Coal gangue-enhanced eco-friendly superabsorbent composite for agriculture application

Improvement of the soil water retention through suitable amendments is one of the methods for the growth of the crop. In this study, a novel degradable superabsorbent, cellulose-g-poly(acrylic acid)/modified coal gangue (CS-g-PAA/MCG), was prepared by grafting poly(acrylic acid) (PAA) onto cellulose (CS) and introducing the solid waste coal gangue (CG) as an inorganic component after modification. The structure, morphology, and thermal stability of the superabsorbent composite were systemically examined by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and thermogravimetric analysis (TGA). Meanwhile, the water absorption capacities of CS-g-PAA/MCG in different pH or various saline solutions as well as the reusability and the water retention capacity in soil were also investigated. The results suggested that the CG–polymeric network interaction was achieved through the electrostatic interactions or the hydrogen bonds and CS-g-PAA/MCG possessed the excellent water absorption capacity, which was 681 g/g in distilled water and 81 g/g in 0.9 wt.% NaCl solution, respectively. What’s more, the plant pot experiments verified the CS-g-PAA/MCG not only significantly improved the soil’s water retention efficiency, but also could be promoted the plants growth. Furthermore, CS-g-PAA/MCG degraded by about 44.71% in 70 days. The study demonstrates the potential of using a low rate of CS-G-PAA/MCG for improvement of the soil water retention with the advantage of offering a non-toxic and eco-friendly solution to mass utilization of industrial solid waste for agricultural application.