Efficient stabilization of soil, sand, and clay by a polymer network of biomass-derived chitosan and carboxymethyl cellulose

Biomass-derived polymers are being increasingly utilized as eco-friendly functional materials in fields ranging from medicine and food to agriculture and environmental engineering. In this report, we developed a novel efficient method for improvement of soil materials based on in situ gelation of a polyion complex formed by biomass-derived carboxymethyl cellulose (CMC) and chitosan (CS). Self-organized network of polymer films and microfibers assembled via electrostatic interactions between oppositely-charged polyions interconnects particles of soil material and imparts the resulted composite with a considerable mechanical strength. Treatment of soil even with a high water content (ca. 30%) by a mixture of CMC and CS at m(CMC + CS)/m(soil) ratio of ca. 1% is sufficient to gain up to 150 kPa compression strength that further increases up to ca. 1 MPa after drying. Similar reinforcement effect by CMC-CS complex was observed for sand, and much higher yield strengths were measured for clay. Mechanical properties of soil materials strengthened by CMC-CS complex depended on structure and stability of CMC-CS polyion network and controlled by the polymerization degrees of macromolecules and the charge ratio between them. Being composed entirely of biomass-derived polymers, the proposed soil treatment system is particularly attractive due to environmental friendliness and sustainability and it can be utilized not only for the soil improvement but also for the construction of functional platforms for soil pollution control and remediation.