, and efficiency in removing various water-soluble toxic substances [19]. Recent studies have shown that sawdust ash can be used as a pozzolan in concrete, and sawdust can replace fine aggregate and sand, which affects the workability, density, mechanical, and shrinkage properties of bricks and brick materials [20]. However, the mechanisms responsible for reducing the mobility and bioavailability of heavy metals under the influence of biochar, as well as the potential risks associated with its use, are not fully understood, hindering its application for soil remediation [21]. Stabilizing heavy metals in soil through its modification has been recognized as a promising, cost-effective, and environmentally friendly remediation approach. Various soil amendments, such as lime, phosphate fertilizers, iron salts, apatite composites, red mud, bentonite,zeolite, silicon, and modified silicon, have been developed to limit heavy metal activity and reduce their accumulation in plants [22]. Nevertheless, large-scale remediation of agricultural soils contaminated with heavy metals has not yet been conducted, mainly due to economic challenges, low efficiency, lack of specificity, and potential secondary contamination. Therefore, it is necessary to develop new soil amendments characterized by high specificity and effectiveness with minimal negative impact on the soil environment to efficiently remediate heavy-metal-contaminated soils [23]. Biochar metal removal studies are superior to other studies in the field because they offer unique advantages resulting from the use of biochar as a sorption material. Unlike traditional remediation methods such as the use of activated carbon or chemicals, biochar is a more sustainable and ecological solution because it is derived from plant biomass and can be produced from agricultural waste. Additionally, biochar not only effectively removes heavy metals but also improves soil properties by increasing its water capacity and organic matter content, which brings additional environmental benefits. Our studies also include an extensive comparison of biochar with other sorption materials, allowing for a more accurate assessment of its efficiency and potential in different application contexts. The aim of this study was to investigate the potential use of natural materials (biomass, biochar) as sorbents for the removal of selected heavy metals (lead (II), cadmium (II), and chromium (VI)) from soil. In the conducted experiments, aspen wood sawdust and the pyrolysis product of sawdust from the same type of wood were used as natural sorbents. Activated carbon was used as a control sorbent.