Guar gum-stabilized soil: a clean, sustainable and economic alternative liner material for landfills

Abstract

Biopolymers have attracted much attention in the field of geo-environmental engineering as they provide a carbon–neutral alternative for soil stabilization and heavy metal removal. This study explores the possibility of using guar gum-stabilized soil (GGSS) as a landfill liner by improving the hydromechanical behaviour and heavy metal attenuation capacity of the poorly graded sand–clay mixture. The results demonstrate that the unconfined compressive strength improved by 1.75 folds, and hydraulic conductivity after 120 days of curing decreased by 2.72 × 105 folds at 2% guar gum addition. Additionally, it withstands adverse environmental conditions and increases the heavy metal attenuation capacity of the soil. Leachate studies show that GGSS has a good capacity to adsorb heavy metals like lead, copper, cadmium and zinc. Micrographs from the scanning electron microscope demonstrate gel plug formation and bioclogging in the soil matrix with the addition of guar gum leading to favorable modifications in the geotechnical properties of the stabilized soil. The durability of the stabilized soil strongly depends on the biopolymer concentration. The soil stabilized with a higher dosage shows better resistance against alternate cycles of wetting and drying than lower dosages due to weak inter-particle connection. Guar-stabilized soil is also more economic than conventional bentonite liners. The study demonstrates that guar gum can be considered as an ideal liner material for landfills with specific advantages like replacing a nonrenewable material, bentonite with clean and renewable material, guar gum. Graphic abstract: [Figure not available: see fulltext.]