Effect of Crosslinked Biopolymers on Strength and Sorption Behavior of Clayey Soil

This study investigates the influence of two crosslinked biopolymers on the compressive strength and sorption behavior of clayey soil. Two admixtures were prepared by individually crosslinking sodium alginate (A) and xanthan gum (X) with chitosan (C) in different ratios (3:1, 1:1, and 1:3). The resulting chitosan–sodium alginate (CA) and chitosan–xanthan gum (CX) biopolymers were incorporated into the soil at a 1% dosage. Additionally, the adsorption capacities of CA and CX in Cd2⁺ and Cr⁶⁺ contaminated soils (300 and 500 mg/kg) were evaluated. The results showed that the highest compressive strength (5.2 MPa) was achieved after 28 days of curing in a sample treated with CX (3:1). Sorption studies indicated that CA-treated samples exhibited higher adsorption capacity due to the greater number of carboxyl (COO⁻) groups, providing more binding sites compared to CX-treated samples. Among all samples, the highest immobilization occurred in Cr⁶⁺-spiked soils, attributed to their higher surface charge and cation exchange capacity. In particular, the sample treated with CA (1:3) showed an increase in sorption potential by 47% and 22% at 300 and 500 mg/kg Cr⁶⁺, respectively, compared to the control.