Biodegradable and multifunctional black mulch film decorated with darkened lignin induced by iron ions for "green" agriculture.

High-value utilization of bleached lignin has been widely used in different fields, whereas the investigation on darkened lignin in composite materials was often ignored. In this work, a sort of eco-friendly and structurally robust sodium carboxymethyl cellulose (CMC)/polyvinyl alcohol (PVA)/sodium lignosulfonate (SLS) black composite mulch film was elaborately designed. The chelation and redox reaction effect between Fe ions and SLS lead to the formation of a more quinones structure on lignin, darkening both lignin and the mulch films. The chelation effect between Fe ions and biopolymer formed three-dimensional structures, which can be used as sacrifice bonds to dissipate energy and improve the mechanical properties of the composite films. In particular, the maximum elongation at break and toughness increased from 48.4 % and 1141 kJ/m3 for the CMC/PVA film to 210.9 % and 1426 kJ/m3 for the optimized CMC/PVA/SLS/Fe black mulch film, respectively. In addition, the optimized black mulch film also possesses good soil water retention, thermal preservation effect, controlled urea release, and well biodegradability. This work offered a novel strategy for designing eco-friendly black mulch with reinforced mechanical strength, slow-release urea, soil moisture retention, and heat preservation performances.

All-biodegradable soy protein isolate/lignin composite cross-linked by oxidized sucrose as agricultural mulch films for green farming.

Microplastics produced from the discarded traditional non-degradable mulch film deteriorate the ecological environment and pose a great threat to human health. Developing eco-friendly and biodegradable materials to substitute traditional plastic mulch film highly contributed to the progress of green agriculture. Herein, a category of eco-friendly and all-biodegradable soy protein isolate (SPI)/oxidized sucrose (OS)/Lignin mulch film was innovatively proposed by employing OS as green cross-linker and lignin as nanofiller under chemical/physical interaction. The cross-linking effect and hydrogen bonds between biopolymers act as sacrificial bonds for energy dissipation and effectively reinforced the intermolecular interactions as well as tensile strength from 6.67 MPa of pristine SPI film to 8.45 MPa of SPI/OS/Lignin film. Moreover, the SPI/OS/Lignin mulch film also presented excellent UV-shielding, moisture retention, heat preservation effect and sustained urea release properties. Benefitting from the above-mentioned merits, higher germination rate of cabbage seed was achieved when the natural soil was covered by such multifunctional mulch film compared to traditional low-density PE film. Our findings paved a solid way in rational designing and fabricating eco-friendly, low-cost and all-biodegradable mulch film to facilitate the crops growth, boosting the development of green farming.