Effects of pH and Fe(III) Concentrations in Xanthan Gum Treatments on Soil Penetrability Resistance

Abstract

Core Ideas Soil penetration resistance is a technique for evaluating the effects of field management on soils. Improving the soil penetration resistance with xanthan and Fe(III) proposed. The highest soil penetration resistance was occurred at pH 9 and 10 mmol L−1 Fe(III). Soil penetration resistance (SPR) measures soil's ability to resist penetration or movement by detrimental factors, such as the erosion process. It is a promising technique for characterizing the quality and strength of sandy soil after sand dune fixation or soil stabilization. This study examines use of xanthan and Fe(III) solutions to improve soil penetration resistance in areas covered by low-strength surface soil. Sandy soil was treated by xanthan solution (0.25%, w/v) with different pH levels (3, 5, 7, and 9) and different Fe(III) concentrations (0, 10, 25, 50, 100, and 200 mmol). The SPR value of treated soils was measured using a pocket penetrometer. Soil penetration resistance increased significantly, and the pH of the xanthan solution increased from 3 to 9 at fixed Fe(III) concentrations. This pH response was likely the result of increased pH levels causing expansions of the xanthan molecule chains, resulting in a greater soil–xanthan side chain interface. Although the pH of xanthan solution was constant, the SPR value increased by increment of Fe(III) concentration from 0 to 10 mmol L−1; however, progressive increments of Fe(III) concentrations from 25 to 200 mmol L−1 resulted in very lower SPR values due to strong interactions between Fe(III) and xanthan chains, leading to gel formation. The optimal SPR value was observed at a xanthan solution pH of 9 and a Fe(III) concentration of 10 mmol L−1. These results provide a better understanding of how xanthan solutions can be formulated to increase the strength of sandy soil after soil stabilization and dune stability.