Evaluation of Green Tea Leaves as an In Situ Capping Material for the Remediation of Lindane-Contaminated Sediments

Organochlorine pesticides (OCPs), such as lindane, persist as toxic pollutants in river sediments, necessitating operative and effective remediation. An alkaline green tea (GT)/Fe²⁺ system shows promise for chemical reductive degradation of lindane through sustained polyphenol release. This study developed a novel in situ capping material (ISCM) composed of tea leaves, bentonite, sodium alginate, and pyrite. The GT ISCM exhibits strong water absorption, swelling, extended polyphenol release, and a stable reducing environment. Using the Taguchi method (L9 orthogonal array), the ISCM formulation was systematically optimized, and Analysis of Variance identified the optimal composition as 10 g bentonite, 0.5 g tea leaves, 0.25 g pyrite, and 0.1 g sodium alginate. Utilizing tea polyphenols as reducing agents, it immobilized lindane and promoted its degradation while preventing the formation of 1,3,4,5,6-pentachlorocyclohexene and trichlorobenzene, byproducts produced during alkaline hydrolysis. Under simulated field conditions, the ISCM significantly reduced lindane release from contaminated sediments into the aqueous phase, demonstrating high removal efficiencies. These findings underscore the potential of GT ISCM as a sustainable strategy for stabilizing and degrading lindane in contaminated sediments, providing a green alternative for OCP remediation.