Composite film with adjustable number of layers for slow release of humic acid and soil remediation.

In this study, to improve the soil amendment performance of film materials, composite films with the adjustable number of layers and controlled slow-release time were prepared using sodium alginate (SA), chitosan (CS) and activated charcoal (AC) as raw materials. The prepared multilayer films exhibited a wide pH response range and excellent slow-release time. The cumulative release of humic acid (HA) increased from 19.87 ± 0.98% to 66.72 ± 1.06% with increasing the pH from 4.0 to 10.0 after 700 h of slow-release. In addition, after 50 d of remediation in red soil, plantation soil, and saline soil, the NH 4 +-N, Olsen-P, Olsen-K, and organic matter contents in the three soils were increased by 2.91–28.62 mg/kg, 46.97–70.43 mg/kg, 55.89–77.01 mg/kg, and 12.47–22.52 g/kg, respectively, and were able to provide sustained crop growth promotion effect. This study demonstrates the promising application of multilayer film in soil remediation and agricultural production. [Display omitted] • Layer-controlled film was prepared by self-assembly method. • Multilayer structure realized the controllability of slow-release time. • The film exhibited a wide pH response used to remediate different soils. • Natural biomass materials provide excellent biodegradability. [ABSTRACT FROM AUTHOR]