Preparation of eco-friendly cryogel absorbent/paper mulch composite with cellulose/ZnCl2 gel as adhesive

Application of polyethylene (PE) mulch in agriculture and horticulture is challenging due to scarce fossil-oil resources and serious environmental pollution. Therefore, bio-based mulches represent a promising alternative for petroleum-derived ones. From the lignocellulose from the whole corn stalk, the eco-benign cryogel absorbent and paper mulch has been modified by tartaric acid (TA) esterification and polyvinyl alcohol (PVA)/cationic starch (CSt) coating, respectively. This work reports a hybrid mulch of these two products via cellulosic partial-dissolution and regeneration processes and its excellent performance of water preservation for cultivation soil. The modification of TA molecules onto cellulose chains were confirmed by FTIR and X-ray diffraction, which showed the formation of ester bonds and crystallinity transition from cellulose I to the coexistence of cellulose II. SEM analyses proved a successful composite of TA-esterified cellulose absorbent and PVA/CSt-coated paper by ZnCl2-dissolved cellulose gel. The abundant H-bonding between interfaces of the coated paper and cellulose-derivative cryogel contributed to the favorable connection and thus mechanical properties, which both dry tensile strength (41.5 MPa) and wet tensile strength (35.6 MPa). The composites showed the reduction of water vapor transmission rate (WVTR) and oxygen transmission rate (OTR), which were 755.43 g/m2 day and 10.6 mL/m2/day, respectively, and enhancement of water absorbency for 210.3 g/g as increasing the cryogel thickness. The green and biodegradable strategy proposed in this study will broaden the application range of composite mulches in agriculture and forestry.